Western North American Naturalist

Volume 61 Number 2 Article 16

4-23-2001

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OCCURRENCE OF NATIVE COLORADO RIVER CUTTHROAT TROUT (ONCORHYNCHUS CLARKI PLEURITICUS) IN THE ESCALANTE RIVER DRAINAGE, UTAH

Dale K. Hepworth1, Michael J. Ottenbacher1, and Charles B. Chamberlain1

ABSTRACT.—Field surveys were conducted during 1997 and 1998 documenting the distribution and abundance of Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) in Escalante River tributaries. This documented occur- rence of native trout in the Escalante River drainage of southern Utah represents an expansion of the known historic range of this subspecies as reported before the 1990s. We found 5 populations of native trout ranging in biomass from 3.0 to 104.2 kg ⋅ ha–1 and occupying 13.2 km of stream of 130 km of estimated historic habitat. Current distribution and abundance of Colorado River cutthroat trout were compared to early introductions of nonnative trout stocked for sport fishing purposes. Native cutthroat trout have been displaced by nonnative cutthroat trout (O. c. bouveri), rainbow trout (O. mykiss), brook trout (Salvelinus fontinalis), and brown trout (Salmo trutta) except where they were isolated by physi- cal or biological barriers. Displacement may have been more extensive except for the remoteness of the drainage and relatively recent introductions of nonnative trout. These conditions limited the overall amount of the drainage stocked, numbers of nonnative trout stocked, and time over which stocking occurred. Discoveries of native trout populations within the Escalante River drainage have allowed expanded conservation of this subspecies by adding new populations to what was known to exist and by increasing the known natural range of this fish.

Key words: cutthroat trout, native trout, Colorado River, Escalante River, drainage, occurrence, abundance, distribu- tion, management, nonnative trout, stocking, history.

Historically, the Colorado River cutthroat made from south of the Fremont River, and trout (Oncorhynchus clarki pleuriticus; here- systematic surveys were not conducted. The after referred to as CRCT) was found in cold- discovery of CRCT in East Boulder Creek (a water habitats of the upper Colorado and tributary to the Escalante River, Utah) in 1990 Green River basins. Its northern distribution caused speculation that the historic distribu- extended into Wyoming, and it was bounded tion could have extended as far south, on the to the east and west in Colorado and Utah, west side of the Colorado River, as the respectively. Within northern Utah, Kershner Escalante River drainage (Behnke 1992). The et al. (1997) described CRCT from streams on Escalante River drainage is contiguous with the north slope of the Uinta Mountains, and the Fremont River drainage but not located as Cope (1955) stated that CRCT were naturally far south as the San Juan River, Colorado, found in numerous streams on the south slope which is the southern distribution of CRCT on of the Uinta Mountains. Subdrainages of the the east side of the basin. If CRCT colonized Colorado River basin containing trout habitat the San Juan River drainage by moving down in central and southern Utah are more frag- the Colorado River, presumably, they also had mented than in northern Utah and separated access to the Escalante River. Nevertheless, it by greater distances. In these areas historic was not known if this single population of fish distribution of CRCT is less certain, but CRCT in East Boulder Creek resulted from an early were known to occur naturally in Fish Lake introduction by man. In 1992 we field identi- (Hazzard 1935) at the headwaters of the Fre- fied another isolated population of CRCT in mont River (also known in its lower reaches as West Boulder Creek that potentially occurs the Dirty Devil River). Behnke and Benson naturally and verified the identification by (1980) considered the Fremont River to be the independent review (Shiozawa and Evans southernmost distribution of CRCT in Utah. 1994). Young et al. (1996) noted that compre- Prior to 1990 no reports of native trout were hensive descriptions of the historic range of

1Utah Division of Wildlife Resources, Box 606, Cedar City, UT 84720.

129 130 WESTERN NORTH AMERICAN NATURALIST [Volume 61

CRCT are not available and reported that main stream and tributaries to the Escalante potential distribution of CRCT could include River are in narrow canyons. Access is limited streams as far south as the San Juan River to roads that typically cross drainages at a few drainage in northern Arizona and New Mexico. locations rather than parallel streams. Previ- Similar to other subspecies of cutthroat ous surveys of trout streams were completed trout, CRCT have undergone large declines in at convenient access sites (McAda et al. 1977). numbers and range during the past century. Much of the main stream of the Escalante Causes of declines include displacement by River is located within the Glen Canyon and hybridization with introduced nonnative National Recreation Area and the Grand Stair- trout, an irreversible impact; habitat losses, case–Escalante National Monument. Trout often at least partially reversible; and overfish- habitat is largely limited to tributary streams ing, generally not a significant factor when located on the Dixie National Forest, which considered alone (Cope 1955, Behnke and includes Box Death Hollow Wilderness Area. Benson 1980, Jespersen 1981, Behnke 1992, Lower portions of some trout streams extend Young 1995a). Kershner et al. (1997) estimated onto lands administered by the national monu- that CRCT have been displaced to <1% of ment. Private land comprises about 2% of the their historic range. Young et al. (1996) defined drainage and is found mostly around the towns conservation populations of CRCT as those of Escalante and Boulder. The Aquarius Plateau isolated from nonnative trout by migration contains numerous small lakes, ponds, and barriers in relatively secure situations and small reservoirs that have been stocked with concluded that only 20 such populations were nonnative trout for angling since at least the known from a total of 318 waters containing 1940s. Many of these lakes were first stocked CRCT. Although additional populations of by pack horse and airplane (Utah Division of CRCT likely exist, surveys need to be con- Wildlife Resources, hereafter refered to as ducted for verification. Identification of other UDWR, unpublished stocking records), which populations of CRCT is critical to properly are still common methods of stocking today. manage these fish and ensure proper recovery efforts. METHODS Our contention was that CRCT were likely native to the Escalante River drainage. We We initially made field identifications of conducted surveys of Escalante River tribu- CRCT by their distinctly different coloration taries in 1997 and 1998 to determine abun- compared to closely related and geographi- dance and distribution of CRCT within this cally adjacent Bonneville cutthroat trout (O. c. drainage and assess the likelihood of natural utah), introduced nonnative cutthroat trout occurrence. In addition, we characterized (primarily O. c. bouveri), and stocked rainbow CRCT occurrence within the drainage relative trout (O. mykiss). Coloration of CRCT fre- to nonnative trout and sport fish stocking prac- quently includes a bright orange or red ven- tices to evaluate impacts of stocking and pro- tral region that extends from the slash marks vide better direction for future management. under the jaw posterior to the anal fin and is most apparent in adult males. Confirmation of STUDY AREA each putative CRCT population was verified by at least one independent review utilizing The Escalante River drainage, located in mitochondrial and nuclear DNA analysis and Garfield and Kane counties of south central meristic data (Behnke 1992, Shiozawa et al. Utah, is one of the most remote regions in the 1993, Shiozawa and Evans 1994, Toline, Hud- state (Fig. 1). Stegner (1954) characterized the son, and Seamons 1999, Toline, Seamons, and remoteness of the area by noting that the Hudson 1999, Hudson and Davis 2000). plateau was not explored until 1872 and that We selected streams to survey by reviewing the Escalante River was the last large river stocking records from UDWR fish hatcheries, drainage added to the map of the United UDWR fish population survey files, and perti- States. Headwaters originate on the Aquarius nent literature on early fish introductions and Plateau at elevations in excess of 3350 m (msl), access into the area (Popov and Low 1950, and the Escalante River terminates at Lake Stegner 1954, Cope 1955). Stream surveys Powell at approximately 1128 m. Much of the were conducted as either field inspections or 2001] NATIVE TROUT IN THE ESCALANTE DRAINAGE 131

Fig. 1. Map of the upper Escalante River drainage, southern Utah, showing trout habitat and distribution of Colorado River cutthroat trout (CRCT). Survey location numbers refer to corresponding survey data in Figure 2 and Tables 2 and 3. population estimates. Streams where remnant stations. All streams were relatively small, and populations of CRCT may have persisted were at least 75% of all captured trout were removed field inspected during 1997–98. Field inspec- during the first electrofishing pass. We made tions included hiking entire stream lengths to population estimates in August and Septem- verify trout distributions. Electrofishing gear ber 1998, when young-of-the-year trout were was used to check for the presence of CRCT still too small to be efficiently sampled, and and determine upstream and downstream dis- thus samples and estimates were restricted to tributions of different fish species. Population yearling and older trout. Total length (TL, estimates were conducted by electrofishing mm) and weight (g) were recorded for all cap- where CRCT were found or already known to tured trout. occur to determine trout abundance and bio- The mean wetted width of streams was mass at specific sites. Distribution and abun- determined by taking measurements at 10 dance of CRCT were compared to past non- randomly selected transects within each elec- native trout introductions and current stock- trofishing survey station. Trout biomass by ing practices on a drainage-wide scale (Fig. 1). unit area was estimated from mean stream Historic conditions were considered to be width and site length, estimated trout num- what likely existed, based on our judgment, at bers, and mean trout weight. We selected 2 the time of exploration and settlement of Utah sites for population estimates on each stream in the mid-1800s. containing CRCT. Survey locations and stream Population estimates were made by the 2- distances were determined with a global posi- pass removal method (Zippin 1958) with block tioning system (GPS) unit and U.S. Geological nets set at the upper and lower ends of 100-m Survey 7.5-minute series topographical maps. 132 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 1. Summary of 1997–98 field inspections, Utah Division of Wildlife Resources fish population survey files, and stocking records on Escalante River tributaries (CRCT = Colorado River cutthroat trout). Headwater fish Stream species Survey Stocking records Steep Creek None Electrofishing, 1977 file report None Frisky Creek Brook and Electrofishing, 1977 file report None, but a tributary to Deer Creek rainbow West Fork Deer Brook, rainbow, Rotenone, 1995 file report Nonnative cutthroat trout, 1941a Creek and nonnative Headwater lakes, rainbow trout, 1941 cutthroat Headwater lakes, brook trout, 1956 East Fork Deer Brook trout and Electrofishing, 1977 file report Rainbow trout, 1941 Creek rainbow trout Headwater lake, nonnative cutthroat, 1952a Headwater lake, brook trout, 1957 Bear Creek Brook trout Electrofishing, current study Rainbow trout, 1942 Headwater lake, brook trout, 1957 East Fork Remnant CRCT Electrofishing, current study Rainbow trout, 1941; probably stocked in Boulder Creek lower reaches West Fork Remnant CRCT Electrofishing, current study Rainbow trout, 1941; probably stocked in Boulder Creek lower reaches Durfey Creek None Electrofishing, current study CRCT introduced in 1992, but failed to reproduce Calf Creek Brown trout and Electrofishing, 1980 file report Brown trout, 1967 nonnative cutthroat Nonnative cutthroat trout, 1979a Sand Creek None Electrofishing, current study Nonnative cutthroat trout, 1988a Lake Creek Brook trout Electrofishing, 1989 file report Headwater lake, brook trout, 1957 Pine Creek Brown trout Electrofishing, current study Brown trout, 1947 Rainbow trout, 1953 West Branch Remnant CRCT Electrofishing, current study None, but a tributary to Pine Creek Pine Creek and brown trout North Creek Brook, rainbow, Electrofishing, current study Headwater lakes, rainbow trout, 1942 and nonnative Headwater lakes, brook trout, 1942 cutthroat Headwater lakes, nonnative cutthroat, 1953a White Creek Remnant CRCT Electrofishing, current study None Twitchell Creek Brook trout Electrofishing, current study Headwater lakes, brook trout, 1942 Water Canyon Remnant CRCT Electrofishing, current study None aNonnative cutthroat trout stocked prior to 1955 were likely from Yellowstone Lake, Wyoming (Cope 1955). Nonnative cutthroat trout stocked after 1955 were from Strawberry Reservoir, Utah, and were the Yellowstone subspecies partially hybridized with CRCT and rainbow trout (Hepworth et al. 1999).

RESULTS (Cottus bairdi), speckled dace (Rhinichthys osculus), flannelmouth sucker (Catostomus lati- Five remnant populations of CRCT were pinnis), bluehead sucker (C. discobolus), and found in the 17 headwater streams evaluated roundtail chub (Gila robusta), but all occurred (Fig. 1, Table 1). Known populations of CRCT downstream from populations of CRCT (Holden in East and West Boulder creeks were docu- and Irvine 1975, McAda et al. 1977, Mueller mented as expected, and additional popula- et al. 1999, UDWR survey files). Other nonna- tions of CRCT were found in the West Branch tive fishes reported in downstream portions of of Pine Creek, White Creek, and Water Canyon. the drainage include red shiner (Cyprinella Four streams had good trout habitat, but trout habitat was marginal in Water Canyon because lutrensis), fathead minnow (Pimephales prome- of the predominance of desert washes, turbid- las), carp (Cyprinus carpio), channel catfish ity, and warm water. Other streams we sur- (Ictalurus punctatus), yellow bullhead (Ictalu- veyed contained populations of brook trout rus natalis), striped bass (Morone saxatilis), (Salvelinus fontinalis), rainbow trout, brown largemouth bass (Micropterus salmoides), and trout (Salmo trutta), and nonnative cutthroat green sunfish (Lepomis cyanellus). trout, or were fishless. Other native fishes Population estimates of CRCT ranged from found in the drainage include mottled sculpin 2 to 74 fish ⋅ 100 m–1 of stream (Table 2). When 2001] NATIVE TROUT IN THE ESCALANTE DRAINAGE 133

TABLE 2. Abundance, population estimates, and size of native Colorado River cutthroat trout (CRCT) and sympatric trout species at electrofishing survey sites (100-m stations) within the Escalante River drainage, southern Utah. Number of trout Length (mm) Weight (g) Survey ______Population ______location 1st 2nd estimate (95% Streama (UTM)b Species pass pass confidence) Mean Range Mean Range 1. Water Lower stream CRCT 2 0 2 (2–2) 121 106–136 15 10–20 Canyon (428135 E 4183725 N) Upper stream CRCT 12 0 12 (12–12) 132 89–216 30 8–115 (427820 E 4183705 N) 2. White Lower stream CRCT 21 2 23 (23–24) 143 80–203 33 5–90 Creek (431050 E Brook 2 1 3 (3–10) 198 180–210 78 50–100 4193396 N) trout 3. White Upper stream CRCT 8 2 10 (10–13) 204 164–229 101 40–150 Creek (429451 E 4194022 N) 4. West Middle CRCT 15 5 22 (20–29)141 100–200 31 10–85 Branch stream Pine (12440737E Brown 58 15 78 (73–86) 166 88–310 55 5–300 Creek 4205698 N) trout 5. West Upper stream CRCT 54 9 65 (63–68)162 73–287 48 5–200 Branch (12440646E Pine 4206022 N) Brown 1 0 1 (1–1) 187 — 65 — Creek trout 6. West Lower stream CRCT 21 4 26 (25–29) 211 103–297 112 10–280 Boulder (456888E Creek 4211787 N) Middle CRCT 12 3 16 (15–19)229 130–300 153 25–325 stream (456717E 4212376 N) 7. East Middle CRCT 6 1 7 (7–8)184 109–242 79 10–150 Boulder stream Creek (460141E Brook 50 16 73 (66–84)198 120–243 84 20–155 4212766 N) trout 8. East Upper stream CRCT 61 11 74 (72–79)121 57–272 32 2–205 Boulder (459418E Creek 4214666 N) aStream numbers refer to data from corresponding survey areas in Table 3 and to locations on Figures 1 and 2. bUTM = Universal Transverse Mercator (metric grid system used on most large-scale land topographic maps). sympatric with CRCT, brook trout densities ranged from 45.3 to 146.1 kg ⋅ ha–1 and aver- ranged from 3 to 73 and brown trout from 1 to aged 99.2. 78 fish ⋅ 100 m–1. Size of CRCT ranged up to East Boulder Creek had the greatest stream 300 mm TL and 325 g. Brook trout in these length (5.6 km) occupied by CRCT; 0.8 km same areas ranged up to 243 mm TL and 155 was above a barrier and occupied by only g, and brown trout reached 310 mm TL and CRCT, and below the barrier the trout popula- 300 g. tion was numerically dominated by brook Biomass of CRCT ranged from 3.0 to 104.2 trout (Fig. 2). West Boulder Creek had the kg ⋅ ha–1 (Table 3). In situations where CRCT greatest stream length occupied exclusively by were isolated from other trout, biomass aver- CRCT (3.2 km) and a high biomass (102 kg ⋅ aged 61.9 and ranged from 3.0 to 104.2 kg ⋅ ha–1). White Creek had the next longest ha–1. When sympatric with nonnative trout, stream length with an exclusive population of CRCT averaged 34.9 and ranged from 8.3 to CRCT (2.1 km) and a biomass of 52.2 kg ⋅ 103.4 kg ⋅ ha–1. In sympatric situations com- ha–1. The West Branch of Pine Creek had a bined totals of native and nonnative trout high biomass of CRCT (103.4 kg ⋅ ha–1) in the 134 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 3. Numbers and biomass of native Colorado River cutthroat trout (CRCT) and sympatric trout species at elec- trofishing survey sites within the Escalante River drainage, southern Utah.

______Trout numbers and biomass Survey location Mean stream Number Number Kg ⋅ Kg ⋅ Streama location width (m) Species ⋅ km–1 ⋅ ha–1 km–1 ha–1 1. Water Canyon Lower stream 1.0 CRCT 20 200 0.3 3.0 Upper stream 1.4 CRCT 120 857 3.6 25.7 2. White Creek Lower stream 2.2 CRCT 231 1050 7.6 34.7 Brook trout 30 136 2.3 10.6 3. White Creek Upper stream 2.0 CRCT 103 517 10.4 52.2 4. West Branch Middle 3.4 CRCT 220 647 6.8 20.1 Pine Creek stream Brown trout 778 2291 42.8 126.0 5. West Branch Upper stream 3.0 CRCT 646 2153 31.0 103.4 Pine Creek Brown trout 10 33 0.7 2.2 6. West Boulder Lower stream 2.9 CRCT 257 886 28.8 99.3 Creek Middle 2.3 CRCT 157 681 23.9 104.2 stream 7. East Boulder Middle 6.7 CRCT 70 104 5.5 8.3 Creek stream Brook trout731 1090 61.4 91.6 8. East Boulder Upper stream 3.0 CRCT 742 2473 23.7 79.1 Creek aStream numbers refer to data from corresponding survey areas in Table 2 and to locations on Figures 1 and 2. extreme upper end, but these fish were re- Although some unrecorded stockings may stricted to a small area (0.4 stream km). Brown have occurred in the Escalante River drainage trout were sympatric with CRCT in the upper prior to 1940 and UDWR records documented reaches of the West Branch of Pine Creek; no several locations stocked in the 1940s, routine CRCT were found in the lower reaches. Water and repeated stockings did not occur until the Canyon was the smallest stream sampled. It 1950s. had a CRCT population (14.4 kg ⋅ ha–1) likely Forty-nine lakes, ponds, and small reser- consisting of <50 adults in 0.7 km of stream. voirs were stocked with nonnative trout in the In total, CRCT occupied 13.2 km of stream Escalante River drainage (UDWR stocking and was the only fish found in 6.4 km. The records). Of these, 33 are currently stocked total linear stream distance currently occupied and 12 are connected to perennial streams. by CRCT represents about 10% of its esti- The remainder are isolated from wild trout mated historic range within the Escalante populations. Ten of the stocked lakes are River drainage (Fig. 1). Nevertheless, popula- located on the Boulder Top, but there are no tions of CRCT are currently restricted to self-sustaining trout populations or perennial headwater tributaries. Populations of CRCT streams on the plateau. Brook, rainbow, brown, are absent from higher-order streams with and nonnative cutthroat trout were stocked as correspondingly greater amounts of habitat early as the 1940s in the Escalante River drain- that historically were likely occupied. age; brook and rainbow trout were stocked DISCUSSION most frequently. Nonnative cutthroat trout were stocked to a lesser extent, and only limited Because of its remoteness, stockings of non- numbers of brown trout were introduced. Non- native trout in the Escalante River drainage native cutthroat trout stocked prior to 1955 have occurred mainly since 1950. Popov and were likely from Yellowstone Lake, Wyoming Low (1950) reported that rainbow, brook, and (Cope 1955). After 1955 cutthroat trout were brown trout were established in most major taken from Strawberry Reservoir, Utah, and river drainages in Utah by the early 1900s but were predominantly the Yellowstone subspecies did not document any wild nonnative trout but partially hybridized with CRCT and rain- populations in the Escalante River drainage. bow trout (Hepworth et al. 1999). 2001] NATIVE TROUT IN THE ESCALANTE DRAINAGE 135

Fig. 2. Approximate stream lengths occupied by native Colorado River cutthroat trout (CRCT) and other sympatric trout species compared to biomass, Escalante River drainage, southern Utah. Footnote a (a) refers to biomass calculated as the mean from 2 survey locations. Stream numbers refer to corresponding survey data in other tables and to locations on Figure 1.

Four of 5 populations of CRCT in the migration barriers are unusual, intermittent Escalante River drainage are isolated from waterfalls have functioned as barriers for nearly nonnative trout by physical barriers. The 50 years despite annual stocking of nonnative Water Canyon population is spatially isolated trout in upstream lakes. Still, such stockings from nonnative trout by >16 km of desert should be discontinued to prevent any chance washes. White Creek is a steep-gradient, 2nd- of downstream fish movements. East Boulder order tributary to North Creek and is isolated Creek is isolated from upstream migrations of by barrier falls a short distance above its mouth. rainbow and brook trout by a series of steep, There are no records of nonnative trout intro- cascading falls, protecting the upper 0.8 km of duced into either Water Canyon or White stream. The longest stream section with an Creek. The upper ends of East and West Boul- isolated population of CRCT (West Boulder der Creek are isolated from nonnative trout in Creek) is protected from upstream migration lakes on the Aquarius Plateau by 180- to 300- of rainbow and brook trout by a hydropower m waterfalls and intermittent outflows from diversion constructed in 1957. The first re- the lakes. Outflows from the upper lakes sea- ported stocking for Boulder Creek, West Boul- sonally flow over the rim of the plateau during der Creek, and East Boulder Creek was rain- spring runoff and into perennial streams con- bow trout in 1941. Only a single stocking taining native trout. Although downstream report was found for West Boulder Creek, and 136 WESTERN NORTH AMERICAN NATURALIST [Volume 61 a specific location where rainbow trout were the 1960s and early 1970s found Calf Creek, released was not given. It is uncertain why lower Boulder Creek, and lower Deer Creek nonnative trout did not gain access to the void of trout. These stream sections and Death headwaters of West Boulder Creek before Hollow are in narrow sandstone canyons, 1957, but low numbers of stocked trout, rela- which have frequent flash floods and high tively long distances from stocked areas to the summer water temperatures. Although brown headwaters, and the possible presence of tem- trout have survived in these streams since at porary barrier falls could have prevented least the 1980s (UDWR survey files), such upstream movements before the hydropower locations were unlikely historic year-round diversion was constructed. Rainbow and brook habitat for CRCT. trout became established in the mid- and lower The Escalante River drainage provided segments of Boulder Creek and displaced naturally fragmented habitat for CRCT, similar native cutthroat trout in these areas. to its natural distribution in the upper Col- The West Branch of Pine Creek does not orado and Green River drainages (Behnke and have a physical barrier isolating CRCT from Benson 1980, Behnke 1992). Warm tempera- other trout, but brown trout are the only non- tures and high sediment loads restricted CRCT native trout currently found in the stream. use of the main rivers for much of the year but Brown and brook trout do not threaten CRCT allowed limited connectivity between tribu- by hybridization but can competitively displace taries. Although fragmentation was increased native trout (Griffith 1988, Behnke 1992). by stocking of nonnative fishes and by habitat Brook trout generally replace CRCT except in modification, CRCT likely occupied the Esca- higher, colder, and steeper-gradient sections of lante River briefly, thus enabling movement streams (DeStasto and Rahel 1994, Young among tributaries in much the same way that 1995a). This appears to be the case in the introduced brown trout managed to colonize headwaters of West Branch of Pine Creek multiple tributaries from the introduction into where CRCT have presumably maintained an Calf Creek. Even though connectivity was advantage over brown trout. According to limited, natural movements of CRCT among UDWR stocking reports, brown trout were streams allowed Escalante River tributaries to first introduced into Pine Creek in 1947 and function as a metapopulation (Young 1995b). rainbow trout in 1953. An established brown Increased fragmentation, however, has in- trout population may have provided a biologi- creased the risk of losing isolated populations. cal barrier to rainbow trout that protected Although it may not be feasible to reconnect CRCT in the upper West Branch of Pine all CRCT populations within the Escalante Creek. No other recorded stockings occurred River drainage because of habitat degredation in Pine Creek until 1962, when an annual and large numbers of nonnative trout, CRCT rainbow trout stocking program was initiated should persist if populations can be increased downstream from the West Branch near a U.S. within available coldwater habitat and actions Forest Service campground. Despite repeated taken to exclude nonnative trout from these stockings through 1983, a wild rainbow trout areas. population never became established. Abundance of CRCT in Escalante River Besides Pine Creek, the only other recorded tributaries was similar to that reported from stocking of brown trout in the Escalante River other locations. Jespersen (1981) found bio- drainage occurred in Calf Creek in 1967. From mass of CRCT to range from 3.1 to 109.4 kg ⋅ Calf Creek, brown trout evidently invaded the ha–1 and average 45.1 kg ⋅ ha–1 in 7 Wyoming lower portions of Death Hollow, Sand, Boulder, streams. Kershner et al. (1997) reported mean and Deer creeks (Fig. 1), using the Escalante abundance of CRCT in 6 Utah/Wyoming River for access. During extended periods of streams to be 48 and 11 kg ⋅ ha–1 in wilderness low flow and clear water, we found brown and nonwilderness areas, respectively. In this trout relatively common in upper reaches of study the mean for populations of CRCT that the river, although it does not provide year- were isolated from nonnative trout was 61.9 round trout habitat. Except for the upper end kg ⋅ ha–1, with an upper value of 104.2 kg ⋅ of Pine Creek, it does not appear that brown ha–1. In comparison, 15 southern Utah streams trout displaced native cutthroat trout at other containing native Bonneville cutthroat trout locations. Surveys conducted by UDWR in ranged from 6 to 64 kg ⋅ ha–1 (Hepworth et al. 2001] NATIVE TROUT IN THE ESCALANTE DRAINAGE 137

1997). Nonnative trout biomass for streams in BEHNKE, R.J., AND D.E. BENSON. 1980. Endangered and southern Utah can exceed 300 kg ⋅ ha–1 (UDWR threatened fishes of the upper Colorado River basin. Bulletin 503A, U.S. Department of the Interior, Fish survey files), although Platts and McHenry and Wildlife Service, Cooperative Extension Ser- (1988) reported average biomass for several vice, Colorado State University, Fort Collins. 35 pp. trout species in small western trout streams to COPE, O.B. 1955. The future of the cutthroat trout in Utah. be 54 kg ⋅ ha–1. Proceedings of the Utah Academy of Science, Arts, It is possible that a few additional popula- and Letters 32:89–93. DESTASTO, J., AND F. J . R AHEL. 1994. Influence of water tions of CRCT may persist in unsampled 1st- temperature on interactions between juvenile Col- or 2nd-order tributaries in the Escalante River orado River cutthroat trout and brook trout in a lab- drainage, but no potential locations are cur- oratory stream. Transactions of the American Fish- rently known. Although only 5 remnant popu- eries Society 123:289–297. GRIFFITH, J.S. 1988. Review of competition between cut- lations of CRCT were found in the Escalante throat trout and other salmonids. American Fisheries River drainage, combined they occupy a higher Society Symposium 4:134–140. percentage of historic habitat than commonly HAZZARD, A.S. 1935. A preliminary study of an exception- found elsewhere (Kershner et al. 1997). The ally productive trout water, Fish Lake, Utah. Transac- discovery of CRCT populations in locations tions of the American Fisheries Society 65:122–128. HEPWORTH, D.K., C.B. CHAMBERLAIN, AND M.J. OTTEN- isolated from nonnative trout and in headwater BACHER. 1999. Comparative sport fish performance areas generally without histories of nonnative of Bonneville cutthroat trout in three small put- stocking supports our contention that CRCT is grow-and-take reservoirs. North American Journal native to this drainage. An understanding of of Fisheries Management 19:774–785. the current abundance and distribution of HEPWORTH, D.K., M.J. OTTENBACHER, AND L.N. BERG. 1997. Distribution and abundance of native Bon- CRCT in the Escalante River drainage in rela- neville cutthroat trout (Oncorhynchus clarki utah) in tion to past sport fish introductions will allow southwestern Utah. Great Basin Naturalist 57:11–20. better coordination between conservation of HOLDEN, P.B., AND J.R. IRVINE. 1975. Ecological survey CRCT and sport fish management. Current and analysis of the aquatic and riparian fauna and flora of Escalante Canyon, Utah. Contract CS12004 conservation plans include developing a wild B034, Final Report to National Park Service and CRCT brood stock, increasing the use of Cooperative Research Unit, Utah State University, CRCT in sport fish programs, and expanding Logan. 10 pp. the range of wild CRCT populations by con- HUDSON, M.J., AND C.J. DAVIS. 2000. Meristic analysis structing fish migration barriers, removing non- results for Bonneville and Colorado River cutthroat trout in the state of Utah, annual report. Publication native trout from specific stream segments and numbr 00-34, Utah Division of Wildlife Resources, lakes, and transplanting CRCT from remnant Salt Lake City. 70 pp. sources. JESPERSEN, D.M. 1981. A study of the effects of water diversion on the Colorado River cutthroat trout (Salmo clarki pleuriticus) in the drainage of the ACKNOWLEDGMENTS North Fork of the Little Snake River in Wyoming. Unpublished master’s thesis, University of Wyoming, This study was funded, in part, by the Fed- Laramie. 83 pp. eral Aid in Sport Fish Restoration Project F- KERSHNER, J.L., C.M. BISCHOFF, AND D.L. HORAN. 1997. 44-R, Utah. We would like to thank the Utah Population, habitat, and genetic characteristics of Colorado River cutthroat trout in wilderness and Division of Wildlife Resources Aquatic Sec- nonwilderness stream sections in the Uinta Moun- tion staff for their support of this project. tains of Utah and Wyoming. North American Journal Thanks are also extended to Utah’s inter- of Fisheries Management 17:1134–1143. agency Colorado River Cutthroat Trout Con- MCADA, C., C. PHILLIPS, C.R. BERRY, AND R.S. WYDOWSKI. servation team for their impetus and direction 1977. A survey of endangered, threatened, and unique fish in southeastern Utah streams within the coal in conservation management of native cutthroat planning area. Contract 77-8236, Utah Cooperative trout. Reviews by Don Archer, Mike Hudson, Fishery Research Unit, Logan. 246 pp. and Tom Pettengill, Utah Division of Wildlife MUELLER, G., L. BOOBAR, R. WYDOWSKI, K. COMELLA, R. Resources, and Robert J. Behnke, Colorado FRIDELL, AND Q. BRADWISCH. 1999. Aquatic survey State University, improved the manuscript. of the lower Escalante River, Glen Canyon National Recreation Area, Utah, 22–26 June 1998. Open-File Report 99-101, U.S. Department of the Interior, U.S. LITERATURE CITED Geological Survey, Denver, CO. 37 pp. PLATTS, W.S., AND M.L. MCHENRY. 1988. Density and bio- BEHNKE, R.J. 1992. Native trout of western North Amer- mass of trout and char in western streams. U.S. For- ica. American Fisheries Society Monograph 6. est Service General Technical Report INT-241, Bethesda, MD. 275 pp. Intermountain Research Station, Ogden, UT. 17 pp. 138 WESTERN NORTH AMERICAN NATURALIST [Volume 61

POPOV, B.H., AND J.B. LOW. 1950. Game, fur animal and Bonneville, Colorado River and Yellowstone cut- fish introductions into Utah. Miscellaneous Publica- throat trout. Report to Utah Division of Wildlife tion 4, Utah Department of Fish and Game, Salt Resources, Utah State University, Logan. 33 pp. Lake City. 85 pp. YOUNG, M.K. 1995a. Colorado River cutthroat trout. Pages SHIOZAWA, D.K., AND R.P. EVANS. 1994. Relationships 16–23 in M.K. Young, editor, Conservation assess- between cutthroat trout populations from thirteen ment for inland cutthroat trout. General Technical Utah streams in the Colorado River and Bonneville Report RM-GTR-256, U.S. Department of Agricul- drainages. Final Report to Utah Division of Wildlife ture, Forest Service, Fort Collins, CO. 61 pp. Resources, Contract 93-2377, Brigham Young Uni- ______. 1995b. Synthesis of management and research versity, Provo, UT. 22 pp. considerations. Pages 55–61 in M.K. Young, editor, SHIOZAWA, D.K., R.P. EVANS, AND R.N. WILLIAMS. 1993. Conservation assessment for inland cutthroat trout. Relationships between cutthroat trout populations General Technical Report RM-GTR-256, U.S. Depart- from ten Utah streams in the Colorado River and ment of Agriculture, Forest Service, Fort Collins, Bonneville drainages. Report to Utah Division of CO. 61 pp. Wildlife Resources, Contract 92-2377, Brigham YOUNG, M.K., R.N. SCHMAL, T.W. KOHLEY, AND V. G . Young University, Provo, UT. 18 pp. LEONARD. 1996. Conservation status of Colorado STEGNER, W. 1954. Beyond the hundredth meridian: John River cutthroat trout. General Technical Report RM- Wesley Powell and the second opening of the West. GTR-282, U.S. Department of Agriculture, Forest Houghton Mifflin Company, Boston, MA. 438 pp. Service, Fort Collins, CO. 32 pp. TOLINE, C.A., J.M. HUDSON, AND T.R. S EAMONS. 1999. ZIPPIN, C. 1958. The removal method of population esti- Quantification of hybridization for seven Utah popu- mation. Journal of Wildlife Management 22:82–90. lations of cutthroat trout. Report to Utah Division of Wildlife Resources, Utah State University, Logan. 24 Received 8 September 1999 pp. Accepted 10 April 2000 TOLINE, C.A., T. SEAMONS, AND J.M. HUDSON. 1999. Mito- chondrial DNA analysis of selected populations of Western North American Naturalist 61(2), © 2001, pp. 139–148

CATASTROPHIC WILDFIRE AND NUMBER OF POPULATIONS AS FACTORS INFLUENCING RISK OF EXTINCTION FOR GILA TROUT (ONCORHYNCHUS GILAE)

D. Kendall Brown1, Anthony A. Echelle1,4, David L. Propst2, James E. Brooks3, and William L. Fisher1

ABSTRACT.—We used the computer program RAMAS to explore the sensitivity of an extinction-risk model for the Gila trout (Oncorhynchus gilae) to management of wildfires and number of populations of the species. The Gila trout is an endangered salmonid presently restricted to very few headwaters of the Gila and San Francisco river tributaries in southwestern New Mexico. Life history data for 10 extant populations were used to examine sensitivity of the species’ viability to changes in a variety of factors including population size, fecundity, life stage structure, number of popula- tions, severity and probability of forest fires, and a regulated fishery. The probability and severity of forest fires and number of populations had the greatest effect on viability. Results indicate that successful conservation of Gila trout requires establishment of additional populations and reduction of the severity of forest fires through a program incorpo- rating more frequent, but less severe, fires.

Key words: Gila trout, Oncorhynchus gilae, endangered species, southwestern New Mexico, management.

In this paper we use an extinction-risk Glenwood, New Mexico, were discontinued in model to explore management strategies for a 1939 and 1947, respectively (Propst et al. 1992). federally listed endangered fish, the Gila trout Since 1923, the New Mexico Department of (Salmonidae: Oncorhynchus gilae). This species Game and Fish has followed a policy of not is endemic to the Gila River system of the stocking nonnative salmonids into areas occu- Colorado River drainage in southwestern pied by Gila trout (Propst et al. 1992). Conser- United States. Historically, the species occurred vation efforts for the species also included cre- throughout the upper San Francisco and Gila ation of more pool habitats by using log struc- river drainages in southwestern New Mexico tures installed by the Civilian Conservation and the Verde River drainage in central Ari- Corps during the 1930s and repatriation of zona (Miller 1950, Behnke 1992). The Verde populations to several streams (Rinne 1982, River population has been extirpated, and the Propst et al. 1992). In the 1970s five relict species has declined by >95% in the remain- populations were replicated into reclaimed der of its range as a result of overexploitation, stream reaches treated with fish toxicant to interactions with stocked, nonnative trouts, remove nonnative salmonids. The reclaimed loss of habitat, and habitat degradation (Sub- reaches were insulated from upstream move- lette et al. 1990, Dowling and Childs 1992, ment by nonnative trout species by natural Propst et al. 1992, Propst 1994). Currently, Gila and artificial barriers (Propst and Stefferud trout are restricted to headwater reaches of a 1997). Each of the 5 relict populations known few small streams subject to catastrophic events at the time was believed genetically distinct such as drought, wildfire, flooding, and anchor (David 1976, Loudenslager et al. 1986), and ice (Rinne 1990). each was stocked into separate reclaimed Efforts to conserve and propagate Gila trout stream reaches. A 6th relict population was began in 1923 when a captive stock was estab- discovered in 1992 in Whiskey Creek, a small lished at the Jenks Cabin Hatchery by the New tributary of the West Fork of the Gila River. Mexico Department of Game and Fish (Miller We used population viability analysis (PVA) 1950). This hatchery and a similar facility at to evaluate population sensitivity to changes in

1Oklahoma Cooperative Fish and Wildlife Research Unit and Zoology Department, Oklahoma State University, Stillwater, OK 74078. 2New Mexico Department of Game and Fish, Santa Fe, NM 87504. 3U.S. Fish and Wildlife Service, 2105 Osuna NE, Albuquerque, NM 87113. 4Corresponding author.

139 140 WESTERN NORTH AMERICAN NATURALIST [Volume 61 variables that affect risk of extinction. Results lower-elevation streams; western box elder from such analyses can suggest hypotheses for (Acer negundo), willow (Salix spp.), New Mexico conservation management (Reed et al. 1998). locust (Robinia neomexicana), narrowleaf cot- To gain such insight, we developed a viability tonwood (Populus angustifolia), and ponderosa model for the species and one for each of its 2 pine (Pinus ponderosa) in mid-elevation streams; major lineages, one comprising populations in and blue spruce (Picea pungens), white fir the Gila River drainage and the other com- (Abies concolor), and quaking aspen (Populus prising populations in the San Francisco River tremuloides) along high-elevation streams drainage (Riddle et al. 1998, R. Leary and F. (Propst and Stefferud 1997). Allendorf, University of Montana, personal The relict and replicated populations of Gila communication). We were specifically inter- trout are located primarily in federally desig- ested in modeling sensitivity of extinction risk nated wilderness areas, where most human to population size, number of populations, and activities are minimized or controlled. Conse- effects of forest fires. We also assessed sensi- quently, wildfire and interactions with intro- tivity of the base model to errors in estimates duced trout seem to be the most important of fecundity and life stage structure. factors affecting survival of existing Gila trout We chose to focus on environmental sto- populations (Propst and Stefferud 1997). Orig- chasticity as the primary controlling factor in inally, wildfires were primarily lightning-caused the viability models of Gila trout, an approach understory fires occurring in spring and early that avoids complications and inaccuracies summer and ceasing with the rainy (monsoon) associated with demographic and genetic sto- season in July–August (Rinne 1996). Within chasticity (Akcakaya 1992). As with any model, the range of Gila trout, historic wildfires con- “relative” effects of varying different parame- sisted primarily of cool-burning understory ters are more reliable than “absolute” proba- fires with return intervals of 3–7 years in pon- bilities of extinction. PVA models are more derosa pine forests and 75–100 years in spruce useful as tools to guide management options forests at higher elevations (Swetnam and than they are as predictors of the fate of a Dieterich 1985). Cooper (1960) concluded that, species (Akcakaya et al. 1995). Gila trout is the prior to the 1950s, crown fires were extremely only trout species listed as endangered under rare or nonexistent in the region. the Endangered Species Act of the United Starting in the early 1900s, however, fuel States and it is listed as threatened by the loads began to increase, likely a result of in- State of New Mexico (Behnke 1992). Our ob- creased livestock grazing and a policy of fire jective was to use PVA to evaluate management options that might contribute toward conser- suppression by the newly established U.S. vation of the species. Forest Service (Swetnam and Dieterich 1985, Covington and Moore 1994). Fire suppression and diminished herbaceous cover caused by STUDY AREA AND HISTORY OF grazing reduced the frequency of wildfires. Lack GILA TROUT CONSERVATION of periodic fires resulted in more woody debris Gila trout are now restricted to streams in on the forest floor, increased sapling densities, narrow, steep-gradient canyons and small, and establishment of brush. These changes have moderate-gradient valleys at elevations of increased the potential for catastrophic crown 1650–2820 m in the Black and Mogollon fires (Rieman and Clayton 1997). mountain ranges of southwestern New Mexico By the early 1900s, populations of Gila trout (Fig. 1; Propst and Stefferud 1997). Canyon were restricted to the upper reaches of a few reaches have swift-running waters with numer- headwater streams primarily because of habi- ous cascades and plunge pools. Valley reaches tat modifications, overfishing, and introduc- have meandering channels, cobble riffles, and tions of nonnative trouts (Miller 1950, Propst fewer pools, most of which are formed around et al. 1992). In these small, isolated systems, log-debris piles and boulders. Base summer refugia from ash flow are limited and opportu- flows range from <0.05 m3 s–1 to 0.65 m3 s–1 nities for recolonization often are nonexistent. (Propst and Stefferud 1997). Riparian vegetation Consequently, in the past decade 6 populations consists of Arizona alder (Alnus oblongifola) of Gila trout have been extirpated by extreme and Arizona sycamore (Platanus wrightii) along fire events followed by intense summer 2001] GILA TROUT VIABILITY 141

Fig. 1. Map of upper Gila River drainage showing populations used in PVA. Names of numbered streams are given in Table 2.

(July–August) rains that washed ash and debris METHODS into the stream (Table 1). The Divide fire in Sampling and Population Estimates 1989 resulted in extirpation of the Main Dia- mond Creek population (Propst et al. 1992). Ten Gila trout populations considered free The Bonner fire in 1995 extirpated popula- of genetic contamination by nonnative con- tions in South Diamond and Burnt Canyon geners in 1996 (Table 2, Fig. 1) were used to creeks (Propst and Stefferud 1997). The Look- develop a baseline PVA model. Subsequently, out fire in 1996 extirpated the populations in 3 of these were found to be genetically intro- Trail Canyon, Woodrow Canyon, and Sacaton gressed by rainbow trout (R. Leary and F. creeks (JEB, DKB, DLP personal observation). Allendorf personal communication). One of In addition to catastrophic loss following these was subsequently eliminated by chemi- fires, Gila trout populations in many streams cal renovation and the stream was restocked within the historic range of the species have with pure Gila trout in 1997. The other 2 rep- been eliminated through hybridization with resent relict populations, and, because they nonnative rainbow trout (Oncorhynchus mykiss; exhibit relatively low levels of genetic intro- Loudenslager et al. 1986, Riddle et al. 1998, gression (Iron Creek, 0.02; McKenna Creek, R. Leary and F. Allendorf personal communi- 0.05), management agencies have decided to cation). We did not model effects of hybridiza- manage them as Gila trout, partly because tion and genetic introgression because man- each may harbor locally adaptive genetic agement options associated with such factors material. For this study we retained the origi- (e.g., treat trout populations as “pure” because nal 10 populations included in the PVA. of low introgression, or renovate the stream Life history data were primarily taken or and restock because of higher levels) are influ- estimated from the literature (Nankervis 1988, enced by level of genetic introgression, and Propst et al. 1992, Propst and Stefferud 1997), the degrees appropriate for different options but population size estimates (N) for 6 streams are debatable and somewhat arbitrary (Camp- were based on field data gathered during May ton 1987, Allendorf and Leary 1988, Dowling through September 1996 and 1997. These 6 and Childs 1992). streams were Iron, McKnight, McKenna, and 142 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 1. Years of occurrence for stockings/restockings and extirpations of Gila trout by forest fire/flood for 17 streams during the 27-year period from 1971 to 1997. Data on stocking history and extirpation are based on Propst et al. (1992) and on information from U.S. Forest Service records and the Gila Trout Recovery Team of the U.S. Fish and Wildlife Service. Drainage Relict population Extirpation Stocking/ (Replicate population) by fire/flood restocking San Francisco River drainage Spruce Creek No Relict (Dry Creek) No 1985 Gila River drainage Iron Creek No Relict (Sacaton Creek) 1996 1990/97 (White Creek) No 1994 McKenna Creek No Relict (Little Creek) No 1982 Main Diamond Creek 1989 Relict/1995 (McKnight Creek) No 1970 (Sheep Corral Creek) No 1972 South Diamond Creek 1995 Relict/1997 (Burnt Canyon) 1995 Relict (Mogollon Creek) No 1989/1997 (South Fork Mogollon Creek) No 1997 (Trail Canyon) 1996 1988/1997 (Woodrow Canyon) 1996 1989/1997 Whiskey Creek No Relict

Mogollon creeks in the Gila drainage and Depletion-shocking efforts consistently cap- – Spruce and Dry creeks in the San Francisco tured about 60% (n = 20, x = 0.57, sx– = 0.05) drainage. For each stream we used a battery- of the population estimate in the 1st pass at powered, backpack electroshocker (24 V, DC) each sample site. This percentage was used in to sample one to three 200-m sites, with num- estimating population size for 4 Gila trout ber of sites dependent on stream length. Prior streams (Main Diamond, Sheep Corral, Whis- to sampling we blocked each site at the upper key, and White creeks) for which only single- and lower ends with fine-mesh nets. Deple- pass electrofishing data were available (Propst tion sampling was conducted by making 3–4 and Stefferud 1997). passes upstream through each site, capturing Stage-specific Structure, stunned fish with dip nets. To minimize injury Survivorship, and Fecundity and ensure equal capture effort between passes, we made no effort to “hunt” individuals. All Gila We estimated stage-specific structure (pro- trout captured were weighed to nearest 0.1 g portionate abundance of different life stages) and measured to nearest millimeter for total from published length-frequency data for each and standard lengths. Number of fish at each Gila trout population (Propst and Stefferud site was estimated by the depletion method 1997). Life stages were defined as follows (Zippin 1958). Population sizes within each (Propst and Stefferud 1997): juveniles (<100 stream were obtained by multiplying estimated mm TL), subadults (100–150 mm TL), and number of fish per meter of stream in the sam- adults (>150 mm TL). Survivorship estimates ple site by total length of stream occupied by (Table 3) were computed from stage-specific Gila trout. Length of stream occupied was taken abundances as described by Caswell (1989). from Propst et al. (1992) and Propst and Stef- Fecundity was estimated from the overall ferud (1997). Estimates of population sizes are mean count of ova (98.6) from 25 field-stripped somewhat questionable because they assume females from Main Diamond and McKnight that observed local densities can be extrapo- creeks (Nankervis 1988, DLP unpublished lated to the entire reach of stream occupied by data). Because RAMAS models each individual Gila trout; however, results reported below as being capable of asexual reproduction, we indicate that the model is robust to this source divided this mean value by 2 to arrive at indi- of error. vidual fecundity (Table 3). Dividing the mean 2001] GILA TROUT VIABILITY 143

TABLE 2. Length of stream occupied and population TABLE 3. Life history variables and mean values (± s) size estimates (N) for Gila trout populations used in viabil- used in the base model of Gila trout viability. ity analyses. Numbers associated with the name of each population correspond with those in Figure 1. Populations Variable Mean without asterisks are those used in the base model. Those Number of life stages 3 with an asterisk are streams that either are presently devoid Fecundity of Gila trout but targeted for restocking, or were Stage 1 (juvenile) 0 restocked subsequent to the viability analysis; these 6 Stage 2 (subadult) 1.88 ± 0.97 were used in the analysis of the effect of adding popula- Stage 3 (adult) 98.57 ± 66.47 tions of Gila trout. Initial stage structure proportions ± Drainage/ Occupied length of Stage 1 (juvenile) 0.72 0.13 ± Population stream (km) N Stage 2 (subadult) 0.25 0.03 Stage 3 (adult) 0.04 ± 0.01 San Francisco River Survivorship drainage Stage 1 (juvenile) 0.491 ± 0.445 1. Spruce Creek 3.7 2236 Stage 2 (subadult) 0.128 ± 0.063 2. Dry Creek 1.9 537 Stage 3 (adult) 0.430 ± 0.068 Gila River drainage Catastrophe probabilitya 2.0% 3. Sacaton Creek * 1.6 1101 Catastrophe effectb 100% 4. Mogollon Creek 14.2 9651 aProbability of catastrophe in a given year for each population. 5. Woodrow Canyon * 0.4 188 bEffect is percent reduction of a population for each catastrophe occurrence. 6. Trail Canyon * 1.8 1211 7. South Fork Mogollon Creek* 1.2 1128 8. Sheep Corral Creek 1.3 149 Monte Carlo simulation of age- or life stage– 9. Whiskey Creek 0.2 20 structured population growth based on Leslie a 10. White Creek 12.0 8248 matrices (Leslie 1945, Ferson et al. 1991) to 11. McKenna Creek 1.2 1038 12. Iron Creek 4.3 1529 model extinction risk for metapopulations. 13. Main Diamond Creek 6.1 5795 The program has been used successfully in 14. Burnt Canyon * 1.5 115 PVAs for leopard darter (Percina pantherina; 15. South Diamond Creek * 5.2 2080 Williams et al. 1999), striped bass (Morone 16. McKnight Creek 8.5 2159 saxatilis; Ginzberg et al. 1990), and bluegill Average (N) 2324 sunfish (Lepomis macrochirus; Ferson et al. aPopulation size estimate based on a nonnative rainbow trout population. 1991). Extinction risk for Gila trout in the PVA models was expressed as the percentage of fecundity of females by 2 assumed a 1:1 sex 1000 replicate simulations in which extinction ratio and successful reproduction by all adult of the species occurred within 100 years. In females every year. Nankervis (1988) found the base model we used forest fires as the that a small proportion (13%) of large subadult major source of environmental catastrophe, females was reproductive, with a minimum and severity of catastrophe was modeled at size at reproduction of 130 mm. We estimated 100% population reduction. Probability of such “subadult” fecundity by multiplying 0.13 by a fire was based upon known effects on popu- the mean proportion of our 130–150 mm indi- lations of Gila trout for the past 27 years viduals (0.47) and then multiplying this con- (1971–1997), the period of time that the species stant by 1/2 of the mean ova count (30.8) for has been intensively monitored. During that time 6 populations were eliminated by forest subadult females. fires and resultant habitat degradation (U.S. Population Viability Forest Service unpublished data; JEB, DKB, Analysis DLP unpublished data). We arrived at proba- bility of catastrophe for the base model (2% We used the computer package RAMAS/ per population per year) by dividing number GIS (Akcakaya 1994) to model population via- of extirpations of Gila trout populations (6) bility. This package appears to be the best of resulting from catastrophic fires, by total num- those available for PVAs on organisms such as ber of stream years (288; computed from data Gila trout, which has relatively large popula- in Table 1) for the species during the past 27 tion sizes and high rates of reproduction com- years. pared with most other species for which PVAs Parameter estimates (Table 3) were used to have been done. The RAMAS algorithm uses a develop a base model for viability of the Gila 144 WESTERN NORTH AMERICAN NATURALIST [Volume 61 trout. We used the statistically conservative To assess effects of catch-and-release, artifi- Komolgorov-Smirnov D-test (Akcakaya 1994, cial-lure, or fly-only angling on local popula- Sokal and Rohlf 1994) to evaluate significance tions, we examined viability of the McKenna of differences in extinction rates between the and McKnight Creek populations with an base model and a variety of other models, annual catastrophe that reduced abundances each differing in a single parameter. Sensitiv- of life stages 2 (subadult) and 3 (adult) by 5%, ity to effect of catastrophe (% reduction in N) 10%, and 15%, respectively, in 3 separate was modeled by decreasing the effect from models for each population. These reductions extirpation (100% reduction) to no reduction seem reasonable because studies indicate that (0%) in increments of 5%. To examine sensitiv- 3–10% of individual trout die as a result of ity to probability of catastrophe, we increased hooking by artificial-lure or fly fishing (Nuhfer the fire-flood return interval from the base and Alexander 1992, Taylor and White 1992, model of once every 27 years (2% per popula- Schill 1996, Schisler and Bergersen 1996). tion per year) to once every 7 (14.3%), 5 (20%), and 3 years (33%). Those rates bracket the RESULTS range of the pre-1900 fire-return interval for the ponderosa pine forest habitat that predom- Under base-model conditions, estimated inates in watersheds supporting Gila trout in probability of Gila trout extinction in 100 years New Mexico (Swetnam and Dieterich 1985). was 36% (Fig. 2). As expected, increased sever- To assess effect of population size, the esti- ity of catastrophe (measured by reduction in abundance per event) and shorter return in- mate for each population was doubled in one tervals were associated with increased risk of model and halved in another. This was a crude extinction (Fig. 2). attempt to model the effect of extending or The base model was relatively insensitive shortening the length of stream occupied by to population size. Doubling and halving pop- the species in each stream. It also allowed ulation sizes had no significant effect on extinc- assessment of the robustness of the base model tion rate (Table 4). Correspondingly, simulat- to error in estimating population size. ing a catch-and-release fishery causing annual To assess effect of fecundity upon viability, mortality of 5–15% of subadults and adults had fecundity estimates were doubled in one model no significant effect on viability of either the and halved in another. To assess sensitivity to McKenna or McKnight Creek populations. life stage structure, we modeled the mean plus Viability of the species was insensitive to or minus 1 standard deviation for the propor- changes within 1 standard deviation of the tionate abundance of each life stage separately; mean in proportional abundances of the 3 life for each of these models, proportional abun- stages. However, the model was sensitive to dances of the other 2 life stages were adjusted large changes in fecundity estimates (F). Dou- by addition or subtraction, with the amount of bling and halving fecundity produced signifi- adjustment depending on the relative contri- cant (P < 0.001) differences from the base bution to stage structure in the base model. model in probability of extinction (1/2F, 47%; Sensitivity to number of populations was F, 36%; 2F, 31%). examined by considering 4 models in which PVA was highly sensitive to number of pop- populations were added to the base model of ulations. The model incorporating the planned 10 streams. First, we added 6 streams presently restocking of 6 additional streams with Gila devoid of Gila trout because of hybridization trout indicated a reduction of extinction risk or fire-flood (Table 2). Projected population- from 36% to 21%. Adding another 5, 10, and size estimates for those were based on past 15 “average” populations lowered the modeled estimates of trout density in those streams risk to 12%, 7%, and 5%, respectively (Table (Propst and Stefferud 1997), which were cal- 4). Probabilities of extinction from each of culated using the previously defined method these models were significantly different from for expanding single-pass catches. For the those of the others. other 3 models we added 5, 10, or 15 popula- Comparing modeled extinction risks of the tions, each having a population size equal to Gila River lineage of Gila trout (45%) and the the average of the original 10 streams in the San Francisco River lineage (81%) to that of all base model. drainages combined (36%) indicates that each 2001] GILA TROUT VIABILITY 145

local population variation. However, the base model was robust to population size estimates, and the questionable fecundity estimates do not invalidate use of the base model for insight into management strategies. Even with more precise models, recommendations from sensi- tivity analyses generally should be treated as hypotheses to be empirically evaluated before implementation by management agencies (Reed et al. 1998). If Gila trout are left unmanaged, as assumed by our base model, risk of extinction would be much higher than indicated because not all risk factors were included. Most importantly, the models do not include population losses resulting from interactions with nonnative trout species (hybridization, competition, and Fig. 2. Effect of catastrophe probability and severity on predation). Such interactions are important in probability of extinction of Gila trout. the decline and current status of Gila trout (Miller 1950, Propst and Stefferud 1997). How- lineage has a significantly higher probability of ever, they were not included in the PVA because extinction than does the species as a whole they allow few management options beyond stream renovation and restocking or strategies (Table 4). The model incorporating the planned to prevent introductions of nonnative trouts. restocking of 6 streams (all in the Gila River Altering the historic fire regime in pon- drainage) gave a significantly lower risk of ex- derosa pine forests of southwestern New Mex- tinction for the Gila River lineage (26%; Table ico from cool-burning understory fires with 4). Adding those 6 populations plus 5 or 10 aver- regular return intervals of 3–7 years (Swetnam age populations also resulted in significantly and Dieterich 1985) to less frequent, but more lower risks (15% and 8%, Table 4). Adding 2 catastrophic, crown fires has frustrated efforts average stream populations to the San Fran- to restore Gila trout to a level where the species cisco River lineage significantly decreased can be downlisted from endangered to threat- extinction risk from 81% to 67% (Table 4). ened (Propst et al. 1992). Correspondingly, our Adding 6 average populations significantly models suggest that viability of Gila trout is reduced the chance of extinction from 67% to especially sensitive to effects of forest fires. 44% (Table 4). Ignoring other factors of catastrophic loss, such as effects of nonnative trouts and drought, the DISCUSSION models suggest that risk of extinction would be extremely low if effects (percentage of pop- The probability of extinction of Gila trout ulation reduction) of potentially catastrophic within 100 years (36%), as computed under fires were reduced by a proactive fire manage- conditions of the base model presented herein, ment program. In our analyses even small is only a benchmark for comparison of the decreases in catastrophe led to substantial effects of different management strategies. reductions in extinction risk (Fig. 2). Results from such models should not be Much of the area occupied by Gila trout is treated as realistic assessments of extinction under prescribed natural fire management that risks (Ackakaya et al. 1995, Reed et al. 1998), allows naturally occurring fires to burn in cer- nor should they be used to classify species tain areas and under certain constraints. These according to endangered status (Taylor 1995). fires, however, may not be adequate to reduce The weakest aspects of our modeling effort fuel loads to a level sufficient to prevent cata- probably are the estimates of population sizes, strophic crown fires of the type observed in which assume uniform densities for each the recent past. Active prescribed burning stream, and the estimates of fecundity, which may be needed to accomplish this goal. Pre- had large variance (Table 3) and assumed no scribed burns in autumn, when fuel moisture 146 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 4. Effects of population size (N) and number of populations on probability of extinction for Gila trout over its extant range and in the Gila and San Francisco drainages separately. Values shown are percent probability of extinction in 100 years. Asterisks signify significant difference from all other models in the subset (P < 0.01).

______Probability of extinction (%) Populations 1/2 N N 2N Gila and San Francisco lineages Existing 40.0 36.0 34.0 Projecteda 21.0 * Projected + 5b 12.0 * Projected + 10b 7.0 * Projected + 15b 5.0 * Gila River lineage Existing 48.0 45.0 44.0 Projecteda 26.0 * Projected + 5b 15.0 * Projected + 10b 8.0 * San Francisco lineage Existing 83.0 81.0 80.0 Existing + 2c 67.0 * Existing + 6c 44.0 * aTen populations in the base model (= existing) plus 6 additional populations in streams designated for restocking with Gila trout. bProjected populations plus 5, 10, or 15 populations with the average size of all existing populations of Gila trout. cExisting populations in Spruce and Dry creeks plus 2 or 6 populations with the average size of all existing populations of Gila trout. levels are high and daily temperatures are low, The model of Gila trout viability was insen- would allow cool, surface-burning fires to sitive to size of individual populations, but it reduce fuel loads while minimizing chance of does not recognize that increased population fire escaping from the prescribed area. Reduc- size requires a corresponding increase in habi- tion of fuel loads by more frequent low-inten- tat, which, for Gila trout, is primarily a func- sity fires should contribute to a more natural tion of length of stream occupied. Increased forest structure, thereby reducing the frequency stream length generally would increase the of catastrophic fires (Pyne et al. 1996). probability of trout surviving catastrophic Our results indicate that prescribed fires events in refugia (i.e., tributaries) not directly with a return interval as short as 3 years would affected by the catastrophe. Wildfires occurring not increase extinction risk for Gila trout, even in the last few years usually have been limited if as much as 50–60% of the local population is to single or small numbers of watersheds where lost with each event. Such losses should, how- resident trout populations often have had no ever, be minimized to reduce genetic and refuge from post-wildfire ash flows associated demographic stochasticity, both of which can primarily with mid- to late-summer rains. negatively affect survival of a population (Boyce Increasing stream lengths often would increase 1993). Further, the suggested beneficial effects the number of tributaries occupied by Gila of more frequent fires of lower intensity trout, thereby reducing the effect of catastro- should be treated as a hypothesis to be tested phe from 100% loss of the population to a loss prior to full-scale implementation in the man- of lesser magnitude, and the models indicate agement of Gila trout. As emphasized by Rie- that such a reduction can have a significant man and Clayton (1997), prescribed fires can effect on risk of extinction (Fig. 2). Further- lead to inadvertent population losses because more, a marked increase in amount of habitat of the large fuel loads that have developed (length of stream) occupied would reestab- during the past 75+ years of fire suppression lish natural connectivity among a number of in the region. Initially, prescribed fires could now-isolated local populations of Gila trout. be viewed as experimental and restricted to Increased connectivity would heighten the rate watersheds projected to be renovated for Gila of recolonization following catastrophic losses trout. Extension to Gila trout streams might in local areas, thereby improving viability of be implemented once the methodology has the species. In New Mexico alone existing pop- been perfected, and perhaps only after estab- ulations occupy <20% of the approximately lishment of more populations of the species. 825 km of stream theoretically available for 2001] GILA TROUT VIABILITY 147 restoration of the species in the Gila River factor greatly increases the viability of the drainage. Similar opportunities exist within the species. Thus, it seems desirable from the historic range of the species in Arizona. standpoint of both management practicality Like many other conservation efforts for and long-term genetic viability of the species endangered and threatened species, recovery to implement an aggressive, proactive pro- of Gila trout is a complicated and politically gram of fire management in watersheds sup- controversial issue. Some public opposition to porting Gila trout. Gila trout recovery efforts has been in response to closures of streams to fishing after they have ACKNOWLEDGMENTS been restocked with the species. The PVA models incorporating an annual “catastrophe” This study was supported by a grant from that reduced adult and subadult abundances the U.S. Geological Survey, Biological Resources by as much as 30% had no significant effect on Division, through the Oklahoma Cooperative viability of the affected populations, indicating Fish and Wildlife Research Unit. The unit is a that a regulated fishery might not increase cooperative program of the U.S. Geological extinction risk for the species. Survey (Biological Resources Division), Okla- Consideration should be given to focusing a homa Department of Wildlife Conservation, high proportion of conservation efforts on the Oklahoma State University, and Wildlife Man- San Francisco River lineage. The PVA indicates agement Institute. Logistical support and that this lineage has a much higher extinction additional funding were provided by the U.S. risk than the Gila River lineage. Additionally, Fish and Wildlife Service, U.S. Forest Service, the 2 populations of the lineage are geographi- and New Mexico Department of Game and cally very close (Spruce Creek is a Dry Creek Fish. We thank B. Wiley, H. Bishop, A.F. tributary), and the past history of Gila trout Echelle, T. Echelle, N. Smith, G. Jimenez, J. demonstrates a high probability for eliminat- Zapata, and A. Hobbes for help in the field; L. ing both populations by a single catastrophic Williams for help with RAMAS and advice on wildfire. modeling; and D. Leslie for reviewing an early Ongoing efforts to conserve Gila trout draft of the manuscript. emphasize 3 general approaches: (1) reducing opportunities for hybridization and other LITERATURE CITED interactions with congeners, (2) increasing AKCAKAYA, H.R. 1992. Population viability analysis and number of streams occupied, and (3) restock- risk assessment. Pages 148–157 in D.R. McCullough ing streams from which the species has been and R.H. Barrett, editors, Wildlife 2001: populations. extirpated by catastrophes or hybridization Elsevier Applied Science, New York. ______. 1994. RAMAS/GIS: linking landscape data with with congeners (U.S. Fish and Wildlife Service population viability analysis (version 1.0). Applied 1993). Our results suggest that a 4th approach Biomathematics, Setauket, NY. is central to the success of this effort, namely, AKCAKAYA, H.R., M.A. MCCARTHY, AND J.L. PEARCE. 1995. an effort to reduce catastrophic effects of wild- Linking landscape data with population viability fires. Besides reducing the expense and effort analysis: management options for the Helmeted Honeyeater (Lichenostomus melanops cassidix). Bio- involved in restocking areas of extirpation, logical Conservation 73:169–176. such an approach would help preserve genetic ALLENDORF, F.W., AND R.F. LEARY. 1988. Conservation and variation. Repeated restocking is likely to result distribution of genetic variation in a polytypic species, in losses of genetic variability as a result of the cutthroat trout. Conservation Biology 2:170–184. BEHNKE, R.J. 1992. Native trout of western North America. genetic drift. For example, all extant popula- American Fisheries Society Monograph 6. American tions of the Main Diamond Creek and South Fisheries Society, Bethesda, MD. Diamond Creek lineages exist only as popula- BOYCE, M.S. 1992. Population viability analysis. Annual tions derived from either captive, hatchery Review of Ecology and Systematics 23:481–506. ______. 1993. Population viability analysis: adaptive man- populations or from other transplanted popu- agement for threatened and endangered species. lations. Such a program will almost certainly Transactions of the 58th North American Wildlife lead to reduced genetic variation (Stockwell et and Natural Resources Conference 58:520–527. al. 1996, Dunham and Minckley 1998). Our CAMPTON, D.E. 1987. Natural hybridization and introgres- models of Gila trout viability were highly sen- sion in fishes: methods of detection and genetic interpretations. Pages 161–192 in N. Ryman and F. sitive to the effect of forest fires and indicate Utter, editors, Population genetics and fishery man- that a small reduction in the effect of this agement. University of Washington Press, Seattle. 148 WESTERN NORTH AMERICAN NATURALIST [Volume 61

CASWELL, H. 1989. Matrix population models. Sinauer gilae: implications for management of an endangered Associates, Inc., Sunderland, MA. species. Copeia 1998:31–39. COOPER, C.F. 1960. Changes in vegetation, structure, and RIEMAN, B., AND J. CLAYTON. 1997. Wildfire and native growth of southwestern pine forest since white set- fish: issues of forest health and conservation of sensi- tlement. Ecological Monographs 30:129–164. tive species. Fisheries 22:6–15. COVINGTON, W. W. , AND M.M. MOORE. 1994. Southwest- RINNE, J.N. 1982. Movement, home range, and growth of ern ponderosa forest structure: changes since Euro- a rare southwestern trout in improved and unim- American settlement. Journal of Forestry 92:39–47. proved habitats. North American Journal of Fish- DAVID, R.E. 1976. Taxonomic analysis of Gila and Gila × eries Management 2:150–157. rainbow trout in southwestern New Mexico. Master’s ______. 1990. Status, distribution, biology, and conserva- thesis, New Mexico State University, Las Cruces. tion of two rare southwestern (U.S.A.) salmonids, the DOWLING, T.E., AND M.R. CHILDS. 1992. Impact of hybrid- Apache trout, Oncorhynchus apache Miller, and the ization on a threatened trout of the southwestern Gila trout, O. gilae Miller. Journal of Fish Biology United States. Conservation Biology 6:355–364. 37:189–191. DUNHAM, J.B., AND W.L. MINCKLEY. 1998. Allozymic vari- ______. 1996. Short-term effects of wildfire on fishes and ation in desert pupfish from natural and artificial aquatic macroinvertebrates in the southwestern habitats: genetic conservation in fluctuating popula- United States. North American Journal of Fisheries tions. Biological Conservation 84:7–15. Management 16:653–658. FERSON, S., H.R. AKCAKAYA, L.R. GINZBURG, AND M. SCHILL, D.J. 1996. Hooking mortality of bait-caught rain- KRAUSE. 1991. Use of RAMAS to estimate ecological bow trout in an Idaho stream and a hatchery: impli- risk: two fish species case studies. Technical Report cations for special-regulation management. North EN-7176, Electrical Power Research Institute, Palo American Journal of Fisheries Management 16: Alto, CA. 348–356. GINZBERG, L.R., S. FERSON, AND H.R. AKCAKAYA. 1990. SCHISLER, G.J., AND E.P. BERGERSEN. 1996. Post-release Reconstructability of density dependence and the hooking mortality of rainbow trout caught on scented assessment of extinction risks. Conservation Biology artificial baits. North American Journal of Fisheries 4:63–70. Management 16:570–578. LESLIE, P.H. 1945. On the use of matrices in certain popu- SOKAL, R.R., AND F. J . R OHLF. 1994. Biometry. W.H. Free- lation mathematics. Biometrika 33:183–212. man and Company, New York. LOUDENSLAGER, E.J., J.N. RINNE, G.A.E. GALL, AND R.E. STOCKWELL, C.A., M. MULVEY, AND G.L. VINYARD. 1996. DAVID. 1986. Biochemical genetic studies of native Translocations and the preservation of allelic diver- Arizona and New Mexico trout. Southwestern Natu- sity. Conservation Biology 10:1133–1141. ralist 31:221–234. SUBLETTE, J.E., M.D. HATCH, AND M. SUBLETTE. 1990. MILLER, R.R. 1950. Notes on the cutthroat and rainbow The fishes of New Mexico. University of New Mexico trouts with the description of a new species from the Press, Albuquerque. Gila River, New Mexico. Occasional Papers of the SWETNAM, T.W., AND J.H. DIETERICH. 1985. Fire history of Museum of Zoology, University of Michigan 529: ponderosa pine forests in the Gila Wilderness, New 1–42. Mexico. Pages 390–397 in J.E. Lotan et al., technical NANKERVIS, J.M. 1988. Age, growth, and reproduction of coordinators, Proceedings: symposium and work- Gila trout in a small headwater stream in the Gila shop on wilderness fire. USDA Forest Service Gen- National Forest. Master’s thesis, New Mexico State eral Technical Report INT 182. University, Las Cruces. TAYLOR, B.L. 1995. The reliability of using population via- NUHFER, A.J., AND G.R. ALEXANDER. 1992. Hooking mor- bility analysis for risk classification of species. Con- tality of trophy-sized wild brook trout caught on arti- servation Biology 9:551–558. ficial lures. North American Journal of Fisheries TAYLOR, M.T., AND K.R. WHITE. 1992. A meta-analysis of Management 12:634–644. hooking mortality of nonanadromous trout. North PROPST, D.L. 1994. The status of Gila trout. New Mexico American Journal of Fisheries Management 12: Department of Game and Fish. New Mexico Wildlife 760–767. (Nov–Dec):22–28. U.S. FISH AND WILDLIFE SERVICE. 1993. Gila trout recov- PROPST, D.L., AND J.A. STEFFERUD. 1997. Population dy- ery plan. U.S. Fish and Wildlife Service, Region 2, namics of Gila trout, Oncorhynchus gilae (Miller), in Albuquerque, NM. the Gila River drainage of the southwestern United WILLIAMS, L.R., A.A. ECHELLE, C.S. TOEPFER, M.G. States. Journal of Fish Biology 51:1137–1154. WILLIAMS, AND W.L. FISHER. 1999. Simulation mod- PROPST, D.L., J.A. STEFFERUD, AND P.R. TURNER. 1992. eling of population viability for the leopard darter Conservation and status of Gila trout, Oncorhynchus (Percidae: Percina pantherina). Southwestern Natu- gilae. Southwestern Naturalist 37:117–125. ralist 44:470–477. PYNE, S.J., P.L. ANDREWS, AND R.D. LAVEN. 1996. Intro- ZIPPEN, C. 1958. The removal method of population esti- duction to wildland fire. John Wiley & Sons, New mation. Journal of Wildlife Management 22:82–90. York. REED, J.M., D.D. MURPHY, AND P. F. B RUSSARD. 1998. Effi- Received 5 October 1999 cacy of population viability analysis. Wildlife Society Accepted 10 April 2000 Bulletin 26:244–251. RIDDLE, B.R., D.L. PROPST, AND T.L. YATES. 1998. Mito- chondrial DNA variation in Gila trout, Oncorhynchus Western North American Naturalist 61(2), © 2001, pp. 149–158

EXCLUSION EXPERIMENTS WITH BACKWATER INVERTEBRATE COMMUNITIES OF THE GREEN RIVER, UTAH

Kenneth P. Collins1,2 and Dennis K. Shiozawa1

ABSTRACT.—The role of biotic interactions in structuring freshwater invertebrate communities has been extensively studied but with mixed results. For example, fish effects on invertebrates are most pronounced in pelagic and soft-sedi- ment benthic habitats that lack structural complexity, yet appear insignificant in benthic rubble habitats. Backwaters of the Green River, Utah, are shallow, structurally simple, quiet-water embayments adjacent to the river. These habitats form in middle to late summer and are colonized by benthic and epibenthic invertebrates that produce standing crops significantly higher than the river. Backwaters are also utilized by a large number of fish species. We used cages to determine if selective exclusion of backwater organisms could significantly change invertebrate community structure. Results showed that backwater invertebrate community components changed significantly in response to exclusion treatments. Two taxa (both predators), the chironomid genus Tanypus (Diptera: Chironomidae) and the corixid genus Trichocorixa (Hemiptera: Corixidae), increased in density in exclusion cages while cladocerans, immature copepods, the cyclopoid copepod Eucyclops speratus, and the chironomid genus Procladius all decreased in density. Diversity of adult copepods was reduced by exclusion treatments, though density of only a single species changed significantly.

Key words: predation, backwater, invertebrate communities, Green River, Colorado River drainage, cage effects.

The impact of predation on density and Ephemeral backwaters of the Green River diversity of aquatic invertebrate prey is are shallow, sand- and silt-bottomed habitats. unclear and seems to depend on habitat type. At least 8 native and 15 nonnative fish species Investigations of freshwater pelagic habitats are found in these backwaters from midsum- have revealed that predator-induced trophic mer through autumn (Haines and Tyus 1990); cascades can be a driving force (Carpenter et most abundant are nonnative red shiners al. 1987). In these structurally simple habitats, (Cyprinella lutrensis) and fathead minnows both vertebrate and invertebrate predators (Pimephales promelas), and native Colorado can have a profound effect on the density and pikeminnow (Ptychocheilus lucius [Haines and diversity of zooplankton (Brooks and Dodson Tyus 1990, K.P. Collins unpublished data]). 1965, O’Brien 1979, Sih et al. 1985, Carpenter Muth and Snyder (1995) found that Green et al. 1987, Kerfoot and Sih 1987). However, River backwater fish diets mainly consist of studies of freshwater benthic communities have Diptera larvae, copepods, cladocerans, rotifers, had mixed results. Streams with stony sub- corixids, nematodes, and fish. strates generally fail to show significant effects Based on structural simplicity of backwater of vertebrate predators on benthic inverte- habitats, we hypothesized that manipulation of brate density or diversity (Reice 1983, Flecker fish access would impact invertebrate commu- and Allan 1984, Reice and Edwards 1986). nity density and diversity. An exclusion experi- Conversely, invertebrates in soft-sediment ment was designed and performed to test this stream habitats respond to variations in fish hypothesis. predation (Wilzbach et al. 1986, Gilliam et al. 1989, Schlosser and Ebel 1989). It has been METHODS suggested that the structural complexity of Study Area stony substrates offers greater refuge from predation than soft, silty substrates (Allan The Green River (Colorado River drainage) 1983, Gilliam et al. 1989) where predators originates in Wyoming and joins the Colorado have greater access to invertebrate prey. River in southeastern Utah. It enters our study

1Department of Zoology, Brigham Young University, Provo, UT 84602. 2Present address: Division of Natural Sciences, Fullerton College, Fullerton, CA 92832-2095. Corresponding author.

149 150 WESTERN NORTH AMERICAN NATURALIST [Volume 61 area at Ouray National Wildlife Refuge 5). Each sample comprised 30 benthic cores (ONWR) 404 km above the Colorado River (19-mm diameter, 10-cm depth) and 5 vertical confluence. At Jensen, Utah (near ONWR), it plankton tows (20-cm diameter, 63-µm mesh) has a 47,723-km2 drainage area with average from each treatment within each backwater. peak flow of 338 m3 s–1 and average low flow Over the duration of the experiment, we took of 106 m3 s–1 (U.S. Geological Survey data). a total of 180 core samples per treatment, and Backwaters are cut off secondary side chan- total area sampled was approximately 510 nels and quiet-water habitats isolated behind cm2. Samples were preserved in 5% formalin. point bars that emerge as river level falls in Core samples were washed through a 63-µm summer; the length of backwaters is greater mesh screen. Diptera larvae (Chironomidae than the width at their mouth. Backwaters in and Ceratopogonidae), Cladocera, Copepoda this study were shallow (approximately 0.75 m (adults, copepodites, and nauplii), Rotifera, to 1.0 m deep) with no current. Secchi disk Corixidae, Nematoda, Oligochaeta, and Gastro- visibility averaged 22 cm, and substrate was tricha were counted from at least 10 benthic soft sediments under a flocculent layer approx- cores randomly chosen from 30 cores from imately 4 cm thick. Backwaters were free of each treatment/backwater combination on each macrophytes. Lack of current and relatively date. We counted organisms from all 5 plank- stable substrate allow backwaters to support ton tows, and all cladocerans and adult cope- higher invertebrate density than the main pods from those samples were identified. Chi- river (Mabey 1993, Wolz and Shiozawa 1995). ronomidae were mounted on slides in Hoyer’s Combination of high food concentration, solution and identified to genus using Mason warmer temperatures, and no current is likely (1968), Wiederholm (1983), and Merritt and what makes backwaters attractive to fish. Cummins (1984). Cladocerans and adult cope- pods were identified to species using keys by Experimental Design Yeatman (1959) and Pennak (1989). A 3-way analysis of variance design was Statistical Analysis used with the following 3 treatments in each of 3 replicate backwaters sampled over a 4- Data were examined with weighted 3-way month period: (a) control—a cageless (2 × 2- analysis of variance (ANOVA) tests on means m) area, marked by posts, which was open for of log-transformed (ln [x + 1]) sample counts foraging to all backwater organisms; (b) for each group of organisms. The ANOVA closed—a caged area (2 × 2-m) that excluded model was: all fish and large, nonflying invertebrates; and Y = µ + B + T + BT + D + BD + TD + BTD (c) perforated—a cage (2 × 2-m) with 2.5-cm- ijk i j ij k ik jk ijk wide by 10-cm-high perforations (approxi- where Yijk is the log-transformed mean of sub- mately 10 cm apart) in each side for a total of sample counts from the jth treatment in the ith approximately 80 perforations per side. Perfo- th backwater on the k date, Bi is the random rations excluded adult carp (Cyprinus carpio) backwater (block) effect, Tj is the fixed treat- and channel catfish (Ictalurus punctatus), but ment effect, and Dk is the fixed date effect. not smaller fish, such as young Colorado pike- Treatment effects F-ratios were calculated minnow, red shiner, and fathead minnow, and using the mean square of the block by treat- large invertebrates. Each cage panel was 1.2 ment interaction as the denominator. Ander- m high and 2 m wide, framed with wood, and son-Darling normality tests showed that in all covered with 1.6-mm fiberglass screen mesh. cases data were normal. Panels were bolted together and secured with We analyzed effects of fish predation on fence posts at each corner. Cages extended richness, evenness, and heterogeneity of chi- 20–40 cm above water, varying with river ronomids and copepods using the same depth. Treatment position within each back- ANOVA design. Chironomids and planktonic water was randomized. copepods were used to test for diversity effects because they are readily identified to Sampling genus and species, respectively. We calculated We installed cages 6–8 August 1992 and richness, evenness, and heterogeneity for each took samples 14–15 August (week 1), 28–29 treatment replicate on each date. Species rich- August (week 3), and 11–12 September (week ness was based on the rarefaction method 2001] BACKWATER INVERTEBRATE COMMUNITIES 151

(Hurlbert 1971, Simberloff 1972), which esti- mates the number of species expected in a random sample of n individuals taken from a collection. Heterogeneity was estimated with the nonparametric Simpson’s reciprocal index (Hill’s N2; Hill 1973). Evenness was calculated using the modified Hill’s ratio (Alatalo 1981). Mean densities and 95% confidence inter- vals of major benthic and planktonic inverte- brate taxa were calculated for each treatment on each date. Plankton densities were calcu- lated on ln (x + 1) transformed count data and then converted back into actual densities because of small sample size and a negative binomial distribution (Elliot 1977).

RESULTS Benthic Invertebrate Densities Four benthic taxa showed significant treat- ment effects. The chironomid genera Tanypus and Procladius were significantly affected by treatment (3-way ANOVA, treatment effect: F2,4 = 30.95, P = 0.004; F2,4 = 9.08, P = 0.033, respectively; Figs. 1b, 1c), and total numbers of immature chironomid (Diptera) larvae showed a marginal treatment effect (3-way ANOVA, treatment effect: F2,4 = 5.85, P = 0.064; Fig. 1a). Tanypus densities were lower in open controls than in perforated and closed treatments on week 3 (Tukey pairwise compar- isons of treatment effect: P = 0.025 for open vs. perforated, and P = 0.043 for open vs. closed), but had no significant pairwise differ- ences among treatments in weeks 1 and 5. This is probably due, in week 5, to high vari- ance in Tanypus density in open controls. Fig. 1. Mean of average log-transformed sample counts Despite a significant overall treatment effect from benthic cores used in 3-way ANOVA for (a) Chirono- for Procladius, Tukey comparisons showed no midae, (b) Tanypus, and (c) Procladius from Green River pairwise differences among treatments for any backwaters, Ouray National Wildlife Refuge, Utah. Verti- cal bars indicate ±1 s; n = 3 for each treatment/date com- date. bination. The closed-cage treatment reduced the abundance of benthic copepodites (3-way ANOVA, treatment effect: F2,4 = 14.50, P = in perforated (though not control) treatments 0.015; Fig. 2a) and nauplii (3-way ANOVA, were significantly higher than in closed treat- treatment effect: F2,4 =8.50, P = 0.036; Fig. ments on week 3 (P = 0.05), and control den- 2b) relative to controls. Tukey pairwise com- sities were marginally higher than closed parisons revealed that on week 3 copepodite treatments on week 5 (P = 0.07). In most densities in controls were significantly higher cases copepodites and nauplii densities in per- than in closed treatments (P = 0.015), and on forated treatments were intermediate between week 5 control densities were marginally control and closed densities (Fig. 2). higher than both perforated and closed treat- Only Oligochaeta and Chironomidae (total) ments (P = 0.092 for open vs. perforated, and showed significant treatment by date inter- P = 0.079 for open vs. closed). Nauplii densities actions (3-way ANOVA, treatment by date 152 WESTERN NORTH AMERICAN NATURALIST [Volume 61

= 0.039 for open control vs. perforated, and P = 0.018 for open control vs. closed). The 3 treatments did not differ in week 5, probably due to large variance around means of perfo- rated and closed treatments on that week. Three planktonic microcrustacean groups had decreased numbers in closed cages rela- tive to controls. Number of cyclopoid copepod Eucyclops prionophorus (3-way ANOVA, treat- ment effect: F2,4 = 8.53, P = 0.036; Fig. 3b) and total cladocerans (3-way ANOVA, treat- ment effect: F2,4 = 11.93, P = 0.021; Fig. 3c) showed significant treatment effects, and num- ber of copepod nauplii showed a marginally significant effect (3-way ANOVA, treatment effect: F2,4 = 4.46, P = 0.096; Fig. 3d). The trend in all 3 cases was for controls to have higher densities than closed treatments (Fig. 3). However, Tukey pairwise comparisons of E. prionophorus showed no significant differ- ences among treatments on any sampling date, and only marginally significant differences for nauplii on week 5 (P = 0.054 and P = 0.096 for open control vs. perforated and closed treat- ments, respectively). Pairwise comparisons of cladoceran treatment means revealed that Fig. 2. Mean of average log-transformed sample counts from benthic cores used in 3-way ANOVA for (a) cope- numbers in closed treatments were significantly podites and (b) nauplii from Green River backwaters, lower than in controls on week 3 (P = 0.07), but Ouray National Wildlife Refuge, Utah. Vertical bars indi- there were no significant differences among cate ±1 s; n = 3 for each treatment/date combination. treatments for weeks 1 and 5. Cladoceran den- sity declined steadily over the study period. However, their abundance decreased more interaction: F4,8 = 4.17, P = 0.041; F4,8 = 4.91, P = 0.027, respectively). Nematodes, the rapidly in closed treatments than in controls most abundant benthic taxon, showed no sig- (Fig. 3b). Cladocerans in perforated treatments nificant treatment effect or treatment by date were intermediate between controls and closed during weeks 3 and 5 (Fig. 3b). interaction (Table 1). Immature copepods (copepodites and nau- Planktonic Invertebrate plii) and rotifers were the most abundant plank- Densities tonic groups (Table 2). Four copepod species (Eucyclops speratus, Eucyclops prionophorus, Four planktonic taxa showed significant or Acanthocyclops vernalis, and Diacyclops bicus- marginally significant treatment effects, but pidatus, although A. vernalis and D. bicuspida- none showed a significant treatment by date tus were in low numbers [Tables 1, 2]) and 3 interaction. Of the 4, only Trichocorixa (Hem- cladoceran species (Ilyocryptus sordidus, Macro- iptera: Corixidae) had higher densities in closed thrix laticornis, Leydigia quadrangularis) were cages relative to controls (3-way ANOVA, collected in plankton samples (Table 2). Of treatment effect: F2,4 = 15.93, P = 0.012; Fig. these, only L. quadrangularis, represented by 3a). As with Tanypus, Trichocorixa densities just 3 specimens, did not also occur in benthic were similar in perforated and closed treat- samples. ments. Tukey pairwise comparisons showed that Trichocorixa density in controls was mar- Diversity ginally lower than in perforated treatments on At least 4 species of cyclopoid copepods week 1 (P = 0.07), and significantly lower than were present in the backwaters (see above). perforated and closed treatments on week 3 (P There was a significant treatment effect on 2001] BACKWATER INVERTEBRATE COMMUNITIES 153 358 14442 2712 4903 23165 848 1707 4234 3261 1930 34589 3464 388 2640 1429 1999 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± life Refuge, 822 252 25093 59377 3715 10883 7917 12280 24074 76526 839 2022 1394 2394 320 0 2603 7839 2655 5226 611 2352 35731 211129 10174 16260 292 688 2172 13543 1508 3892 1904 7298 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 395 1058 14882 87234 2896 14019 141 0 0 6553 16343 16699 78234 771 2668 2177 2704 199 235 1760 5526 1750 4586 517 706 37313 243024 8079 41604 212 452 2151 16235 945 5056 1255 7055 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 7621 57060 1977 12532 238 126 238 0 0 0 3328 32244 7647 132752 1535 3112 2259 3065 1373 8217 1344 6383 238 1680 27473 221682 4454 30999 281 208 2655 12449 1473 3408 1448 3707 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 5803 23962 2436 8717 4766 5960 8742 39084 1326 4298 2015 3892 2265 3527 2192 3162 33001 178556 4850 17961 258 487 2354 15326 1800 5291 1830 4115 ± ± ± ± ± ± ± ± ± ± ± ± ± ± 14941 22670 2662 11573 84 0 122 5100 15755 9161 61391 1160 4360 1116 3762 282 0 0 798 1470 5056 1345 5173 281 0 122 37067 185561 6917 23621 442 396 3069 17795 986 5761 597 4821 278 0 0 179 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 3141 41640 909 10539 1921 24691 3834 53985 2559 3570 3761 2961 2068 4689 2079 3871 230 0 0 122 24089 211296 1573 30068 458 860 1709 13808 1367 3410 1606 1411 230 235 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 8193 4468 3200 2665 2191 5644 7978 12855 1430 7564 3203 6584 548 0 436 1783 3292 1558 3175 385 0 559 23597 133294 3829 5800 134 510 1855 11993 1381 3527 1610 4821 320 118 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Week 1Week 3 Week 5 Week ) and 95% confidence intervals for major benthic invertebrate taxa in core samples, Green River backwaters, Ouray National Wild –2 m ⋅ 1436 15071 1039 6774 1810 6232 6766 23208 1443 5050 1199 7407 170 470 716 4468 595 4115 288 353 150 0 0 43 88 0 118 18388 142697 1343 13268 262 120 1484 11344 788 3880 893 4938 173 235 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 45 176 223 134 2998 1875 ______spp. 2709 spp. 126 spp. 2772 1. Average density (number 1. Average ABLE Ilyocryptus sordidus Macrothrix laticornis Eucyclops speratus E. prionophorus Acanthocyclops vernalis Diacyclops bicuspidatus Chironomus Tanypus Tanypus Procladius T Gastrotricha 3649 Rotifera 3000 Copepodites 6422 Nauplii 20434 Cladocera 4879 Adult CopepodaAdult 2277 Utah. Average densities calculated by pooling core sample data from all 3 sites for each treatment/date combination. Utah. Average TaxonNematoda 140683 Control Perforated Closed Control Perforated Closed Control Perforated Closed Oligochaeta 3244 Ceratopogonidae 203 Chironomidae 7825 154 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 3. Mean of average log-transformed sample counts from vertical plankton tows used in the 3-way ANOVA for (a) Corixidae, (b) Eucyclops prionophorus, (c) Cladocera, and (d) nauplii from Green River backwaters, Ouray National Wildlife Refuge, Utah. Vertical bars indicate ±1 s; n = 3 for each treatment/date combination. heterogeneity and evenness (3-way ANOVA, We collected 10 chironomid genera in the treatment effect: F2,4 = 11.27, P = 0.023; F2,4 = benthos: Chironomus, Glyptotendipes, Crypto- 13.57, P = 0.016, respectively; Figs. 4a, 4b), and chironomus, Polypedilum, Stempellinella, Nim- a marginally significant effect on species rich- bocera, Tanytarsus, Lenziella, Tanypus, and ness of planktonic copepods (3-way ANOVA, Procladius. Only Chironomus and Tanypus were treatment effect: F2,4 = 6.42, P = 0.056; Fig. 4c). abundant. Abundances of Tanypus and Procla- All 3 measures showed a trend of decreased dius were significantly affected by treatments. copepod diversity in perforated and closed There was no treatment effect on any of the cages. Tukey pairwise comparisons showed a diversity measures for chironomids. significant effect on species richness between controls and closed treatments (P = 0.05) and DISCUSSION a marginally significant effect between perfo- Density Effects rated and closed treatments (P = 0.08) on week 3, but no pairwise differences on weeks Two taxa, the chironomid genus Tanypus 1 or 5. Heterogeneity showed a marginally sig- and the corixid genus Trichocorixa, had in- nificant effect between perforated and closed creased abundances in closed-cage treatments. treatments on week 1 (P = 0.097) and between Higher densities in closed treatments could controls and closed treatments on week 5 (P = be caused by increased survivorship due to 0.10). Pairwise comparisons of treatment effects absence of fish predators, favorable conditions on heterogeneity between controls and perfo- created by the cage, or increased immigra- rated were significant for week 5 (P = 0.025). tion/decreased emigration in the cage. Pat- Pairwise comparisons of treatment effects on terns in Figures 1b and 3a do not rule out any evenness between controls and closed cages of these possibilities. Average number of were marginally significant on week 3 (P = organisms in perforated cages is indistinguish- 0.098) and significant on week 5 (P = 0.028). able from closed cages in both cases. This pat- Controls and perforated treatments also tern suggests that either few fish entered the showed significant differences for evenness on perforated cages or those that entered did not week 5 (P = 0.009). prey upon Tanypus and Trichocorixa. 2001] BACKWATER INVERTEBRATE COMMUNITIES 155 4 5 5.1 7.0 5.1 3.4 3 7 8 3 1.7 1.9 ± ± ± ± ± ± ± ± ± ± ± ± National 36 120 392 3.3 4.1 4.9 2.7 1.7 2.1 4.9 8.5 2 426 5 60 7 32 4 22 1.1 1.4 0.83 2.3 ± ± ± ± ± ± ± ± ± ± ± ± 5 128 5 291 2.8 5.5 3.1 3.4 3.0 1.2 1.2 11.2 4 306 3 56 3 21 5 23 2.3 0.77 4.6 0.38 ± ± ± ± ± ± ± ± ± ± ± ± combination. 4 81 4 41 2.0 29 6 336 4 1536 6.1 14.4 6.6 4.1 2.3 6.4 6 0.83 6 331 4.1 8.8 1.5 2.0 ± ± ± ± ± ± ± ± ± ± ± ± 6 157 7 146 2.7 2.0 8 228 6 781 11 9.8 12 8.0 1.7 2.2 4.7 23 4 265 3.3 3.1 4.3 1.3 ± ± ± ± ± ± ± ± ± ± ± ± 6 125 7 108 3.3 5.7 2.6 5.5 11 193 8 27 14 25 3.2 1.9 2.2 17.3 3 201 2.6 3.2 6 547 ± ± ± ± ± ± ± ± ± ± ± ± 7 97 9 85 2.8 6.5 7.3 2.7 3.3000000 6 532 9 1022 13 63 26 50 6.7 4.6 6.3 3.0 40 226 5.9 6.2 ± ± ± ± ± ± ± ± ± ± ± ± ±

Fig. 4. Mean values of diversity measures for copepods 5 173 6 135 4.4 3.1 4.3 8.5 4.3 4.7 4 345 8 144 16 55 7.5 7.3 5 17.6 16 5291 14.3 6.8 7 861 collected in vertical plankton tows and used in 3-way ± ± ± ± ± ± ± ± ± ± ± ± ± ANOVA of (a) heterogeneity, (b) evenness as measured by

Week 1Week 3 Week the modified Hill’s ratio, and (c) species 5 Week richness estimated using rarefaction method, from Green River backwaters, ) and 95% confidence intervals for major planktonic invertebrate taxa in vertical plankton tows, Green River backwaters, Ouray

–2 Ouray National Wildlife Refuge, Utah. Vertical bars indi-

m cate ±1 s; n = 3 for each treatment combination. ⋅ 5 150 5 115 2.7 8.0 4.0 5.8 1.8 5.3 6 505 118 1627 315 13 174 5.6 14.3 2.3 21 13 1890 3.0 11.3 ± ± ± ± ± ± ± ± ± ± ± ± ± 79 5.6 5.4 1.5 7.3 123 ______2. Average density (number 2. Average ABLE T Euclyclops speratus E. prionophorus Acanthocyclops vernalis Diacyclops bicuspidatus Ilyocryptus sordidus Macrothrix laticornis Taxon CopepodaAdult 96 Control Perforated Closed Control Perforated Closed Control Perforated Closed Wildlife Refuge, Utah. Averages were calculated by pooling vertical plankton tow data from all 3 sites for each treatment/date Refuge, Utah. Averages Wildlife Copepodites 322 NaupliiCladocera 1518 191 Corixidae 3.4 Rotifera 2652 Gastrotricha 2.9 156 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Trichocorixa and Tanypus are large (relative 1990, Diehl 1992). This is further supported to other backwater invertebrates) predators by a meta-analysis indicating that benthic in- and may have been depleted by fish through vertebrate predators have more than twice the size-selective predation. However, Chironomus, impact on other benthic invertebrates that a detritivore, was more abundant and larger vertebrate predators do (Wooster 1994). Clado- than Tanypus, and yet appeared unaffected by cerans, copepodites, and nauplii in our study treatments. This suggests that if lower density all had greater abundances in controls than in of Tanypus in controls was the result of fish closed cages. predation, then it is more likely attributable to Closed-cage treatments had a negative effect behavior than size. Studies show that predatory on 4 taxa: Procladius, Eucyclops prionophorus, chironomids are more susceptible to fish pre- immature Copepoda (both copepodites and dation. For example, Gilinsky (1984) found that nauplii), and Cladocera. One explanation of the dominant predatory midge in a pond was this effect is increased levels of invertebrate most affected by fish predation, Goyke and predators like Trichocorixa and Tanypus in Hershey (1992) observed that Arctic ponds closed treatments. Both feed on benthic organ- without fish had a significantly higher propor- isms, making it possible that they reduced the tion of predaceous chironomids than ponds number of immature copepods and Procladius. with fish, and Macchiusi and Baker (1991) However, E. prionophorus and cladocerans showed that size-selective predation on midges showed a significant treatment effect for indi- can be explained by differential activity of the viduals in plankton tows only. This makes it midges. Spatial distribution of midges may more likely that they were affected by Tri- also be important in their susceptibility to fish chocorixa, which feeds in the water column as predation. For instance, in soft benthic sedi- well as benthos. No invertebrate predator effect ments of Utah Lake more than 85% of larval on oligochaetes was detected even though Tanypus stellatus occur within the top 2.5 cm predatory and omnivorous chironomids (such of sediments, but only 33% of larval Chirono- as Tanypus and Chironomus), as well as Tri- mus frommeri are found in the same zone chocorixa, are known oligochaete predators. (Shiozawa and Barnes 1977). However, since uneaten portions of oligochaetes Differential migration rates between the can often regenerate, their biomass may de- inside and outside of cages may also help ex- crease in the presence of predators while their plain our results. First and 2nd instar Tricho- overall numerical density remains the same corixa are small enough to fit through the (Loden 1974, Wisniewski 1978). exclosure mesh, and 76% of individuals we Other possibilities to explain the lower measured were 1st or 2nd instars. It thus is numbers of some taxa in closed-cage treat- possible that elevated numbers of corixids in ments include decreased survivorship due to perforated and closed treatments were the less favorable conditions within cages, and result of immigration. However, the few Tri- lower rates of immigration. Patterns in Figures chocorixa caught in controls were early instars 1–3 do not rule out any of the possible scenar- as well. It is unclear whether increased den- ios but may give some insight. Figures 2a, 2b, sity of Trichocorixa in cages was a result of 3b, and 3c all indicate that densities in perfo- increased survivorship or immigration. As for rated cages were intermediate to those in Tanypus, it seems more likely that increased closed treatments and controls. Fish may have survivorship played a larger role since they entered perforated cages and reduced the are less mobile than Trichocorixa and there- number of invertebrate predators, which in- fore less likely to migrate into cages. creased survivorship of some taxa relative to We did not find significant evidence of the closed treatment. If this is the case, then direct effects of exclusion on copepods, clado- the difference in abundance between control cerans, or nematodes although all 3 are in the and closed areas might represent an indirect diets of backwater fishes (Muth and Snyder effect of fish predation (i.e., fish decrease in- 1995). Studies of predation on benthic inverte- vertebrate predators which indirectly benefits brates have attributed similar results to com- prey of those predators). Another possibility is pensatory predation from invertebrate preda- that perforated cages allowed greater access to tors (Crowder and Cooper 1982, Cooper et al. some taxa than closed treatments, or physical 2001] BACKWATER INVERTEBRATE COMMUNITIES 157 conditions in perforated treatments were inter- ACKNOWLEDGMENTS mediate to those in controls and closed treat- ments. If either is true, then lower numbers of This research was funded, in part, by the some taxa in closed cages may simply be an U.S. Fish and Wildlife Service. We thank D. artifact of the cages. Creer, D. Davis, K. Jordan, R. Rassmussen, and A. Stockman for field and laboratory assistance. Diversity Effects We thank J. Barnes, J. Gilliam, B. Maurer, J. The heterogeneity, evenness, and possibly Rice, P. Marsh, and 2 anonymous reviewers for species richness of planktonic copepods appear their constructive comments and critiques of enhanced in open water, and yet only a single the manuscript. We thank G. Fellingham and species showed any density differences. It is L. Stefanski for statistical assistance. possible that compensatory predation by inver- tebrate predators, in closed cages, equalized LITERATURE CITED densities of copepods in the controls and closed ALATALO, R.V. 1981. Problems in the measurement of treatments but did not have the same impact evenness in ecology. Oikos 37:199–204. as fish on copepod diversity. Another possibil- ALLAN, J.D. 1983. Predator-prey relationships in streams. ity is that as rare species were recruited into Pages 191–229 in J.R. Barnes and G.W. Minshall, the backwaters, they were unable to gain access editors, Stream ecology: application and testing of general ecological theory. Plenum, New York. to the closed cages, thereby lowering diver- BROOKS, J.L., AND S.I. DODSON. 1965. Predation, body size, sity. However, we believe this was not the case and composition of plankton. Science 150:28–35. since Figure 4a clearly shows that controls and CARPENTER, S.R., J.F. KITCHELL, J.R. HODGSON, P.A. closed cages follow the same upward and down- COCHRAN, J.J. ELSER, M.M. ELSER, E.M. LODGE, ET AL. 1987. Regulation of lake primary productivity by ward trends. More specifically, the increase in food web structure. Ecology 68:1863–1876. heterogeneity from week 3 to week 5 in the COOPER, S.D., S.J. WALDE, AND B.L. PECKARSKY. 1990. Prey open control as well as the closed treatments exchange rates and the impact of predators on prey indicates that at least some of the rare species populations in streams. Ecology 71:1503–1514. CROWDER, L.B., AND W.E. COOPER. 1982. Habitat struc- appearing in the backwaters were also recruited tural complexity and the interaction between blue- into the closed treatments. gills and their prey. Ecology 63:1802–1813. Two chironomid taxa, Tanypus and Procla- DIEHL, S. 1992. Fish predation and benthic community dius, showed significant treatment effects on structure: the role of omnivory and habitat complex- density, but we were unable to find significant ity. Ecology 73:1646–1661. ELLIOT, J.M. 1977. Some methods for the statistical analy- treatment effects on chironomid diversity. We sis of samples of benthic invertebrates. Freshwater identified chironomids to generic level, which Biological Association, Scientific Publication 25. may have been too coarse a scale for diversity FLECKER, A.S., AND J.D. ALLAN. 1984. The importance of questions, and chironomid community diver- predation, substrate and spatial refugia in determin- ing lotic insect distributions. Oecologia (Berlin) 64: sity may have required more time to respond 306–313. to treatments than the copepod community GILINSKY, E. 1984. The role of fish predation and spatial (Diehl 1992). In addition, the structural com- heterogeneity in determining benthic community plexity of the benthic substrate may allow for a structure. Ecology 65:455–468. GILLIAM, J.F., D.F. FRASER, AND A.M. SABAT. 1989. Strong fairly diverse (11 genera) community that is effects of foraging minnows on a stream benthic not significantly affected by predation (Gilin- invertebrate community. Ecology 70:445–452. sky 1984). GOYKE, A.P., AND A.E. HERSHEY. 1992. Effects of fish pre- The impact of predation on density and dation on larval chironomid (Diptera: Chironomidae) communities in an Arctic ecosystem. Hydrobiologia diversity of invertebrates seems to depend on 240:203–211. habitat type. Our results suggest that back- HAINES, G.B., AND H.M. TYUS. 1990. Fish associations and water fish communities of the Green River may environmental variables in age-0 Colorado squaw- significantly impact several invertebrate taxa. fish habitats, Green River, Utah. Journal of Freshwa- However, with our design we were unable to ter Ecology 5:427–435. HILL, M.O. 1973. Diversity and evenness: a unifying nota- distinguish between fish effects and other tion and its consequences. Ecology 54:427–432. effects created by treatment cages. Future stud- HURLBERT, S.H. 1971. The non-concept of species diver- ies will be required to separate these effects sity: a critique and alternative parameters. Ecology and more completely address the role of pre- 52:577–586 KERFOOT, W.C., AND A. SIH, EDITORS. 1987. Predation: dation in structuring Green River backwater direct and indirect impacts on aquatic communities. invertebrate communities. University Press of New England, Hanover, NH. 158 WESTERN NORTH AMERICAN NATURALIST [Volume 61

LODEN, M.S. 1974. Predation by chironomid (Diptera) lar- SHIOZAWA, D.K., AND J.R. BARNES. 1977. The microdistri- vae on oligochaetes. Limnology and Oceanography bution and population trends of larval Tanypus stel- 19:156–159. latus Coquillet and Chironomus frommeri Atchley MABEY, J.W. 1993. Planktonic and benthic microcrusta- and Martin (Diptera: Chironomidae) in Utah Lake, ceans from floodplain and river habitats of the Ouray Utah. Ecology 58: 610–618. Refuge on the Green River, Utah. Master’s thesis, SIH, A., P. CROWLEY, M. MCPEEK, J. PETRANKA, AND K. Brigham Young University, Provo, UT. STROHMEIER. 1985. Predation, competition, and prey MACCHIUSI, F., AND R.L. BAKER. 1991. Prey behaviour and communities: a review of field experiments. Annual size-selective predation by fish. Freshwater Biology Review of Ecology and Systematics 16:269–311. 25:533–538. SIMBERLOFF, D. 1972. Properties of the rarefaction diver- MASON, W.T., JR. 1968. An introduction to the identifica- sity measurement. American Naturalist 106:414–418. tion of chironomid larvae. Federal Water Pollution WILZBACH, M.A., K.W. CUMMINS, AND J.D. HALL. 1986. Control Administration, U.S. Department of the Inte- Influence of habitat manipulation on the interactions rior, Cincinnati, OH. between cutthroat trout and invertebrate drift. Ecol- MERRITT, R.W., AND K.W. CUMMINS, EDITORS. 1984. An ogy 67:898–911. introduction to the aquatic insects of North America. WIEDERHOLM, T., EDITOR. 1983. Chironomidae of the Kendall/Hunt Publishing Co., Dubuque, IA. Holarctic region: keys and diagnoses. Borgstroms MUTH, R.T., AND D.E. SNYDER. 1995. Diets of young Col- Tryckeri AB, Motala, Sweden. orado squawfish and other small fish in backwaters WISNIEWSKI, R.J. 1978. Effect of predators on Tubificidae of the Green River, Colorado and Utah. Great Basin groupings and their production in lakes. Ekologia Naturalist 55:95–104. Polska 26:493–512. O’BRIEN, W.J. 1979. The predator-prey interaction of WOLZ, E.R., AND D.K. SHIOZAWA. 1995. Soft sediment ben- planktivorous fish and zooplankton. American Scien- thic macroinvertebrate communities of the Green tist 67:572–581. River at the Ouray National Wildlife Refuge, Uintah PENNAK, R.W. 1989. Freshwater invertebrates of the County, Utah. Great Basin Naturalist 55:213–224. United States. 3rd edition. John Wiley and Sons, NY. WOOSTER, D. 1994. Predator impacts on stream benthic REICE, S.R. 1983. Predation and substratum: factors in prey. Oecologia 99:7–15. lotic community structure. Pages 325–345 in S. Bartell YEATMAN, H.C. 1959. Cyclopoida. Pages 795–815 in H.B. and T. Fontaine, editors, Dynamics of lotic ecosys- Ward and G.C. Whipple, editors, Freshwater biology. tems. Ann Arbor Science, Ann Arbor, MI. 2nd edition. John Wiley and Sons, Inc., New York. REICE, S.R., AND R.L. EDWARDS. 1986. The effect of ver- tebrate predation on lotic macroinvertebrate com- Received 20 January 1999 munities in Quebec, Canada. Canadian Journal of Accepted 15 February 2000 Zoology 64:1930–1936. SCHLOSSER, I.J., AND K.K. EBEL. 1989. Effects of flow regime and cyprinid predation on a headwater stream. Ecological Monographs 59:41–57. Western North American Naturalist 61(2), © 2001, pp. 159–181

FISHTAIL MESA: A VEGETATION RESURVEY OF A RELICT AREA IN GRAND CANYON NATIONAL PARK, ARIZONA

Peter G. Rowlands1 and Nancy J. Brian2

ABSTRACT.—Relict sites are geographically isolated areas that are undisturbed by direct and indirect human influ- ences. These sites facilitate long-term ecological monitoring by providing a reference for gauging impacts occurring elsewhere. Knowledge gained through comparing vegetation change on matched relict and proximal disturbed areas can help partition the causes of change into natural and human-produced components. Fishtail Mesa in Grand Canyon National Park is a 439-ha relict site that is inaccessible to domestic livestock. Human visitation is infrequent and irregu- lar, and fires have never been suppressed or managed. In 1958, U.S. Forest Service range scientists conducted a survey of Fishtail Mesa to gather reference data on vegetation, wildlife, and soils. Vegetation sampling was conducted using a method called the “elb.” We returned to Fishtail Mesa in May 1996 to perform a general vegetation and floristic survey, assess the extent of vegetation change after 38 years, and evaluate the suitability of the site as a location for long-term surveillance of ecological change. Fishtail Mesa’s vegetation consists primarily of a Pinus edulis (pinyon) and Juniperus osteosperma (Utah juniper) woodland with an Artemisia tridentata (sagebrush) understory, or tree-type (310.9 ha), and an Artemisia and Poa fendleriana (mutton grass) steppe, or shrub-type (127.5 ha). Since 1958 vegetation changes in both shrub- and tree-types have been limited to only a few species. In the shrub-type we detected slight increases from 1958 to 1996 in both Pinus and Juniperus, and reexamination of 1958 photo sites confirmed that Pinus and Juniperus are reoc- cupying the shrub-type. Artemisia cover declined from 1958 to 1996, whereas Poa increased from near trace amounts in 1958 to moderate cover in 1996. In the tree-type, Poa has increased from 1958 to 1996, while Artemisia, Juniperus, and Pinus showed no apparent change. Other species such as Ephedra torreyana (Torrey joint-fir), Opuntia polyacantha (prickly pear), and Gutierrezia sarothrae (snakeweed) have decreased. Vegetation analysis aided by TWINSPAN revealed that the shrub-type is defined more on the basis of absence of Pinus and Juniperus rather than any special asso- ciation of differential species with a high preference for this type. We interpret the “invasion” of the shrub-type by Pinus and Juniperus as a “reoccupation.” Indirect ordination using DECORANA inferred 2 environmental gradients, a mois- ture gradient and perhaps a substrate texture gradient, that appeared to influence vegetation distribution on Fishtail Mesa. Fishtail Mesa is a valuable relict area for studying the effects of livestock grazing and prescribed fire. It should be designated a Federal Research Natural Area based on its vegetation communities, size, and protection afforded by its location in Grand Canyon National Park.

Key words: relict area, Grand Canyon, Pinyon-Juniper Woodland, Sagebrush Steppe, TWINSPAN, DECORANA.

Vegetation and soils of Fishtail Mesa, a relict narrow canyons impassable to livestock and area in Grand Canyon National Park, Arizona, motor vehicles. These relict areas, validated as were originally studied in May 1958 (Jameson to their undisturbed state by exhaustive inven- et al. 1962). The purpose of the original re- tory and research, can be considered practi- search was to document Fishtail Mesa as a ref- cally pristine reference sites where ecological erence relict area and collect baseline data on processes and components are unmanaged. vegetation, soils, and wildlife. The U.S. Forest Specifically, relict refers to communities that Service hoped that ecological studies of Fish- have either (1) persisted through severe tail Mesa would help to interpret the effects of warming and drying of the interior West’s cli- livestock grazing on similar, grazed areas on mate over the past few thousand years (Betan- Forest Service lands located on the nearby court 1990), or (2) been uninfluenced by settle- North Rim. Southwestern national parks often ment activities, chiefly domestic livestock graz- contain many similarly isolated areas that are ing. In this paper we stress the 2nd criterion. relatively unaltered by human activity. On the Relict areas are scientifically interesting because Colorado Plateau, comparatively small places of their isolated faunas and verifiable lack of with pristine or relict communities abound on herbivory or human interference (Turner 1982, buttes, mesas, boulder-strewn slopes, or in Johnson 1983, Van Pelt et al. 1991).

1Division of Resources Management, Organ Pipe Cactus National Monument, Route 1, Box 100, Ajo, AZ 85321. 2Science Center, Grand Canyon National Park, Box 129, Grand Canyon, AZ 86023. Corresponding author.

159 160 WESTERN NORTH AMERICAN NATURALIST [Volume 61

For the land use manager, relict areas are Mesa due to the absence of livestock grazing standards or baselines for gauging impacts and associated land use management practices occurring elsewhere in the parks (Jeffries and coupled with minimal exploitation by native Klopatek 1987, Hermann 1989, Beymer and wildlife. On the other hand, we also hypothe- Klopatek 1992). They help define productive sized that evidence would be found showing potentials of forests and rangelands (Passey et reoccupation of Sagebrush Steppe (or shrub- al. 1982) and are sanctuaries for plant and ani- type) vegetation by Pinus and Juniperus after mal life, some of which are considered endan- exclusion of these trees as part of a natural, or gered or threatened. The National Park Ser- at least near-natural, fire cycle envisioned by vice (NPS) has commissioned 2 relict area sur- Jameson et al. (1962). We also thought that veys, conducted by the Nature Conservancy, Fishtail Mesa, because of its narrow shape and on the Colorado Plateau. The first, by Tuhy island-like situation, would be an ideal place and McMahon (1988), identified 21 relict or to examine the influence of the so-called rim near-relict sites in Glen Canyon National effect on vegetation distribution. According to Recreation Area. The second, by Van Pelt et Halvorson (1972), Grand Canyon produces al. (1991), covered all the remaining Colorado strong, convective air movement resulting in Plateau parks, with the notable exception of hot, dry winds rising from the warmer canyon Grand Canyon National Park. Over 100 addi- bottom. These winds have the immediate effect tional relict sites were identified. of drying and heating upland areas adjacent to Since publication of Jameson et al.’s (1962) the rim. Storms from the prevailing wind research, Fishtail Mesa has been compared direction are forced away from the rim by the with other relict sites (Mason et al. 1967, warm updrafts. This rim effect creates a zone Schmutz et al. 1967, 1976, Mason and West of increased aridity for some distance, up to 1970, Thatcher and Hart 1974, Turner 1982). 400 m or more, away from the rim. Because of But, on the whole, research on Colorado Pla- the long, narrow shape of Fishtail Mesa, almost teau relict areas has been scanty. Besides the parallel to the prevailing winds, a substantial Jameson et al. (1962) report, Johnson (1983) rim effect should be discernible as a vegetation studied island biogeography of isolated buttes gradient from shrub-type along the rim to in Canyonlands National Park and the mam- tree-type within the interior of Fishtail Mesa. mals, reptiles, and insects that were able to colonize through the filter of very steep cliffs. METHODS AND MATERIALS Other than the Mason and West (1970) publi- cation, he cites no relevant relict area research. STUDY AREA.—Fishtail Mesa is an isolated, Only 2 studies of Grand Canyon relict areas semiarid 439-ha mesa located immediately have been published. Jameson et al. (1962) is east of the confluence of Kanab Creek and the the subject of this paper. Later, Beymer and Colorado River in Grand Canyon National Klopatek (1992) published findings on the Park, Arizona (Fig. 1). A narrow ridge separates effects of historical grazing on microphytic the 1867-m-high mesa top from the “main- crusts on the South Rim of Grand Canyon land” of the Kaibab Plateau, located 1.6 km to National Park using Shiva Temple, another the northeast. The National Park Service allows isolated butte, as a comparison site. They lightning-caused fires to burn. It is protected reported that visible crust cover was reduced from domestic livestock grazing by the steep, from 23.3% on ungrazed sites to 5.3% on some 610-m cliffs that encircle it. Its relative isolation previously grazed sites. from native ungulate grazing is compromised The study of Fishtail Mesa provides an un- only by mule deer, which scale the northern usual opportunity to examine some hypothe- edge of the mesa to browse seasonally. ses regarding vegetation change in an unman- Precipitation records for Grand Canyon aged setting. Our principal study objective National Park (Green and Sellers 1964, Sellers was to document vegetation change since 1958 and Hill 1974) indicate that average annual and to evaluate Fishtail Mesa as a relict site rainfall on Fishtail Mesa is probably about 350 for long-term surveillance of ecological change. mm ⋅ yr–1. Forty-five percent occurs during We surmised that there would be little change winter and spring (December through April) in the shrub component of the Pinyon-Juniper and 34% during the summer monsoon season Woodland (or tree-type) vegetation on Fishtail (July through September; Jameson et al. 1962). 2001] RESURVEY OF FISHTAIL MESA 161

Summer thundershowers can be sudden and land) and Artemisia tridentata–Poa fendleriana locally heavy. Precipitation is deficient in all association (Sagebrush Scrub or Sagebrush seasons relative to potential evapotranspira- Steppe) are the primary plant assemblages on tion, and there is little or no surface runoff. Fishtail Mesa (Jameson et al. 1962). We refer The average growing season is 141 days. Aver- to these as the tree-type and shrub-type, age January temperature is –1.7ºC and average respectively. Jameson et al. (1962) reported 2 July temperature is 20.4°C. The area is semi- other minor plant communities: a patch of arid and microthermal (Thornthwaite 1931). Stipa speciosa (desert needlegrass) grassland The mesa has a gently rolling topography in the approximate center of the mesa’s shrub- and varies in elevation from 1769 to 1867 m. type, and a small patch of Gutierrezia Permian-aged Kaibab limestone forms the sur- sarothrae along the rim. These 2 minor com- face (McKee 1938, Hopkins 1990). Thin, small munities are not considered in this paper. A areas of Quaternary deposits are found in the revised 1996 vegetation map (Fig. 1) delin- central portion of the mesa along small, eates 3 plant communities: a Pinyon-Juniper ephemeral drainages and at the bases of slopes. Woodland with sagebrush understory (tree- Aeolian deposits of very minorly reworked type) with 25–60% tree cover (71% of the sands are trapped near vegetation. mesa top), a Big Sagebrush Steppe (shrub- Soils on Fishtail Mesa are shallow and type) with <10–24% tree cover (29%), and a poorly developed. The 5 soil units originally Stipa Grassland (0.1%). described by Jameson et al. (1962) include a Jameson and his colleagues conjectured sandy limestone (ca 47% of the mesa top), nor- that (1) 20% of the original tree-type had been mal limestone (ca 27%), cherty limestone converted to shrub-type by fires, (2) these (17.5%), steep rocky slopes (4%), and alluvium areas made up about 60% of the shrub-type, (4%). We noted a 6th unit of gypsum (0.5%). and (3) there was little reinvasion of the burns Most soils are lithic ustochrepts, while the by pinyon and juniper trees. They did not esti- alluvium is a typic haplustalf. The interested mate the age of the burns due to lack of reli- reader can consult Jameson et al. (1962) for able data, but concluded that fires must have profile descriptions of the soil units. occurred long ago since Juniperus snags with Unlike other relict areas in Grand Canyon, only heartwood remaining were left standing. such as Shiva Temple (Beymer and Klopatek GENERAL STUDY DESIGN.—We resurveyed 1992), microphytic (microbiotic, or cryptogamic) vegetation and soils of Fishtail Mesa 10–15 May crusts are not abundant on Fishtail Mesa. 1996, within a week of its initial survey 38 When observed, crusts were diffuse and did years previously by Jameson et al. (1962). One not form dense, discrete patches. Only traces of the original researchers (Jameson) assisted of such crusts were encountered on the 8 sam- in the fieldwork. Jameson et al. (1962) employed ple sites, not enough to perform any spatial or U.S. Customary units for all their field mea- abundance comparisons with statistical rigor. surements. For the sake of consistency, we Furthermore, since microphytic crusts were duplicated both units and methods. For this never considered in the Jameson et al. (1962) publication all measurements are converted survey, temporal comparisons were also not into SI units to a computed accuracy of at least possible. When encountered, crust cover was 2 decimal points. included with litter. The method they used was an adaptation of Vegetation of Fishtail Mesa could be de- the line intercept (Canfield 1941, Parker and scribed as a southern extension of the Great Savage 1944, Bonham 1989) technique called Basin Desertscrub Formation (Young et al. 1977, an “elb” (Fig. 2), or “elb-strip” (Woodin and Turner 1982). The occurrence of a significant Lindsey 1954). The term elb, short for “elbow,” graminoid component (Bouteloua gracilis [blue refers to the sampling unit whereby 2 orthogo- grama], Hilaria jamesii [galleta], and Stipa spp.) nal, 121.9-m baselines served as line inter- in the sagebrush vegetation type, as on Fish- cepts (LIs). A sequence of 400 Parker loop tail Mesa, leads some authors to classify such (PL; Parker 1951) observations was also made communities as a shrub steppe (Turner 1982), at 0.3-m intervals along the LI. A 6.1 × 121.9- or sagebrush savanna (Clements 1930). At the m belt transect, split into four 30.5-m sections association level, the Pinus edulis–Juniperus and superimposed on the LI, together consti- osteosperma association (Pinyon-Juniper Wood- tuted each elb “arm.” Elb arms were oriented 162 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 1. Fishtail Mesa 1996 vegetation map. at right angles to produce an L-shaped plot shrub-type (elbs 1, 2, 4, 5), but due to time (Fig. 2) and were recorded as left (L) and right constraints, they installed only 3 1/2 in the (R) when observed from the origin. The elb tree-type (elbs 3, 6, 7, 8, the latter consisting sampling design was originally applied to the of only a single arm). For more specific details, study of Fishtail Mesa vegetation to avoid the we refer the reader to Jameson et al. (1962) linear influence of topography whereby a ran- and Woodin and Lindsey (1954), who estab- dom straight line might fall largely within or lished the elb methodology. We were able to parallel to a gully, ridge, slope base, or geolog- relocate most of the previously placed steel ical stratum, thereby obscuring the sampling fence posts and angle irons marking the 30.5- results. A set of long, orthogonal strips was m increments along each of the elbs. Missing supposed to even out the variances in vegeta- markers were relatively easy to reestablish tion response (e.g., cover) to environmental based on the locations of those remaining. factors (Woodin and Lindsey 1954). In 1958, VEGETATION FIELD MEASUREMENTS AND IN- Jameson et al. (1962) established 7 1/2 perma- VENTORY.—In 1958, LI measurement accuracy nent 244-m elbs. They established 4 in the was claimed to be the nearest 0.25 cm. In 2001] RESURVEY OF FISHTAIL MESA 163

diameter loop placed at specified intervals along a permanent transect. At least 100 points should be sampled. In this study we observed 400 PLs at 0.3-m intervals along each elb arm baseline. We noted both basal and foliage cover hits for trees and shrubs and basal cover hits for forbs and grasses. If no vegetation was encountered within the loop, the presence of bare ground, litter, soil crusts, or exposed rock was noted. Data from the 6.1 × 121.9-m belt transects were used to measure density, abundance, and frequency of tree species. In 1958 only live trees >0.9 m in height were recorded and measured. In 1996 we measured trees of all heights and ages, including snags. Tree seedling diameters were measured at ground level. Due to the low branching characteristic Fig. 2. Diagram of the left and right arms of an elb of Pinus and Juniperus, poles, mature trees, showing elb transect with central baseline line intercept, and snags were measured at 0.3 m above the belt transect, angle irons, and elb marker posts. ground (hereafter referred to as basal diameter or BD), as opposed to breast height (≈ 1.5 m). 1996 we set LI measurement accuracy to a We recorded the position of all trees with more realistic 1.25 cm. When plant cover was respect to elb arm baselines using Cartesian x- less than this, we recorded it as a “trace,” and y-coordinates. We also recorded canopy equal to a nominal value of 0.03 cm. We mea- diameter and tree height. Canopy cover was sured understory vegetation cover along the 2 estimated as the area of a circle; when the LIs forming the baseline of the elb arms. We canopy was not circular, canopy cover was refer to cover in 2 different ways within this estimated as the area of an ellipse. Trees with paper. Absolute cover of a species is the cover most of the base located inside the strip of a species (total length of its vegetative parts perimeter were counted, while those outside intercepted by the LI or PL hits) with respect were omitted. to size of the sample (length of the LI or num- We compared differences in absolute cover values for the study years 1958 and 1996 using ber of PLs observed). Absolute cover derived ∆ from LIs is “linear” cover. Statistical compar- percent change ( %): isons were always made using linear cover or, (Vp–Vf) in the case of PLs, the number of hits. Relative ∆% = ______× 100 (1) cover of any plant species is the cover of that [ Vf ] species relative to the total cover of all species encountered. Multiplying absolute cover and where Vp is the present value of a variable and relative cover values by 100 yields absolute Vf is the former value of the same variable. percent cover (AC) and relative percent cover Cover values for 1958 (Jameson et al. 1962) (RC), respectively. We used RC for TWIN- were presented as AC for each species accord- SPAN and DECORANA computations. ing to shrub- and tree-type and not for indi- To conform to the original Jameson et al. vidual elbs or elb arms. Original 1958 LI val- (1962) study, we also made PL observations ues (ft ⋅ LI–1) for each species had to be back- (Parker 1951, Driscoll 1958, Parker and Harris calculated from AC because we discovered 1959). These observations provided indepen- that field data sheets had been lost. Percent dent estimates of plant cover for comparison cover was converted to a decimal, multiplied with LI data. The PL method is basically a fre- by 3200 ft total elb length for the shrub-type quency technique to enable rapid estimation (2800 for the tree-type), and then divided by 8 of plant cover and community composition. for the shrub-type (7 for the tree-type). Even One records “hits” on plants, or portions so, resulting values are actually overall means thereof, occurring within a 1.9-cm- (0.75-in-) of cover as ft ⋅ LI–1 for each species according 164 WESTERN NORTH AMERICAN NATURALIST [Volume 61 to vegetation type. Values from 1958 for indi- To increase the number of samples, we ana- vidual elb arms could not be recalculated. lyzed the 1996 data according to separate elb Similarly, 1958 PL percent cover estimates arms. That is, the right and left arms of each also had to be back-calculated from data con- elb were considered to be independent sam- tained in Jameson et al. (1962). Where appro- pling units. We believe this decision is a rea- priate, values were converted to metric. sonable one because of the great length of TREE CORES.—We collected samples from each elb arm and the right-angle orientation of 4–6 living Pinus trees located outside the elbs the elbs to one another. Thus, the shrub-type to ascertain tree age. Height and basal diame- was represented by 8 sampling units and the ter measurements were also recorded, and tree-type by 7. The decision affected only the then cores or cross-sectional slabs were taken 1996 data that we collected. Temporal com- at 0.3 m above the ground. Pinyon cores were parisons are based on the recalculated 1958 glued to wooden mounts, sanded, and pol- data, as described above (Jameson et al. 1962). ished until rings were visible (Stokes and Smi- QUANTITATIVE VEGETATION ANALYSIS.—We ley 1968). Rings were counted using a 10–30X employed the Shannon diversity index, H፱ zoom microscope. In cases where the core (Kent and Coker 1992), which was calculated missed the pith, we estimated missing rings from plant species’ RC using the 1958 and using a pith locator. False rings were identified 1996 LI observations. Computation of species’ using anatomical criteria (Stokes and Smiley RC values in 1996 was done according to indi- 1968). Tree ages should be considered esti- vidual tree- and shrub-type elb arms. The mates since no cross-dating and analysis for Shannon index is defined as: missing rings was done, and there is general disagreement among researchers on how well s ፱ ring counts represent growth (Despain 1989). H = – ∑ pi ln pi (3) If some error can be tolerated, Despain (1989) i =1 has demonstrated that ring counting can esti- mate 10-year diameter growth rates. Conse- where H፱ is the Shannon index, s is the num- quently, we estimate that an error of as much ber of species, and ln is the natural logarithm. th as 5% could have been introduced into our The term pi is the relative abundance of the i Pinus age estimates based on ring counts. The species expressed as: date of 1850 was chosen as the presettlement date for tree-ring analyses. Juniperus were not ____Ai pi = (4) cored, as this long-lived tree is subject to ∑A highly irregular diametric growth and gener- ally does not yield easily countable tree-rings. where Ai is the abundance (cover, biomass, Age-size relations of the trees were estab- density, etc.) of the ith species and ∑A is the lished by fitting basal diameters and tree-ring total abundance of all species in the sample. counts to the Chapman-Richards equation We chose H፱ because it is normally distributed (Clutter et al. 1983, Tausch and Tueller 1990). and more sensitive to rare species than other The Chapman-Richards model is derived from such indices (Magurran 1988). Also, according basic biological considerations and has proven to Kent and Coker (1992), H፱ is often preferred to be very flexible in modeling growth of both because species abundances are standardized individuals and populations (Clutter et al. to proportions. Species richness estimates were 1983). In this paper the equation takes the 3- made using the “jackknife” statistical method parameter form: with 95% confidence limits from replicate samples (Heltshe and Forrester 1983). diameter = A(1 – e–BAge)C (2) To better understand the relationships be- tween the two codominant tree species, Pinus and was fitted using the Levenburg-Marquardt and Juniperus, and the 2 major vegetation nonlinear fitting algorithm. Three constants, types on Fishtail Mesa, we believed it neces- A, B, and C, are the parameters of the Chap- sary to conduct both a vegetation classification man-Richards equation. These parameters are and ordination. Species and elb arm (stand) estimated by nonlinear regression and deter- vegetation data were classified using 2-way mine the exact shape of the generated curve. indicator species analysis, or TWINSPAN (Hill 2001] RESURVEY OF FISHTAIL MESA 165

1979a, Kent and Coker 1992). The method is over time. Vegetation maps were prepared based on progressive, iterative refinement of a using ortho-rectified 1978 color aerial photog- single-axis reciprocal averaging ordination (i.e., raphy, with a scale of 1:12,000. Accuracy in correspondence analysis). Eventually, these scale was ±10 m. Data from 1996 post- progressive ordinations lead to the delineation processed Global Positioning System (±3 m) of one or more differential species according coordinate data collected from the mesa per- to their scores (+ or –) on the single ordina- imeter and elbs were used in the map prepa- tion axis, or positive and negative differential ration. All maps produced by this study comply species. The concept of differential species is with national map accuracy standards estab- based on presence and absence, but Hill (1979a) lished by the United States Geological Survey. introduced the concept of pseudospecies as a All 1996 plant voucher specimens have been way of adapting abundance data to a qualita- deposited in the Grand Canyon National Park tive equivalent which can then be used in the herbarium. construction of a classification dichotomy (Kent and Coker 1992). In this study relative RESULTS percent vegetation cover data were used to define 9 pseudospecies based on an octal scale FIRE.—We noted, as did Jameson et al. conversion: 0–0.5% = 1, 0.5–1% = 2, 1–2% = (1962), patches of standing Juniperus snags 3, 2–4% = 4, 4–8% = 5, 8–16% = 6, 16–32% with only heartwood showing. Similar to = 7, 32–64% = 8, and >64–100% = 9 pseudo- Jameson et al. (1962), we assumed that these species. snags were from Juniperus that died 80 to 100 The same vegetation data were also used to years ago. We also observed standing snags on obtain an indirect ordination by means of several transects. The Juniperus:Pinus ratio detrended correspondence analysis (DECO- was 19:1. This is to be expected since Pinus RANA or DCA), an eigenvector-based ordina- trunks, unlike the more resistant Juniperus, rot tion procedure related to reciprocal averaging quickly at the root collar and subsequently and based upon an occurrence of a set of species topple. We observed no direct evidence of any in a set of samples (i.e., elbs; Hill 1979b). Effi- recent burns such as charred tree trunks, cacy of the DCA was assessed by relating eco- burned and dead shrubs, or charcoal. No fire logical distances for n*(n–1)/2 = 105 samples scars were observed on any of the 40+ Pinus (i.e., elb arm) pairs calculated for the original increment cores collected for population age- species by samples matrix with the similarly size assessment. calculated distances derived from the final 2- SPECIES RICHNESS AND DIVERSITY.—The dimensional stand ordination. The distance shrub-type exhibited greater species richness, metric employed was the Czekanowski coeffi- with 31 species, as opposed to the tree-type cient or “percent similarity.” In our study we with 26 species. A weighted calculation of employed 15 elb arm samples; thus, 105 simi- species richness, allowing for one less elb arm, larity coefficients are possible. Since no quan- gave a crude estimate for the tree-type of 30. titative observations on physical factors such Application of the jackknife statistical tech- as soil structure, moisture and chemistry, or nique to the Fishtail Mesa data produced a microclimatology were made, DCA results from 1st-order, jackknifed species richness estimate this study are intended as an adjunct to for the shrub-type of 42 ± 6 plant species, TWINSPAN. The Multivariate Statistical Pack- whereas the estimate for the tree-type was 36 age (MVSP V.3.01) developed by Kovach (1998) ± 9 species. Because there is considerable over- was used to perform DCA, whereas PC-ORD lap in the 2 species richness estimates, we (McCune and Mefford 1999) was used to gen- believe species richness to be essentially the erate the TWINSPAN 2-way ordered table. same for both vegetation types. However, REPHOTOGRAPHY, MAPS, AND OTHER DOCU- there was a significant difference in mean MENTATION.—Black-and-white scenic and land- species diversity, as measured by H፱, between scape photographs were taken to replicate the shrub-type (H፱ = 0.760, n = 8) and tree- ፱ photographs taken in 1958. Existing aerial type (H = 1.448, n = 7) (t[13;α=0.05] = 6.174; photography of Fishtail Mesa taken in 1940 P =3.4E-05). This is probably the result of and again in 1944 was also examined to deter- dominance by sagebrush in the shrub-type. A mine if changes in vegetation could be observed 38-year comparison of community composition, 166 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 3. Rank-abundance curves for Fishtail Mesa shrub- and tree-types: 1958 vs. 1996. as rank abundance, for the shrub- and tree- In the shrub-type, Artemisia was by far the types is shown in Figure 3. Species diversity principal cover dominant (19–20% AC), fol- (H፱) of the shrub-type was 0.62 in 1958 and lowed by Poa, Ephedra, and Pinus. Results 0.90 in 1996. Similarly, H፱ of the tree-type was from PL and LI observations showed that bare 1.59 in 1958 and 1.73 in 1996. We cannot ground, including litter, accounted for 73–76% claim any degree of significance. of the samples in the shrub-type. Litter consti- SPECIES COMPOSITION.—The current species tuted 6% and exposed rock 0.1% of 3200 PL composition of Fishtail Mesa’s vegetation is observations taken within the shrub-type. In summarized in Table 1 and includes results the tree-type, cover dominance of Artemisia, from both LI and PL observations. Only the 8 Pinus, and Juniperus was almost equal (9–10% most abundant species throughout Fishtail AC). Bouteloua, Yucca, Ephedra, and Shepher- Mesa are included. All other species contributed dia rotundifolia (roundleaf buffalo berry) were <1% cover each. Both methods yielded simi- the prevalent secondary species. Each of the lar values, although in general, especially where remaining species comprising the tree-type the more uncommon species are concerned, contributed only minor amounts of cover the PL method was much less efficient. The (<0.3% AC) to the vegetation composition of elb arm LIs in the shrub-type encountered 31 the tree-type. Results from PL and LI observa- plant species, but only 15 were encountered tions showed that bare ground, including litter, using the PLs. Likewise, LIs associated with accounted for 62–64% of the samples in the the 7 tree-type elb arms encountered 26 tree type. Litter constituted 4% and exposed species as opposed to 15 by the PLs. rock <0.1% of 2800 PL observation taken Artemisia is currently the primary plant within the tree-type. species (15–16% AC) on Fishtail Mesa, fol- Changes in plant cover during the 38-year lowed by Pinus and Juniperus with a com- period of record (1958–1996), based on LI ob- bined AC of 9–10%. Poa had the 4th highest servations and PL samples, of selected domi- overall cover, followed by Bouteloua gracilis, nant plant species and total vegetation cover Yucca baccata (banana yucca), and Ephedra are shown in Tables 2 and 3. In the shrub-type torreyana. Combined vegetation cover esti- the intercepted cover (in m ⋅ elb arm–1) of Poa mated from all 8 elbs was 30–31% AC. Results increased dramatically, with percent change from PL and LI observations showed that bare (∆%) varying between 5675% and 8263%, de- ground, including litter, accounted for 69-70% pending on the Vp parameter (mean, upper, or of the samples throughout Fishtail Mesa. Lit- lower confidence limit of 1996 cover) used to ter constituted 5% and exposed rock <0.1% of calculate it. Likewise, Ephedra exhibited a 6000 PL observations taken throughout Fish- definite but less dramatic increase in cover. tail Mesa. Pinus and Juniperus were not recorded in 1958, 2001] RESURVEY OF FISHTAIL MESA 167 based on % ∆ = 7 elb arms) n e (4 and 3.5 elbs, respectively) overall tion cover. These calculations were based on the tion cover. 6.62 –5.34 10.24 25.83 5.516.29 –33.62 –56.83 10.07 –5.69 53.77 45.45 5.36 –44.58 –0.25 44.09 0.43 –98.13 –57.94 –17.76 1.20 1760.00 2960.00 4160.00 95% confidence 1996 confidence ± ± ± ± ± ± meson et al. (1962), but confidence interval calcula- ± e another. One elb in the tree-type contains only one e another. ence limits, also. Individual line intercept data associ- (PL) observations. ) and based on line intercept measurements, in the shrub-type and tree-type on Fishtail % Relative % Absolute % Relative % Absolute % ∆ based on Year % ∆ = 8 elb arms) ( Tree-type n 1996 lower 1996 upper 1996 lower 1996 upper Mean intercepted plant cover in linear meters per elb arm and percent change between 1958 1996 Shrub-type ( 3.14 45.03 54.26 64.24 42.47 46.82 0.24 — — — 12.30 11.60 0.99 — — — 12.61 13.88 2.98 –29.98 –19.76 –11.3 12.09 12.06 0.27 6.10 32.93 66.7 1.07 0.45 1.04 5675.00 6975.00 8262.50 0.10 3.06 95% confidence 1996 confidence 1996 ± ± ± ± ± ± ± 1996 Year Relative % Absolute % cover within the cover within the cover within the cover within the 8.62.82.71.5 8.20.7 1.1 2.2 1.3 0.6 2.6 0.8 0.8 0.4 2.6 0.2 0.4 0.7 0.4 10.8 0.2 0.1 0.0 10.4 2.1 0.0 0.1 0.0 2.1 2.6 0.0 <0.1 0.0 2.3 <0.1 0.5 0.0 0.0 0.6 6.9 4.9 0.0 4.8 6.4 1.9 1.0 1.2 4.1 0.7 2.5 1.8 1.0 1.7 2.4 0.7 0.4 0.4 1.5 0.3 0.4 LI PL LI PL LI PL LI PL LI PL LI PL 49.815.315.1 50.7 17.6 14.6 14.9 4.6 4.5 16.2 5.6 4.7 79.5 1.7 81.8 0.4 1.5 0.6 19.2 21.4 0.4 0.1 27.2 0.4 0.2 25.7 25.6 26.2 30.6 9.9 25.9 9.8 9.3 9.5 11.6 9.8 ______0.82 1.09 0.08 5.66 29.19 23.42 Absent 0.23 Absent 0.90 ______2. Plant cover differences between 1958 and 1996, shown as percent change ( 1. Summary of current dominant perennial plant species, according to cover, on Fishtail Mesa within the shrub-type and tree-typ on Fishtail 1. Summary of current dominant perennial plant species, according to cover, Plant species cover mesa-wide cover mesa-wide shrub-type shrub-type tree-type tree-type ABLE ABLE T T Juniperus osteosperma Combined cover/elb arm 33.95 52.37 Pinus edulis Artemisia tridentata Plant species 1958 confidence limit limits mean limits 1958 confidence limit limits mean limits Ephedra torreyana (7.5 elbs). Values are expressed as both absolute cover and relative percent cover based on line intercept (LI) and Parker loop as both absolute cover and relative percent based on line intercept (LI) Parker are expressed (7.5 elbs). Values Pinus edulis Juniperus osteosperma fendleriana Poa Bouteloua gracilis baccata Yucca Ephedra torreyana Shepherdia rotundifolia Bare ground (incl. litter) 70.2 69.1 75.8 73.3 63.7 62.1 Artemisia tridentata fendleriana Poa Mesa. Both vegetation types are represented by 4 sample sites (elbs) containing two 120-m line intercepts at right angles to on changes in cover were calculated for selected dominant plant species and total vegeta arm and one 120-m line intercept. Percent mean of the intercepted plant cover per elb arm (in units meters arm) and, for 1996 data, upper and lower confid from Ja The 1958 values shown were back-calculated in the text. ated with each elb arm were not available for 1958 as explained tions could not be made. 168 WESTERN NORTH AMERICAN NATURALIST [Volume 61 based on % ∆ = 7 elb arms) n ot available for 1958 as explained in the text. The in the text. ot available for 1958 as explained 21.5 –9.7 5.3 20.2 17.718.921.5 –47.0 –37.1 –58.9 –3.0 6.2 –9.2 41.0 49.2 40.4 4.70.9 66.7 –92.9 223.3 –28.6 380.0 35.7 95% 1996 lower 1996 upper lated for selected dominant plant species and total ± ± ± ± ± ± ± samples at 0.3-m intervals along each elb arm baseline. based on Year % ∆ = 8 elb arms) ( Tree-type n 1996 lower 1996 upper 1996 ), based on the Parker loop method, between 1958 and 1996 in the shrub-type and tree-type on Fishtail Mesa. Four sample Mesa. Four loop method, between 1958 and 1996 in the shrub-type and tree-type on Fishtail ), based on the Parker % ∆ Shrub-type ( 11.8 –24.0 –14.6 –5.1 144.0 151.6 3.21.0 — — — — — — 43.7 43.3 46.4 39.3 10.7 –28.9 –19.0 –9.1 40.2 39.0 0.9 –64.3 –4.2 –33.3 1.4 1.0 6.8 43.3 270.0 496.7 3.0 9.7 95% confidence 1996 confidence confidence 1996 confidence confidence ± ± ± ± ± ± ± Plant cover as estimated by mean number of Parker loop hits per elb arm and percent change between 1958 1996 Plant cover as estimated by mean number of Parker 1996 Year 2.4 2.3 3.0 11.1 107.9 87.4 AbsentAbsent 1.6 0.6 ______3. Plant cover differences (percent change = ABLE T Plant species 1958 confidence limit limits mean limits 1958 limit limits mean limits Pinus edulis Juniperus osteosperma Combined hits/elb arm 125.0 106.8 sites (elbs) represent both vegetation types. Each elb contains 2 sequences, at right angles to one another, of 400 Parker loop of 400 Parker sites (elbs) represent both vegetation types. Each elb contains 2 sequences, at right angles to one another, One elb in the tree-type contained only one arm and therefore only one sequence of Parker loop samples. Percent change is calcu loop samples. Percent One elb in the tree-type contained only one arm and therefore sequence of Parker loop data associated with each elb arm were n loop hits per elb arm. Parker vegetation cover based on the mean number of Parker from Jameson et al. (1962), but confidence interval calculations could not be made. 1958 values shown were back-calculated Ephedra torreyana Artemisia tridentata Poa fendleriana Poa 2001] RESURVEY OF FISHTAIL MESA 169 whereas in 1996 intercepted cover of Pinus However, Pinus and Juniperus were not com- was observed on a single elb arm LI (elb 4R) pletely faithful to the tree-type. Pinus was pre- and Juniperus was observed in 2 (4L and 5R). sent in at least one shrub-type elb arm LI in Artemisia exhibited an overall decrease; ∆% moderate abundance (13% AC, 12% RC). Juni- varied between approximately –30% and –11%. perus was present in 2 shrub-type elb arm LIs Mean combined plant cover per LI increased (0.1% AC, 0.4% RC). Poa was absent from approximately 45% to 64% (Table 2). In the both arms of one tree-type elb arm LI and also tree-type, intercepted cover of Poa increased occurred in one shrub-type elb arm LI. Other- sizably by 1760% to 4160%. The cover of wise, it was faithful to the tree-type. Ephedra appears to have decreased in the DECORANA ORDINATION.—The first 2 tree-type by 98% to –18%. Determination of axes produced by DCA (Figs. 4, 5) accounted changes in the abundance of the other plant for 70.3% of the variation within the original species listed under the tree-type, as well as species-samples matrix. Although this is not as mean total plant cover per LI, is problematical important as it would be in a principal compo- as the statistics show (Table 2). nent analysis (Kent and Coker 1992), it does Values of ∆% derived from PL sampling indicate a successful ordination in the first 2 (Table 3) were largely comparable, with respect dimensions. Only 4.5% more variation was to general patterns, to corresponding values accounted for by the addition of a 3rd axis. derived from the LI sampling (Table 2). There The efficacy of the ordination in representing were 2 exceptions from the shrub-type. the original species by samples matrix in only Ephedra apparently decreased in cover over 2 dimensions is corroborated by R2 values the 38-year time interval and mean combined resulting from comparisons of ecological dis- plant cover per LI increased. PL-based results tance between the original data matrix and from the tree-type are generally conformable ordination distances (Table 5). The cumulative with those derived from LIs even though spe- R2 increases from 0.870, when only the 1st cific values differ. PL observations also con- ordination axis is considered, to 0.970, when firmed the encroachment of Pinus and Junipe- both ordination axes are used to calculate rus on the shrub-type elbs. ordination distances. Note the close corre- TWINSPAN RESULTS.—We found that sev- spondence between the species order (bottom eral of the more commonly observed species, to top) in the TWINSPAN 2-way ordered though important overall, were not useful as table (Table 4) and the species scores (left to differential or association-defining species. right) along DCA axis 1 in the species ordina- These ubiquits included Poa, Opuntia, Artem- tion (Fig. 4). The stand ordination (Fig. 5) isia, and Ephedra. The first 2 species were revealed 5 major elb arm groups that corre- present in most elb arm LI samples for both sponded nicely with their arrangement in the tree- and shrub-types. Opuntia was absent TWINSPAN 2-way ordered table. only from 2 elb arm LIs, and Ephedra was WOODLAND TREE DEMOGRAPHICS.—In 1996 present in all elb arm LI samples except one Pinus density in the shrub-type was 17 ± 15 (Table 4). These common and, in the case of trees ⋅ ha–1, whereas Juniperus density was 17 Artemisia, dominant species did not define the ± 19. Total estimated tree density within the shrub-type vegetation on Fishtail Mesa since shrub-type was 34 ± 31 trees ⋅ ha–1. However, they also formed the understory of the Pinyon- these estimates are based on only a few sam- Juniper Woodland. In general, Poa, Artemisia, pled trees, 10 each of Pinus and Juniperus. and Ephedra tended to increase in relative The density of Pinus and Juniperus in the tree- importance from the tree-type to the shrub- type (n = 7 elb arms) was 471 ± 196 and 250 ± type and were therefore classified by TWIN- 113 trees ⋅ ha–1, respectively. Total estimated SPAN with the shrub-type species group after tree density within the tree-type was 720 ± the 1st (primary) TWINSPAN division. Opun- 306 trees ⋅ ha–1. tia showed no apparent trend in abundance It is difficult to compare estimates of tree values but had relatively high importance in density observed in 1958 and 1996. The 1958 tree-type (Table 4). Therefore, it was classified data were reported by 186-m2 (2000-ft2) sec- into the tree-type species group. tions within 2 soil types, a limestone and Differential species for the tree-type included sandy limestone upland (elbs 1, 2, 3, 5, 6, 7) and primarily Pinus, Juniperus, and Poa (Table 4). cherty ridges (elb 8). Apparently, the alluvial 170 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 4. Two-way ordered table produced by TWINSPAN in PC-ORD. The 2 heavy solid lines mark primary stand dotted line marks a quaternary division. Tree-type samples are in the upper left with dark gray shading, while shrub-

______Sampling units on Fishtail Mesa ______Tree-type elbs Elb Elb Elb Elb Elb Elb Elb Plant species 8 6L 6R 7L 7R 3L 3R Shepherdia rotundifolia – 4––– 44 Lesquerella gordonii – –––– 1– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Arceuthobium divaricatum – –1–– –– Cowania mexicana – 411– –– Echinocactus triglochidiatus – 1––– –– Phoradendron juniperinum –24–––– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Yucca baccata 7 544– –– – Juniperus osteosperma 6 7887 56 Pinus edulis 4 6888 88 ------Coryphantha vivipara 1 –––– –– Fallugia paradoxa 4 –––– –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Bouteloua gracilis 7 2211 –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Castilleja chromosa – –––– 1– Opuntia polyacantha 1 3111 33 ______- Phlox longifolia – –1–– –– Astragalus calycosus – 11–1 11 Poa fendleriana 5 5566 44 Artemisia tridentata 7 7756 88 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Euphorbia fendleri – –––– –– Penstemon sp. – –––– –– Achnatherum hymenoides – –––– –– Sphaeralcea grossulariaefolia – –––– –– Lomatium nevadense – –––– –– ------Leucelene ericoides – –1–– –– Astragalus pinonis – –111 –1 Hymenoxys richardsonii – –1–– –– Ephedra torreyana 4 112– 41 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Kraschenninkovia lanata – –––– –– ...... Eriogonum corymbosum – –––1 –– ------Erigeron concinnus – –––– –– Arabis perennans – –––– –– Coleogyne ramosissima – –––– –– Stipa speciosa – –––– –– Astragalus newberryi – –––– –– Atriplex canescens – –––– –– Stipa comata – –––– –– Gutierrezia sarothrae – –––– –– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Chrysothamnus greenei – –1–– –– Streptanthus arizonicus – –––– –1 Sitanion hystrix – 1––– –1 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – Stands division level 0 0000 00 0 1111 11 0000 11 – - 2001] RESURVEY OF FISHTAIL MESA 171 and species divisions. Heavy dashed lines mark secondary divisions. Dashed lines mark tertiary divisions and the fine type samples are in the lower right with light gray shading.

______Sampling units on Fishtail Mesa Shrub-type elbs ______Species Elb Elb Elb Elb Elb Elb Elb Elb division 2L 4L 5L 5R 4R 1L 1R 2R level – – – – – – – – 11111 – – – – – – – – 11111 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – 11110 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 11101 – – –1–4 – ––– 11101 – – – – 6 – – – 11101 ------– – – – – – – – 11100 – – – – – – – – 11100 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 3––– – ––– 110 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –––– – 1–– 10 ______2–11 1 34– 10 –1–– – ––– 01 1111 1 1–1 01 6576 5 656 01 9999 9 999 01 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 1 – – – – – 0011 – – – 1 – – – – 0011 1 – 1 – – – – – 0011 1 – – – – – – – 0011 1 – – – – – – – 0011 ------– – – 1 1 – – – 0010 – 1 3 1 4 – – – 0010 –1–1 – –11 0010 2 4 4 3 3 4 4 1 0010 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 2 1 – – – – 2 – 00011 ...... 1 – 1 1 1 2 3 1 000101 ------– – – – – – – 1 000100 – – – – – – – 1 000100 – – – – – – – 3 000100 – – – – – – 2 – 000100 –––– 1 1–1 000100 –––– – 21– 000100 –––– – 51– 000100 –––– 1 5–3 000100 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 4 – 0000 –––– 1 1–3 0000 – 1 – – – 4 1 3 0000 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – 1111 1 111 0000 0 111 0000 1 – – 172 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 4. Detrended correspondence analysis—species plot—of the current vegetation on Fishtail Mesa. See Appendix for alpha code index for scientific and common names. soil type (elb 4) was not included in the 1958 mation of tree density within size classes in study. Also, trees <0.9 m high were not sam- the manner of Goff and West (1975), the distri- pled. After eliminating trees <0.9 m from our bution curve was fitted, with significant results, data and employing Jameson et al.’s (1962) to a 4th-degree polynomial as shown in the 2 reporting scheme, we found approximately 5.0 inset graph of Figure 6 (R = 0.96; F[α=0.05,;3,7] Pinus trees in limestone uplands, identical to = 52.5; P = 3.6E-05). The size-density rela- that reported for 1958. Similarly, we found 3.0 tionship for Juniperus was best fitted by a 2nd- Juniperus trees in limestone uplands compared degree polynomial, but the regression was not 2 to 4.2 for 1958. We found 1.0 Pinus trees on significant (R = 0.19; F[α=0.05;3,7] = 2.075; P cherty ridges, compared to 3.2 reported for = 0.196) and quite anomalous in terms of the 1958; there were no Juniperus trees in 1996 “rotated sigmoid-curve” ideal (Fig. 6, inset). compared to 3.1 in 1958. The relationship is actually somewhat bimodal, In 1996 we found substantially more Pinus with a peak at the 1–5 cm and again at the trees in the <1 cm stem diameter class in the 15–20, 20–25, and 25–30 cm classes. Density tree-type than Juniperus in any stem diameter depressions occurred in the 5–10 and 10–15 class (Fig. 6). Establishment of seedling Junipe- cm diameter classes and at the largest diame- rus was sparse to nonexistent. After thorough ter classes, i.e., >30 cm (Fig. 6, inset). This sampling, only 3 Juniperus seedlings were dis- pattern suggests that recruitment to the Jun- covered throughout the elbs in the tree-type iperus population on Fishtail Mesa is low and vegetation, and none were discovered in shrub- perhaps pulselike. type elbs. In general, numbers of both trees in The age-size (basal diameter) relationship, the shrub-type were low for all classes, and for which age was directly determined, was age-size relations could not be ascertained. conducted for 40 Pinus. These data were fitted The size-density distribution curve for Pinus, to the Chapman-Richards function. Both upper calculated from observations gained from all and lower 95% confidence limits are shown to tree-type elb strip plots, exhibits a classic, assess the possible error in the diameter esti- inverse J-shaped distribution curve (Fig. 6). mate. Observations were analyzed both as a This type of curve indicates plants with high complete set (Fig. 7a) and separately for shrub- reproduction, where the probability of death type trees and tree-type trees (Fig. 7b). The decreases exponentially as plants age (Pearl age-size relation as predicted by the Chap- 1928, Begon et al. 1996). After log10 transfor- man-Richards function was significant, but 2001] RESURVEY OF FISHTAIL MESA 173

Fig. 5. Detrended correspondence analysis—elb plot—of the current vegetation on Fishtail Mesa. with moderate scatter around the regression shrub-type. In the tree-type change determi- line. Separate analysis improves the fit to the nation, except for a substantial increase in Chapman-Richard function (Fig. 7). cover of Poa, is problematic, but the cover of REPHOTOGRAPHY.—Panoramic rephotogra- most plants has probably remained stable. phy of the shrub-type shows little change in We found that Poa was a significant sec- standing dead juniper snags and growth of the ondary member of shrub- and tree-types on surrounding shrub vegetation. Only finger- Fishtail Mesa. Its absence on the mainland in sized tips of snag branches have been removed the postsettlement era (Jameson et al. 1962, in the past 38 years. Before-after photographs Schmutz et al. 1967) was probably due to land of elb 5R (Fig. 8) are shown as an example. It management practices. Whereas Poa had 0.06% is clear, however, from the increase in pinyon and 0.07% absolute cover in shrub- and tree- tree density in both the foreground and back- types in 1958 (Jameson et al. 1962), we found ground of the 1996 photographs, compared with 2.6% and 2.5%, respectively, in 1996. The dra- the 1958 photographs, that Pinus trees are matic increase in cover values of Poa between invading or reoccupying this shrub-type site. 1958 and 1996 may be a response of the plant to climatic changes, such as recovery from the DISCUSSION 1950s drought (Neilson 1986), protracted absence of fire, or a combination of such factors. Comparison of 1958 and 1996 data from LI Results of change determination derived observations shows that species cover compo- from PL observations for the 4 major species sition of Fishtail Mesa vegetation types, with a in shrub- and tree-types are likewise difficult few notable exceptions, has not changed appre- to interpret but parallel LI results. Where ciably over the past 38 years. Most observed exceptions occured, such as the contradictory changes in plant cover do not appear to be sig- results for change in combined plant cover nificant (Tables 3, 4) and may even reflect dif- within the shrub-type over the time period of ferences in measurement precision and obser- concern, the PL methodology is probably sus- vation technique of field personnel. Within the pect due to its inherent inefficiency relative to shrub-type, Artemisia has declined, whereas direct cover-measuring techniques such as the Poa has increased. Absolute cover of trees LI (Bonham 1989). (Pinus and Juniperus) increased in the shrub- Since TWINSPAN is based on progressive, type between 1958 and 1996, but only in 2 refined reciprocal averaging, species and stand elbs. Other species like Ephedra, Opuntia, and orderings in the 2-way ordered table (Table 4) Gutierrezia have decreased since 1958. Pinus reflect, to an extent, an ecological gradient. In and Juniperus appear to have increased in the general, the 2-way ordered table classified 174 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 5. Summary statistics for the eigen-analysis component of the Fishtail Mesa DCA. Coefficients of determina- tion (R2) relate ordination distances to the distance metric of the original data matrix. The distance metric employed was percent similarity, otherwise known as Czekanowski’s coefficient (sometimes mistakenly referred to as Sørenson’s coeffi- cient or Jaccard’s coefficient [Kent and Coker 1992]), as defined in the Methods section. Distance comparisons between the original and ordination matrices were based on the n(n–1)/2 possible comparisons for 15 samples.

Eigen-analysis ______DECORANA axis number statistcs 1234 Eigenvalue 0.496 0.106 0.039 0.019 Percent of total 57.904 12.409 4.540 2.223 Cumulative percent 57.904 70.313 74.854 77.077 Coefficients of determination (R2)—incremental 0.870 0.100 –0.008 — Coefficients of determination (R2)—cumulative 0.870 0.970 0.962 — stands and species according to an inferred there were no distinct species subgroups due moisture gradient, with less xeric-adapted to the influence of the ubiquits. species and plant associations in the upper left We interpret the species sequence along quadrant of Table 4, replaced by more xeric DCA axis 1 as a reflection of a complex moisture species and plant associations in the lower gradient. We attribute this to the previously right quadrant. Stand order from left to right described rim effect. Species typical of the across the top of the table reflects one compo- more xeric shrub-type vegetation (group A, nent of this moisture gradient. Less xeric tree- Fig. 4) were gradually supplanted from left to type vegetation in the mesa interior is re- right along axis 1 by plant species more typical placed by more xeric shrub-type vegetation of the tree-type vegetation (groups C, D, E; along the mesa rim and exposed interior sites. Fig. 4). Ubiquits and occasional species with Elb 4R was unique in that the transect ran little or no faithfulness to either vegetation across a small valley with deep, fine alluvial type were aggregated in group B. fill. Elbs 1L, 1R, and 2R were located on the Species typical of the shrub-type and ubiq- southern, most exposed tip of the mesa, sub- uit/occasional species showed little dispersal ject to warm, dry air rising from the canyon along DCA axis 2 (Fig. 4), whereas tree-type below. species (groups C–E) are well dispersed along With the possible exception of Eriogonum the axis. We interpret DCA axis 2 as possibly corymbosum (wild buckwheat), no plant species reflecting a gradient of soil textures. The in the shrub-type group could be interpreted agglomeration of species in group C (Yucca, as a differential species. The only abundant Poa, Coryphantha vivipara var. arizonica [pin- species in this group were the ubiquits dis- cushion cactus], and Fallugia paradoxa [Apache cussed above, which tended to reach their plume]) are more typical of sample sites with greatest levels of abundance here. Only Stipa rocky, clayey soils, often with bedrock close to comata (needle-and-thread), previously mis- the surface. Species comprising group E identified by Jameson et al. (1962) as S. spe- (Opuntia spp., Castilleja chromosa [Indian paint- ciosa, and Gutierrezia exhibited RC values in brush], Shepherdia rotundifolia, Pinus, and the 8–16% category (i.e., class 5 in Table 4). Lesquerella gordonii [Gordon bladderpod]) Thus, the shrub-type is defined more by the were observed to be more typical of fine- to absence of Pinus and Juniperus rather than moderately fine-textured soils. any special associations of differential species The stand ordination (Fig. 5) reflects the with a high preference for this vegetation same inferred ecological gradients as the type. TWINSPAN results and species abun- species ordination. All shrub-type elb arms dance and constancy patterns discussed above were clustered on the left of the ordination show a clear demarcation at the primary divi- (xeric), whereas tree-type elb arms were sion level between woodland (tree-type) species aggregated, though more loosely, on the right and samples and shrub-steppe (shrub-type) (less xeric). Elb 4R group II (Fig. 5) was some- species and stands. Not surprisingly, Pinus, what distinct from the main group of shrub- Juniperus, and Yucca form a distinct associa- type elbs (group I) just as it was in the tion within the tree-type. In the shrub-type TWINSPAN results (Table 4). Elb 4R was the 2001] RESURVEY OF FISHTAIL MESA 175

Fig. 6. Tree density and size (diameter) classes in centimeters for tree- and shrub-type elbs for Pinus and Juniperus. only shrub-type elb that had a substantial in density of Pinus beginning with the seed- amount of Pinus cover, and it may be undergo- ling class (<1 cm) declined smoothly, and a ing reoccupation or invasion. Relative cover of well-defined plateau region at the intermedi- both Pinus and Juniperus was high throughout ate size classes never occurred (Fig. 6). This this sample group, and soil textures varied in suggests only a moderate decline in mortality composition. between intermediate size classes. In other The depiction of tree reproduction in 1996 words, the Pinus population at Fishtail Mesa (Fig. 6) is that of a large number of Pinus may be approaching an all-aged condition, but seedlings and immature plants, with low it is not there yet. Assuming that no cata- reproduction of Juniperus. A clearer picture of strophic changes occur in the future, such as a the tree age-size relationship emerged when stand-replacing fire, the Pinus population in within-class tree density data were log10 trans- the tree-type vegetation of this relict area may formed (Fig. 6). The Pinus size-density rela- eventually become fully mature and all-aged. tionship approximated a “rotated sigmoid Almost all tree cores taken from tree-type curve” (Goff and West 1975, West et al. 1981) vegetation fell below the regression line in typical of an all-age stand with differential Figure 7 and therefore show some degree of recruitment from one size class to the next. growth suppression. This may indicate that Mortality is high and growth rates are slow in intraspecific competition, as described by the smaller size classes, resulting in a very Tausch and Tueller (1990), is an active factor steep curve. Recruitment to the canopy, how- within the Pinus population of the tree-type. ever, increases the growth rate and reduces Not surprisingly, the majority of Pinus cores mortality. As a result, the slope of the curve collected from the shrub-type lie above the decreases. High germination and seedling regression line, showing increased growth establishment followed by space and light rates over their woodland counterparts. competition result in rapid mortality and It has been shown that size-age patterns of reduced growth of young stems in older stands Pinus populations are more accurately reflected (West et al. 1981). On Fishtail Mesa the decrease when suppressed trees are removed from 176 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 7. Pinyon age-size relationship (A) using basal diameter and annual ring counts collected from trees adjacent to and outside all 8 elb arms and (B) according to shrub-type and tree-type. analysis (Tausch and Tueller 1990). In our re- 0.659). First, there was great improvement in search we felt the pattern of growth suppres- R2 values for the curve fits (R2 = 0.87 for the sion in relation to location and vegetation type shrub-type Pinus and R2 = 0.76 for the tree- was an important issue; thus, the entire data type Pinus). Second, Pinus growing within the set was retained. However, we did separate woodland communities on Fishtail Mesa were Pinus cores taken from the tree-type from generally growth-suppressed relative to site those taken from the shrub-type and removed location and community type, but only in com- the 5 elb 4 samples from the latter (Figs. 7a, parison to trees located within the shrub-type. 7b). Both data subsets were fitted to the Chap- Thus, different trees of similar age within the man-Richards function individually (R2 = study area may exhibit basal diameters that 2001] RESURVEY OF FISHTAIL MESA 177

A

B

Fig. 8. Landscape photographs of shrub-type elb 5, right arm, in (A) 1958 and (B) 1996. Note that Pinus density and size of individuals have increased throughout the depicted scene. Standing weathering snags in the mid-ground are still present. differ by as much as 20 cm. This is no doubt lyzed. Since 1850 is 146 years prior to our due to differences in microsite characteristics field research completed in 1996, the basal and perhaps competitive suppression from diameter estimate at 146 years ± the 95% con- adjacent dominant Pinus, as described by fidence limits is a reasonable value for attribu- Tausch and Tueller (1990). tion of presettlement, postsettlement, and in- Based on the evidence given in Figure 7b, determinate status. In the tree-type the basal and if 1850 is taken as a presettlement date, diameter (BD) estimate for a Pinus 146 years old ± then 5 Pinus core samples taken from the tree- (BDest[146]) is 22.4 4.7 cm. Pinus with BDs type and only 1 from the shrub-type represent greater than 27 cm are probably presettlement presettlement Pinus within the sample ana- trees, while those with BDs smaller than ca 17 178 WESTERN NORTH AMERICAN NATURALIST [Volume 61 cm are probably postsettlement trees. Trees studied details of 1940 and 1994 aerial pho- with BDs in between are indeterminate. Like- tographs of the south end of Fishtail Mesa, wise, for Pinus growing in the shrub-type, the where locations of individual tree canopies ± BD estimate (BDest[146]) is 30.9 7.4 cm. Pinus can be seen in both photographs. Patches in growing in the shrub-type with a BD greater the 1940 aerial photograph that lacked tree than ca 38 cm are probably presettlement cover supported Sagebrush Steppe vegetation. trees, and Pinus smaller than ca 23 cm are The same areas in the 1994 aerial photograph probably postsettlement trees. Trees with BDs showed tree canopies, suggesting that since in between are indeterminate. 1940 Pinus and/or Juniperus have colonized These findings strengthen our hypothesis the patches. We surmise that Artemisia will that Pinus are actively reoccupying the shrub- decline under the woodland canopy as well as type on Fishtail Mesa. Exceptions like elb 2 in the shrub-type, albeit perhaps more slowly are explained on the basis of site characteris- in the latter. In the long term of 100–300 years, tics involving the rim effect that creates a vegetation dynamically responds to fire or moisture gradient that is reflected in the vege- reflects changing climatic conditions. At this tation as revealed by indirect ordination (Figs. point in time, we consider Fishtail Mesa to be 4, 5). On an isolated mesa in the Grand Canyon, a Sagebrush Steppe with slowly expanding the most noticeable rim effect should be on Pinyon-Juniper Woodland patches. In the ab- the windward side. In the case of Fishtail sence of fire, Pinus and Juniperus could even- Mesa, this is the southwestern portion (Fig. 3, tually reoccupy most of the mesa and the extreme lower left). The southern tip of the Sagebrush Steppe would exist as patches near mesa is very narrow, without an interior, and the rim. for the most part dry and devoid of woodland. In conclusion, we found that several of the In general, throughout Fishtail Mesa wood- more important species components of Fish- land is noticeably denser away from the south- tail Mesa’s vegetation types have not signifi- west rim, strongly implicating the rim effect. cantly changed over the last 38 years. But, some Under the current climatic regime, it is un- species have undergone differential reduc- likely that Pinus would ever establish there. tions in cover, like Artemisia, or increases, like Juniperus and Pinus have possibly reoccu- pied the Sagebrush Steppe on Fishtail Mesa Poa. We surmise that Fishtail Mesa has experi- for millennia, and it appears that the mesa’s enced repeated waves of Juniperus establish- vegetation is presently in the middle of such a ment within the Artemisia-Poa steppe, fol- cycle. Fire has apparently not been an impor- lowed by a secondary wave of establishment tant factor for many years on Fishtail Mesa. by Pinus. Subsequently, reproduction of Junipe- Based upon the apparent stability of vegeta- rus in the densely wooded areas declined and, tion on Fishtail Mesa as seen by elb strip concomitantly, germination and seedling estab- methodologies, direct observation, and photo- lishment of Pinus increased in the maturing graphic interpretation, fires on Fishtail Mesa juniper woodland. Eventually Pinus may be- are apparently infrequent to rare. The last fire come dominant in number, height, and canopy on the mesa may date from the turn of the cover. Artemisia beneath the tree canopy will century or earlier. It is entirely possible that decline but, because of the relatively open remnant standing snags on the mesa could nature of the canopy, will always be an associ- actually be remnants of trees killed during the ate species and the dominant shrub. Following major drought which took place in the South- episodic events of drought, parasitism, disease, west during the 1950s (Neilson 1986). Also, or lightning-caused wildfire, wooded areas none of the 40+ Pinus cores collected for pop- will revert to a Sagebrush Steppe if residual ulation age-size determination showed any sagebrush plants or their seeds remain. Por- evidence of fire scarring. Fire may have tions of Fishtail Mesa are representative exam- caused the death of the original trees; how- ples of a dynamic, unmanaged, all-age stand (or ever, drought, mistletoe infestation, or insect nearly so) of Pinyon-Juniper Woodland. Arid- attack cannot be ruled out. ity near the mesa rim due to the rim effect will On a shorter time scale, aerial photographs ensure, at least during this climatic era, that provide corroboration of increasing tree cover some Artemisia-Poa steppe vegetation will on Fishtail Mesa over the last 50–60 years. We always persevere on Fishtail Mesa. 2001] RESURVEY OF FISHTAIL MESA 179

Retaining examples of pristine natural envi- D. Smith, associate editor, Western North ronments is one of the National Park Service’s American Naturalist, as well as those from one missions. It is important for inspiration, edu- anonymous reviewer. Funds for the publica- cation, and interpretation, as well as for park- tion of this manuscript were provided by a based and academic study of research natural grant from the Grand Canyon Association areas. These relict areas offer baselines for through the 1999 Annual Grants Program gauging impacts occurring elsewhere, defining administered by Grand Canyon National Park. productive potentials of woodlands, providing sanctuaries for native species, and studying LITERATURE CITED ecological processes (Hanson 1939, Callahan 1984, 1991, Van Pelt and Tuhy 1991). The AXELROD, D.I. 1950. Evolution of desert vegetation in western North America. Pages 217–298 in D.I. Axel- study of dynamic ecology, or succession, is rod, editor, Studies in Late Tertiary paleobotany. often hampered because of the length of time Carnegie Institute of Washington Publication, Wash- involved, the absence of control over desirable ington, DC. communities, and the difficulty of securing BEGON, M., J.L. HARPER, AND C.R. TOWNSEND. 1996. Ecology: individuals, populations, and communities. long-term management cooperation (Clements Blackwell Science, Oxford, U.K. 1930). Fishtail Mesa offers an excellent natural BETANCOURT, J.L. 1990. Late Quaternary biogeography of area research site or benchmark for long-term the Colorado Plateau. Pages 259–292 in J.L. Betan- study and surveillance of a Pinus-Juniperus court, T.R. Van Devender, and P.S. Martin, editors, Packrat middens, the last 40,000 years. University of woodland and Artemisia-Poa steppe. Its large Arizona Press, Tucson. size makes it particularly well suited for such BEYMER, R.J., AND J.M. KLOPATEK. 1992. Effects of graz- an effort. The descriptive historical record ing on cryptogamic crusts in pinyon-juniper wood- begins in the 1930s, with aerial photography lands in Grand Canyon National Park. American Midland Naturalist 127:139–148. available from 1940. Permanent study areas BLACKBURN, W.H., AND P. T. T UELLER. 1970. Pinyon and with fixed photo sites were established in juniper invasion in black sagebrush communities in 1958. Our study recorded additional vegeta- east-central Nevada. Ecology 51:841–848. tion, soil, faunal, and GPS data. Furthermore, BONHAM, C.D. 1989. Measurements for terrestrial vegeta- tion. Wiley and Sons, New York. field data, notes, photography, herbarium speci- CALLAHAN, J.T. 1984. Long-term ecological research. Bio- mens, rectified maps, and electronic data are Science 34:363–167. archived in the Grand Canyon National Park’s ______. 1991. Long-term ecological research in the United Museum Collections where they will receive States: a federal perspective. Pages 9–21 in P. G . Risser, editor, Long-term ecological research: an inter- permanent curatorial care. We hope that future national perspective. Wiley and Sons, New York. surveys will build upon these efforts to pro- CANFIELD, R. 1941. Application of line interception in vide further insight into changes in naturally sampling range vegetation. Journal of Forestry 39: functioning ecosystems of the Pinyon-Juniper 388–194. CLEMENTS, F.E. 1930. The relict method in dynamic ecol- Woodland and Sagebrush Steppe. ogy. Ecology 22:39–67. CLUTTER, J.L., J.C. FORTSON, L.V. PIENAR, G.H. BRISTER, ACKNOWLEDGMENTS AND R.L. BAILEY. 1983. Timber management, a quan- titative approach. Wiley and Sons, New York. DESPAIN, D.W. 1989. Radial growth relationships in Utah The resurvey of Fishtail Mesa benefited from juniper ( Juniperus osteosperma) and pinyon pine the interest, enthusiasm, and participation of (Pinus edulis). Doctoral dissertation, University of Donald (Don) Jameson, the previous, princi- Arizona, Tucson. pal ecologist. Don was actively involved, first DRISCOLL, R.S. 1958. A loop method for measuring ground cover characteristics on permanent plots. Journal of during the 2 years of correspondence about Range Management 11:94. the study and then during the week of data GOFF, F.G., AND D.C. WEST. 1975. Canopy-understory inter- collection in May 1996. He collected all Parker action effects on forest population structure. Forest loop data and answered numerous questions Science 21:98–108. GREEN, C.R., AND W. D. S ELLERS. 1964. Arizona climate. about methodology. His participation, experi- University of Arizona Press, Tucson. ence, and historical perspective made this HANSON, H.C. 1939. Check areas as controls in land use. resurvey especially meaningful. We were sad- Science Monthly 48:130–146. dened when Don passed away on 30 August HALVORSON, W.L. 1972. Environmental influence on the pattern of plant communities along the North Rim of 1998. We appreciate the constructive comments the Grand Canyon. American Midland Naturalist of our reviewers, Robert M. Webb and Stanley 87:223–235. 180 WESTERN NORTH AMERICAN NATURALIST [Volume 61

HELTSCHE, J.F., AND N.E. FORRESTER. 1983. Estimating USDA Soil Conservation Service Technical Bulletin species richness using the jackknife procedure. Bio- 1169. metrics 39:1–11. PEARL, R. 1928. The rate of living. Knopf, New York. HERMANN, R. 1989. Long-term monitoring for environ- SCHMUTZ, E.M., A.E. DENNIS, A. HARLAN, D. HENDRICKS, mental change in national parks. Abstract, Ecologi- AND J. ZAUDERER. 1976. An ecological survey of cal Society of America Annual Meeting, Toronto, Wide Rock Butte in Canyon de Chelly National Ontario. Monument, Arizona. Journal of Arizona Academy of HILL, M.O. 1979a. TWINSPAN: a FORTRAN program for Science 11:114–125. arranging multivariate data in an ordered two-way SCHMUTZ, E.M., C.C. MICHAELS, AND B.I. JUDD. 1967. table by classification of the individuals and attri- Boysag Point: a relict area on the North Rim of Grand butes. Microcomputer Power, Ithaca, NY. Canyon in Arizona. Journal of Range Management ______. 1979b. DECORANA: a FORTRAN program for 20:363–369. detrended correspondence analysis and reciprocal SELLERS, W.D., AND R.H. HILL. 1974. Arizona climate, averaging. Microcomputer Power, Ithaca, NY. 1931–72. University of Arizona Press, Tucson. HOPKINS, R.L. 1990. Kaibab Formation. Pages 225–245 in STOKES, M.A., AND T.L. SMILEY. 1968. An introduction to S.S. Beus and M. Morales, editors, Grand Canyon tree-ring dating. University of Chicago Press, geology. Oxford University Press, New York. Chicago, IL. JAMESON, D.A. 1965. Arrangement and growth of pinyon STUTZ, H.C. 1978. Explosive evolution of perennial Atriplex and one-seed juniper trees. Plateau 37:121–127. in western America. Great Basin Naturalist Memoirs JAMESON, D.A., J.A. WILLIAMS, AND E.W. WILTON. 1962. 2:161–168. Vegetation and soils of Fishtail Mesa, Arizona. Ecol- TAUSCH, R.J., AND P. T. T UELLER. 1990. Foliage biomass ogy 43:403–410. and cover relationships between tree- and shrub- JEFFRIES, D.L., AND J.M. KLOPATEK. 1987. Effects of graz- dominated communities in pinyon-juniper wood- ing on the vegetation of the blackbrush association. lands. Great Basin Naturalist 50:121–134. Journal of Range Management 40:390–392. TAUSCH, R.J., N.E. WEST, AND A.A. NABI. 1981. Tree age JOHNSON, D.W. 1983. Ecology and biogeography of iso- and dominance patterns in Great Basin pinyon- lated butte communities on the Colorado Plateau. juniper woodlands. Journal of Range Management Doctoral dissertation, University of Colorado, Boulder. 34:259–264. KENT, M., AND P. C OKER. 1992. Vegetation description and THATCHER, A.P., AND V.L. HART. 1974. Spy Mesa yields analysis; a practical approach. Wiley and Sons, New better understanding of pinyon-juniper in range eco- York. system. Journal of Range Management 27:354–357. KOVACH, W.L. 1998. MVSP Plus, version 3.0, user’s manual. THORNTHWAITE, C.W. 1931. The climates of North Amer- Kovach Computing Services, Pentraeth, Wales. ica according to a new classification. Geographical MAGURRAN, A. 1988. Ecological diversity and its measure- Review 21:633–655. ment. Croom Helm, London, U.K. TUHY, J.S., AND J.A. MCMAHON. 1988. Vegetation and MASON, L., AND N.E. WEST. 1970. Timber Top Mesa: a relict plant communities of Glen Canyon National relict area in Zion National Park. Utah Academy Recreation Area. Final report for contract CX1200- Proceedings 47:284–285. 6-B-76, submitted to Glen Canyon National Recre- MASON, L.R., H.M. ANDREWS, J.A. CARLEY, AND E.D. ation Area, National Park Service, Page, AZ, by Utah HAACKE. 1967. Vegetation and soils of No Man’s Land State University, Logan, UT. Mesa relict area, Utah. Journal of Range Manage- TURNER, R.M. 1982. Great Basin desertscrub. Desert ment 20:44–49. Plants 4:145–155. MCCUNE, B., AND M.J. MEFFORD. 1999. PC-ORD. Multi- VAN PELT, N.S., AND J.S. TUHY. 1991. Relict vegetation variate analysis of ecological data. Version 4.0. MjM sites: urgent inventory need for desert parks. Park Software, Gleneden Beach, CA. Science 11(3):20. MCKEE, E.D. 1938. The environment and history of the VAN PELT, N.S., C.D. SCHELTZ, D.W. JOHNSON, J.S. TUHY, Toroweap and Kaibab Formation of northern Arizona AND J.R. SPENCE. 1991. Survey and analysis of relict and southern Utah. Publication 492, Carnegie Insti- plant communities within National Park units of the tute of Washington, Stanford, CA. Colorado Plateau (Volumes I to III). Final report for NEILSON, R.P. 1986. High-resolution climatic analysis and Cooperative Agreement CA 1440-8-8001, submitted Southwest biogeography. Science 232:27–34. to the Rocky Mountain Regional Office, National PARKER, K.W. 1951. A method of measuring trend and Park Service, Lakewood, CO, by The Nature Con- range condition on National Forest ranges. USDA, servancy, Salt Lake City, UT. Forest Service, Washington, DC. WEST, D.C., H.H. SHUGART, AND J.W. RANNEY. 1981. Pop- PARKER, K.W., AND L.E. HARRIS. 1959. The 3-step method ulation structure of forests over a large area. Forest for measuring condition and trend of forest ranges: a Science 27:701–710. resume of its history, development and use. USDA, WOODIN, H.E., AND A.A. LINDSEY. 1954. Juniper-pinyon Forest Service, Southeastern Forest Experiment Sta- east of the Continental Divide, as analyzed by the tion: 55–69. line-strip method. Ecology 35:473–489. PARKER, K.W., AND D.A. SAVAGE. 1944. Reliability of the YOUNG, J.A., R.A. EVANS, AND J. MAJOR. 1977. Sagebrush line interception method in measuring vegetation of steppe. Pages 763–793 in M.G. Barbour and J. the southern Great Plains. Journal of the American Major, editors, Terrestrial vegetation of California. Society of Agronomy 36:97–110. Wiley and Sons, New York. PASSEY, H.B., V.K. HUGIE, AND E.W. WILLIAMS. 1982. Relationships between soil plant community and cli- Received 7 June 1999 mate on rangelands of the intermountain West. Accepted 11 April 2000 2001] RESURVEY OF FISHTAIL MESA 181

APPENDIX. Alpha code index for scientific and common names for plants listed in Figure 3. Alpha code Scientific name Common name Ach.hym Achnatherum hymenoides Indian ricegrass Ara.per Arabis perennans Rock cress Arc.div Arceuthobium divaricatum Pinyon dwarf mistletoe Art.tri Artemisia tridentata Big sagebrush Ast.cal Astragalus calycosus Gray’s locoweed Ast.new Astragalus newberryi Newberry milk-vetch Ast.pin Astragalus pinonis var. atwoodii Pinyon milk-vetch Atr.can Atriplex canescens Four-wing saltbush Bou.gra Bouteloua gracilis Blue grama Cas.chr Castilleja chromosa Indian paint brush Chr.gre Chrysothamnus greenei Green’s rabbit brush Col.ram Coleogyne ramosissima Black brush Cor.viv Coryphantha vivipara var. arizonica Pincushion cactus Cow.mex Cowania mexicana var. stansburiana Cliff rose Ech.tri Echinocactus triglochidiatus Hedgehog cactus Eph.tor Ephedra torreyana Torrey joint-fir Eri.con Erigeron concinnus Tidy fleabane Eri.cor Eriogonum corymbosum Wild buckwheat Eup.fen Euphorbia fendleri var. chaetocalyx Fendler spurge Fal.par Fallugia paradoxa Apache plume Gut.sar Gutierrezia sarothrae Snakeweed Hym.ric Hymenoxys richardsonii Pinque Jun.ost Juniperus osteosperma Utah juniper Kra.lan Krascheninnikovia lanata Winter fat Les.gor Lesquerrella gordonii Gordon bladderpod Leu.eri Leucelene ericoides White aster Lom.nev Lomatium nevadense Parish wild parsley Opu.pol Opuntia polyacantha Prickly pear Pen.spp Penstemon sp. Beard tongue Phl.lon Phlox longifolia Phlox Pho.jun Phoradendron juniperinum Mistletoe Pin.edu Pinus edulis Pinyon pine Poa.fen Poa fendleriana Mutton grass She.rot Shepherdia rotundifolia Roundleaf buffalo berry Sit.hys Sitanion hystrix Squirrel tail Sph.gro Sphaeralcea grossulariaefolia Globe mallow Sti.com Stipa comata Needle-and-thread Sti.spe Stipa speciosa Desert needlegrass Str.ari Streptanthus arizonicus Twist flower Yuc.bac Yucca baccata Banana yucca Western North American Naturalist 61(2), © 2001, pp. 182–194

ESTABLISHMENT, GROWTH, AND EARLY SURVIVAL OF WOODY RIPARIAN SPECIES AT A COLORADO GRAVEL PIT

James E. Roelle1, Douglas N. Gladwin1, and Brian S. Cade1

ABSTRACT.—Presence of a wetted edge during the period of seedfall was an effective predictor of suitable establish- ment (defined as germination and survival to the 1st autumn) locations for Populus deltoides subsp. monilifera, Salix amygdaloides, S. exigua, and Tamarix ramosissima seedlings during 3 successive years of a gravel pit revegetation pro- ject in Fort Collins, Colorado. At locations predicted to be suitable for establishment, position within the pit (possibly reflecting additional moisture provided by seepage) was a significant factor in determining whether establishment actu- ally occurred. Cover of herbaceous species, which became established at the same time as, or after, woody seedlings, was positively related to probability of establishment for 8 of 11 species-year combinations, probably reflecting more favorable moisture conditions at certain locations. Herbaceous cover also was positively related to seedling height at the end of the 1st summer of growth for 9 of 11 species-year combinations. Neither establishment nor 1st-summer growth was consistently related to overall decline in the water table as estimated by the drop in surface-water level during the growing season. Flooding in the 1st spring after establishment was negatively related to subsequent survival for 5 of 8 species-year combinations. The 4 species established at different elevations in the pit, depending on location of the wet- ted edge during the period of seedfall, and there was no evidence that differential mortality subsequently altered their distribution along the elevation gradient. However, the primary objective in this study was to restore native woody species, and we attempted to maintain conditions conducive to meeting this objective. Differential postestablishment mortality may be more important in structuring the riparian community in more rigorous riverine environments.

Key words: seedlings, survival, Populus, Salix, Tamarix, drawdown, herbaceous cover, flooding.

Riparian areas in the western United States, and is timed to coincide with recession of often dominated by members of the willow flood flows following snowmelt (Scott et al. family (Salicaceae), are widely recognized as 1993). Reworking and deposition of alluvial providing important wildlife habitat and sig- sediments by floods historically provided ideal nificant benefits to society. Trees and shrubs conditions for cottonwood germination and composing western riparian communities are establishment, at least in some years (Strom- structurally complex compared to the surround- berg et al. 1991, Friedman et al. 1997, Strom- ing landscape and support diverse assemblages berg 1997). However, dams and diversions of mammals, birds, reptiles, and amphibians have significantly altered flow patterns of (Stevens et al. 1977, Brode and Bury 1984, many western streams, particularly by reduc- Knopf 1985, Finch and Ruggiero 1993). Recent ing spring flood peaks. Suitable germination years have seen increasing concern about a sites that are high enough to provide security variety of impacts to these communities, much from scouring by floods and ice, yet low of which has focused on alteration of stream enough to allow roots to establish contact with flow patterns by dams and diversions and the subsurface water table, are produced less resulting detrimental effects on riparian vege- frequently (Bradley and Smith 1986, Scott et al. tation, particularly cottonwoods (Populus spp.; 1997). As a result, recruitment can no longer Bradley and Smith 1986, Rood and Heinze- keep pace with mortality in many areas. Milne 1989, Rood and Mahoney 1990). A number of authors have expressed this Cottonwoods produce abundant wind- and relationship in the form of conceptual or quan- water-borne seeds adapted to germinate on titative models designed to predict where (rela- bare, moist soils in full sunlight. In the west- tive to stream elevation) cottonwood establish- ern U.S., seed release is in spring or early ment will occur during a particular sequence summer, depending on latitude and elevation, of hydrologic events (Bradley and Smith 1986,

1U.S. Geological Survey, Midcontinent Ecological Science Center, 4512 McMurry Avenue, Fort Collins, CO 80525.

182 2001] WOODY RIPARIAN SPECIES IN COLORADO 183

Friedman et al. 1997, Auble and Scott 1998, METHODS Mahoney and Rood 1998, Shafroth et al. 1998). Field Sampling The central component of these models is the location of a disturbed and wetted edge, pro- The overall objective at the WREN Pit was duced by declining stream stage, during the to test the feasibility of restoring a former period when germinable seeds are present. gravel pit to woody riparian forest through The period of seed germinability is usually natural seedfall and hydrologic manipulation. taken as the period of seed release, either Details of water manipulations and vegetation observed directly or estimated from general sampling methods can be found in Roelle and phenological information. An additional inter- Gladwin (1999). Briefly, the WREN Pit resem- val during which seeds are likely to remain bles a flat-bottomed bowl with 2 islands in the germinable under natural conditions is some- middle. The bottom of the pit, which lies below times added to the end of the period of seed the elevation of the adjacent Cache la Poudre release. Elevation of the wetted edge at a par- River, was graded to slope toward the south- ticular site is usually estimated from stream east corner, where a drain pipe and screw gate flow records and stage-discharge relations, allowed control of the outflow (Fig. 1). Grad- sometimes in association with visible clues ing removed nearly all vegetation in the pit, such as debris lines. leaving a bare, heterogeneous surface of clay, Various models differ in their treatment of overburden, sand, gravel, and cobble. In the mortality factors that may be important follow- spring of 1994, we filled the pit with water ing germination. For example, Mahoney and and then allowed the water to drain slowly to Rood (1998) limited both the upper and lower provide a gradually receding fringe of moist bounds of the predicted establishment zone. soil suitable for germination of wind- and water-borne seeds produced by mature Popu- They argued that there is an upper elevational lus and Salix along the Cache la Poudre River. limit to establishment, above which seedling Though not desirable from a restoration per- roots will not be able to grow deep enough to spective, Tamarix seed was also supplied by establish contact with the subsurface water several stands within about 1 km of the pit. table in the initial growing season, and a lower For all 4 species, we also monitored the timing limit, below which subsequent scouring by of seed release. stream flow and ice are likely to remove seed- When water in the pit was at its highest lings. Rate of water table decline was also a level, we randomly located 67 points 2 m component of their model, reflecting the fact (measured on the ground surface) above the that there is a limit to how fast seedling roots water’s edge. Following drawdown, we estab- can grow and thus maintain contact with sub- lished a transect extending from each of these surface water as stream stage declines. starting points to the new water’s edge, located The efficacy of such models in predicting a 0.5-m2 sample plot every 2 m along each tran- establishment of cottonwoods and other woody sect, and counted seedlings of the 4 species in riparian species is of obvious interest in under- each plot. We also estimated surface cover standing and assessing the impacts of both (0–25%, 25–50%, 50–75%, or 75–100%) at each past and future stream flow alterations. In this plot and measured the height of up to 5 seed- article, using data from a riparian revegetation lings of each species. If more than 5 individu- project at an abandoned gravel mine (the als were present, we measured those closest to WREN Pit) in Fort Collins, Colorado, we the center of the plot. Following seedling counts, examine the importance of factors included in plot locations and elevations were surveyed such models relative to establishment, growth, using a total station. and survival of seedlings of Populus deltoides The drawdown process was repeated in Marshall subsp. monilifera (Aiton) Eckenwalder, 1995 and 1996 at successively lower elevation Salix amygdaloides Andersson, S. exigua Nut- intervals. Each year we began the drawdown tall, and the exotic Tamarix ramosissima Lede- at approximately the lowest elevation where bour (Great Plains Flora Association 1986). there had been significant establishment of Information regarding distribution of the 4 cottonwoods and willows in the previous year species along an elevational gradient is also and extended the sampling transects down to presented. the new water’s edge. In all 3 years water levels 184 WESTERN NORTH AMERICAN NATURALIST [Volume 61

mean seedling density among zones (Roelle and Gladwin 1999). H20: Location of seedling establishment is unrelated to position within the pit, presence of herbaceous cover, or magnitude of the draw- down. On plots that have a wetted edge dur- ing the period of seedfall, other factors may be important in determining whether establish- ment actually occurs. We used logistic regres- sion to examine the effects of position within the pit, herbaceous cover, and total drawdown on presence or absence of seedlings on plots in zone 2 at the end of the 1st growing season. Plots were assigned to 1 of 4 cover classes as described above, total drawdown was calcu- Fig. 1. Location of the WREN Pit. lated as the plot elevation minus the lowest water level recorded during the growing sea- as determined by a staff gauge were recorded son (assumed to end on 15 October), and sur- 4–5 times each week. Drawdowns and water veyed x,y (easting, northing) plot locations level monitoring were terminated after the were used to represent position within the pit. 1996 census. We conducted a final census in In these regressions we did not use a model 1997 to calculate survival of seedlings estab- selection procedure (i.e., all independent vari- lished in previous years. The 1997 census was ables were included in all models, regardless restricted to P. deltoides and S. amygdaloides. of significance). Vegetative reproduction of S. exigua made it H30: Growth of seedlings in the summer of difficult to identify individuals, a prerequisite establishment is unrelated to position within for calculating survival. Control measures the pit, presence of herbaceous cover, or magni- applied to T. ramosissima in 1997 prevented tude of drawdown. Experimental studies have survival calculations for this species. shown that the rate of water table decline can affect growth of Populus seedlings (Mahoney Analysis and Rood 1991, 1992, Segelquist et al. 1993). Information obtained in field sampling was We used ordinary least-squares regression to used to test 4 hypotheses. examine the impact of total drawdown on H10: Location and rate of seedling establish- plant height in the setting of our revegetation ment are unrelated to the presence of a wetted project. Herbaceous cover and position were edge during seedfall. For each year and species, also included as covariates. For these analyses we assigned plots to 1 of 3 elevation zones. we used all plots where establishment occurred, Zone 1 included all plots above the highest not just those in zone 2. As in the logistic water level that occurred during the period of regressions described above, all independent seedfall. Zone 2 included all plots inundated variables were entered into each of these least- by the highest water level and subsequently squares regressions. Inspection of residuals exposed (by the drawdown) during the seed- from these regressions revealed a pattern of fall period. Zone 3 included all plots below increasing variance (larger residuals) at higher zone 2 (i.e., exposed after the period of seed- values for predicted height. In an attempt to fall). Because of differences in the timing of reduce heteroscedasticity, we regressed the seedfall, zones were specific to a species; for absolute values of these residuals against pre- example, a given plot in a particular year dicted height and used the inverse square of might be in zone 2 for P. deltoides and zone 1 predicted values as weights in a least-squares for S. exigua. For each species we tested for regression. differences in presence/absence among the H40: Seedling survival in the 1st year fol- zones at the end of the 1st growing season lowing establishment (autumn to autumn) is using a chi-square statistic. A negative binomial unrelated to position within the pit, presence of generalized linear model was used to estimate herbaceous cover, or duration of flooding in the standard errors and to test for differences in spring. We calculated 1st-, 2nd-, and 3rd-year 2001] WOODY RIPARIAN SPECIES IN COLORADO 185 survival rates for all plots (regardless of draw- we were unable to specify elevation zones for down zone) in which seedling age was known T. ramosissima in 1996. Thus, we have infor- with certainty (i.e., we eliminated those plots mation regarding establishment for 11 species- where establishment occurred in >1 year). year combinations. Chi-square analyses indi- These rates represent survival from one autumn cate that presence/absence differed among the to the next; thus 1st-year survival represents 3 elevation zones for all 11 combinations (Table seedlings that live from the 1st autumn follow- 1). Percent occurrence was highest in zone 2, ing establishment to the next autumn. For where a wetted edge was present during the these calculations and all subsequent analyses, period of seedfall, for 9 of 11 combinations. In survival rates were truncated at 1.0. Flooding the 2 cases that do not fit this pattern (P. del- is known to be an important mortality factor for toides and S. amygdaloides in 1994), percent seedlings under some circumstances (Gladwin occurrence was highest in zone 1. Tests using and Roelle 1998). Each year our lowest plots a negative binomial model also indicated that were reflooded for an indefinite period in the mean seedling densities differed among zones autumn in an attempt to eradicate T. ramosis- for all 11 species-year combinations (Table 1). sima seedlings. These and additional plots were Mean densities were always highest in zone 2, also flooded in the spring following establish- but in 1994 mean densities of P. deltoides and ment as we raised the water level to begin a S. amygdaloides in zone 1 were similar to new drawdown. Ordinary least-squares regres- those in zone 2. sion was used to examine relationships be- For plots in zone 2, logistic regression mod- tween survival and days inundated in the els incorporating position within the pit (east- spring following establishment. Position and ing, northing), cover, and total drawdown cover (in the 2nd summer) were also included accounted for a maximum of 30% of total vari- as covariates in these analyses. We compared ability in establishment (0.06 ≤ Rho ≤ 0.30; P alternate regression models in a generalized ≤ 0.0037). Regression coefficients for easting linear modeling context; based on comparison and northing were always negative (indicating of residual deviances and partial residual plots, a lower probability of establishment to the none was preferable to the linear least-squares east and north), and coefficients for both posi- model. Finally, we graphically examined the tion variables differed from zero for 10 of 11 relative position of surviving cohorts along the species-year combinations (Fig. 2). Cover and elevation gradient. probability of establishment were positively Because of the multiplicity of estimates in related in 8 of 11 regressions (Fig. 2). Cases the above regression models, some adjustment where coefficients for cover did not differ to P-values for a family of simultaneous esti- from zero all occurred in 1994 (P. deltoides, S. mates may be appropriate. We considered the amygdaloides, and T. ramosissima). Total draw- parameter estimates for a given species in an down ranged from 4 cm to 67 cm for various individual year to be the family of comparisons combinations of species and year (Table 2) and for simultaneous inference. Using Sidak’s tended to be greater for those species (P. del- method for simultaneous inference (Westfall toides, S. amygdaloides) that establish earlier in and Young 1993:44–45), adjusted probabilities the year. The relationship between total draw- given k simultaneous estimates with unad- down and probability of establishment was less k justed probabilities are Padj = 1 – (1 – Punadj) . clear than for other covariates (Fig. 2). Populus Thus, the unadjusted probabilities reported deltoides and S. amygdaloides each had a nega- here can be referenced to the following ad- tive relationship in 1995 and 1996, as did T. justed probabilities given k = 5 simultaneous ramosissima in 1995. For S. exigua, total draw- parameter estimates: Punadj = 0.0102 has Padj down was not related to probability of estab- = 0.0500, Punadj = 0.0020 has Padj = 0.0100, lishment in any of the 3 years. and P = 0.0002 has P = 0.0010. unadj adj Growth

RESULTS First-year growth of seedlings generally re- flected the phenology of seed production (Table Establishment 3); seedlings of P. deltoides and S. amygdaloides, Because of a failure of the seed crop (prob- the earliest seed producers, were tallest, fol- ably due to winter dieback of mature plants), lowed by those of S. exigua and T. ramosissima. 186 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 1. Percent occurrence and mean density (number ⋅ m–2) of seedlings in the 3 zones defined by presence or absence of a wetted edge during the period of seedfall. N is the number of plots. Deviance is from a negative binomial generalized linear model. P > Mean P > Year/ % Chi-square chi- density Deviance chi- ± Zone N present (df) square sx– (df) square Populus deltoides subsp. monilifera 1994 1 94 9.6 0.21 ± 0.115 2 325 8.6 13.65 (2) 0.0012 0.29 ± 0.064 7.45 (2) 0.0241 3 194 1.0 0.02 ± 0.073 1995 1 722 7.8 0.81 ± 0.089 2 599 50.6 301.78 (2) <0.0001 7.78 ± 0.410 539.15 (2) <0.0001 3 166 34.3 3.60 ± 0.424 1996 1 1295 4.5 0.67 ± 0.064 2 553 47.6 501.50 (2) <0.0001 15.47 ± 0.817 1484.84 (1) <0.0001 3 1 0.0 ------Salix amygdaloides 1994 1 94 16.0 2.49 ± 0.433 2 315 15.9 26.45 (2) <0.0001 2.65 ± 0.246 107.65 (2) <0.0001 3 204 2.0 0.04 ± 0.106 1995 1 722 3.9 0.26 ± 0.055 2 599 22.0 100.34 (2) <0.0001 1.93 ± 0.116 208.98 (2) <0.0001 3 166 15.7 0.77 ± 0.149 1996 1 1295 0.1 0.00 ± 0.033 2 553 16.3 217.33 (2) <0.0001 1.75 ± 0.101 431.87 (1) <0.0001 3 1 0.0 ------Salix exigua 1994 1 218 11.9 0.51 ± 0.139 2 340 32.4 46.61 (2) <0.0001 4.99 ± 0.377 186.17 (2) <0.0001 3 55 1.8 0.04 ± 0.205 1995 1 1213 6.3 0.63 ± 0.059 2 240 50.0 329.29 (2) <0.0001 15.66 ± 1.104 1289.78 (2) <0.0001 3 34 11.8 0.35 ± 0.306 1996 1 1484 0.1 0.00 ± 0.029 2 364 21.7 330.60 (2) <0.0001 2.22 ± 0.128 559.51 (1) <0.0001 3 1 0.0 ------Tamarix ramosissima 1994 1 324 8.6 0.39 ± 0.094 2 284 34.9 64.65 (2) <0.0001 2.89 ± 0.233 131.32 (1) <0.0001 3 5 0.0 1995 1 1321 1.3 0.06 ± 0.034 2 161 63.4 746.17 (2) <0.0001 14.15 ± 0.834 2335.91 (2) <0.0001 3 5 20.0 0.40 ± 0.667 2001] WOODY RIPARIAN SPECIES IN COLORADO 187

Least-squares regressions using the covariates position, cover, and total drawdown explained 19–40% of the variance in mean seedling height at the end of the 1st growing season (0.19 ≤ R2 ≤ 0.40; P ≤ 0.041). In contrast to its relationship to the probability of establish- ment, the covariate easting (x location) was positively related to mean plant height (i.e., seedling height increased to the east) in 6 of 11 species-year combinations (Fig. 3). On the other hand, the relationship between the covariate northing (y location) and mean plant height was negative for 6 of 11 combinations of species and year. Cover was positively related to mean plant height in 9 of 11 cases, the only exceptions being P. deltoides in 1996 and T. ramosissima in 1994. As with probabil- ity of establishment, the relationship between drawdown and mean plant height was vari- able, with 4 of 11 coefficients being positive and 4 negative. Survival Truncation of survival rates to 1.0 affected 101 of 1631 (6.2%) species-plot combinations Fig. 2. Logistic regression coefficients and 95% confi- used in calculating 1st-year survival rates, 39 dence intervals for relations between seedling establish- of 469 (8.3%) used in calculating 2nd-year sur- ment and the covariates position (easting, northing), cover, vival rates, and 0 of 32 (0.0%) used in calculat- and drawdown. Sample sizes (number of plots) are as in ing 3rd-year survival rates. First-year survival Table 2, zone 2. rates ranged from a low of 0.14 for T. ramosis- sima in 1996 to a high of 0.55 for S. exigua in 1996 (Table 4). With the exception of T. ramo- zero. The maximum number of days inun- sissima, 1st-year survival rates were highest in dated was greater in 1995 for all species (Table 1996 and lowest in 1995. All species showed 5), but this did not result in a stronger effect of increased survival in the 2nd year, as did P. flooding in that year (Fig. 4). deltoides and S. amygdaloides in the 3rd year. Distribution of plots with surviving seedlings Second-year survival for S. exigua may be over- along the elevation gradient of the WREN Pit estimated due to vegetative reproduction. did not change substantially through the 4 Least-squares regressions relating position, years in which censuses were conducted (Fig. cover (in the 2nd summer after establish- 5). Surviving P. deltoides and S. amygdaloides ment), and days flooded (in the spring after were at the highest elevations for cohorts establishment) to 1st-year survival were signif- established in a particular year, with S. exigua icant (P ≤ 0.0356) for 7 of 8 species-year com- and T. ramosissima at lower elevations. The binations, the lone exception being P. deltoides lower end of the distribution for several cohorts in 1995. Again, however, proportion of vari- was “trimmed,” probably by both autumn and ance explained by these models was low (0.04 spring flooding. This effect is particularly ≤ R2 ≤ 0.29). Regression analysis showed no noticeable for T. ramosissima established in consistent relationships between 1st-year sur- 1994 (Fig. 5). vival and the covariates position and cover (Fig. 4). Number of days that a plot was inun- DISCUSSION dated in the spring following establishment, Establishment however, tended to be negatively related to survival, with 5 of 8 species-year combinations Presence of a bare, wetted edge was a good having regression coefficients differing from predictor of establishment for all 4 species 188 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 2. Range of total drawdown (cm) experienced by seedlings on sample plots. Populus deltoides Salix Tamarix Year subsp. monilifera amygdaloides Salix exigua ramosissima 1994 27–67 28–67 11–5 4–39 1995 23–59 23–59 9–32 4–23 1996 9–67 9–67 9–51 —

± TABLE 3. Mean (cm) sx– of seedling heights averaged by plot. Number of plots is in parentheses. Populus deltoides Salix Tamarix Year subsp. monilifera amygdaloides Salix exigua ramosissima 1994 11.0 ± 1.20 (39) 11.8 ± 1.19 (69) 5.2 ± 0.39 (137) 3.8 ± 0.22 (127) 1995 11.2 ± 0.42 (416) 18.6 ± 0.94 (186) 7.0 ± 0.50 (200) 3.3 ± 0.16 (120) 1996 10.6 ± 0.43 (321) 15.1 ± 0.88 (91) 7.8 ± 0.58 (80) — studied. Several other investigators have re- ported comparable results. For example, Auble et al. (1997), working on Boulder Creek in Colorado, found that establishment of Populus deltoides subsp. monilifera was limited to bare, moist surfaces created by spring flooding. Shafroth et al. (1998) obtained similar results for Populus fremontii, Salix gooddingii, Bac- charis salicifolia, and Tamarix ramosissima along the Bill Williams River in Arizona. Inaccuracies in estimating whether or not a plot was moist during the period of seedfall likely accounted for many of the prediction errors in our study, particularly at the upper ends of the establishment zones. For example, establishment of P. deltoides and S. amygda- loides was similar in zones 1 and 2 in 1994 (Table 1). Of 24 species-plot combinations in which establishment of P. deltoides or S. amyg- daloides occurred in zone 1 in 1994, all plot elevations were within 9 cm of the top of zone 2 (i.e., the water level at the start of draw- down, as measured by a staff gauge), and 22 were within 2 cm. Plots this close to surface water level at the start of drawdown could eas- Fig. 3. Least-squares regression coefficients and 95% ily have been moist due to capillary rise. A confidence intervals for relations between 1st-year component to account for capillary rise might seedling height and the covariates position (easting, nor- improve predictions; in the case of the WREN thing), cover, and drawdown. Sample sizes (number of Pit, however, capillary rise would likely have plots) are as in Table 3. to be estimated separately for each plot because of the variability of the substrate. Water stand- ing in perched depressions at the start of seed- for the time that seeds remain germinable fall could account for additional inaccuracies after they are released. The period of germin- in predictions at the upper ends of establish- ability has been estimated at about 1 week for ment zones. At the lower ends of establish- Salix spp. (Ware and Penfound 1949, Dens- ment zones, predictions might be improved by more and Zasada 1983), 1–2 weeks for Populus adding a (species-specific) period to account spp. (Moss 1938, Ware and Penfound 1949), 2001] WOODY RIPARIAN SPECIES IN COLORADO 189

± TABLE 4. Mean sx– of plot survival rates. Number of plots is in parentheses. Survival rates >1.0 were truncated to 1.0. Year 1st-year rate 2nd-year rate 3rd-year rate Populus deltoides subsp. monilifera 1995 0.21 ± 0.060 (35) — — 1996 0.41 ± 0.019 (414) 0.58 ± 0.149 (12) — 1997 0.33 ± 0.020 (276) 0.81 ± 0.020 (230) 0.83 ± 0.126 (8) ------Salix amygdaloides 1995 0.30 ± 0.048 (67) — — 1996 0.38 ± 0.030 (183) 0.46 ± 0.078 (31) — 1997 0.37 ± 0.039 (89) 0.58 ± 0.043 (102) 0.69 ± 0.082 (24) ------Salix exigua 1995 0.35 ± 0.037 (130) — — 1996 0.55 ± 0.031 (190) 0.77 ± 0.049 (60) — 1997 — — — ------Tamarix ramosissima 1995 0.19 ± 0.031 (127) — — 1996 0.14 ± 0.025 (120) 0.67 ± 0.069 (34) — 1997 — — — and 8 weeks for Tamarix spp. (Horton et al. inhibit germination and growth. Friedman et 1960). In most of these trials, however, seeds al. (1995), for example, found that removing were stored in the laboratory rather than under sod to expose bare mineral soil significantly field conditions. enhanced establishment of Populus deltoides subsp. monilifera and Salix amygdaloides. Position Stromberg et al. (1991) found that densities of We initially included x- and y-coordinates in Populus fremontii and Baccharis salicifolia our regression analyses of other factors affect- were negatively related to herbaceous cover, a ing establishment, growth, and survival of result they attributed to the difficulty of seeds seedlings to account for any variability due to penetrating vegetation to make contact with position before examining the effects of cover, the soil. They also reported that seedlings grow drawdown, and flooding. We were somewhat better (in spring and summer of establish- surprised to find a consistent effect of position ment) on less densely vegetated plots. Johnson on establishment, which tended to decrease to et al. (1976) and Walker et al. (1986) found the north and east for all species and years. similar negative effects of leaf litter on cotton- The most likely explanation for this effect is wood and willow establishment, though other that seepage from the Cache la Poudre River factors (e.g., reduced light, reduced soil tem- and a pond (Fig. 1) often provided additional peratures) may also be important under an moisture to the west and south banks of the existing forest canopy. pit, thus resulting in conditions more favor- In cases where herbaceous cover establishes able for establishment. Reasons for the gener- simultaneously with or after seedlings, inter- ally positive relationships between easting (y actions may be more complicated. Stromberg location) and seedling height remain unclear. (1997) found that Tamarix chinensis seedlings Other factors that may be important in position were sparsely distributed in plots with >50% effects include soil texture, chemistry, and cover of sweet clover (Melilotus spp.) but were water relations; location of seed sources and abundant in plots with <50% sweet clover the target area relative to wind patterns; and cover. Densities of Populus fremontii seedlings, depth to groundwater. on the other hand, were not affected by the presence of sweet clover. Their explanation of Cover this pattern was that T. chinensis seedfall Previous studies have shown that herba- occurred after sweet clover had germinated ceous cover or leaf litter present during the and expanded to cover much of the ground, period of cottonwood and willow seedfall can whereas P. fremontii seedlings established 190 WESTERN NORTH AMERICAN NATURALIST [Volume 61

ment and herbaceous cover (Fig. 2) are an in- dication that both herbs and woody seedlings established better on wetter sites. The 3 species-year combinations for which the rela- tionship between herbaceous cover and estab- lishment was nonsignificant (Fig. 2) all occurred in 1994, the 1st year in which we conducted a drawdown. In 1994 surface water in some parts of the pit extended into areas where site preparation had not removed existing vegeta- tion. Such vegetation may have interfered with seed deposition and resulted in different rela- tionships between cover and establishment than in other years. The hypothesis that plots with greater herbaceous cover are simply favorable sites where both herbs and woody seedlings may thrive is perhaps further sup- ported by the positive relationships between cover and woody seedling height in the 1st summer (Fig. 3). However, we did not find consistent relationships between 1st-year sur- vival (from the autumn following establish- ment to the next autumn) and herbaceous Fig. 4. Least-squares regression coefficients and 95% cover during the 2nd summer of growth (Fig. confidence intervals for relations between 1st-year seed- 4). This may indicate that cover was dense ling survival and the covariates position (easting, north- enough on some plots in the 2nd summer to ing), cover, and flooding. Sample sizes are as in Table 4. result in significant competition for light, water, and nutrients. before sweet clover. Even though P. fremontii Drawdown seedlings were overtopped by sweet clover in Tolerance of woody riparian seedlings, par- early summer, they were subsequently exposed ticularly Populus spp., to drawdown or water to full sunlight as sweet clover senesced and table decline has been examined in both therefore survived well. Shafroth et al. (1998) laboratory and field studies. Laboratory inves- reported that plots in which woody riparian tigations have generally involved measuring seedlings established tended to have greater plant response to controlled drawdown rates. herbaceous cover than those without estab- Mahoney and Rood (1991), for example, re- lishment. They also found a correlation between ported that rates of water table decline ≥4 cm herbaceous cover and lower, wetter sites and ⋅ day–1 limited survival of seedlings of a nat- hypothesized either that these sites were sim- ural poplar hybrid (Populus deltoides × P. bal- ply more favorable for plant growth in the arid samifera) through the 1st growing season environment of Arizona or that herbaceous (which is equivalent to establishment as defined cover became established after seedlings. for our study), and that a decline of 1 cm ⋅ In our study it is clear that herbaceous cover day–1 resulted in maximum root elongation. In generally developed either simultaneously with a similar study of Populus deltoides subsp. or after woody seedlings because site prepara- monilifera seedlings, Segelquist et al. (1993) tion resulted in bare substrate throughout found that drawdown rates ≥0.7 cm ⋅ day–1 most of the pit, and flooding prevented estab- affected establishment and that shoot height, lishment of any vegetation prior to drawdown. shoot biomass, root length, root biomass, and Thus, in zone 2, where we examined effects of total biomass were greatest at a rate of 0.4 cm ⋅ factors such as cover on establishment, there day–1. was little cover to interfere with seed deposi- The approach in field studies has generally tion on most plots. We suspect that positive been to measure the elevation of established relations between woody seedling establish- seedlings relative to elevation of the adjacent 2001] WOODY RIPARIAN SPECIES IN COLORADO 191

TABLE 5. Flooding characteristics of the plots for which 1st-year survival could be calculated. Populus deltoides Flooding subsp. Salix Tamarix Year characteristic monilifera amygdaloides Salix exigua ramosissima 1995 Range (days) 0–83 0–84 0–94 0–89 Mean (days) 13.8 11.2 38.6 51.1 Percent of plots flooded 57.1 58.2 87.7 94.5 1996 Range (days) 0–35 0–25 0–35 0–42 Mean (days) 3.3 3.0 8.0 21.4 Percent of plots flooded 23.4 25.7 46.3 90.8 stream at some reference flow (usually late sum- bound (60 cm) suggested by Mahoney and Rood mer or autumn), the difference representing (1998) is probably not applicable in the con- overall water table decline or drawdown expe- text of the WREN Pit, where we attempted to rienced by the seedlings. The assumptions in maintain winter water levels low enough that this approach are that seedlings become estab- established seedlings would not be affected by lished at the wetted edge as flood flows recede ice, and where scouring by stream flow is not and that the subsurface water table roughly a problem. Finally, subsurface water relation- parallels water level in the stream. While sub- ships in the WREN Pit are probably more surface water levels have rarely been measured complicated than in most floodplain situations, in studies of this nature, Mahoney and Rood due to the fact that most alluvial sand and (1998) argued that it is reasonable to assume a gravel was removed. horizontal water table in the generally coarse Flooding alluvial substrates adjacent to most western streams. Mahoney and Rood (1998) recently Several authors have reported that inunda- summarized information from these kinds of tion by standing water can be a significant studies in the context of their “Recruitment Box” mortality factor for some riparian seedlings model, concluding that Populus establishment (Gladwin and Roelle 1998). Populus and Tama- is most likely to occur at elevations 60–150 cm rix have been best studied in this regard, and, above the growing season “base flow.” Above in general, results indicate that susceptibility 150 cm, seedlings are likely to die from desic- to inundation decreases significantly after the cation (i.e., their roots are not able to grow fast 1st year. Gladwin and Roelle (1998) found sig- enough to maintain contact with the subsur- nificant mortality of both P. deltoides and T. face water table, even taking into account cap- ramosissima seedlings inundated for 25 days illary rise). Below 60 cm, the probability of in autumn (15 September through 10 October) surviving future scouring by stream flow or ice following establishment, but no significant is low. Mahoney and Rood (1998) also incorpo- effect of inundation for 28 days in the follow- rated a maximum drawdown rate of 2.5 cm ⋅ ing spring (21 May through 18 June). In the day–1 as part of their recruitment model. current study, however, spring flooding (as we While generalizations from these kinds of raised the water level in the pit to begin the studies are difficult (Shafroth et al. 1998), we new drawdown) had a consistent negative effect established a target drawdown rate of 1.0 cm ⋅ on 1st-year survival (Fig. 4), although regres- day–1 for our work at the WREN Pit. Our sion coefficients were significant for only 5 of overall objective was to test the utility of nat- 8 species-year combinations. ural seedfall and hydrologic manipulation as a Reasons for this apparent difference in the revegetation technique, and we viewed 1.0 cm effects of spring flooding are unclear. In 1995 ⋅ day–1 as a conservative choice that would many seedlings were flooded earlier (begin- prevent seedlings from becoming hydrologi- ning April 1) and longer (up to 94 days) than cally stranded but still promote root elongation. those in the study reported by Gladwin and Thus, it is perhaps not surprising that there Roelle (1998). In 1996, however, starting date was no consistent relationship between draw- (11–26 May, depending on species) and dura- down and establishment (Fig. 2) or growth in tion (up to 42 days) of flooding were more sim- the 1st summer (Fig. 3). In addition, the lower ilar to those reported by Gladwin and Roelle 192 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Physical and chemical characteristics of flood water are also known to influence plant response (Whitlow and Harris 1979), and any number of differences in such parameters may have existed between the WREN Pit and the pond in which Gladwin and Roelle (1998) did their spring treatment. Detailed study of the response of seedlings to flood waters differing with respect to factors such as salinity and dis- solved oxygen is warranted. Seedling Distribution A temporal pattern in seed production by Fig. 5. Distribution of plots with surviving seedlings various species of Populus, Salix, and Tamarix along the elevation gradient of the WREN Pit. Boxes rep- has been reported by several authors. With resent 25th–75th percentiles; whiskers extend to 5th and 95th percentiles. Long-dash horizontal lines connect some variation due to species and geographic medians for cohorts established in 1994, short-dash lines location, Populus usually produces seed earli- for cohorts established in 1995, and solid lines for cohorts est in the growing season and for a relatively established in 1996. short time, followed by Salix (often for a some- what longer time) and then Tamarix, which usually has the longest and latest period of seed (1998). It is possible that date of initiation and production (Warren and Turner 1975, Stromberg duration of flooding relative to the precise 1997, Shafroth et al. 1998, Roelle and Gladwin phenology of plant growth are important deter- 1999). If the common mode of establishment minants of vulnerability, especially for rela- of these species is seed germination on bare, tively young seedlings just emerging from their moist surfaces remaining as stream flows recede 1st dormant season. However, given that there following spring or early summer floods, then were no consistent differences in the results in the median establishment elevation for Popu- 1995 compared with 1996, it seems unlikely lus should be highest, followed by Salix and that date of initiation or duration of flooding then Tamarix, usually with some overlap be- was primarily responsible for the fact that tween species. For any given year, this is results in the current study were different from exactly the pattern observed at the WREN Pit those of Gladwin and Roelle (1998). Interpre- (Fig. 5). tation is further complicated by the fact that In contrast, several investigators have found some plots were flooded for a period of un- different patterns in juvenile and mature stands known duration each autumn as we attempted of these same species (Stromberg et al. 1996, to control T. ramosissima. Allred and Schmidt 1999, Shafroth 1999), with The hypothesis that survival over the 1st Tamarix occupying relatively higher positions winter is positively related to seedling size than in the establishment pattern described was also considered. If seedlings at lower ele- above. There are 2 possible explanations for vations were smaller (due to later germination) such differences in distribution between seed- and if smaller seedlings had poorer survival lings and older plants. First, the various species than larger ones, then the apparent flooding might have been established in different flood effect could be an artifact, because smaller events, perhaps in different years (i.e., the (lower) seedlings were more likely to be establishment pattern described above did not flooded. However, we found no consistent apply to a particular site). For example, a rela- relationship between seedling size and eleva- tively large flood in late summer (when only tion in the current study. Furthermore, P. del- Tamarix is producing seed) might lead to toides seedlings in the current study were establishment of Tamarix above Populus and somewhat taller (Table 3) at the end of the 1st Salix that established during smaller flood summer than those used by Gladwin and events. Second, and perhaps more likely, dif- Roelle (1998; Table 1), and T. ramosissima seed- ferential mortality among species might have lings were about the same size. altered their relative distribution through 2001] WOODY RIPARIAN SPECIES IN COLORADO 193 time. Many factors that have been proposed to BRODE, J.M., AND R.B. BURY. 1984 The importance of account for the invasive success of Tamarix riparian systems to amphibians and reptiles. Pages 30–36 in R.E. Warner and K.M. Hendrix, editors, (e.g., high tolerance of drought, inundation, California riparian systems. University of California and salinity; vigorous resprouting after fire; Press, Berkeley. lack of herbivory) might be responsible for DENSMORE, R., AND J. ZASADA. 1983. Seed dispersal and such differential mortality (Smith et al. 1998). dormancy patterns in northern willows: ecological and evolutionary significance. Canadian Journal of Thus far, there is no evidence of differential Botany 61:3207–3216. mortality at the WREN Pit sufficient to alter the FINCH, D.M., AND L.F. RUGGIERO. 1993. Wildlife habitats distribution of established seedlings (Fig. 5). and biological diversity in the Rocky Mountains and This is perhaps not surprising, however, in that Northern Great Plains. Natural Areas Journal 13: the basic objective of our work at the WREN 191–203. FRIEDMAN, J.M., M.L. SCOTT, AND G.T. AUBLE. 1997. Water Pit was restoration of native woody species. To management and cottonwood forest dynamics along this end, we attempted to provide conditions prairie streams. Pages 49–71 in F. Knopf and F. Sam- suitable for Populus and Salix, and these con- son, editors, Ecology and conservation of Great Plains ditions appear also to be conducive to Tamarix vertebrates. Ecological Studies, Volume 125. Springer- establishment and growth. Conditions at the Verlag, New York. FRIEDMAN, J.M., M.L. SCOTT, AND W. M. L EWIS, JR. 1995. WREN Pit were thus relatively benign (e.g., Restoration of riparian forest using irrigation, artificial slow drawdown, shallow groundwater, lack of disturbance, and natural seedfall. Environmental scouring) compared to most riverine situa- Management 19:547–557. tions, where differential mortality following GLADWIN, D.N., AND J.E. ROELLE. 1998. Survival of plains cottonwood (Populus deltoides subsp. monilifera) and establishment may be much more important in saltcedar (Tamarix ramosissima) seedlings in response structuring the riparian community. to flooding. Wetlands 18:669–674. GREAT PLAINS FLORA ASSOCIATION. 1986. Flora of the Great Plains. University of Kansas Press, Lawrence. ACKNOWLEDGMENTS HORTON, J.S., F.C. MOUNTS, AND J.M. KRAFT. 1960. Seed germination and seedling establishment of phreato- T. Shoemaker and R. Wilkinson, Department phyte species. Station Paper 48, U.S. Department of of Natural Resources, City of Fort Collins, and Agriculture, Forest Service, Rocky Mountain Forest D. Lemesany, G. Lindsay, and M. Sheahan of and Range Experiment Station, Fort Collins, CO. JOHNSON, W.C., R.L. BURGESS, AND W.R. KEAMMERER. Western Mobile–Northern (now Lafarge) pro- 1976. Forest overstory vegetation and environment vided access to the WREN Pit property and on the Missouri River floodplain in North Dakota. logistic support. P. Anderson, A. Fitzpatric, Ecological Monographs 46:59–84. and D. Hamilton assisted with fieldwork, and KNOPF, F.L. 1985. Significance of riparian vegetation to D. Crawford and J. Shoemaker provided assis- breeding birds across an altitudinal cline. Pages 105–111 in R.R. Johnson, C.D. Ziebell, D.R. Patton, tance with graphics. G. Auble and J. Friedman P.F. Ffolliott, and R.H. Hamre, technical coordina- reviewed earlier drafts of the manuscript. This tors, Riparian ecosystems and their management: paper was prepared by employees of the U.S. reconciling conflicting uses. General Technical Report Geological Survey as part of their official RM-120, U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experi- duties; it thus cannot be copyrighted. ment Station, Fort Collins, CO. MAHONEY, J.M., AND S.B. ROOD. 1991. A device for study- LITERATURE CITED ing the influence of declining water table on poplar growth and survival. Tree Physiology 8:305–314. ALLRED, T.M., AND J.C. SCHMIDT. 1999. Channel narrow- ______. 1992. Response of a hybrid poplar to water table ing by vertical accretion along the Green River near decline in different substrates. Forest Ecology and Green River, Utah. Geological Society of America Management 54:141–156. Bulletin 111:1757–1772. ______. 1998. Stream flow requirements for cottonwood AUBLE, G.T., AND M.L. SCOTT. 1998. Fluvial disturbance seedling recruitment—an integrative model. Wet- patches and cottonwood recruitment along the upper lands 18:634–645. Missouri River, Montana. Wetlands 18:546–556. MOSS, E.H. 1938. Longevity of seed and establishment of AUBLE, G.T., M.L. SCOTT, J.M. FRIEDMAN, J. BACK, AND seedlings in species of Populus. Botanical Gazette V. J. L EE. 1997. Constraints on establishment of plains 99:529–542. cottonwood in an urban riparian preserve. Wetlands ROELLE, J.E., AND D.N. GLADWIN. 1999. Establishment of 17:138–148. woody riparian species from natural seedfall at a for- BRADLEY, C.E., AND D.G. SMITH. 1986. Plains cottonwood mer gravel pit. Restoration Ecology 7:183–192. recruitment and survival on a prairie meandering ROOD, S.B., AND S. HEINZE-MILNE. 1989. Abrupt down- river floodplain, Milk River, southern Alberta and stream forest decline following river damming in northern Montana. Canadian Journal of Botany 64: southern Alberta. Canadian Journal of Botany 67: 1433–1442. 1744–1749. 194 WESTERN NORTH AMERICAN NATURALIST [Volume 61

ROOD, S.B., AND J.M. MAHONEY. 1990. Collapse of ripar- Department of Agriculture, Forest Service, Rocky ian poplar forests downstream from dams in western Mountain Forest and Range Experiment Station, prairies: probable causes and prospects for mitiga- Fort Collins, CO. tion. Environmental Management 14:451–464. STROMBERG, J.C. 1997. Growth and survivorship of Fre- SCOTT, M.L., G.T. AUBLE, AND J.M. FRIEDMAN. 1997. Flood mont cottonwood, Goodding willow, and salt cedar dependency of cottonwood establishment along the seedlings after large floods in central Arizona. Great Missouri River, Montana, USA. Ecological Applica- Basin Naturalist 57:198–208. tions 7:677–690. STROMBERG, J.C., D.T. PATTEN, AND B.D. RICHTER. 1991. SCOTT, M.L., M.A. WONDZELL, AND G.T. AUBLE. 1993. Flood flows and dynamics of Sonoran riparian Hydrograph characteristics relevant to the establish- forests. Rivers 2:221–235. ment and growth of western riparian vegetation. STROMBERG, J.C., R. TILLER, AND B. RICHTER. 1996. Effects Pages 237–246 in H.J. Morel-Seytoux, editor, Pro- of groundwater decline on riparian vegetation of ceedings of the Thirteenth Annual American Geo- semiarid regions: the San Pedro, Arizona. Ecological physical Union Hydrology Days. Hydrology Days Applications 6:113–131. Publications, Atherton, CA. WALKER, L.R., J.C. ZASADA, AND F. S . C HAPIN III. 1986. The SEGELQUIST, C.A., M.L. SCOTT, AND G.T. AUBLE. 1993. role of life history processes in primary succession Establishment of Populus deltoides under simulated on an Alaskan floodplain. Ecology 67:1243–1253. alluvial groundwater declines. American Midland WARE, G.H., AND W. T. P ENFOUND. 1949. The vegetation Naturalist 130:274–285. of the lower levels of the floodplain of the South SHAFROTH, P.B. 1999. Downstream effects of dams on Canadian River in central Oklahoma. Ecology 30: riparian vegetation: Bill Williams River, Arizona. 478–484. Doctoral dissertation, Arizona State University, WARREN, D.K., AND R.M. TURNER. 1975. Saltcedar (Tamarix Tempe. 156 pp. chinensis) seed production, seedling establishment, SHAFROTH, P.B., G.T. AUBLE, J.C. STROMBERG, AND D.T. and response to inundation. Journal of the Arizona PATTEN. 1998. Establishment of woody riparian veg- Academy of Science 10:135–144. etation in relation to annual patterns of streamflow, WESTFALL, P.H., AND S.S. YOUNG. 1993. Resampling-based Bill Williams River, Arizona. Wetlands 18:577–590. multiple testing: examples and methods for p-value SMITH, S.D., D.A. DEVITT, A. SALA, J.R. CLEVERLY, AND adjustment. John Wiley and Sons, New York. 340 pp. D.E. BUSCH. 1998. Water relations of riparian plants WHITLOW, T.H., AND R.W. HARRIS. 1979. Flood tolerance from warm desert regions. Wetlands 18:687–696. in plants: a state-of-the-art review. Technical Report STEVENS, L.E., B.T. BROWN, J.E. SIMPSON, AND R.R. JOHN- E-79-2, U.S. Army Engineer Waterways Experiment SON. 1977. The importance of riparian habitat to Station, Vicksburg, MS. migrating birds. Pages 156–164 in R.R. Johnson and D.A. Jones, technical coordinators, Importance, Received 20 September 1999 preservation and management of riparian habitat: a Accepted 11 April 2000 symposium. General Technical Report RM-43, U.S. Western North American Naturalist 61(2), © 2001, pp. 195–203

NATURAL ENEMY ASSEMBLAGES ON NATIVE AND RESEEDED GRASSLANDS IN SOUTHWESTERN MONTANA: A FAMILY-LEVEL ANALYSIS

Kevin M. O’Neill1, William P. Kemp2, Catherine Seibert3, Marni G. Rolston1, James A. Bess4, and T. Keith Philips5

ABSTRACT.—We conducted a 2-year survey, using sweep sampling and family-level taxon identification, of the preda- tory and parasitoid insects on grassland sites in the Gallatin Valley of southwestern Montana. The 25 sites were divided into 4 habitat classes: 2 native habitat types (Stipa comata/Bouteloua gracilis and Festuca idahoensis/Agropyron spicatum) and 2 that had been reseeded with either crested wheatgrass (Agropyron cristatum) or smooth brome (Bromus inermis). Our major goal was to make quantitative comparisons of the abundance of insects among native and reseeded habitats. Of 51 families in 5 insect orders identified, 7 Hymenoptera (Encyrtidae, Braconidae, Ichneumonidae, Pteromalidae, Eulophidae, Scelionidae, and Torymidae), 3 Hemiptera (Lygaeidae, Nabidae, and Reduviidae), 1 Coleoptera (Coccinelli- dae), and 1 Diptera (Asilidae) comprised 90% of the natural enemies sampled. Ordination analyses provided no strong evidence that the 4 habitat classes contained distinct overall natural enemy communities. However, contiguous native and reseeded sites usually had relatively different overall natural enemy assemblages, suggesting that vegetation was often a more important correlate of community composition than was close spatial proximity of sites. Furthermore, sev- eral common families exhibited differential abundances across habitat classes in one or both years. For example, in 1989, Eulophidae, Pteromalidae, and Torymidae were more abundant on native Festuca/Agropyron sites, whereas Encyrtidae and Nabidae were more abundant on Festuca/Agropyron sites reseeded with Bromus inermis. Although analyses of insect assemblages classified to the family level provide somewhat limited information on functional ecological differences among habitats, they allow one to survey a broad array of taxa to identify focal groups for future conservation and land management studies.

Key words: rangeland, habitat type, Encyrtidae, Braconidae, Nabidae, Lygaeidae, Geocoris.

Even within a limited region, a great diver- effects upon insects, whereas others may act sity of native vegetation assemblages are en- more indirectly and subtly through alteration compassed by the term grassland. In one clas- of trophic interactions or microclimate. sification system commonly used for western Grasslands of the Gallatin Valley of south- U.S. grasslands, relatively discrete communities western Montana comprise a mosaic of native referred to as “habitat types” are defined by habitat types that has been further diversified their native vegetation assemblages (Mueggler by reseeding many sites with exotic grasses and Stewart 1980), soils, and climates (Weaver and alfalfa (Medicago sativa) during the 1960s 1979a, 1979b, 1980). Natural grassland habitat and 1970s as part of range management pro- diversity represented by different native vege- grams aimed at improving early season grazing tation assemblages is further increased by (Kemp et al. 1990a). To examine the implica- management practices, such as grazing, burn- tions of such habitat variation, we have docu- ing, and reseeding with exotic grasses (Arenz mented the composition of assemblages of and Joern 1996), that have implications for selected phytophagous insects on a wide both pest management and insect conserva- range of sites in the valley for which we have tion (Kemp et al. 1990b, Bock and Bock 1995, characterized habitat type (Kemp et al. 1990a, Tscharntke and Greiler 1995). Some of these 1990b, Bess 1997, Wachter et al. 1998). To com- management techniques (e.g., burning; Evans plement these species-level diversity studies, 1984) have immediate, direct, and profound we also surveyed families of predatory and

1Department of Entomology, Montana State University, Bozeman, MT 59717. 2USDA/ARS Bee Biology and Systematics Laboratory, Utah State University, Logan, UT 84322-5310. 3Department of Plant Sciences, Montana State University, Bozeman, MT 59717. 4Otis Enterprises, 13501 S. 750 W., Wanatah, IN 46390. 5Department of Biology, Western Kentucky University, Bowling Green, KY 42101-3576.

195 196 WESTERN NORTH AMERICAN NATURALIST [Volume 61 parasitoid insects present on these habitats. The sites sampled were divided into 4 habitat classes: 2 native habitats (Stipa comata/Boute- loua gracilis and Festuca idahoensis/Agropyron spicatum habitats) and 2 that had been reseeded with either crested wheatgrass (Agropyron cristatum) or smooth brome (Bromus inermis). Sites were distributed along an approximately 50-km east–west gradient over which mean elevation decreased by 11% and mean annual precipitation decreased by 22%. Our specific aims were (1) to make quantitative compar- isons, among native and reseeded grassland communities, of total abundance of natural enemies and of abundance of specific families and (2) to identify families of natural enemies that were abundant enough to be fruitful for future detailed community studies at our sites. Fig. 1. Map of northern Gallatin County, Montana, show- ing location of sites: SB sites (closed squares), AM sites MATERIALS AND METHODS (open squares), FA sites (closed circles), and BM sites Site Descriptions (open circles). Vegetation at the sites sampled in this study had been previously classified to habitat type site. Contiguous sites are given identical site by Kemp et al. (1990a) using the scheme of numbers (e.g., SB1 adjoins AM1, FA1 adjoins Mueggler and Stewart (1980). All 25 sites sam- BM1, etc.). However, native sites designated pled are in the northern part of Gallatin County, SB7, SB8, FA5, FA6, and FA7 are not contigu- Montana, USA, within an area defined by lati- ous with reseeded sites. tudes 46°00′N to 45°45′N and longitudes ° ′ ° ′ Sampling Predators 111 00 W to 111 40 W. The 25 sites include and Parasitoids 14 within the Stipa comata/Bouteloua gracilis habitat type, 6 of which have been reseeded We sampled each site 3 times in 1988 and 4 with crested wheatgrass (Agropyron cristatum) times in 1989. The 3 sample periods in 1988 and alfalfa (Medicago sativa). The 2 habitat were 24 May–16 June, 18–21 July, and 22–25 classes, referred to here as SB (N = 8) and August. The 4 periods in 1989 were 22–27 AM (N = 6), respectively, occur along a 28-km June, 6–11 July, 31 July–2 August, and 12–18 northeast–southwest line in the western por- September. The range of dates during each tion of the valley in the vicinity of Three Forks sample period was constrained by availability and Logan, Montana (Fig. 1). We also sampled of suitable weather. A sample consisted of 200 11 sites within the Festuca idahoensis/Agropy- sweeps with a 38-cm-diameter muslin sweep ron spicatum habitat type, 4 of which had net, each sweep intersecting vegetation while been reseeded with smooth brome (Bromus traversing an arc of 180° parallel to the soil inermis) and alfalfa. These 2 habitat classes, surface. We marked off linear transects at the designated here as FA (N = 7) and BM (N = 4), beginning of the study to ensure that each respectively, occur along a 34-km north–south sample was taken at the same location during line in the eastern portion of the valley near each visit. All samples were taken between the foothills of the Bridger Mountains (Fig. 1). 0930 h and 1600 h under clear skies (i.e., <15% Reseeding with crested wheatgrass or brome cloud cover) and light winds (i.e., <25 km ⋅ had been done to provide grazing earlier in h–1). To reduce variation in sampling tech- the season, as both grasses begin their growth nique, all samples were taken by the same 2 in early spring. We refer to SB and FA as people. The 1988 samples used in this study “native” habitat classes, and AM and BM as were the same as those used to analyze com- “reseeded” habitat classes. Each of the re- munities of Acrididae (Kemp et al. 1990) and seeded sites is paired with a contiguous native Cicadellidae (Bess 1997) at the same sites. 2001] GRASSLAND INSECT ASSEMBLAGES IN MONTANA 197

For each sample we counted the number of using Mann-Whitney tests (with abundance as individuals from families of predatory and par- the dependent variable). We chose nonpara- asitoid insects (Fig. 2). Most families contain metric tests because most of the data sets were only predatory or parasitoid species (Krombein nonnormal and because we wished to avoid et al. 1979a, 1979b, Borror et al. 1989, Goulet allowing 1 or 2 very large samples to influence and Huber 1993). However, some families the results. (e.g., Carabidae, Cleridae, Meloidae, Calliphor- idae, Sarcophagidae, and Torymidae) contain RESULTS some noncarnivorous species but were deemed Overview of Families Collected important enough from an ecological stand- point to include in the study. Although these In the 175 samples from both years, 12,977 families may have contained a few phytopha- individuals of 51 families were counted, 4157 gous species, they were unlikely to have a in 1988 and 8820 in 1989. Numbers collected major influence on the overall analysis because in 1989 were greater than in 1988, partly together they comprised only 5% of the total because one more sample was taken at each sample over 2 years. For the Lygaeidae, most site in 1989. However, numbers collected in of which are phytophagous (Borror et al. 1989), 1989 were still greater than expected based on only members of the predator genus Geocoris the number of samples (chi-square goodness- were included. of-fit, χ2 = 620.7, P < 0.001, df = 1), primar- ily because of the huge number of encyrtid Data Analyses wasps collected. Although Encyrtidae com- We made 3 kinds of comparisons among prised only 4% of all specimens in 1988, habitats. First, we used detrended correspon- encyrtids made up 47% of 1989 samples (and dence analysis (DCA) using CANOCO (ver- 64% of insects collected on SB sites). The sion 3.12; ter Braak 1987–1992) to examine most abundant encyrtids in the samples were patterns of similarity in predator/parasitoid Copidosoma bakeri (Howard) and C. celaenae communities among different sites. DCA is an Howard. In 1989 most (77%) Encyrtidae were ordination technique that summarizes count collected during September, a period not sam- data from a site × taxon matrix and arranges it pled in 1988. However, the number collected in 2-dimensional space. In site-based DCAs during the 3 earlier sampling periods in 1989 presented here, increased distance between was still over 5 times that collected on corre- samples in an ordination reflects decreased sponding dates in 1988. In addition, Torymi- similarity in the communities at those sites. dae were absent in 1988 samples but com- For DCA analyses we used only families of prised over 3% of the individuals in 1989, Hymenoptera, Hemiptera, and Diptera because appearing in 56% of that year’s samples and they were abundant and showed the most occurring throughout the summer. variation among sites. Second, we examined Among 28 families of Hymenoptera col- whether the 12 most abundant families in our lected, 4 constituted 82% of the Hymenoptera samples differed in abundance among the 4 and 56% of all insects sampled (Fig. 2). The habitat classes. In this analysis we combined top 4 families (as well as the Scelionidae) were all samples collected at each site, conducting collected at all 25 sites, with the Braconidae separate analyses for the 2 years. Overall dif- and Ichneumonidae being collected at all sites ferences among the 4 habitats were examined in each of the 2 years. In contrast, 9 hymenop- using Kruskal-Wallis 1-way analyses of vari- teran families were represented by <10 speci- ance (with abundance as the dependent vari- mens each in the combined samples. Among able). We tested for differences in the abun- the Hymenoptera there was a significant posi- dance of specific families between SB and AM tive correlation between total number of indi- sites, and between FA and BM sites using viduals collected for each family and number Mann-Whitney tests (with abundance as the of species listed within each family in North dependent variable). Finally, data from the America in Krombein et al. (1979a, 1979b; rs = sites at the western end of the valley (SB and 0.60, P < 0.001, N = 28). Three families of AM) were combined and contrasted with com- non-Hymenoptera, the Lygaeidae, Nabidae, bined data from eastern (FA and BM) sites and Coccinellidae, comprised another 23% of 198 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 2. Relative abundance of families of predatory and parasitoid Hymenoptera and non-Hymenoptera collected over 2 years of sampling. Numbers in parentheses indicate number of sites (out of 25) at which the family was collected. Asterisks indicate families for which just a single individual was collected over the course of the study. the combined samples and were collected at 12% for axis 2. Small clusters of sites within most sites (Fig. 2). Several other non-hymen- similar habitat classes did appear on the plots, opteran families were lower in abundance but for example SB sites 1, 3, and 8 in 1988 and were present at most sites, including the Asili- SB sites 1, 3, 5, and 6 in 1989. There was also dae (24 sites) and Sarcophagidae (23 sites). Six a diffuse cluster of FA sites separated from non-hymenopteran families were each repre- other habitats on the right side of the 1989 sented by <10 specimens. plot. The latter may have been related to the fact that FA was the only class of sites that did Site Comparisons not exhibit a large flush of Encyrtidae in 1989. In 1988 mean total abundance of predators Sites from different habitat classes were often and parasitoids differed across the 4 habitats, intermingled on the plots. DCA analyses pro- primarily because samples on the eastern sites vide little evidence that spatial proximity of (FA and BM) harbored more individuals than sites is important in determining assemblage those in the west (Table 1). This pattern did of families at a site. None of the 6 contiguous not hold in 1989 because of the increase in pairs of SB and AM sites were each other’s abundance of Encyrtidae in the western side nearest neighbors on DCA plots for 1988 or of the valley, where they comprised 64% of the 1989 (in 1989, SB6 was the site most similar to samples from SB sites and 51% of those from AM6, but not vice versa). Among the 4 con- AM sites. In neither year did total abundance tiguous pairs of FA and BM sites, only FA3/ of all natural enemies differ between reseeded BM3 and FA4/BM4 were each other’s nearest and native habitats at the same end of the val- neighbors on the DCA plots, but only in 1988. ley (Mann-Whitney tests, P > 0.05 in 2 SB/AM Although DCA provided little support for and 2 FA/BM comparisons). the hypothesis that overall predator and para- Based on their positions in DCA analyses, sitoid assemblages varied consistently among we found no strong evidence that sites classi- habitat classes, data reveal several important fied a priori into the same vegetation category differences in patterns of abundance for par- tended to have distinct overall assemblages ticular families. In 1988, three of the major of families of Hymenoptera, Diptera, and hymenopteran families exhibited significant Hemiptera combined (Fig. 3). In 1988 axis 1 variation in abundance across habitat classes accounted for 39% of the variance, whereas (Fig. 4). For the Eulophidae and Scelionidae, axis 2 accounted for 21%; corresponding val- overall differences were due to higher abun- ues for the 1989 plot were 34% for axis 1 and dance on the eastern sites, whereas for the 2001] GRASSLAND INSECT ASSEMBLAGES IN MONTANA 199

TABLE 1. Mean numbers of specimens collected (all families combined) within the 4 habitat classes. ± Number ______Mean sx– collected Habitat of sites 1988 1989 Stipa comata/Bouteloua gracilis (SB) 8 118.0 ± 11.5a 356.6 ± 83.7a Agropyron cristatum/Medicago sativa (AM) 6 96.9 ± 14.1 452.5 ± 90.1 Festuca idahoensis/Agropyron spicatum (FA) 7 237.3 ± 41.3a 265.0 ± 42.5a Bromus inermis/Medicago sativa (BM) 4 312.5 ± 113.4 278.0 ± 116.0 Overall Kruskal-Wallis analyses P = 0.02 P = 0.40 Mann-Whitney analyses: western (SB + AM) vs. eastern (FA + BM) sites. P = 0.003 P = 0.15 aMann-Whitney comparison with reseeded site from same year, P > 0.05.

Pteromalidae, differences appeared to be due to higher abundance on FA compared to BM sites. In 1989, five hymenopteran families dis- played variation across habitat classes. Encyr- tidae, by far the most abundant family, was more abundant on western sites, whereas Eulo- phidae and Ichneumonidae were more abun- dant in the east. Three families, Eulophidae, Pteromalidae, and Torymidae, were more abun- dant on FA than BM sites, while the opposite was true for the Encyrtidae. Among the 5 major non-hymenopteran fam- ilies in 1988, only the 3 Hemiptera exhibited significant variation in abundance across habi- tat classes, each for different reasons (Fig. 5). Lygaeidae (Geocoris spp.) were relatively low in abundance on AM sites, Reduviidae were abundant only on FA sites, and Nabidae were most abundant within the 2 eastern habitat classes (especially on BM, although numbers were highly variable among the 4 BM sites). In 1989 only Nabidae varied significantly among habitats, again because of greater abundance in the east and on BM sites in particular.

DISCUSSION

In an analysis of vegetation assemblages at the sites discussed in this paper (Kemp et al. 1990a), we obtained a good separation of all 4 Fig. 3. Detrended correspondence analyses of total community types using DCA. Native SB and samples for 1988 and 1989. Polygons are arbitrarily drawn reseeded AM communities had similar total to surround sites classified a priori as belonging to a par- numbers of plant species, but AM sites had a ticular vegetation class (based on Kemp et al. 1990a). lower proportion of grasses (vs. forbs). SB and AM sites (mean elevation = ~1350 m) occur on the western side of the Gallatin Valley where annual precipitation averages about ~31 cm ⋅ of grasses. FA and BM sites (mean elevation = year–1. In comparing native FA and BM com- ~1520 m) occur on the eastern side of the munities, we found that FA sites had a higher Gallatin Valley, where annual precipitation mean number of plant species and percentage averages ~40 cm ⋅ year–1). 200 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 4. Mean abundance on each of 4 vegetation types of the 7 most abundant families of Hymenoptera. Overall Kruskal-Wallis (K-W) analyses examine whether abundance of each family varies across the 4 habitat classes. Mann- Whitney (M-W) analyses examine whether abundance for all western (SB + AM) differs from all eastern (FA + BM) sites. Habitat classes with different letters associated with them differ significantly in abundance from classes at the same end of the valley (i.e., SB vs. AM or FA vs. BM; Mann-Whitney tests, P < 0.05). See Table 1 for number of sites for each habitat.

DCA analyses of the combined Hymenop- more abundant on BM sites. The observation tera, Diptera, and Hemiptera provided no that most paired native/seeded sites were not strong evidence that the 4 habitat classes con- adjacent to one another on the DCA plots also tained distinct overall natural enemy commu- suggests that reseeding can modify natural nities. However, analyses of specific families enemy communities despite the fact that other give several indications of potentially impor- site characteristics are unaffected by reseed- tant differences among habitat classes. Twelve ing (e.g,. precipitation, elevation, and soil type). of 23 comparisons (52%) across all 4 habitat At this point it is impossible to determine which classes revealed differences in abundance of ecological correlates of reseeding and habitat specific families, 2 of which showed signifi- fragmentation are responsible for differences cant differences during both years (i.e., Eulo- in natural enemy assemblages between FA phidae and Nabidae). and BM habitats. One major hypothesis would A portion of the differences among habitat be that, in changing plant community compo- classes was apparently associated with reseed- sition, reseeding restructures the phytophagous ing. Eight of 46 (17%) comparisons between insect community (Kemp et al. 1990a, Bess native and reseeded habitats revealed differ- 1997) and therefore modifies the resource base ences in abundance of specific families, indi- for parasitoids and predators (many of which cating that reseeding may have an important may be specialists). Natural enemy assemblages influence on natural enemy communities. Seven in native habitats may also be affected by habi- of these differences occurred between FA and tat area reduction and isolation from other native BM sites. Eulophidae (1989), Torymidae (1989), habitats with which they could exchange com- Pteromalidae (both years), and Reduviidae mon species. Recently, Kruess and Tscharntke (1988) were more abundant on FA sites, where- (2000) found evidence that habitat fragmenta- as Encyrtidae (1989) and Nabidae (1989) were tion in agricultural landscapes caused greater 2001] GRASSLAND INSECT ASSEMBLAGES IN MONTANA 201

Fig. 5. Mean abundance on each of the 4 vegetation types of the 5 most abundant families of non-Hymenoptera. See Figure 4 for explanation. See Table 1 for number of sites for each habitat. reductions in parasitoid diversity than in her- There were also instances of significant vari- bivore diversity. Reseeding, through its effect ation in abundance within habitat classes dur- on the physical structure of vegetation, may ing a single year, for example, Braconidae on also alter wind speeds and patterns of insola- AM sites in 1988, Ichneumonidae and Nabidae tion near the ground (Geiger 1966). Resulting on BM sites in 1988, Coccinellidae on AM sites microclimate changes may have important in 1989, Encyrtidae on SB, AM, and BM sites effects on activity and developmental patterns in 1989. Such variation is an indication that (1) of small ectotherms, such as insects. For exam- site-specific habitat characteristics not incor- ple, dense vegetation may preclude early morn- porated in our habitat classification or (2) local ing thermoregulation by eliminating ground- stochastic events may be important in deter- level basking sites (Anderson et al. 1979). mining predator and parasitoid abundance. According to a strict habitat type classifica- Thus, our habitat classes (along with their tion (in the sense of Mueggler and Stewart shared characteristics) are at best rough pre- 1980), SB and AM sites on the western side of dictors of local abundance (at the family level). the valley belong to one habitat type (Stipa In combination these analyses suggest that comata/Bouteloua gracilis), whereas the FA reseeding and natural habitat variation (both and BM sites (in the east) belong to another within and between habitat classes) interact in (Festuca idahoensis/Agropyron spicatum). After a complex fashion to influence the composition combining the western and eastern sites into of natural enemy communities on grasslands. their respective habitat types, 7 of 23 compar- Phytophagous insect communities also dif- isons (30%) revealed differences in abundance fer among habitat classes discussed in this of specific families between the western and paper. Using the same 1988 samples from which eastern (higher and relatively mesic) sides of predators and parasitoids were extracted, Kemp the valley. The most obvious differences were et al. (1990a, 1990b) found that native and higher abundance of Nabidae in eastern sites reseeded grassland habitats in the Gallatin Val- in both years and higher abundance of Encyr- ley harbored different grasshopper assemblages. tidae on western sites in 1989. Even stronger differences in grasshopper 202 WESTERN NORTH AMERICAN NATURALIST [Volume 61 assemblages were found when grasslands of include generalist predators (e.g., Nabidae and surrounding mountain ranges were included Lygaeidae [Geocoris]). (Wachter et al. 1998). In addition, Bess (1997), Along with agriculture and urban develop- also using the same 1988 samples (as well as ment, reseeding native grasslands with exotic others from 1991 on the same sites), found species, such as crested wheatgrass, smooth that leafhopper (Cicadellidae) assemblages dif- brome, and alfalfa, has fragmented native fered between native and reseeded sites, and prairie habitats of the western U.S. Although between sites with differing native vegetation. the effect of habitat fragmentation on specific Elsewhere, others have also investigated the insect communities is usually unknown, the effect of deliberate modification of grassland task of documenting the composition of insect vegetation on insect communities. Rushton et communities on multiple sites is daunting. One al. (1989) found that reseeding pastures to approach is to choose a narrow array of taxa of replace native vegetation reduced diversity of known ecological importance on grasslands predatory beetles and spiders. Spangler and and to conduct species-level analyses. Even McMahon (1990) found a higher biomass of such a focused taxonomic approach can be sap-feeding Miridae on grasslands reseeded to labor intensive. For example, an analysis of the monocultures. However, they found no differ- grasshoppers collected at 39 sites in a single ence either between native and reseeded habi- year required identification of nearly 20,000 tats or between reseeded monocultures and grasshoppers in 40 species (Kemp et al. 1990a), bicultures in overall abundance of selected whereas a similar 2-year study of leafhoppers predatory arthropods (i.e., Lygaeidae [Geocoris], at 12 sites required sorting over 44,000 speci- Nabidae, and Coccinellidae). mens to 57 species or genera (Bess 1997). For In the studies by Kemp (1990a), Spangler other taxa we may not always have a priori and MacMahon (1990), and Bess (1997), focal knowledge of which groups are most abundant taxa from grassland samples were identified to at specific sites. Thus, one advantage of a fam- species or genus. In the present study we opted ily-level analysis is that it allows one to survey for family-level analyses to examine a wide a broad array of taxa to pinpoint groups for range of taxa (51 insect families in 5 orders). “priority attention and commitment of re- However, counts at the family level may ob- sources” (New 1996) for future conservation scure important pieces of ecological informa- and land management studies. In our case we tion. First, family-level analyses give no indi- identified several taxa that were abundant and cation of within-family diversity or evenness at variable in distribution across habitat classes the species level. Second, members of a single (e.g., Braconidae, Encyrtidae, Eulophidae, family may fulfill a number of different func- Ichneumonidae, Pteromalidae, Scelionidae, tional roles within ecosystems (Beattie et al. Torymidae, Lygaeidae, and Nabidae). There- 1993). At our sites, for example, some Asilidae fore, those conducting studies on similar grass- and Sphecidae prey on grasshoppers (O’Neill land habitats in the northern U.S. Rocky Moun- 1995), while others take beneficial natural ene- tains might consider these families as fruitful mies of grasshoppers (e.g., sarcophagid and candidates for future species- or generic-level bombyliid flies; Rees and Onsager 1985) or analyses of natural enemy communities. pollinators (O’Neill and Seibert 1996). Never- theless, we found habitat-specific differences ACKNOWLEDGMENTS in abundance of predators and parasitoids that may have important impacts on phytophagous We thank Jeffrey Holmes, Geoff Fitzgerald, insect communities on grasslands. For exam- Cathy Curtiss, Erin O’Brien, and David Wachter ple, Encyrtidae are endoparasitoids of scale for assistance with fieldwork and sample pro- insects and eggs of other insects and are con- cessing. Stephen Harvey provided assistance sidered “one of most important chalcidoid fam- and advice on vegetation analysis, and Greg ilies for biological control” (Goulet and Huber Zolnerowich identified the encyrtids. James 1993). Similarly, many Eulophidae are para- Fisher, Robert Nowierski, Ruth O’Neill, and sitoids of leafmining insects (Goulet and Huber Tad Weaver reviewed the manuscript. This 1993) and some Scelionidae are parasitoids of work was supported by USDA Agricultural grasshopper eggs (Dysart 1995). Other taxa Research Service, USDA Animal and Plant that exhibited differences among habitats may Health Inspection Service Plant Protection 2001] GRASSLAND INSECT ASSEMBLAGES IN MONTANA 203 and Quarantine, and the Montana Agricultural 53–70 in B. Ekbom, M.E. Irwin, and Y. Robert, edi- Experiment Station (Publication 2000-1). tors, Interchanges of insects between agricultural and surrounding landscapes. Kluwer Academic Pub- lishers, Boston, MA. LITERATURE CITED MUEGGLER, W., AND W. S TEWART. 1980. Grassland and shrubland habitat types of western Montana. United ANDERSON, R.V., C.R. TRACY, AND Z. ABRAMSKY. 1979. States Department of Agriculture, Forest Service Habitat selection in two species of short-horned GTR INT-66. grasshoppers: the role of thermal and hydric stresses. NEW, T.R. 1996. Taxonomic focus and quality control in Oecologia 38:359–374. insect surveys for biodiversity conservation. Aus- ARENZ, C.L., AND A. JOERN. 1996. Prairie legacies—inver- tralian Journal of Entomology 35:97–106. tebrates. Pages 91–110 in F.B. Samson and F.L. O’NEILL, K.M. 1995. Digger wasps (Hymenoptera: Sphe- Knopf, editors, Prairie conservation: preserving cidae) and robber flies (Diptera: Asilidae) as preda- North America’s most endangered ecosystem. Island tors of grasshoppers (Orthoptera: Acrididae) on Mon- Press, Washington, DC. tana rangeland. Pan-Pacific Entomologist 71:248–250. BESS, J.A. 1997. The leafhopper species assemblages asso- O’NEILL, K.M., AND C. SEIBERT. 1996. Foraging behavior ciated with native and replanted grasslands in south- of the robber fly Megaphorus willistoni (Cole) west Montana. Master’s thesis, Montana State Uni- (Diptera: Asilidae). Journal of the Kansas Entomo- versity, Bozeman logical Society 69:317–325. BEATTIE, A.J., J.D. MAJER, AND I. OLIVER. 1993. Rapid bio- REES, N.E., AND J.A. ONSAGER. 1985. Parasitism and sur- diversity assessment: a review. Pages 442–460 in A.J. vival among rangeland grasshoppers in response to Beattie, editor, Rapid biodiversity assessment. Mac- suppression of robber fly (Diptera: Asilidae) preda- quarie, Sydney, Australia. tors. Environmental Entomology 14:20–23. BOCK, J.H., AND C.E. BOCK. 1995. The challenges of grass- RUSHTON, S.P., M.L. LUFF, AND M.D. EYRE. 1989. Effects land conservation. Pages 199–222 in A. Joern and of pasture improvement and management on the K.H. Keeler, editors, The changing prairie: North ground beetle and spider communities of upland American grasslands. Oxford University Press, New grasslands. Journal of Applied Ecology 26:489–503. York. SPANGLER, S.M., AND J.A. MACMAHON. 1990. Arthropod BORROR, D.J., C.A. TRIPLEHORN, AND N.F. JOHNSON. 1989. faunas of monocultures and polycultures in reseeded An introduction to the study of insects. 6th edition. rangelands. Environmental Entomology 19:244–251. Saunders College Publishing, Philadelphia, PA. 875 TER BRAAK, C.J.F. 1987–1992. CANOCO—a FORTRAN pp. program for canonical community ordination. Micro- DYSART, R.J. 1995. New host records for North American computer Power, Ithaca, NY. Scelio (Hymenoptera: Scelionidae), parasitic on grass- ______. 1988. CANOCO: an extension of DECORANA to hopper eggs (Orthoptera: Acrididae). 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Patterns tudinal gradient of the northern Rocky Mountains. of vegetation and grasshopper community composi- Pages 14–29 in T. Youngberg, editor, Proceedings of tion. Oecologia 83:299–308. the 5th North American Forest Soils Conference, _____. 1990b. Habitat and insect biology revisited: the Fort Collins, CO. Oregon State University Press, search for patterns. American Entomologist 36:44–49. Corvallis. KROMBEIN, K.V., P.D. HURD, D.R. SMITH, AND B.D. BURKS. ______. 1979b. Climates of fescue grasslands of moun- 1979a. Catalog of Hymenoptera in America north of tains in the western United States. Great Basin Nat- Mexico. Volume 1, Symphyta and Apocrita (Parasit- uralist 39:284–288. ica). Smithsonian Institution Press, Washington, DC. ______. 1980. Climates of vegetation types of the north- 1198 pp. ern Rocky Mountains and adjacent plains. American ______. 1979b. Catalog of Hymenoptera in America north Midland Naturalist 103:392–398. of Mexico. Volume 2, Apocrita (Aculeata). Smithson- ian Institution Press, Washington, DC. 1011 pp. Received 12 January 2000 KRUESS, A., AND T. T SCHARNTKE. 2000. Effects of habitat Accepted 31 May 2000 fragmentation on plant-insect communities. Pages Western North American Naturalist 61(2), © 2001, pp. 204–212

VARIATION IN THE LIFE HISTORY AND ABUNDANCE OF THREE POPULATIONS OF BRUNEAU HOT SPRINGSNAILS (PYRGULOPSIS BRUNEAUENSIS)

Greg C. Mladenka1 and G. Wayne Minshall2

ABSTRACT.—Bruneau hot springsnail density, size class structure, recruitment, and mortality were measured monthly over approximately 2 years and compared to environmental variables at 3 hot spring sites in southwestern Idaho. Food resources (attached algae) and water chemistry were similar among sites, but temperature, population density, and size structure differed significantly. Density was highest at a warm, fairly constant temperature site. A cooler, highly variable temperature site and a site where temperatures frequently approached or exceeded thermal maxima tolerance limits had lower densities. Size class structure varied seasonally and distinctly among sites, with recruitment occurring year-round at temperatures <36°C. Mortality affected different size classes at different sites, with smaller snails incurring greatest mortality at site 3 (highest temperature variability). Growth rates were positively correlated with temperatures up to 36°C. Mean snail size differed among sites and also appeared to be related to temperature, with the variable tempera- ture sites having larger snails. Although these snail populations are found in a range of water temperatures, they appear best adapted to springs with mean temperatures between 32° and 33°C and low thermal variance.

Key words: Pyrgulopsis bruneauensis, Bruneau Hot Springs, hydrobiid, snail, thermal springs, life history, endan- gered species.

Hydrobiid snails are one of the most com- (a spring originating from the ground as a flow- mon Prosobranch families occupying marine, ing stream) and madicolous habitats (thin sheets brackish, and freshwater habitats worldwide. of water flowing over rock faces [Ward 1992]). Thirty-one genera containing more than 200 The species is confined to these thermal sys- species are known from North America (Burch tems (Mladenka 1992). Taylor (1982) gave a 1982, Hershler 1998). Certain hydrobiid gen- brief physiological and biological description era are well studied (van der Schalie and Davis of the snail, and Fritchman (1985) studied its 1965, 1968, Gore 1967, Liang and van der reproduction under laboratory conditions, but Schalie 1975, French 1977, Lassen and Clark no other studies of its biology are known. This 1979, Forbes and Lopez 1990). Hydrobiids study addresses aspects of life history varia- inhabiting mound springs in South Australia tion in the hydrobiid Pyrgulopsis bruneauensis were investigated by Ponder et al. (1989). A inhabiting 3 distinct thermal sites in a local- recent systematic review of Pyrgulopsis in the ized area of southwestern Idaho. We examined Great Basin region of the western USA was recruitment, growth, mortality, and density of conducted by Hershler (1998). O’Brien and P. bruneauensis in relation to key environmen- Blinn (1999) examined distribution of Pyrgu- tal factors, especially temperature. lopsis montezumensis in relation to a CO2 gra- dient in a thermal spring outflow in Arizona; STUDY SITES however, little else is known of the life histories of hydrobiid snails in the arid North American We found Pyrgulopsis bruneauensis in more West. than 100 small warm springs and seeps along The Bruneau hot springsnail (Pyrgulopsis 8 km of the lower Bruneau River. However, all bruneauensis Hershler 1990) is an endemic, en- springs derive from a single geothermal aquifer dangered species inhabiting hot springs adja- consisting of fractured volcanic rock (Beren- cent to the Bruneau River south of Mountain brock 1993). The surrounding area is high Home, Idaho. Pyrgulopsis bruneauensis occu- desert that receives <25 cm of precipitation pies flowing thermal waters in both rheocrene yearly, predominantly during winter months.

1156 South 16th, Pocatello, ID 83201. 2Stream Ecology Center, Department of Biological Sciences, Idaho State University, Pocatello, ID 83209.

204 2001] SPRINGSNAIL LIFE HISTORY AND ABUNDANCE 205

During this study air temperatures varied Alkalinity (as CaCO3), pH, hardness, and spe- from –7°C in January 1990 to 39°C in June cific conductance at 25°C were determined and August 1991. Mean annual temperature monthly. We performed tests to determine was 29.4°C (s = 7.2), with a mean low temper- specific conductance and pH in the field using ature of 4.5°C (s = 5.9). an electronic meter (Orion Instruments model We studied P. bruneauensis at 3 noncon- 26). Other analyses were done at the Idaho tiguous sites having different temperature and State University Stream Ecology Center accord- flow regimes. Water chemistry was relatively ing to standard methods (APHA 1989). Samples constant within sites during this study and were analyzed for total phosphorus and nitro- similar among sites (Table 1). Mean pH was gen quarterly for 1 year. Nitrogen and phos- 8.6 for all sites. Hardness ranged from 21.8 to phorus analyses were conducted at Desert 26.7 mg ⋅ L–1 and total alkalinity from 91 to Research Institute Water Laboratory, Reno, NV. ⋅ –1 102 mg L (both as CaCO3). Mean conduc- Dissolved oxygen was measured 3 times dur- tivity ranged from 267 to 287 µS ⋅ cm –1. Total ing spring and summer 1990 using an oxygen phosphorus ranged from 0.028 to 0.047 mg ⋅ probe (Orion Instruments O2 electrode, model L–1 and nitrate nitrogen from 0.40 to 0.60 mg ⋅ 97-08). L–1. Site 2 maintained the most constant tem- Food abundance was measured monthly at perature (measured monthly) of the 3 sites each site. A known area of periphyton was (range = 25.0–34.5°C), whereas site 3 had the scraped from rocks and transferred to a pre- ° widest temperature range (8.0–32.0 C). Site 1 ashed filter of known mass as described in – ° had the highest temperatures (x = 34.9 C, s Cushing et al. (1983). Samples were analyzed ° = 1.1, max. = 37 C). for biomass and chlorophyll a (APHA 1989). Sites ranged in size and habitat type from a We determined temperature tolerance by × nearly vertical 1.5-m-high 1.3-m-wide rock placing 5 snails in 11-cm-diameter × 6-cm- face and its 1.0-m-wide × 2.0-m-long outflow × high plastic dishes, all receiving water via a (site 2) to a 1-m-wide 10-m-long stream seg- submersible pump in a 15-L plastic bucket ment (site 1). Study sites were typical of other containing a submersible heater. Water was springs containing Bruneau hot springsnails. continuously aerated and filtered. Complete The study sites are located near the Bruneau flow-through time for the system was 40 min- River tributary Hot Creek, just downstream of utes. Periphyton from field sites was provided Bruneau Canyon (NE 1/4 Sec 3, T8S, R6E). in all dishes as a food source. Snails were Site 1, on Hot Creek, had a mean discharge acclimated to the dishes for 2 days at 30°C. of 0.016 m3 ⋅ s–1 during the study. In general, During the high-temperature tolerance exper- higher flows occurred from late autumn through iment, water temperature remained at 30°C spring, while lower flows, corresponding to the for a control group, while temperature in the irrigation season, occurred during the remain- ° der of the year. Water temperature ranged from experimental group was raised 1 C per 24- 25° to 37°C (except during a rainstorm runoff hour period. At the end of each 24-hour period, event in September 1991 when it decreased to locations of all snails were recorded (in or out 14.5°C; Fig. 1). Cobbles, gravel, and sand of water). Water temperature was increased comprised the streambed, and sedge ( Juncus) until all snails (in the experimental group) exited grew along the stream banks. Sand and silt the water. We conducted a parallel experiment accumulated in the study reach from Decem- to determine low-temperature tolerance. Tem- ber 1990 through the study’s conclusion, with perature in this experimental group was low- ° most cobble substrate becoming completely ered 1 C per 24-hour period, at which point buried by June 1991. Sites 2 and 3 are east- snails were checked for their ability to right facing madicolous habitats with associated themselves after being inverted. Water tem- outflows over gravel and cobble substrate bor- perature was lowered until <50% snails could dering the west side of Bruneau River down- right themselves in 1 minute. Using a different stream of its confluence with Hot Creek. apparatus, we conducted another high-temper- ature tolerance experiment following the proce- METHODS dures previously described. In this 2nd experi- ment, 20 snails were placed in each of four 1-L We measured temperature monthly with beakers. Water was heated and aerated inde- maximum-minimum recording thermometers. pendently in each beaker. 206 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Using field size histograms and laboratory snails. Newly hatched P. bruneauensis were rearing, we estimated growth rates. Snails were about 0.3 mm long, but some growth occurs kept in 40-L glass aquaria half filled with hot before sexual maturity is reached. We arbitrar- spring water and equipped with air stones ily considered snails ≤0.57 mm long to be placed inside 20-cm lengths of 3-cm-diameter juveniles. We feel this is a conservative esti- clear plastic tubing to create a slight current. mate as male genitalia were not evident at Periphyton from the field was maintained in shell heights <1.4 mm. A rough estimate of the aquaria at levels exceeding snail food re- the number of juveniles produced per female quirements. Distilled water was added, when was calculated by dividing the number of required, to maintain water levels and dis- juveniles by 0.5 of the snails ≥1.4 mm present solved solute concentrations. Twenty-five juve- in the previous month’s sample (sex ratios nile snails were placed in each of 3 aquaria were determined to be 1:1). Therefore, in this maintained at temperatures of 15°, 30°, and paper recruitment refers to the presence of 34°C. Shell heights were determined at approx- snails ≤0.57 mm long. imately 20-day intervals for 87 days using a To assess broad, cumulative differences in dissection microscope equipped with an ocular mortality among sites, we collected shells of micrometer. A statistical comparison employ- dead individuals (n = 56, 103, and 102 at sites ing analysis of variance was done after 39 days 1, 2, and 3, respectively) on 3 October 1990 to ensure adequate sample sizes, since some from the substrate at each site using a strainer mortality occurred. (7.5-cm-diameter) and measured them as in Snail density was estimated employing ran- live snails. dom quadrat counts in the area of a ring (A = Site-specific size differences between male 60.8 cm2). We made visual counts of all encir- and female snails were analyzed with t tests. cled Pyrgulopsis bruneauensis in 20 locations Comparisons among site density and structure at each site. An inverted petri dish of the same were done using analysis of variance. Water size as the inside diameter of the ring elimi- chemistry was analyzed in the laboratory using nated water turbulence and allowed clear standard methods (APHA 1989). An analysis of variance was performed on each water chem- viewing of substrate and snails at site 1 and istry parameter (questionable alkalinity and deeper outflow areas at site 2 (site 3 was hardness data from the first 3 months’ samples entirely madicolous and did not require this were excluded from analysis). When analysis technique). From February 1990 through of variance revealed significant differences, November 1991, we monitored density monthly. we employed Tukey’s test to determine signifi- Snails for size-structure analysis were col- cant differences among means. Sex ratios were lected at each site from at least 5 rocks. After compared to a 1:1 ratio using a chi-square test. gently removing rocks from the water, we Relationships between density and food abun- rinsed the snails with a 500-mL hypodermic dance (biomass), temperature, and flow were syringe into a 10-cm-diameter petri dish. After analyzed using 1st-order regressions. thorough mixing, the sample was viewed under a dissection microscope with an ocular microm- RESULTS eter. Each month (from 16 February 1990 through 15 December 1991), we measured Temperature and water chemistry data are shell heights of the first 100 snails from each presented in Table 1. Sites had very similar site to the nearest 0.14 mm at 40X magnifica- water chemistry with the exception of higher tion. Snails were then returned to their habi- alkalinity at site 1 (F = 49.51, P < 0.0005) and tat. During March 1991 (site 3) and August higher N at site 3 (F = 8.12, P < 0.01). Water 1991 (sites 1, 2), 49, 36, and 36 snails >1.4 temperature varied seasonally at all sites (Fig. mm long were also sexed and enumerated at 1); however, mean maximum water tempera- sites 1, 2, and 3, respectively. Male genitalia ture differed significantly among sites (F = were extruded and clearly evident as snails 109.4, P < 0.0005). Site 1 reached the highest attempted to right themselves after being maximum temperature (37°C), while site 3 inverted. had the most variable regime and lowest mean We did not determine reproduction or high temperature (26.8°C, s = 3.7). Site 2 water fecundity directly, to avoid sacrificing the temperature fluctuated least among sites, with 2001] SPRINGSNAIL LIFE HISTORY AND ABUNDANCE 207

TABLE 1. Physicochemical variables for the Bruneau Hot Springs study sites. Means and standard deviations (in parentheses) for pH, hardness, conductivity, and alkalinity are for 18 March 1990–16 November 1991. Temperature (C°) Oxygen Phosphorus Nitrogen ______Hardness Conductivity Alkalinity (mg ⋅ L–1 (mg ⋅ L–1 (mg ⋅ L–1 µ ° ⋅ –1 Site Max. Min. pH (mg CaCo3)(S @ 25 C) (mg L ) dissolved) as P) as N) 1 34.9 (1.1) 30.5 (3.7) 8.6 (0.2) 26.7 (6.2) 287 (13) 102 (3) 6.6 (0.3) 0.034 (0.015) 0.60 (0.01) 2 33.3 (0.8) 30.8 (2.3) 8.6 (0.2) 23.7 (9.3) 267 (42) 91 (4) 6.3 (0.7) 0.028 (0.025) 0.60 (0.01) 3 26.8 (3.7) 17.4 (3.8) 8.6 (0.3) 21.8 (5.2) 276 (29) 92 (4) 6.9 (0.4) 0.047 (0.010) 0.40 (0.12)

Fig. 1. Size histograms and maximum and minimum water temperatures for the Bruneau hot springsnail study sites versus time. X-axis tick marks represent 10 snails per unit. Horizontal tick marks represent 0.14-mm size classes (n = 100 ⋅ sample–1). Circles and squares represent maximum and minimum water temperatures, respectively.

a mean maximum temperature of 33.3°C (s = biomass. There were no significant differences 0.8). in biomass or chlorophyll a among sites. Periphyton biomass varied widely within We determined the maximum tolerable and among sites (Fig. 2), with site 1 showing temperature to be 36°C in the laboratory. greatest variation (range = 2.24–74.13 mg ⋅ When water temperatures approached or m–2 ash-free dry weight). Mean biomass at exceeded this temperature at site 1, snails sites 1, 2, and 3 was 14.31 (s = 15.96), 16.34 (s became concentrated along spring margins, on = 8.82), and 21.97 g ⋅ m–2 (s = 10.65), respec- algal mats, and in areas of upwelling water, tively. Chlorophyll a concentrations paralleled where water temperature was 1–7°C lower 208 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 2. Mean snail density, maximum water temperature, and periphyton biomass (ash-free dry weight) versus time for the Bruneau hot springsnail study sites. Note differences in scale on y-axes. Error bars represent ±1 s for the mean of 3 density estimates. than recorded in the main flow. The low-tem- noticeably absent on a number of sampling perature tolerance limit was not as distinct; dates at site 1 (Fig. 1), with the highest pro- however, >50% snails failed to right them- portion of juveniles recorded from November selves within 1 minute when temperatures through April. As a result, distinct cohorts of were below 10°C. snails are clearly evident. In contrast, juve- Snails raised in laboratory aquaria at 15°, niles were present in nearly all samples at the 30°, and 34°C grew at 0.020, 0.029, and 0.034 other sites. Site 2 exhibited the most stable mm ⋅ d–1, respectively. Snails attained differ- size structure; however, mature snails were ent sizes at 15° (x– = 0.792 mm, s = 0.069) and the smallest among the sites. Site 3 exhibited 34°C (x– = 1.32 mm, s = 0.260; F = 26.93, P bimodal distribution for nearly all samples, < 0.05). Size increases estimated from field while other sites did not. size histograms (Fig. 1) were 0.022, 0.010, and Shells of dead snails were bimodally dis- 0.024 mm ⋅ d–1 for sites 1, 2, and 3, respec- tributed at site 1, but large size classes pre- tively. dominated among composite samples of live Snail density varied among sites and sea- snails prior to and during this time (Fig. 3). sonally within sites (Fig. 2). Although high Size distribution of dead snails at site 2 was densities (2997 ⋅ m–2, March 1991) were found similar to size distribution among living snails, seasonally at site 1 (x– = 909 ⋅ m–2, s = 795), whereas at site 3 there was a greater propor- the greatest mean density (8900 ⋅ m–2, s = tion of dead snails in smaller size classes com- 3936) occurred at site 2 (F = 17.79, P < pared to size distribution of living snails. 0.0005). Site 3 had a mean density of 1782 ⋅ Newly hatched, Pyrgulopsis bruneauensis m–2 (s = 953). are nearly transparent and have a mean shell Mean snail size differed among sites (F = height of 0.3 mm. When snails reach approxi- 597.03, P < 0.0001; Table 2), with the largest mately 0.7 mm, they become nearly black. snails and mean size at site 1. Juveniles were Male genitalia are clearly evident in snails 2001] SPRINGSNAIL LIFE HISTORY AND ABUNDANCE 209

TABLE 2. Mean snail size and standard deviation for the niles were present in site 1 December 1990 Bruneau Hot Springs study sites. samples following decreased maximum water Standard temperatures that had been apparent since Site Mean deviation F-value P September (Fig. 1). Site 1 abundance peaked 1 1.57 0.72 194.15 <0.0001 in March, apparently a result of increased re- 2 1.11 0.39 20.92 <0.0001 cruitment. Generally, thermal stability resulted 3 1.51 0.71 10.85 <0.0001 in higher snail density, with site 2 consistently having highest abundance (Fig. 2). Size distri- bution histograms of P. bruneauensis at site 3 exceeding a shell height of 1.4 mm. Snails were bimodal for nearly every sample during lacking male genitalia at that size and greater the study (Fig. 1). This suggests continuous low were considered female. The percentage of recruitment into larger size classes. males at all sites did not significantly differ Comparisons of mortality histograms (Fig. from 50%. Mean male and female sizes were 3) indicated differences in size-specific mor- significantly different only at site 1 (P < 0.05), tality among sites. Mortality at site 1, which with females being slightly larger (x– = 2.25 was generally warmer than and intermediate mm, s = 0.371) than males (x– = 2.02 mm, s = in temperature variability compared to sites 2 0.230). and 3, tended toward a bimodal distribution, The estimated number of juveniles produced indicating increased mortality in both small per female ranged from 0 to 18.5 ⋅ month–1 for and large size classes. The histogram from site the sites. The approximate number of juve- 3 (cooler, more variable temperature) indicates niles per female ranged from a mean of 1.24 (s increased mortality among juveniles. Given = 2.79) at site 1 to 0.80 (s = 1.56) at site 2. that the sites were otherwise relatively similar, Site 3 had a mean of 1.19 (s = 3.89); however, slower growth at site 3 may be a prominent differences among sites were not statistically mechanism preventing recruitment into larger significant. size classes. This could be a result of lower minimum temperatures or large temperature DISCUSSION fluctuations. We feel that collection and measurement of Marked differences in recruitment patterns empty shells followed by comparison with a and densities of P. bruneauensis among study living population give insights into general dif- sites were especially correlated with differ- ferences in age-specific mortality among sites ences in thermal regimes. Snail density at site even though smaller size classes may have been 1 (a site which occasionally exceeded 36°C) underrepresented in the samples because of was inversely related to temperature (P < 0.02), possible shorter shell disintegration times. whereas the relationship for site 3 (always Although hydrobiid snails are relatively dense <36°C) was positive (P < 0.005; Fig. 4). At and soon settle out of the current (T. Frest per- site 3 highest densities were reached during sonal communication), different-sized shells periods of continually warm ambient air tem- may have drifted differentially after the ani- perature when discharge was observed to be mals decomposed. However, numerous low- low (not directly measured). velocity areas were available for shell entrain- Recruitment was evident throughout the ment, and juvenile shells were found in each study at site 3 except in December 1990 and sample. While shells do accumulate and de- August 1991, and occurred at sites 1 and 2 compose over time, they should accumulate when not inhibited by excessive water tem- and decompose similarly at sites with similar peratures (Fig. 1). Recruitment at site 1 was water chemistry (as in our sites), and compar- seasonal, and the highest proportion of juve- isons among sites give a general indication of niles was recorded from November through how age classes are affected by mortality. Our April. Because sites had different temperature conclusions relative to temperature effects regimes, seasonality of recruitment depended could be affected by our method of tempera- upon when or if the thermal limit was ex- ture measurement. Hourly temperature data ceeded. At sites 1 and 2 increased density fol- obtained after this study from the same sites lowed increased recruitment during periods of indicate occasional, short-duration tempera- optimal temperatures. For example, many juve- ture fluctuations. We could not distinguish 210 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 3. Histograms illustrating percentage of mean live snail shell heights (mean of live samples taken over a 3-month period leading into and including the dead shell sampling) and shell heights of dead snails for the Bruneau hot springsnail study sites. short-duration (1–2 hours) from longer-dura- other sites because of shallow, dispersed tion changes. Since hydrobiid hatching times flows), we found a strong correlation (r2 = can be as short as 8 days (Otori et al. 1956, Chi 0.70, P < 0.001, y = –1912.24 + 174109.82x). and Wagner 1957, Liang and van der Schalie Discharge and temperature were inversely 1975, Lassen and Clark 1979), a short-dura- correlated (r2 = 0.39, P < 0.01, y = 37.48 – tion temperature increase or decrease could 160.64x); however, discharge measurements mask a period of optimal temperature for re- reflected rather steadily changing flows and production. Reproduction could occur and be were not impacted by discrete, short-term reflected in size and density data, while our events. Given such a high correlation with den- temperature data would not indicate optimal sity and the fact that we did not measure flow conditions existed during that period. during May 1990 and September 1991 flood When we compared discharge to density at events, it may be that in this case these mea- site 1 (discharge could not be measured at surements give a better indication of general 2001] SPRINGSNAIL LIFE HISTORY AND ABUNDANCE 211

eral anonymous reviewers also provided valu- able suggestions. This study was funded by a grant from the U.S. Fish and Wildlife Service, Boise, Idaho, Field Office.

LITERATURE CITED

APHA. 1989. Standard methods for the examination of water and wastewater. 17th edition. American Public Health Association, Washington, DC. 1100 pp. BERENBROCK, C. 1993. Effects of well discharges on hy- draulic heads in and spring discharges from the geo- thermal aquifer system in the Bruneau area, Owyhee County, southwestern Idaho. U.S. Geologic Survey Water-Resources Investigations Report 93-4001. 58 pp. BOWLER, P.A., AND P. O LMSTEAD. 1989. The current status of the Bruneau hot springs snail, an undescribed monotypic genus of freshwater hydrobiid snail, and Fig. 4. Linear regressions of snail density versus maxi- its declining habitat. Presented at the Twenty-first mum temperature for Bruneau hot springsnail study sites. Annual Symposium of the Desert Fishes Council at Note logarithmic scale on y-axis. the University of New Mexico, Albuquerque, 16 November 1989. 12 pp. BURCH, J.B. 1982. Freshwater snails (Mollusca: Gastro- trends (including temperature) than our actual poda) of North America. EPA report 600/3-82-026. temperature measurements. CHI, L.W., AND E.D. WAGNER. 1957. Studies on reproduc- Of the other environmental factors we mea- tion and growth of Oncomelania quadrasi, O. nos- sured, water chemistry remained fairly con- phora, and O. formosa, snail hosts of Schistosoma japonicum. American Journal of Tropical Medicine stant throughout the study. Chlorophyll a was and Hygiene 6:949–960. not significantly correlated with recruitment CUSHING, C.E., K.W. CUMMINS, G.W. MINSHALL, AND R.L. or density. Biomass correlated with density VANNOTE. 1983. Periphyton, chlorophyll a, and dia- only at site 2, and only when densities at mid- toms of the Middle Fork of the Salmon River, Idaho. range temperatures (i.e., excluding outliers) Holarctic Ecology 6:221–227. FORBES, V.E., AND G.R. LOPEZ. 1990. The role of sediment 2 were compared (r = 0.47, y = 8009.74 + type in growth and fecundity of mud snails (Hydro- 229.72x, P < 0.05). This could indicate that biidae). Oecologia 83:53–61. other factors such as competition for limited FRENCH, J.R.P., III 1977. A laboratory guide for culturing food resources affect this system in the Oncomelania hupensis (Gastropoda: Hydrobiidae). Bulletin of the Chinese Malacological Society 4:47–54. absence of critical temperature influences. FRITCHMAN, H.K. 1985. The Bruneau hot spring snail: an Site 2 had the smallest mean snail size and unidentified, possibly endangered hydrobiid from lowest number of juveniles/female, also indi- Hot Creek and the Indian Bathtub, Owyhee Co. cating competition for food resources may Idaho. Remarks on its biology. Unpublished report, Bureau of Land Management, Boise District Office, have been occurring to a greater extent than at Boise, ID. 10 pp. other sites. However, during most of the time GORE, J.F.1967. A northernmost record and ecological data at these sites, temperature appears to override on Hydrobia salsa in Maine. Nautilus 80:112–113. such relationships. HERSHLER, R. 1990. Pyrgulopsis bruneauensis, a new springsnail (Gastropoda: Hydrobiidae) from the Snake River plain, southern Idaho. Proceedings of ACKNOWLEDGMENTS the Biological Society of Washington 103:803–814. ______. 1998. A systematic review of the hydrobiid snails This paper is dedicated to the memory of (Gastropoda: Risooidea) of the Great Basin, western Kelly Sant, who was conducting further stud- United States. Part I. Genus Pyrgulopsis. Veliger 41: ies on P. bruneauensis as part of his master’s 1–132. LASSEN, H.H., AND M.E. CLARK. 1979. Comparative thesis prior to his untimely death. The authors fecundity in three Danish mudsnails (Hydrobiidae). wish to thank C.T. Robinson for guidance with Ophelia 18:171–178. statistical analyses of the data and many useful LIANG, Y., AND H. VAN DER SCHALIE. 1975. Cultivating comments on the manuscript. J. Schomberg Lithoglyphopsis aperta Temcharoen, a new snail host and C. Myler generated revisions of several for Schistosoma japonicum, Mekong strain. Journal of Parasitology 61:915–919. figures. J. Janovy provided extensive construc- MLADENKA, G.C. 1992. The ecological life history of the tive criticism of the original manuscript. Sev- Bruneau hot springs snail (Pyrgulopsis bruneauensis). 212 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Final report to the U.S. Fish and Wildlife Service, TAYLOR, D.W. 1982. Status report on the Bruneau hot Boise Field Office, Boise, ID. 116 pp. springs snail. Conducted for the U.S. Fish and Wild- O’BRIEN, C., AND D.W. BLINN. 1999. The endemic spring life Service, Boise Field Office, Boise, ID. 8 pp. snail Pyrgulopsis montezumensis in a high CO2 envi- VAN DER SCHALIE, H., AND G.M. DAVIS. 1965. Growth and ronment: importance of extreme chemical habitats as stunting in Oncomelania (Gastropoda: Hydrobiidae). refugia. Freshwater Biology 42:225–234. Malacologia 3:81–102. OTORI, Y.L., S. RITCHIE, AND G.W. HUNTER III. 1956. The ______. 1968. Culturing Oncomelania snails (Proso- incubation period of the eggs of Oncomelania noso- branchia: Hydrobiidae) for studies of oriental schis- phora. American Journal of Tropical Medicine and tosomiasis. Malacologia 6:321–367. Hygiene 5:559–561. WARD, J.V. 1992. Biology and habitat. Pages 123–124 in PONDER, W.F., R. HERSHLER, AND B. JENKINS. 1989. An Aquatic insect ecology. John Wiley and Sons, New endemic radiation of hydrobiid snails from artesian York. 438 pp. springs in northern South Australia: their taxonomy, physiology, distribution, and anatomy. Malacologia Received 13 May 1999 31:1–140. Accepted 10 April 2000 Western North American Naturalist 61(2), © 2001, pp. 213–222

RELATIONSHIP BETWEEN HOME RANGE CHARACTERISTICS AND THE PROBABILITY OF OBTAINING SUCCESSFUL GLOBAL POSITIONING SYSTEM (GPS) COLLAR POSITIONS FOR ELK IN NEW MEXICO

James R. Biggs1, Kathryn D. Bennett1, and Phil R. Fresquez1

ABSTRACT.—We compared the ability of global positioning system (GPS) radio collars deployed on elk (Cervus ela- phus nelsoni) to obtain valid positions (position acquisition rate [PAR]) in seasonal home ranges with differing vegetation and topographical characteristics. We also compared GPS collar PARs under varying levels of cloud cover and within differing daily time periods. We recorded a mean PAR of 69% (n = 10 elk, s = 14%) for collared elk. Multiple regression analysis of seasonal home range characteristics indicated that vegetation cover type and slope, either as individual vari- ables or in combination with one another, were not significant predictors of GPS collar PARs. We did not observe statis- tical differences in position acquisition rates between cloud cover classes or varying cloud base heights. PAR was signifi- cantly higher between 1600 h and 2000 h (mountain standard time) compared to 0000 h–1200 h, which may have been due to elk behavior. We believe using GPS collars is a more effective and efficient method of tracking elk in our study area than using very-high-frequency (VHF) collars since GPS collars can be programmed to obtain fixes automatically, have fewer logistical problems, and are more economical with long-term data collection efforts.

Key words: radio collar, global positioning system, position acquisition rate, elk.

Radio telemetry has provided increased the transmitters, temperature, topography, and opportunities to examine activity patterns, animal movement (White and Garrott 1990). habitat use, and behavior of wildlife species Due to these influences, mean errors of loca- (Samuel and Fuller 1994). At present there are tions can range from 0.5 to 1.5 km and may 3 methods of telemetry used for tracking large exceed 8 km. These systems are best suited for mammals: (1) mobile very-high-frequency tracking large-scale movements of highly (VHF) radio-telemetry systems, which consist mobile animals rather than detailed habitat or of a receiver that picks up transmissions from resource utilization (Rodgers et al. 1996, a radio-collared animal via triangulation from Kennedy et al. 1998). the ground or that is located by aircraft A recent development in satellite tracking (Samuel and Fuller 1994); (2) VHF receivers is attaching geographic positioning system attached to permanent tracking stations in a (GPS) units to radio collars. Whereas PTTs defined study area (Deat et al. 1980, Loft and transmit signals to receivers on satellites to Kie 1988, Hansen et al. 1992); and (3) satellite calculate a position, GPS systems receive sig- telemetry. nals transmitted from 3 or more satellites to Satellite systems were developed in the calculate a position. The system utilizes on- 1980s and also use radio collars implanted board microelectronics that calculate GPS with transmitters (platform transmitter termi- locations from a set of 24 orbiting satellites nals, PTT), but the signal is picked up via (Wells et al. 1987). In addition, GPS telemetry, satellites orbiting the earth and data are re- depending on the manufacturer and model, layed to a servicing center. This system requires offers 3 basic methods of data retrieval: (1) col- that the elevation of the PTT be estimated lar stores all location data until the collar is before its location is calculated and, as a result, retrieved and data are downloaded; (2) collar large errors in the estimated location can stores and transmits location data to a storage occur if the specified elevation is incorrect satellite for data retrieval by a data manage- (Keating 1995). Error can also be introduced ment center (discussed in this paper); or (3) into these systems by frequency stability of collar stores data and provides a local point-to-

1Ecology Group, Los Alamos National Laboratory, Los Alamos, NM 87545.

213 214 WESTERN NORTH AMERICAN NATURALIST [Volume 61 point communication link for retrieval (Rodgers ployed on elk inhabiting montane ecosystems and Anson 1994, Rodgers et al. 1996). in north central New Mexico under different Availability of satellites and environmental levels of cloud cover, in differing vegetation factors can influence both the accuracy and cover and terrain types within animal home ability of GPS systems to acquire a location. ranges, and within various daily and seasonal Until May 2000 the most important signal error periods. was related to selective availability (SA). SA was the intentional degradation of the satellite STUDY AREA signal by a time-varying bias that was controlled by the Department of Defense to limit the The study area is located within and around accuracy of GPS to non-U.S. military and gov- Los Alamos National Laboratory (LANL). LANL ernment users (Trimble Navigation 1996). The is located in north central New Mexico on the effect of SA was minimized through the use of Pajarito Plateau and the east Jemez Mountains, differential correction (correct the bias at one approximately 120 km north of Albuquerque location with measured bias errors at a known and 40 km west of Santa Fe. Stretching 33–40 position). However, on 1 May 2000, President km in a north–south direction and 8–16 km Clinton ordred the U.S. military to cease the from east to west, the plateau ranges in eleva- intentional degradation of satellite signals. This tion from about 1680 m to 2250 m and slopes order will enable the GPS user to obtain more gradually eastward from the edge of the east accurate non-differentionally corrected posi- Jemez Mountains. Elevations reach approxi- tions. Accuracy can also be affected by the mately 3050 m within 1.6 km of the LANL number of satellites available to calculate the boundary. Intermittent streams flowing south- location. A GPS receiver must simultaneously eastward have dissected the plateau into a receive signals from at least 3 satellites to cal- number of fingerlike, narrow mesas separated culate a location. The number of satellites by deep, narrow canyons ranging in depth used in calculating the position determines from 15 m to 330 m. whether a 2-dimensional (3 satellites) or 3- A variety of vegetation communities cover dimensional (4 satellites) position is obtained. the study area as dictated by the wide range of Altitude is fixed in 2-dimensional locations elevational zones. The Rio Grande floodplain and based on the previous 3-dimensional loca- borders the east edge of LANL and contains tion. Therefore, 2-dimensional locations can the lowest elevations in the area. It is charac- have an increase in horizontal error compared terized by a Plains and Great Basin Riparian- to 3-dimensional (Moen et al. 1997). If 4 Deciduous Forest (Brown 1982) with cotton- simultaneous signals are received, a 3-dimen- wood (Populus spp.) and willow (Salix spp.). sional location can be calculated and horizon- Piñon pine (Pinus edulis) and juniper ( Junipe- tal error is decreased. rus monosperma) are common at higher eleva- Environmental factors that could affect the tions (1860–2070 m) and occur on much of the position accuracy and position acquisition rate mesa tops. Ponderosa pine (Pinus ponderosa) (PAR; percentage of locations that a GPS col- is common on the higher mesa tops and along lar successfully acquires from roving satellites many of the north-facing canyon slopes, and based on total number of attempts) are pri- species of fir (Pseudotsuga menziesii and Abies marily related to topography and plant cover spp.) can be found along the higher north-fac- (Rodgers et al. 1995) but may also include ing slopes intermixing with ponderosa pine. weather as it relates to animal behavior (i.e., Species of the Rocky Mountain Subalpine animals seeking shelter during heavy precipi- Conifer Forest and Woodland occur along the tation events). Because the use of GPS collars extreme western edge of LANL and are more is such a newly evolving technique, few stud- prevalent at the higher elevations of the ies have investigated its usefulness and effec- nearby Jemez Mountains. tiveness in tracking animals under various en- Most canyon stream channels in and adja- vironmental conditions (Rempel et al. 1995, cent to LANL are ephemeral and therefore Moen et al. 1996, Rodgers et al. 1996, Edenius not considered wetlands. However, permanent 1997). flows from springs and laboratory facility out- The objective of this study was to evaluate falls result in a small number of permanent or position acquisition rates of GPS collars de- near-permanent streams within short stretches 2001] GPS RADIO COLLAR POSITION ACQUISITION RATES 215 of certain canyons. The area that is now LANL hours and minutes. Because of data storage has not been exposed to livestock grazing or limitations of the collar, the following informa- hunting since the mid-1940s. tion was not stored on the collar: type of GPS fix (either 2-dimensional or 3-dimensional), METHODS specific satellites used in the calculation of the position, and current satellite geometry as We collared 6 elk (5 cows and 1 bull) dur- indicated by the position dilution of precision ing March and April 1996 using clover traps. (Trimble Navigation 1996). Therefore, differ- We retrieved collars from all 6 animals within ential correction of GPS collar data and deter- 6 to 18 months following collar deployment. mination of 2-dimensional versus 3-dimen- Four collars were refurbished by the manufac- sional positions were not conducted during turer and deployed on different animals (3 this study. While SA was enabled, accuracy of cows and 1 bull) in either 1997 or 1998, result- nondifferentially corrected GPS collar location ing in a total of 10 collared animals from data could vary from <1 m to as much as which data were collected. No animals died or approximately 100 m, while differentially cor- were injured during capture. Estimated age of rected data can provide consistently accurate cow elk ranged from 1 to 7 years. The 6 ani- estimates of true locations to within several mals collared in 1996 were captured either in meters (Rodgers et al. 1996). Because SA was shallow canyons dominated by piñon pine– enabled during our study, locational error was juniper or on a mesa top dominated by pon- calculated using an ST14GPS collar placed in derosa pine. Animals collared in 1997 and different habitats and terrain throughout LANL 1998 were captured either on mesa tops domi- property (Bennett et al. 1997). The mean loca- nated by ponderosa pine or on a mesa top tional error was 108 m, and no significant dif- dominated by piñon pine and juniper. ferences were found in the mean error between mesa tops and canyons. There were Collar Programming no significant differences (α = 0.05) in loca- We collared each animal with a Telonics, Inc. tional error for the test collar with respect to (Mesa, AZ; use of company name does not vegetation cover type and topography; there- imply endorsement by the U.S. Department of fore, we assume a similar error rate for collars Energy) model ST14GPS receiver equipped deployed on elk. Bennett et al. (1997) reported with a VHF beacon transmitter with an esti- that 95% of the time a position was obtained mated battery life of 12 to 14 months. To maxi- from the GPS collar, it was within 122 m of the mize battery life while still obtaining sufficient actual location. This was higher than the 100 hourly data throughout a 24-hour period, we m expected by U.S. military design specifica- programmed each collar to attempt to acquire tions for units operating in 3-dimensional a GPS position every 23 hours. A 23-hour mode, suggesting an influence of 2-dimensional interval allowed the collar to attempt to make locations. a GPS fix each day 1 hour earlier than the pre- Position acquisition rates were calculated vious day. All data (usually 3 to 5 positions) by dividing total number of successful fixes were uplinked from the collar to a data-stor- acquired by each collar by total number of age satellite every 3 to 4 days and subsequently fixes attempted by the collar. Number of fixes retrieved by a servicing center (e.g., Argos attempted was based on the preprogrammed Inc.; use of company name does not imply interval rate of 23 hours during the life of the endorsement by the DOE). Raw data (stored collar while deployed on the animal. Length of in a compressed format using an absolute fix the data collection period was determined by followed by historical fixes relative to the collar battery life or death of the animal as a absolute fix) were sent to us from Argos via e- result of vehicle collision or hunter harvest. mail, after which they were stored on a PC computer for processing, which was required Vegetation/Topography to convert the data into longitude, latitude, Analysis Julian Day, and Greenwich Mean Time (GMT). Because we could collect habitat data only Longitude and latitude were converted into at locations of successfully acquired GPS loca- UTMs using the projection command of ARC/ tions and because we did not know locations INFO (ESRI 1991). GMT was represented in of animals when fixes were not obtained, we 216 WESTERN NORTH AMERICAN NATURALIST [Volume 61 used a combination of seasonal home range We conducted vegetation analyses using polygons and GIS vegetation and topographi- GIS and a land cover map developed at LANL cal coverages to compare PARs in each col- (Koch et al. 1997). A 1992 Landsat thematic lared animal’s seasonal home range to vegeta- mapper image was classified into 30 classes tion and slope characteristics of each home using the Iterative Self-Organizing Data range. Seasons were defined as follows: spring Analysis Technique (ERDAS 1994). These 30 (March–April), calving (May–June), summer classes were aggregated into 10 land cover (July–August), fall (September–October), and types through field surveys, aerial photo inter- winter (November–February). These periods pretation, and incorporation of topographic are most representative of the differing sea- information. Resulting cover types also included sonal movement and resource-use patterns developed and other nonvegetative coverages, observed in our study area (White 1981, Allen as well as cover types not occurring within the 1996, Long et al. 1997, Biggs et al. 1999) and study area. Therefore, only 4 cover types were coincide with other on-going studies of elk on used in our analysis: ponderosa pine forest, LANL property. Most individuals migrating open cover (grass/shrubland), mixed-conifer/ onto LANL property do so in late fall (i.e., spruce-fir forest, and piñon-juniper/juniper November), and calving in our study area gen- woodland. In addition to these cover types, erally takes place during May and June. Dur- small isolated patches of aspen (Populus ing these periods home range polygons can be tremuloides) occur within the study area, but highly variable and encompass a greater area because these represent a very small amount compared to other seasonal periods. Additional of total cover (<1.0%), this cover type was information used in defining these periods omitted from further analysis. Each seasonal was taken from previous elk studies on move- home range polygon was intersected with the ment patterns and habitat use in other moun- vegetation cover type polygons. The total tainous regions of New Mexico and western amount of each cover type was then calculated states where terrain and plant species compo- for each home range. sition are relatively similar to our study area The same method for calculating PARs by (Findley et al. 1975, Hoffmeister 1986, McCor- cover type was used for calculating PARs by qoudale et al. 1986). We used the adaptive slope type. The percentage of each home kernel method of program CALHOME (Kie range that consisted of each of 8 slope cate- et al. 1994) to estimate each collared animal’s gories (0–5º, 5–10º, 10–15º, 15–20º, 20–25º, home range using 95% of all animal locations 25–30º, 30–40º, and >40º) was calculated. We (95% utilization distribution). Based on a used a multiple linear regression to test the visual inspection of each animal’s home range, interaction of slope and habitat characteristics the polygon boundaries did not appear to be of each seasonal home range with the PAR in dictated by cover type or terrain; therefore, that home range. we assume that at least 95% of the unknown Cloud Cover locations where fixes were not obtained fell within the home range polygon. Optimum Data on hourly cloud cover during 1996–97 grid cell size and bandwidth (a smoothing for Los Alamos County were obtained from parameter) were automatically determined by the National Climate Data Center, Asheville, the program. The program also produces a North Carolina. Cloud cover data were reported least-squares cross-validation (LSCV) score, primarily on the hour and were matched by which is a measure of how well the bandwidth date and time to GPS collar fix attempts (pro- fits the data; the lower the LSCV, the better grammed to collect on the hour). However, in the fit (Worton 1989, Kie et al. 1994). In a few some cases no cloud cover data were available cases grid cell size and bandwidth were manu- during the time a GPS collar fix was attempted. ally altered to produce a lower LSCV (Kie et In these cases the closest cloud cover data al. 1994), resulting in what is believed to be a available to within 1 hour of the GPS collar fix better representation of the home range poly- attempt were used. Data from elk collared only gon. Once home range polygons were calcu- in 1996 were used in this analysis. To mini- lated by CALHOME, the output data set of mize the potential influence of steeper terrain X,Y UTM coordinates was imported to the and heavier vegetation canopy cover associ- GIS. ated with some portions of the study area, we 2001] GPS RADIO COLLAR POSITION ACQUISITION RATES 217 restricted the analysis to animals with home forested cover types (ponderosa pine, mixed ranges that occurred primarily on LANL prop- conifer; Table 2). Open cover types also made erty and overlapped the location at which up a relatively large amount of the overall veg- cloud cover data were collected. Position acqui- etative cover within fall home ranges (47%) sition rates were analyzed by cloud ceiling when PARs were at their lowest (45%). How- (height of base of cloud cover at <1000 m, ever, composition of taller forested cover types 1000–2000 m, and >2000 m) and sky cover was relatively similar (45%) to open cover (clear; scattered = 1/8–1/2 cloud cover; bro- types during that period. Ponderosa pine and ken = 5/8–7/8 cloud cover; overcast; obscured mixed conifer constituted >50% of cover dur- = foggy conditions). Because PARs are pro- ing calving and summer, during which time portions, they can be described by binomial PARs were also low. Although lower PARs distribution (Freund and Walpole 1987). There- were observed in seasonal home ranges that fore, to determine whether PARs were signifi- had a greater composition of tall forest cover cantly different between cloud cover classes, types, multiple regression analysis showed we constructed 95% confidence intervals (CI) that cover type was not a significant predictor around each cloud cover class PAR to see if of GPS position acquisition rate (R2 = 0.19, 37 CIs overlapped. If they did not overlap, they df, P = 0.09). were considered significantly different (Fre- Topography und and Walpole 1987). Over 50% of all seasonal home ranges con- Hourly Period sisted of 0–5º and 5–10º slopes (Table 2). How- Position acquisition rates were analyzed by ever, there was a greater composition of slopes day based on 6 hourly blocks within a 24-hour above 5º in home ranges during calving, sum- period: 0000–0400, 0400–0800, 0800–1200, mer, and fall, at which times GPS collar PARs 1200–1600, 1600–2000, and 2000–2400 h. were lowest. Analysis using multiple regres- Analysis was conducted on data from all 10 sion showed that slope was not a significant animals combined. To determine if PARs were predictor of PAR (R2 = 0.19, 34 df, P = 0.26). significantly different between hourly periods, Furthermore, addition of cover type to the we constructed 95% CIs around each hourly model did not improve it (R2 = 0.25, 30 df, P period PAR to see if CIs overlapped. = 0.48). Cloud Cover RESULTS We did not observe any statistically signifi- Of 10 collared elk, 5 were harvested and 3 cant differences (α = 0.05) in PARs between died as a result of vehicle collisions. The GPS cloud cover classes nor did we observe any collar operational life (calculated for animals significant differences in PARs between vary- that survived beyond the operational life of ing cloud base heights. However, PAR was the GPS collar) averaged 15 months (n = 5, generally lower during overcast conditions range = 11.6 –17.7 months). Over 1900 fixes and when cloud base heights were <1000 m. were obtained between March 1996 and June 1998 for all 10 elk combined. Approximately Hourly Period 69% (s = 14%) of GPS location attempts were We observed a significant difference (α = successful and ranged from 54% to 96% for 0.05) between PARs of hourly time periods individual animals. Mean yearly PAR ranged (Fig. 1). PAR was significantly higher during from 59% in 1996 to 81% in 1998, was highest the period 1600–2000 h than during 0000– in spring (77%) and winter (74%), and was 1200 h. PAR was generally higher from noon lowest in fall (45%; Table 1). to midnight compared to the period from mid- night to noon. Vegetation Cover Type

GPS position acquisition rates were highest DISCUSSION during spring and winter, at which times the relatively open cover types (grass/shrubland, We compared position acquisition rates of piñon-juniper/juniper woodland) were more GPS collars deployed on Rocky Mountain elk prevalent in home ranges than were taller in north central New Mexico with respect to 218 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 1. GPS position acquisition ratesa (PARs) for radio-collared elk by season and year, Los Alamos National Labo- ratory, New Mexico, March 1996–June 1998. Number of Total number of Year Season animals locational fixes PAR (%) 1996 Spring 5 137 64.3 Calving 6 227 59.1 Summer 6 191 50.0 Fall 5 151 47.2 Winter (1996–97) 4 371 72.8 Mean PAR 58.7 1997 Spring 4 204 79.7 Calving 4 148 57.8 Summer 2 96 73.8 Fall 1 21 32.8 Winter (1997–98) 1 98 76.6 Mean PAR 68.0 1998 Spring 4 186 84.9 Calving 2 99 77.3 Mean PAR 81.1 ------MEAN SEASONAL PAR (%) Spring Calving Summer Fall Winter 76.6 61.7 55.2 44.8 73.5 aPAR is defined as the percentage of locations that a GPS collar successfully acquires from roving satellites based on total number of attempts.

TABLE 2. Vegetative cover and slope composition of elk seasonal home ranges, Los Alamos National Laboratory, New Mexico, 1996–1998.

______Season Spring Calving Summer Fall Winter (n = 13) (n = 12) (n = 8) (n = 6) (n = 5)

COVER TYPEa Open cover 11.6 15.9 12.3 11.9 9.1 Piñon-juniper/ juniper woodland 40.5 24.6 23.9 35.6 57.6 Ponderosa pine 35.6 30.6 25.6 23.7 18.7 Mixed conifer 4.3 22.3 31.0 21.7 6.0 SLOPE CLASS 0–5º 40.4 25.7 26.1 26.9 35.7 5–10º 31.3 26.5 24.7 24.5 27.0 10–15º 13.5 15.9 16.8 17.5 16.6 15–20º 8.6 13.5 14.4 14.9 11.1 20–25º 3.9 10.1 10.4 9.7 5.9 25–30º 1.6 5.3 5.1 4.6 2.4 30–40º 0.9 2.9 2.7 1.9 1.3 aCertain cover types were omitted from analysis; therefore, the sum of cover types for home ranges does not equal 100%. cloud cover and seasonal home range habitat rain and cover types would be to compare PARs characteristics. We also compared PARs be- within specific vegetation cover types and slope tween seasonal and hourly periods. categories based only on successfully acquired We elected to compare position acquisition GPS positions. We chose not to apply this rates of GPS collars in elk seasonal home method since we did not know where the ani- ranges to assess the relationship between home mal was during an unsuccessful attempt, thus range habitat characteristics and the general preventing us from comparing habitat charac- effectiveness of using GPS radio collars in our teristics of successfully acquired GPS posi- study area. An alternative method of assessing tions with unsuccessful attempts. If we were the effectiveness of GPS collars in varying ter- to assess PARs of specific cover and slope 2001] GPS RADIO COLLAR POSITION ACQUISITION RATES 219

this study and rates found with the test collar may be a result of several factors. First, if ani- mals are moving at a pace greater than normal walking while a GPS position is being attempted, a fix may not be obtained within the allotted receiving time. Backpack trial tests performed by Edenius (1997) in northern Sweden indicated that a movement rate of 3–4 km ⋅ h–1 may reduce PAR under forest canopy. We observed a reduction in PAR during stud- ies of the test collar as it was in the process of being transported by a vehicle at speeds above 8 km ⋅ h–1 between test locations. In contrast, Fig. 1. Position acquisition rates by hourly time period. Moen et al. (1996) reported that movement by Significant differences between hourly time periods were determined by calculating 95% confidence intervals; GPS-collared moose did not affect PAR. Sec- nonoverlapping confidence intervals indicated a signifi- ond, the test collar was placed on an elevated cant difference. stand simulating the height of an adult elk with the collar situated in a normal position types based only on successfully acquired GPS (dorsal GPS antenna, ventral transmitter). If a positions without accounting for missing GPS collar shifts when a GPS fix is being attempted positions, we could over- or underestimate (such as when an animal is bedded down), the specific habitat (slope, cover) PARs. Further- GPS unit may be out of “sight” of the roving more, potential error associated with each satellites and thus might be unable to success- point (108 m) could result in inaccurate inter- fully acquire a fix (Rodgers et al. 1995). This pretation since the location could occur within interference may also occur with VHF collars. any 1 of 4 GIS coverage pixels (a pixel is 30 × However, the user has the option of altering 30 m), each of which could contain different position for further location attempts, whereas cover and slope types. Unless we have a very the amount of time a GPS collar attempts a fix high PAR within a relatively homogenous habi- is preprogrammed into the collar and mini- tat type with respect to vegetation and terrain, mized to reduce battery use (e.g., 3 minutes). we will be unable to accurately identify PARs Third, analysis of the test collar data tested for a specific cover or slope type. One way to only a single type of error, that of acquiring a correct for this would be to program a collar to GPS position. Because a hand-held uplink attempt to acquire a fix in very short time receiver was used to obtain position data in intervals (i.e., ≤10 minutes), thereby allowing the collar testing, PAR error (or data loss) asso- the researcher to fill in the voids of missing ciated with satellite uplink and data transmis- data based on successfully acquired positions. sion was untested. However, this would not In this study we programmed collars to acquire appear to be a significant source of data loss a fix every 23 hours. As a result, animals could since the collar continuously uplinks data over move large distances between position fix the course of an extended period of time (6 attempts through multiple habitat and slope hours on every 3 days in the case of this study), types, making it virtually impossible to iden- thus providing multiple opportunities for suc- tify what type of terrain and cover type the cessful data transmission. Although we report animal was in when a fix was not successfully a lower overall mean PAR for collared animals acquired. compared to the test collar, PAR increased We calculated PARs for individual animals considerably following refurbishment of the ranging from 54% to 96%, similar to what has collars (1996 vs. 1998). This may be due par- been found in other studies of GPS collars tially to advancements made in the antenna (Rodgers et al. 1995, Moen et al. 1996, Rodgers system following initial deployment of collars et al. 1996, Edenius 1997). PARs of about 86% on the animals. Technological advances in col- in the study area have been reported using a lar components, particularly the antenna, may test collar (Bennett et al. 1997), and in this have resulted in higher PARs in the collars de- study we report a mean PAR of 69% for col- ployed on animals after 1996 (Stan Tomkiewicz, lared animals. The difference between rates in Telonics, Inc., personal communication), thus 220 WESTERN NORTH AMERICAN NATURALIST [Volume 61 affecting overall results of the data analysis. peratures. Lowest PARs were observed for elk More extensive comparisons of future genera- that spent most of their time in more moun- tions of these collars to current versions of the tainous terrain within ponderosa pine and collar should be performed. mixed-conifer habitats. These areas also con- Although the combination of cover type sist of steep mountain slopes with narrow and terrain did not produce a model that sig- canyons, which may limit the satellite observa- nificantly predicted GPS collar PAR, we ob- tion and transmission success rate of the GPS served lower rates in animals with home collar. ranges that had a greater composition of tall The initial high cost of GPS collars can pro- forested cover types and steeper terrain, and hibit the purchase of multiple collars, which in higher PARs in animals with home ranges turn can reduce sample size of the target consisting of more open cover types and less species being studied. Conversely, costs asso- steep terrain. Other studies have also shown a ciated with use of VHF collars (e.g., aircraft decline in PAR as tree density, tree height, time) may limit the number of animals that and canopy closure increased (Rempel et al. can be collared, thus reducing the quality of 1995, Rodgers et al. 1996, Edenius 1997, Moen the study (Rodgers et al. 1996). Depending on et al. 1997). The noticeable effect of high- study objectives (i.e., detailed daily movement relief terrain on the ability of GPS collars to patterns vs. general seasonal migration routes), acquire fixes has also been observed in other VHF collars could be used in conjunction studies (Moen et al. 1997, Rutter et al. 1997). with GPS collars to reduce overall costs. GPS position acquisition rates tended to The preprogramming capability of GPS col- decrease with overcast conditions. Lower rates lars for obtaining positions provides the user during overcast conditions may be related an opportunity to select specific periods of the more to animal behavior than to ability of the day/night during which to monitor the target GPS unit to observe roving satellites. Although animal. Although the version of GPS collar certain meteorological conditions may diffuse used in this study required all programming to the signal between satellites and the GPS col- be performed by the manufacturer prior to lar, this would more likely affect accuracy of deploying the collar on to the animal, more location fix than PAR (Trimble Navigation recently developed versions allow the user to 1996). If we assume that greater cloud cover program the collar while in-hand. Additionally, and lower cloud base heights indicate periods other manufacturers’ models of GPS collars of precipitation events (i.e., snowfall, rainfall), allow the user to make programming changes then thermoregulatory responses may cause to the collar while the collar is still on the ani- animals to move into more thickly forested areas mal via a remote radio communication link be- and/or onto steeper slopes, either of which tween the GPS collar and a command unit oper- may result in some reduction in PAR. ated by the user (Rogers et al. 1996). Develop- We also report higher PARs between noon ment and application of GPS radio collars for and midnight compared to midnight and noon, use in animal studies is relatively new to the which is in contrast to what has been found in field of wildlife research but shows much other studies. Moen et al. (1997) reported lower promise as an effective means of tracking PARs of GPS-collared moose during daytime wildlife. However, only a limited number of hours and suggested this was due to animals studies have evaluated the usefulness of these seeking shade during daytime increases in collars for tracking wildlife, particularly with temperature. Although our results differed, we respect to assessing PARs under varying envi- did find lower (but not statistically significant) ronmental conditions (i.e., weather, topogra- PARs during warmer months when animals phy, terrain). were likely attempting to cool themselves by We believe the use of GPS collars to be seeking greater canopy cover and steeper more effective than VHF units in tracking elk slopes during daytime hours. Also, terrain in our study area based on (but not limited to) varies dramatically within home ranges of greater estimated accuracy of locations, pre- some of the collared animals during summer programming capability of the collars, reduc- months, from approximately 2100 to 3000 m, tion in logistical concerns (i.e., access to remote indicating that animals may utilize higher, or restricted areas), and reduction of person- cooler elevations during periods of warm tem- nel needs and costs as the study progresses. 2001] GPS RADIO COLLAR POSITION ACQUISITION RATES 221

Wildlife researchers should evaluate their data ESRI. 1991. ARC/INFO command references guide. requirement needs (frequency of location Environmental Systems Research Institute, Red- lands, CA. positions) and labor costs of tracking animals FINDLEY, J.S., A.H. HARRIS, D.E. WILSON, AND C. JONES. using VHF telemetry prior to the use of GPS 1975. Mammals of New Mexico. University of New radio collars. Researchers should also identify Mexico Press, Albuquerque. 360 pp. potential effects that terrain and cover types FREUND, J.E., AND R.E. WALPOLE. 1987. Mathematical statistics. Prentice Hall, Inc., Englewood Cliffs, NJ. within their study area could have on GPS col- 376 pp. lar PAR and locational error with respect to HANSEN, M.C., G.W. GARNER, AND S.G. FANCY. 1992. their study objectives. Comparison of three methods for evaluating activity of Dall sheep. Journal of Wildlife Management 56:661–668. ACKNOWLEDGMENTS HOFFMEISTER, D.F. 1986. Mammals of Arizona. University of Arizona Press and Arizona Game and Fish Depart- This study was funded by the Environ- ment. 602 pp. ment, Safety, and Health Division of Los KEATING, K.A. 1995. Mitigating elevation-induced errors Alamos National Laboratory, Los Alamos, New in satellite telemetry locations. Journal of Wildlife Mexico. Special thanks go to R. Robinson, M. Management 59:801–808. KENNEDY, M.L., A.E. HOUSTON, G.W. COOK, AND J.R. Salisbury, T. Haarmann, D. Keller, and L. OUELLETTE. 1998. Use of satellite telemetry for mon- Naranjo for field crew support and H. Hino- itoring movements of coyotes: a pilot study. Wildlife josa, L. Lujan-Pacheco, and T. Hiteman for Society Bulletin 26:557–560. editing and formatting the manuscript. We KIE, J.G., J.A. BALDWIN, AND C.J. EVANS. 1994. CALHOME home range analysis program, electronic user’s man- thank L. Hansen and S. Loftin for reviewing ual. U.S. Forest Service, Pacific Southwest Research the manuscript and M. Mullen for statistical Station, Fresno, CA. advice. KOCH, S.W., T.K. BUDGE, AND R.G. BALICE. 1997. Devel- opment of a land cover map for Los Alamos National Laboratory and vicinity. Los Alamos National Labo- LITERATURE CITED ratory Report LA-UR-97-4628. 8 pp. LOFT, E.R., AND J.G. KIE. 1988. Comparison of pellet- ALLEN, C.D. 1996. Elk response to the La Mesa fire and group and radio triangulation methods for assessing current status in the Jemez Mountains. Pages 179–195 deer habitat use. Journal of Wildlife Management in C.D. Allen, editor, Fire effects in southwestern 52:524–527. forests: proceedings of the Second La Mesa Fire LONG, D.H., W.D. HACKER, AND S.M. FETTIG. 1997. Elk Symposium, 29–31 March 1994, Los Alamos, New degradation of forest resources in Bandelier National Mexico. General Technical Report RM-GTR-286, Monument. In: Abstracts of the 30th Joint Annual Rocky Mountain Forest and Range Experiment Sta- Meeting of the Wildlife Society, New Mexico and tion, U.S. Department of Agriculture, Fort Collins, Arizona Chapters, and American Fisheries Society, CO. Arizona-New Mexico Chapter, February 1997. BENNETT, K.D., J.R. BIGGS, AND P.R. FRESQUEZ. 1997. MCCORQOUDALE, S.M., K.J. RAEDEKE, AND R.D. TABER. Determination of locational error associated with 1986. Elk habitat use patterns in the shrub steppe of GPS radio collars in relation to vegetation canopy Washington. Journal of Wildlife Management 50: and topographical influences of north-central New 664–669. Mexico. Los Alamos National Laboratory. Report MOEN, R., J. PASTOR, AND Y. C OHEN. 1997. Accuracy of LA-13252-MS. 14 pp. GPS telemetry collar locations with differential cor- BIGGS, J.R., K.D. BENNETT, AND P.R. FRESQUEZ. 1999. rection. Journal of Wildlife Management 61:530–539. Resource use, activity patterns, and disease analysis MOEN, R., J. PASTOR, Y. COHEN, AND C.C. SCHWARTZ. of Rocky Mountain elk (Cervus elaphus nelsoni) at 1996. Effects of moose movement and habitat use on the Los Alamos National Laboratory. Report LA- GPS collar performance. Journal of Wildlife Man- 13536-MS. 44 pp. agement 60:659–668. BROWN, D.E. 1982. Biotic communities of the American REMPEL, R.S., A.R. RODGERS, AND K.F. ABRAHAM. 1995. Southwest, United States, and Mexico. In: Desert Performance of a GPS animal location system under plants. Volume 4. University of Arizona, Tucson. boreal forest canopy. Journal of Wildlife Manage- DEAT, A., C. MAUGET, R. MAUGET, D. MAUREL, AND A. ment 59:543–551. SEMPERE. 1980. The automatic, continuous and fixed RODGERS, A.R., AND P. A NSON. 1994. Animal-borne GPS: radio tracking system of the Chize Forest: theoretical tracking the habitat. GPS World 5:20–32. and practical analysis. Pages 439–451 in C.J. Amlaner, RODGERS, A.R., R.S. REMPEL, AND K.F. ABRAHAM. 1995. Jr., and D.W. 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SAMUEL, M.D., AND M.R. FULLER. 1994. Wildlife radio- WHITE, G.C. 1981. Biotelemetry studies on elk. Los Alamos telemetry. Pages 370–418 in T.A. Bookhout, editor, Scientific Laboratory Report LA-8529-NERP. Research and management techniques for wildlife WHITE, G.C., AND R.A. GARROTT. 1990. Analysis of wildlife and habitats. 5th edition. The Wildlife Society, radio-tracking data. Academic Press, Inc., San Diego, Bethesda, MD. CA. 383 pp. TRIMBLE NAVIGATION LTD. 1996. GPS mapping systems WORTON, B.J. 1989. Kernel methods for estimating the uti- general reference. Trimble Navigation, Sunnyvale, lization distribution in home range studies. Ecology CA. 72 pp. 70:164–168. WELLS, D.E., N. BECK, D. DELIKARAOGLOU, A. KLEUSBERG, E.J. KRAKIWSKY, G. LACHAPELLE, R.B. LANGLEY, ET Received 11 March 1999 AL. 1987. Guide to GPS positioning. 2nd edition. Accepted 12 April 2000 Canadian GPS Associates, Fredericton, New Bruns- wick, Canada. 600 pp. Western North American Naturalist 61(2), © 2001, pp. 223–228

BREEDING BIOLOGY OF MOUNTAIN PLOVERS (CHARADRIUS MONTANUS) IN THE UINTA BASIN

Ann E. Ellison Manning1,2 and Clayton M. White1,3

ABSTRACT.—The known Mountain Plover population breeding on the Myton Bench, Duchesne County, Utah, is small, composed roughly of 30 adults and young after each breeding season. Currently, its location is peripheral to the species’ main range. This shrub-steppe breeding habitat differs from the shortgrass prairie habitat with which this bird is historically associated. Between 1996 and 1998 we made observations at nesting sites located consistently in 2 con- centrated areas surrounded by large tracts of similar habitat. Activity may be focused in these specific areas because of breeding-site fidelity; this behavior is common among most shorebirds and has been documented for the Mountain Plover in Colorado. Also, Mountain Plovers are social and tend to choose nest sites near others. Most nests in Utah were located within close proximity of mounds of white-tailed prairie dogs (Cynomys leucurus), and all were situated near roadways or oil well pads. Mountain Plovers were often observed with broods on these bare areas at night. We conclude that Mountain Plovers on the Myton Bench are distributed in clumped breeding colonies within large areas of appar- ently favorable habitat.

Key words: Mountain Plover, Charadrius montanus, nesting distribution, Uinta Basin.

The Mountain Plover (Charadrius montanus) Knolls (Utah Division of Wildlife Resources is typically associated with shortgrass prairie [UDWR] 1994). A pair of Mountain Plovers habitat, composed primarily of blue grama was also observed 11 April 1989 on a sage- (Bouteloua gracilis) and buffalo grass (Buchloe brush bench about 1.5 km east of Pelican dactyloides; Graul 1975). The Mountain Plover Lake, Uintah County (D.A. Boyce, U.S. Forest has been considered endemic to the Great Service, personal communication). In our cur- Plains and has coexisted with grazing herbi- rent study, 1993–1998, recorded population vores including the black-tailed prairie dog numbers have been small but fairly consistent (Cynomys ludovicianus), pronghorn (Antilo- (UDWR 1997). The objectives of this study carpa americana), and bison (Bison bison; Knopf were to describe the density and distribution 1996b). Currently, the Mountain Plover’s breed- of the Mountain Plover on the Myton Bench, ing range primarily includes portions of Col- Utah. Structure and composition of the Utah orado, Montana, and Wyoming, but there are habitat, a departure from the characteristic peripheral populations in Oklahoma, Texas, plover habitat, will be described elsewhere. and Utah (Knopf 1996a). In 1993 surveys con- ducted by the Bureau of Land Management STUDY AREA (BLM) confirmed a Mountain Plover popula- tion of unknown size breeding in Utah on the We conducted surveys from Castle Peak Myton Bench, Duchesne County, Uinta Basin and Wells Draws east to the border of Pariette (Day 1994). Prior to 1992, C. montanus had Wetlands Wildlife Habitat Management Area, been recorded in Utah only as a casual migrant approximately 20 km southwest of Myton, in Box Elder, Weber, Salt Lake, Daggett, Davis, Duchesne County, Utah. The study area gen- Iron, Tooele, Wasatch and Washington coun- erally encompasses N38°00′ to N40°07′, and ties (Woodbury et al. 1949, USFWS 1996). W109°02′ to W110°10′. This region has a There were 6 historical sightings in the Uinta highly variable, broken topography ranging Basin (White et al. 1983). In addition to these, from approximately 1500 m to 1920 m eleva- Dan Gardner, BLM, photographed 1 adult and tion. Climate and habitats of the Uinta Basin a nearby nest with 3 eggs in 1978 at Crow represented within the study area are typical

1Department of Zoology, Brigham Young University, Provo, UT 84602. 2Present address: 276 S. 1000 E., Salt Lake City, UT 84102. 3Corresponding author.

223 224 WESTERN NORTH AMERICAN NATURALIST [Volume 61 of the shrub-steppe habitat type found in the band and a red color band above the left knee. Great Basin (Goodrich and Neese 1986). Vege- A 3-g Trans-Astable (Advanced Telemetry Sys- tative complexes vary from essentially bare tems) standard radio transmitter was affixed to sand and/or gravel to low-growing black sage- each adult bird on the back below the neck brush (Artemisia nova). Greasewood (Sarcoba- with a light coating of waterproof epoxy adhe- tus vermiculatus), shadscale (Atriplex spp.), sive, a method used in other study areas in and occasional big sagebrush (Artemisia tri- California and Colorado (Knopf and Rupert dentata) stands are sporadically present in 1995, 1996, F. Knopf personal communica- deeper draws and throughout the area. Moun- tions). Mountain Plovers that lost their trans- tain Plover surveys have been conducted in mitters were retrapped if they were still nest- this same area since 1993 (UDWR 1995). ing. Birds with transmitters were monitored from the ground while still attending the nest. METHODS Once chicks hatched and adults and broods moved away from nest sites, surveys were Fieldwork was conducted May to mid- conducted from a fixed-wing aircraft to obtain August 1996–1998. Approximately 15,028 ha better coverage of a large area with a limited were surveyed, including the documented transmitter signal. Mountain Plover use and sighting areas that After chicks had hatched, surveys were also occupy about 1625 ha. Although surveys were done in a vehicle on roadways at night with a done at varying times throughout the day, we spotlight. Pre-fledged young were caught by spent more time and emphasis in May before hand and banded with USFWS and red color Mountain Plovers began nesting, as courtship bands. behavior made them more visible. To find as many Mountain Plovers as possible, surveys RESULTS were conducted by truck (roadways only), on ATVs (off road), and on foot. Call playbacks The first dates that we observed Mountain were used early in the breeding season to find Plovers in the study area were 3 May 1996, 11 Mountain Plovers by soliciting a response from April 1997, and 9 April 1998. Exact dates of courting adults. Locations in which Mountain their arrival on the Myton Bench are not Plovers had been observed in the past were known. The total number of Mountain Plovers searched largely on foot in a grid pattern so (adults and young) observed in 1996 was 16; that the entire area was visible without the aid there were 29 in 1997 and 30 in 1998 (Table of binoculars. To cover more ground, we also 1). For all 3 years most observations occurred searched adjacent areas on foot, though tran- in areas where sightings had been made in sects were not as close together as locations of previous years, or adjacent to those areas. Typ- previous Mountain Plover use. Regions beyond ical habitat for Mountain Plovers in the Uinta these locations were surveyed using binocu- Basin Myton Bench area is characterized by lars from roadways in a truck. As there is no black sagebrush and shadscale vegetation in reliable way to assess large tracts of land to the 8–25 cm height range (UDWR 1995). determine appropriate Mountain Plover nest- Three nests were found in 1996, the first on ing areas (because habitat is so uniform and 5 June. No nests were located in 1997. In plovers are clumped), based on our experi- 1998 the first of 5 nests was found on May 29, ence, knowledge of the terrain, and appear- and eggs were hatching that day. The latest 2 ance of the landscape, we used 7.5-minute of 5 nests found in 1998 were abandoned. At topographic maps and judged the habitat to one of those nests an adult was trapped, determine where to focus search efforts. banded, and fitted with a transmitter. Thirteen Once nests containing eggs were located, days later another adult was trapped at the adults were subsequently trapped. After adult same nest. We assume that the 2nd adult birds left the eggs, we placed a small wire trapped was the male of the breeding pair. cage with an open door over the nest. As adults Nests of nearest neighbors were located about returned to incubate, the door was tripped and 240–370 m apart. Four of the five 1998 nest adults captured. Mountain Plovers were fitted sites were located an average of 8.5 m (range, with a U.S. Fish and Wildlife Service (USFWS) 3 to >100 m) from a white-tailed prairie dog 2001] BREEDING BIOLOGY OF MOUNTAIN PLOVERS 225

TABLE 1. Mountain Plover counts, reproductive success, and temporal occurrence on the Myton Bench, 1992–1998. 1992 1993 1994 1995 1996 1997 1998 Total observed 7 31 24–28 29 16 29 30 Number of clutches — 322305 Number of broods — 864276 Number of young — 15 9 9 6 16 14 Young per adult — 0.94 0.47 0.45 0.60 1.23 0.88 Date of 1st observation — 4/28 5/8 4/6 5/3 4/11 4/9 Date of last observation — 7/26 8/15 8/1 8/13 8/13 8/14

mound. No prairie dog activity was noted at accounts for about 10% of the area surveyed. the 5th nest. The five 1998 nest sites were Based on our experience, we estimate that located an average of 68.6 m (range, 3–182 m) perhaps 70% of the entire area has appropriate from surface disturbance, usually roads. nesting characteristics. Yearly totals of about In 1996, of 3 transmitters fitted to Moun- 30 Mountain Plovers reported for the Myton tain Plovers, 2 came off after 2–3 days. The Bench are probably conservative estimates 3rd bird left the area, and we were unable to considering the amount of potential habitat. locate the signal with the receiver. No adults Although much search time was spent outside were trapped in 1997. In 1998 five transmit- areas where Mountain Plovers are concen- ters were attached to Mountain Plovers; 2 trated, most observations were made in areas transmitters came off and were recovered. known to support nesting Mountain Plovers. One adult left the nest area soon after it was For example, although much of Eightmile Flat trapped, and the radio signal was not picked was surveyed in earlier years for prairie dogs, up until 2 months later, approximately 1 km and Mountain Plovers were recorded on 5 from the nest site. It is not known if the trans- occasions, no nests or young were seen. Sur- mitter was still attached to the bird at that veying this area would double the area of con- time. The remaining 2 adults with transmitters centrated searches; however, access by auto- were monitored for 2–3 weeks while at the mobile is restricted because of lack of road nest site and shortly after the eggs hatched, systems. It is important to note that the Moun- but no substantial movement patterns were tain Plover is drably marked and often squats observed before we were unable to locate motionless in response to disturbance, making transmitter signals again. it difficult to find (Knopf 1996). The Myton Bench population seems to DISCUSSION fluctuate slightly around 30 birds, with young- of-the-year accounting for half the total. It is Although documentation of this small but possible that breeding adults remain in and somewhat consistently stable population has adjacent to nesting areas during the breeding been recent, its occurrence on the Myton season, while nonbreeding adults go elsewhere Bench, Utah, probably had ancient origins. in the region and are not included in the count. The historical distribution of bison included Or, nonbreeding adults may remain near nest the Uinta Basin near the periphery of its range sites of other pairs and, because individuals (Hornaday 1889); it is likely the Mountain are not recognizable by bands, may appear to Plover followed bison herds westward as they be a member of the breeding pair. Graul provided suitable habitat for breeding. And, (1975) reported Mountain Plovers are slightly like the bison, they too are on the periphery of colonial and nesting territories may overlap. their breeding range in this geographically Nests in Colorado were found to be clumped isolated location. in a given area, even where habitat was good The distribution of known nesting popula- over broad areas and population numbers were tions of Mountain Plovers in the Uinta Basin low (2 nests and 1 additional brood per 65 ha; is essentially concentrated in 2 nesting areas Graul 1972). While the plover population on of 585 and 1040 ha amidst 15,034 ha of seem- the Myton Bench is small, 4 of 5 nests in 1998 ingly favorable habitat. The breeding area were clumped together, perhaps as a result of 226 WESTERN NORTH AMERICAN NATURALIST [Volume 61 the social nature of this species, even though son (Olson and Edge 1985). Prairie dog towns they are surrounded by large areas of similar in Wyoming are smaller and more scattered and apparently suitable habitat. than in Montana; however, a nest and several Breeding-site fidelity may also influence adults and chicks were seen on a dog town, nesting distribution. In Colorado some adults and chicks tended to remain in the general (5 of 8 banded) returned to the same breeding area of the nest (Parrish et al. 1993). area each year, and some young (2 banded as Nest sites in the Myton Bench area (n = downy young) came back to breed in the area 11) were located an average of 69 m (range, in which they hatched (Graul 1973). Our obser- 3–182 m) from well pads and/or roadways. vations of Mountain Plover breeding activity Wells and roads were in existence before have been recorded in the same areas on the annual nest-site selection by Mountain Plovers. Myton Bench since survey work began in Mountain Plover nests in the Powder River 1993. It is likely that Mountain Plovers are Basin, Wyoming, were found near animal or returning to breed at the same sites year after wheel tracks, and birds were seen foraging on year because of long-established traditions. the tracks in the morning and evening (Parrish Breeding-site fidelity is prevalent among most et al. 1993). Observations have been made on shorebird species and best documented in the the Laramie plains, Wyoming, of adults bring- Piping Plover (Charadrius melodus; Haig and ing young close to roads to feed (Laun 1957). Oring 1988) and Spotted Sandpiper (Actitis McCafferty (1930, as cited in Laun 1957) re- macularia; Reed and Oring 1993). Prior knowl- ported many young birds killed by automo- edge of an area may increase success in ob- biles while feeding near roadways; vehicle taining food, territories, and mates. Territory activity may be responsible, in part, for the defense and predator avoidance may also be decrease of Mountain Plovers on the Laramie more effective (Haig and Oring 1988). Suc- plains. Spotlight surveys in Utah yielded many cessful breeding in an area one year does not observations of adults and young on well pads ensure success in following years; however, and roads at night in addition to those during experience gained in an area may be an advan- daylight hours. Because our night work with tage in reproductive success over an individ- spotlights was of short duration when plovers ual’s lifetime (Gratto et al. 1985, Haig and were found, we do not believe we unduly Oring 1988). exposed Mountain Plovers to predation during Mountain Plover distribution is also likely those times. Our observations also indicated related to prairie dog activity. White-tailed that vehicular traffic does not appear to alter prairie dogs (Cynomys leucurus) are common foraging or incubation behavior; and, while on the Myton Bench but distributed unequal- vehicle mortality may be of concern, no cases ly across the landscape rather than highly have been documented in Utah. clumped, and 4 of 5 nests located in 1998 The Mountain Plover is rare in Utah and has were found near active prairie dog mounds. been declining over the whole of its breeding Also, broods in Utah do not seem to move far range since the 1960s. It is a species charac- from the nest site, about 800–900 m (Fig. 1), terized by habitat specificity (Rotenberry and and adults have been observed frequently on Wiens 1980). The historical use of certain white-tailed prairie dog mounds. Gilbert areas for breeding on the Myton Bench over (1980) and Terborgh (1986) designated prairie other places indicates the relative importance dogs an ecological keystone species, meaning of protecting these nesting grounds from fur- they create suitable habitat conditions sup- ther oil and gas development. Though Moun- porting populations of other species, including tain Plovers tend to select nest sites near areas Mountain Plovers. Mountain Plovers prefer of surface disturbance (see Knopf and Miller areas of short vegetation or bare ground, and 1994 for Colorado conditions), and additional prairie dogs provide such areas as a result of bare ground resulting from increased develop- their grazing and mound construction. Hori- ment may seem beneficial to this bird, added zontal visibility on Montana dog towns was human activity associated with oil and gas significantly greater than visibility at adjacent expansions in Utah may have adverse effects areas (Knowles et al. 1982). Mountain Plovers on this small population. Intensive surveys, select this habitat for nesting as well as all perhaps using playback calls over adjacent other activities throughout the breeding sea- regions and especially where other breeding 2001] BREEDING BIOLOGY OF MOUNTAIN PLOVERS 227 Fig. 1. Observations of adult Mountain Plovers, brood sites, and nest sites on the Myton Bench, Utah, 1992–1998. Fig. 228 WESTERN NORTH AMERICAN NATURALIST [Volume 61 season observations have been made, may re- Museum, 1886–1887. U.S. National Museum, Wash- veal other clusters of nesting Mountain Plovers. ington, DC. KNOPF, F.L. 1996a. Mountain Plover (Charadrius mon- An area of special concern is Eightmile Flat. tanus). In: A. Poole and F. Gill, editors, The Birds of Should this prove to be the case, every addi- North America, No. 211. The Academy of Natural tional, related breeding location potentially Sciences, Philadelphia, PA, and The American increases the heterogeneity of Mountain Ornithologists’ Union, Washington, DC. Plovers in Utah and adds robustness to its ______. 1996b. Prairie legacies—birds. In: F.B. Samson and F.L. Knopf, editors, Prairie conservation: pre- small populations. serving North America’s most endangered ecosys- tem. Island Press, Covelo, CA. ACKNOWLEDGMENTS KNOPF, F.L., AND B.J. MILLER. 1994. Charadrius montanus— montane, grassland, or bare-ground plover? Auk Funding for this research came from the 111:504–506. KNOPF, F.L., AND J.R. RUPERT. 1995. Habits and habitats of Utah Division of Wildlife Resources and the Mountain Plovers in California. Condor 97:743–751. Bureau of Land Management. The BLM pro- ______. 1996. Reproduction and movements of Mountain vided on-site housing, and we thank personnel Plovers breeding in Colorado. Wilson Bulletin 108: at the Vernal office for their instrumental con- 28–35. KNOWLES, C.J., C.J. STONER, AND S.P. GIEB. 1982. Selec- tributions, especially Tom Dabbs, Tim Faircloth, tive use of black-tailed prairie dog towns by Moun- and Steve Madsen. We thank the UDWR for tain Plover. Condor 84:71–74. use of their equipment and help from Steve LAUN, H.C. 1957. A life history study of the Mountain Cranney and other personnel in the North- Plover, Eupoda montana Townsend, on the Laramie eastern Regional Office. Help from Tim Cher- plains, Albany County, Wyoming. Master’s thesis, University of Wyoming, Laramie. vick, Jon Holst, Brad Mecham, and other OLSON, S.L., AND D. EDGE. 1985. Nest site selection by Inland Production Co. personnel was much Mountain Plovers in northcentral Montana. Journal appreciated. Brandon Plewe was instrumental of Range Management 38:280–282. in producing the data maps, and Dennis L. PARRISH, T.L., S.H. ANDERSON, AND W. F. O ELKLAUS. 1993. Mountain Plover habitat selection in the Powder Eggett provided statistical consultation. We River basin, Wyoming. Prairie Naturalist 25:219–226. also thank Jerran T. Flinders and Duke S. REED, J.M., AND L.W. ORING. 1993. Philopatry, site fidelity, Rogers for reviewing this manuscript, and 2 dispersal, and survival of Spotted Sandpipers. Auk anonymous reviewers for their comments and 110:541–551. suggestions. We are also indebted to Michelle ROTENBERRY, J.T., AND J.A. WIENS. 1980. Habitat struc- ture, patchiness, and avian communities in North Landers, Wendy Mendel, and Amy Taylor for American steppe vegetation: a multivariate analysis. their invaluable assistance in the field. Ecology 61:1228–1250. TERBORGH, J. 1986. Keystone plant resources in the tropi- LITERATURE CITED cal forest. Pages 331–344 in M.E. Soulé and B.A. Wilcox, editors, Conservation biology. Sinauer Asso- ciates, Inc., Sunderland, MA. DAY, K.S. 1994. Observations of the Mountain Plover UTAH DIVISION OF WILDLIFE RESOURCES (UDWR). 1994. (Charadrius montanus) breeding in Utah. South- Wildlife surveys on the Monument Butte oil field. western Naturalist 39:298–300. Unpublished report, Utah Division of Wildlife GILBERT, L.E. 1980. Food web organization and conserva- Resources, Northeastern Region. tion of Neotropical diversity. Pages 11–34 in M.E. ______. 1995. Mountain Plover surveys on the Myton Soulé and B.A. Wilcox, editors, Conservation biol- Bench. Unpublished report, Utah Division of Wild- ogy. Sinauer Associates, Inc., Sunderland, MA. life Resources, Northeastern Region. GOODRICH, S., AND E. NEESE. 1986. Uinta Basin flora. ______. 1997. Mountain Plover surveys on the Mounu- USDA Forest Service, Intermountain Region, Ogden, ment Butte Oil Field. Unpublished report, Utah Divi- UT. sion of Wildlife Resources, Northeastern Region. GRATTO, C.L., R.I.G. MORRISON, AND F. C OOKE. 1985. UNITED STATES FISH AND WILDLIFE SERVICE (USFWS). Philopatry, site tenacity, and mate fidelity in the 1996. Candidate notice of review, FWS/DTE. Un- Semipalmated Sandpiper. Auk 102:16–24. published memorandum dated December 17, 1996. GRAUL, W.D. 1972. Breeding biology of the Mountain WOODBURY, A.M., C. COTTAM, AND J.W. SUGDEN. 1949. Plover (Charadrius montanus), 1969–1972. Technical Annotated check-list of the birds of Utah. Bulletin of Report 199, U.S. International Biological Program. the University of Utah 39(16):13. ______. 1973. Adaptive aspects of the Mountain Plover WHITE, C.M., H.H. FROST, D.L. SHIRLEY, G.M. WEBB, social system. Living Bird 12:69–93. AND R.D. PORTER. 1983. Bird distributional and ______. 1975. Breeding biology of the Mountain Plover. breeding records for southeastern Idaho, Utah, and Wilson Bulletin 87:6–31. adjacent regions. Great Basin Naturalist 43:717–727. HAIG, S.M., AND L.W. ORING. 1988. Mate, site, and terri- tory fidelity in Piping Plovers. Auk 105:268–277. Received 29 July 1999 HORNADAY, W.T. 1889. The extermination of the American Accepted 27 April 2000 bison. Pages 367–548 in Report of the U.S. National Western North American Naturalist 61(2), © 2001, pp. 229–235

NEST SITE SELECTION BY MOUNTAIN PLOVERS (CHARADRIUS MONTANUS) IN A SHRUB-STEPPE HABITAT

Ann E. Ellison Manning1,2 and Clayton M. White1,3

ABSTRACT.—Habitat use by Mountain Plovers was studied in Duchesne County, Utah, from 1996 to 1998. This area is a shrub-steppe habitat and is different from the shortgrass prairie where current Mountain Plover breeding densities are greatest. Mountain Plovers prefer areas of short, sparse vegetation. Habitat surveys quantified vegetation and open space composition at nest and randomly selected sites. Data gathered in 1998 showed significant differences between nest and random sites in maximum vegetation height (P = 0.0021) and percentage total rock cover (P = 0.0027). As per- centage rock cover also reflects open space, these results are consistent with general habitat characteristics preferred by the Mountain Plover. White-tailed prairie dogs were present significantly more often near the 5 nest sites located in 1998 than the 20 random sites. Insects collected from the same nest areas and random points reflected food items known to be in the Mountain Plover diet, but there were no significant differences in diversity of insects between nest and random sites.

Key words: Mountain Plover, Charadrius montanus, breeding habitat, Uinta Basin.

The Mountain Plover (Charadrius montan- (Knopf and Miller 1994). On the Pawnee us), a species native to grasslands, typically National Grassland, Colorado, Mountain Plovers breeds in open, flat shortgrass prairie. Histori- prefer to nest in areas where mean grass cally, shortgrass prairies were composed of height is <8 cm in April when breeding sites treeless bottoms and uplands vegetated by are being selected (Graul 1975). In California blue grama (Bouteloua gracilis) and buffalo during winter Mountain Plovers strongly grass (Buchloe dactyloides). Bison (Bison bison), select alkaline flats, recently burned fields, pronghorn (Antilocapra americana), and prairie and grasslands which have been heavily grazed. dogs (Cynomys sp.) evolved as the primary Flat, cultivated lands are also used for forag- herbivores on this landscape. Because native ing and roosting (Knopf and Rupert 1995). grasslands have been altered by the removal Knopf and Miller (1994) suggested that Moun- of primary native grazers and by agricultural tain Plovers are a species of disturbed prairie use of the Great Plains, there is less suitable or semidesert, rather than strictly restricted to breeding habitat available, as tall vegetation typical shortgrass prairie. In 1993 surveys con- hinders the ability of this bird to detect preda- firmed a Mountain Plover population, of un- tors (Knopf 1996). As a result of such alterations, known size, breeding in Utah on the Myton native species are declining in number, and Bench, Duchesne County, Uinta Basin (Day exotic species diversity and density are increas- 1994). Prior to 1992 there were 12 documented ing (Knopf 1994). Because of long-term declines, historical sightings of Mountain Plovers in the Mountain Plover was listed as a candidate Utah, and 6 were in the Uinta Basin (Audubon species under the U.S. Endangered Species Field Notes 1966, Waller 1967, White et al. Act on 3 May 1993 and is currently under con- 1983, S. Madsen, BLM, personal communica- sideration for a threatened designation. tion). Observed population numbers have Breeding Mountain Plovers occur geogra- always been small but fairly consistent from phically from Montana south to New Mexico 1993 to 1998 (UDWR 1997). (Knopf 1996). Studies of breeding populations Habitat characteristics in the Uinta Basin in Colorado and Montana found Mountain are notably different from typically standard Plovers selecting nest sites in areas of low shortgrass prairie breeding areas. In Utah veg- herbaceous vegetation and sparse shrub cover etation is sparse; sagebrush communities are

1Department of Zoology, Brigham Young University, Provo, UT 84602. 2Present address: 276 S. 1000 E., Salt Lake City, UT 84102. 3Corresponding author.

229 230 WESTERN NORTH AMERICAN NATURALIST [Volume 61 dominated by Artemisia spp. with a compo- 1500 m to 1920 m elevation. Climate and nent of grasses including Sandberg bluegrass habitats of the Uinta Basin represented within (Poa secunda), Indian ricegrass (Sorghastrum the study area are typical of the shrub-steppe nutans), and needle-and-thread (Stipa comata; habitat type found in the Great Basin (Good- Goodrich and Neese 1986). White-tailed prairie rich and Neese 1986). Vegetative complexes dogs are resident, thinly spread rather than in range from essentially bare sand and/or gravel dense clustered towns, and are known to be to low-growing black sagebrush (A. nova). an ecological “keystone” species in creating Greasewood (Sarcobatus vermiculatus), shad- suitable habitat for other species, including scale (Atriplex confertifolia), and occasional the Mountain Plover (Gilbert 1980, Terborgh big sagebrush (A. tridentata) stands are spo- 1986). Prairie dogs graze on vegetation, and radically present throughout the area. their mounds, being relatively bare, provide open space. Because of their habitat require- METHODS ments, Mountain Plovers are strongly associ- ated with active black-tailed prairie dog towns Mountain Plover surveys have been con- in Montana in their breeding, nesting, and feed- ducted in the study area since 1993 (UDWR ing areas (Knowles et al. 1982, Olson 1985). 1995). Vegetation surveys were completed at Where Mountain Plovers breed in Utah, oil and all known nest sites from 1993 to 1998 (n = gas development contributes to the amount of 11) and at 20 randomly selected sites. Random surface disturbance and bare ground. These points were selected by choosing 20 sections habitat modifications may have some benefits, from the total study area and fixing the sample and Mountain Plovers are known to raise point as close to the center of the section as broods near excessive local disturbance (Knopf possible. At each site we measured a 10-m- and Miller 1994). radius macroplot and sampled ten 1-m2 The diet of the Mountain Plover through- quadrats within the macroplot. We then esti- out its breeding range consists mainly of mated percentage of each of the following: ground-dwelling and winged invertebrates total vegetative cover, shrub, forb, grass, total perched on the ground; foraging is oppor- rock cover, large rock (>7 cm), medium rock tunistic (Knopf 1996). (2–7 cm), and small rock (<2 cm). We also It is of interest that a small Mountain Plover counted the number of species noted as population is able to breed in Utah. There are shrubs, forbs, grasses and grasslikes. Measure- no data to indicate whether the Myton Bench ments were taken of maximum and average population is a relic; thus, it is important to vegetation heights. Presence or absence of know which habitat characteristics the Moun- white-tailed prairie dogs was noted. Distance tain Plover prefers when selecting a nest site from nearest prairie dog mound, roadway, and in this atypical region. Information is also well pad was recorded at each nest site. Slope needed to understand the impacts of intensive and aspect at each nest site were also recorded. oil development and associated vegetative In 1998 potential prey availability was sam- changes on this population. The objectives of pled. We collected insects from nest areas and this study were to quantify habitat parameters random sites before and during Mountain at Mountain Plover nest sites in the Uinta Plover nesting time and then again after hatch- Basin and measure available food resources at ing. Collection areas were approximately cir- these sites. cular, extending about 0.2 km in radius from each nest or at randomly selected points. Forty STUDY AREA minutes was spent at each collection site, and anything visible to the surveyors was caught Surveys were done from Castle Peak and with sweep net or forceps. All insects col- Wells Draws east to the border of Pariette lected were classified to the level of family by Wetlands Wildlife Habitat Management Area, Richard W. Baumann, Monte L. Bean Life approximately 20 km southwest of Myton, Science Museum, Brigham Young University. Duchesne County, Utah. The study area gen- Using discriminant analysis, stepwise dis- erally encompasses T8S to T9S, and R16E to criminant analysis, and Wilcoxon 2-sample R18E. These areas have a highly variable, bro- tests, we compared 14 habitat characteristics ken topography ranging from approximately at nest and random sites. The diversity of 2001] NEST SITE SELECTION BY MOUNTAIN PLOVERS 231 insects collected at nest and random sites was al large visual barriers are not as great a hin- estimated with the Shannon function (Pielou drance to the Mountain Plover in Utah as in 1977) and then compared with Wilcoxon rank other parts of the breeding range. sums tests. A pooled t test for small samples Regardless of degree of slope, the prairie was used to compare Utah nest sites with nest dog plays an important role for Mountain sites in Montana and Wyoming. Plovers as 4 of 5 nest sites in Utah in 1998 were located an average of 8.5 m from a RESULTS AND DISCUSSION white-tailed prairie dog mound (Table 1). Of these, some were abandoned mounds and oth- The breeding area in Duchesne County, ers had prairie dogs present. No prairie dog Utah, varied from typical shortgrass prairie activity was noted at the 5th nest. Stepwise Mountain Plover nesting habitat in a major discriminant analysis of all habitat parameters way, primarily in general terrain composition, measured in Utah ranked presence of white- which is a highly variable, broken topography tailed prairie dogs 2nd in importance in classi- (UDWR 1994). Of 11 known nest sites in Utah fying a site as nest or random (F = 8.121, P = (1993–1998), only 3 were located on flat, open 0.0081). When compared to adjacent areas, ground. All others were situated on the top or black-tailed prairie dog towns in Montana had at the base of slopes, or very near large rocky a greater amount of bare ground and total outcroppings. Five nest sites found in 1998 plant cover was less; horizontal visibility on were located an average of 68.6 m from sur- black-tailed prairie dog towns was significant- face disturbance, usually roads (Table 1). Else- ly greater than at adjacent areas (Knowles et where, Mountain Plovers usually nest on a flat al. 1982). Activities of black-tailed prairie dogs area on the top of a hill or in a valley (Graul increase the number of perennial and annual 1975). In Montana black-tailed prairie dog plant species within their towns (Bonham and towns used by Mountain Plovers were level Lerwick 1976). Mountain Plovers select this with slopes rarely >12% (Knowles et al. 1982). habitat for nesting as well as all other activities In Colorado and Wyoming nests were almost throughout the breeding season (Olson and exclusively found on slopes of <5% and 2%, Edge 1985). White-tailed prairie dog mounds respectively (Graul 1975, Parrish et al. 1993). in Utah are virtually devoid of vegetation. All nest sites in Utah were on a slope ≤10% Mountain Plovers were often noted atop these (Table 1). The Prairie Falcon (Falco mexicanus) mounds, which likely provide vantage points is a common aerial predator in Colorado (F.L. for predator watch. In other areas Mountain Knopf personal communication) that flies low Plovers and other species of plover have a ten- to surprise prey by coming over ridges at fast dency to nest near conspicuous objects, such speeds. Mountain Plovers often turn their as old cow manure piles (Graul 1975). How- heads sideways to scan the sky for raptors and ever, aside from white-tailed prairie dog prefer open, flat habitat (Knopf 1996, Graul mounds, nests in Utah were not observed to 1975). We saw few aerial predators, other than be in close proximity to particular objects. Golden Eagles (Aquila chrysaetos), in the Myton Comparison of habitat surveys from 11 nest Bench study area. Only a single Prairie Falcon sites and 20 randomly selected sites showed was seen. Therefore, we suspect that occasion- that differences exist between locations selected

TABLE 1. Relationship of Mountain Plover nest sites found in 1998 on the Myton Bench to white-tailed prairie dog mounds and oil development, and slope and aspect descriptors.

______Nest 12345x– Distance to nearest prairie dog mound (m) >100 3 15 12 4 8.5 Distance to nearest road or oil well pad (m) 3 41 20 182 97 68.6 Slope (%) 0 10 0 9 0 3.8 Aspect none south none north none — 232 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 2. Wilcoxon 2-sample tests of habitat parameters measured at Mountain Plover nest sites and randomly selected sites in 1998. Significant differences (P) were determined at the α = 0.05 level and are indicated by an asterisk (*). Presence or absence of prairie dogs is categorical data (1 = yes, 0 = no). Nest sites Random sites ______(n = 11) ______(n = 20) Variable x– (range) sx– (range) sP % total vegetation cover 29.6 (1–75) 11.8 34.9 (0–90) 15.8 0.1541 % shrub cover 54.9 (0–100) 30.2 45.9 (0–100) 29.8 0.1427 % forb cover 13.6 (0–95) 23.5 8.9 (0–100) 13.9 0.8202 % grass cover 31.4 (0–100) 25.3 44.1 (0–100) 28.9 0.0793 Maximum vegetation height (cm) 23.1 (3–60) 10.6 31.1 (0–137) 14.5 0.0021* Average vegetation height (cm) 11.5 (3–35) 5.3 14.2 (0–137) 11.9 0.2226 % total rock cover 61.6 (15–99) 17.3 36.8 (0–90) 23.5 0.0027* Presence of prairie dogs 0.6 (0–1) 0.5 0.3 (0–1) 0.4 0.1111

by Mountain Plovers and the larger surround- ing area (Table 2). The 14 habitat parameters we measured separated 100% of nest sites from randomly selected sites (Fig. 1). Stepwise discriminant analysis indicated that, in addi- tion to prairie dog presence, percentage total rock cover (F = 14.555, P = 0.0007) and num- ber of species of forb (F = 2.413, P = 0.1319) were the most important habitat variables in predicting whether a plot was from a nest or random site. Mean percentage total rock cover at nest sites was 61.6%, which was signifi- cantly higher than randomly selected sites (36.8%, P = 0.0027). Although stepwise dis- criminant analysis did not show maximum vegetation height as a principal factor in determining the type of site, a Wilcoxon 2- Fig. 1. Discriminant analysis of 1998 nest (n = 11) and sample test demonstrated that maximum veg- random (n = 20) sites. Each point is plotted by its score as etation height was significantly shorter at nest a nest category (x-axis) and as a random category (y-axis). All nest points were correctly classified as nests; 75% of sites than at random sites (P = 0.0021; Table random points were correctly classified as random. 2). After young left the area in July, maximum plant height at nest sites was measured at 23.1 cm, and average vegetation height was 11.5 cm. Mean vegetation height at nest sites in 1993). We assumed that component groups Montana measured at a similar time during (shrubs, grasses, cacti), which make up per- the season was only 4.35 cm (Olson and Edge centage total cover, were independent, and we 1985), and in Wyoming <10 cm (Parrish et al. found no significant differences when sites in 1993). Graul (1975) recorded the mean height Utah were tested against sites in Montana (P of blue gramma–buffalo grass in Colorado at = 1.6797) and Wyoming (P = 1.711). Mean <8 cm in April. Although vegetation is slightly percentage grass cover in Colorado was even taller in Utah, percentage total plant cover is higher at 68% (Knopf and Miller 1994). Con- similar to other breeding areas. For example, versely, Utah had a high percentage of open Utah mean plant cover at nest sites was 29.6%, space between plants (about 70%), and Knopf cover in Montana was 38.7% (Olson and Edge (1994) suggested that Mountain Plovers have a 1985), and in Wyoming 26.4% (Parrish et al. minimum requirement of 30% bare ground. 2001] NEST SITE SELECTION BY MOUNTAIN PLOVERS 233

Mountain Plovers did not select bare areas for and random sites collected early in the breed- actual nest sites in Montana (Olson and Edge ing season (P = 0.4384), or those collected late 1985), but rather preferred the increased visi- (P = 0.1864). Mountain Plover diet consists bility created by open spaces near nest sites mainly of arthropods. Baldwin (1971, as cited for foraging and other activities. in Knopf 1996) found ground-dwelling beetles Habitat data were collected each field sea- to account for 60% of the diet by mass, with son after young left the vicinity of the nest. grasshoppers and crickets 24.5% and ants 6.6%. Results from the 3 seasons differ in the num- These groups were represented in the Myton ber of sample nest points and, during 1996, Bench collections. In Montana ground-dwelling location of random points. There was also beetles were found in significantly greater overall variance between years in annual veg- numbers on black-tailed prairie dog towns etation growth. To account for these differing than off towns (Olson 1985). Although cole- sets of data, years were examined separately opterans and orthopterans constituted >85% and then together (Table 3). Because in every of the summer diet of Mountain Plovers in year some nest sites were locations used by Colorado, they showed much more flexibility Mountain Plovers in previous years and some in selecting food items than expected during were current season sites only, we performed winter. A comparison of diets of Mountain separate tests for each year with and without Plovers from 3 different sites in California old nest sites. Results from the current year’s showed diversity in frequency of different nest sites only must be regarded cautiously as arthropod orders taken across sites. Collective- the sample size is small. Significant differences ly, coleopterans were still important (25.9%), occur between years of data collection in per- while hymenopterans were 2nd most common centage total vegetation cover, maximum and at 24.9% (Knopf 1998). In this study collecting average plant height, and number of forb was opportunistic, and consequently all inver- species present. Such variation likely corre- tebrates potentially available to the Mountain lates with each year’s precipitation, though Plover as a food source may not be repre- rainfall data were not recorded. Of 6 contrasts sented. However, any bias that may exist in between nest and random sites, 4 showed per- this method would be the same for both nest centage rock cover significantly higher at nest and random sites. Insect availability on and off sites than random sites. Three contrasts showed prairie dog towns in Montana was very similar, maximum vegetation height at nest sites sig- nificantly lower than random sites. As rock but Olson’s (1985) findings suggested prey vul- cover is interpreted to represent open space, nerability was greater on dog towns because of these results are consistent with other studies short, sparse vegetation. Mountain Plover for- that describe Mountain Plover habitat as hav- aging consists of short runs and then brief ing short vegetation with a bare ground com- stops to survey the ground for insects (Knopf ponent of at least 30% (Knopf and Miller 1994). 1996). The open space and short vegetation of Despite differences between the Uinta Basin the shrub-steppe habitat in the Uinta Basin is and shortgrass prairie habitats, the combina- likely favorable to this foraging behavior. tion of these ecological components in Utah is The Mountain Plover breeding site in Utah compatible with Mountain Plover needs, and is unique compared with other breeding areas the small population maintains a rather consis- because of its shrub-steppe habitat structure. tent number of individuals. We do not have As the breeding range of Mountain Plovers data, however, to indicate whether this small shrinks with increased development of native population is a separate deme or draws indi- shortgrass prairies, perhaps this species is be- viduals from elsewhere to maintain its numbers. ing pushed to adopt alternative habitats. The Insect collections taken from both nest and Uinta Basin is home to a combination of floral random sites were similar. Twelve orders were and faunal species that provide ecological ele- represented, with Hymenoptera (31.0%) and ments comparable to other areas in which the Orthoptera (23.0%) collected most often (Fig. Mountain Plover is known to breed, but fur- 2). The average number of insects collected at ther study is needed to understand the rela- nest sites was 16.6 (s = 6.53), and at random tionship of members of this population to other sites 17.5 (s = 6.19). There was no significant breeding groups, as well as the full extent of difference in diversity of insects between nest Mountain Plover breeding populations in Utah. 234 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 3. Comparisons of habitat parameters using Wilcoxon 2-sample tests. Data were analyzed for each year’s cur- rent nest sites, and also with all known nest sites at the time of data collection. Randomly selected points (n = 20) in 1996 were different from points sampled in 1997 and 1998. Data between years were also examined. P-values indicating a significant difference at the α = 0.05 level are reported. All years 1996 nest 1998 nest 1998 nest 1997 nest 1996 nest 1996 nest v. (n = 3) (n = 5) (n = 11) (n = 6) (n = 6) v. 1997 all years v. 1996 v. 1998 v. 1998 v. 1997 v. 1996 Variable v. 1998 random random random random random random % total vegetation cover 0.0001 0.0381 % shrub % forb % grass 0.0269 Maximum vegetation height (cm) 0.0001 0.0142 0.0022 0.0021 Average vegetation height (cm) 0.0001 0.0381 0.0514 Number of shrub species Number of forb species 0.0023 Number of grass species Presence of prairie dogs 0.0391 0.0275 % total rock cover 0.0001 0.0381 0.0027 0.0136 % small 0.0082 0.0389 % medium 0.0011 0.0351 0.0286 0.0137 % large 0.0158 0.0404

Fig. 2. Insect collections from Mountain Plover nest sites and randomly selected sites taken before nesting (early) and after young left the site (late). The 4 major orders collected are represented. 2001] NEST SITE SELECTION BY MOUNTAIN PLOVERS 235

ACKNOWLEDGMENTS _____. 1996. Mountain Plover (Charadrius montanus). In: A. Poole and F. Gill, editors, The birds of North Funding for this research came from the America, No. 211. The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Utah Division of Wildlife Resources and the Union, Washington, DC. Bureau of Land Management. The BLM pro- _____. 1998. Food of Mountain Plovers wintering in Cali- vided on-site housing, and we thank personnel fornia. Condor 100:382–384. at the Vernal office for their instrumental con- KNOPF, F.L., AND B.J. MILLER. 1994. Charadrius montanus— montane, grassland, or bare-ground plover? Auk 111: tributions, especially Tom Dabbs, Tim Faircloth, 504–506. and Steve Madsen. We thank the UDWR for KNOPF, F.L., AND J.R. RUPERT. 1995. Habits and habitats of use of their equipment and help from Steve Mountain Plovers in California. Condor 97:743–751. Cranney and other personnel in the North- KNOWLES, C.J., C.J. STONER, AND S.P. GIEB. 1982. Selec- eastern Regional Office. Help from Tim Cher- tive use of black-tailed prairie dog towns by Moun- tain Plover. Condor 84:71–74. vick, Jon Holst, Brad Mecham, and other OLSON, S.L. 1985. Mountain Plover food items on and ad- Inland Production Co. personnel was much jacent to a prairie dog town. Prairie Naturalist 17: appreciated. Kimball T. Harper outlined habi- 83–90. tat sampling methods, Richard W. Baumann OLSON, S.L., AND D. EDGE. 1985. Nest site selection by Mountain Plovers in northcentral Montana. Journal was instrumental in insect identification, and of Range Management 38:280–282. Dennis L. Eggett provided statistical consulta- PARRISH, T.L., S.H. ANDERSON, AND W. F. O ELKLAUS. 1993. tion. We also thank Jerran T. Flinders and Duke Mountain Plover habitat selection in the Powder River S. Rogers for reviewing this manuscript, and basin, Wyoming. Prairie Naturalist 25:219–226. Lewis Oring and an anonymous reviewer for PIELOU, E.C. 1977. Mathematical ecology. John Wiley and Sons, Inc., New York. comments and suggestions. We are indebted to TERBORGH, J. 1986. Keystone plant resources in the tropi- Michelle Landers, Wendy Mendel, and Amy cal forest. Pages 331–344 in M.E. Soulé and B.A. Taylor for their invaluable assistance in the Wilcox, editors, Conservation biology. Sinauer Asso- field. ciates, Inc., Sunderland, MA. UTAH DIVISION OF WILDLIFE RESOURCES (UDWR). 1994. Wildlife surveys on the Monument Butte oil field. LITERATURE CITED Unpublished report, Utah Division of Wildlife Re- sources, Northeastern Region. AUDUBON FIELD NOTES. 1966. Waders 20:77. _____. 1995. Wildlife surveys on the Monument Butte oil BONHAM, C.D., AND A. LERWICK. 1976. Vegetation changes field. Unpublished report, Utah Division of Wildlife induced by prairie dogs on shortgrass range. Journal Resources, Northeastern Region. of Range Management 29:221–225. _____. 1997. Mountain Plover surveys on the Mounument DAY, K.S. 1994. Observations of the Mountain Plover Butte Oil Field. Unpublished report, Utah Division (Charadrius montanus) breeding in Utah. Southwest- of Wildlife Resources, Northeastern Region. ern Naturalist 39:298–300. WALLER, R.H. 1967. New and additional records of birds GILBERT, L.E. 1980. Food web organization and conserva- in the Virgin River valley. Condor 69:420–422. tion of Neotropical diversity. Pages 11–34 in M.E. WHITE, C.M., H.H. FROST, D.L. SHIRLEY, G.M. WEBB, Soulé and B.A. Wilcox, editors, Conservation biol- AND R.D. PORTER. 1983. Bird distributional and ogy. Sinauer Associates, Inc., Sunderland, MA. breeding records for southeastern Idaho, Utah, and GOODRICH, S., AND E. NEESE. 1986. Uinta Basin flora. adjacent regions. Great Basin Naturalist 43:717–727. USDA Forest Service, Intermountain Region, Ogden, UT. Received 29 July 1999 GRAUL, W.D. 1975. Breeding biology of the Mountain Accepted 27 April 2000 Plover. Wilson Bulletin 87:6–31. KNOPF, F.L. 1994. Avian assemblages on altered grass- lands. Studies in Avian Biology 15:247–257. Western North American Naturalist 61(2), © 2001, pp. 236–240

RUFFED GROUSE (BONASA UMBELLUS) DRUMMING LOG AND HABITAT USE IN GRAND TETON NATIONAL PARK, WYOMING

Matt L. Buhler1 and Stanley H. Anderson2

ABSTRACT.—We described 15 Ruffed Grouse (Bonasa umbellus) drumming logs and adjacent habitat within Grand Teton National Park, Wyoming. Drumming logs and adjacent habitat differed from 30 random non-drumming sites. Drumming logs had fewer limbs (8; P = 0.003) and a smaller percentage of bark remaining (12%; P = 0.0001). These logs were in advanced stages of decay but were still firm to the touch. Additionally, drumming logs were found close to clearings but in areas with increased amounts of undergrowth and mature trees. Adjacent habitat analysis (0.04-ha circu- lar plot centered on logs) indicated drumming locations had significantly greater average canopy height, more vegetative cover consisting of conifer and total canopy cover, and more vertical foliage between 0.3 m and 3.0 m in height. Adjacent habitat was in advanced stages of maturity as indicated by significant numbers of both large-diameter logs and large- diameter lodgepole pine (Pinus contorta) and quaking aspen (Populus tremuloides) snags. Tree species dominating the canopy and subcanopy were large-diameter Engelmann spruce (Picea engelmannii), lodgepole pine, and quaking aspen. Subalpine fir (Abies lasiocarpa) and quaking aspen saplings were more numerous at used sites. Ruffed Grouse drummed in coniferous areas within close proximity of quaking aspen.

Key words: conifer forest, drumming logs, Grand Teton National Park, habitat use, Ruffed Grouse, Bonasa umbellus, screening cover, Wyoming.

Ruffed Grouse (Bonasa umbellus) drumming habitat. We were specifically interested in the sites have been described primarily in eastern amount of horizontal and vertical cover sur- or midwestern deciduous forests (White and rounding the drumming site as well as the Dimmick 1979, Hale et al. 1982, Backs 1984, condition of the log used as a stage. While Thompson et al. 1987). These sites typically drumming, male Ruffed Grouse can be detected have increased shrub and woody stem densities, from some distance. We wondered if, to avoid canopy closure, and understory foliage, indi- predation, Ruffed Grouse were using areas cating that males are using areas with thick that contained more vegetative cover. vegetation growth (Boag and Sumanik 1969, Drumming was assumed to increase the Stoll et al. 1979, Stauffer and Peterson 1985a, male’s vulnerability to predation. Primary pred- Thompson et al. 1987). Dense stands of eastern ators of Ruffed Grouse in northwestern Wyo- red cedar ( Juniperus americana) in the under- ming conifer forests are Northern Goshawks story have been described as being important (Accipiter gentilis), American marten (Martes at drumming sites in Missouri (Thompson et al. americana), coyote (Canis latrans), bobcat (Felis 1987, Thompson and Fritzell 1989). Quaking rufus), and red foxes (Vulpes vulpes). Dense aspen has also been found to be important to horizontal and vertical screening cover, how- Ruffed Grouse (Boag and Sumanik 1969, Gul- ever, make it difficult to pinpoint a grouse’s lion 1977, Stauffer and Peterson 1985a, 1985b, exact location and thus make it harder for Gormley 1996). predators to approach undetected. Increased amounts of screening cover appear to be crucial for drumming sites because of STUDY AREA the conspicuous nature of the male (Boag and Sumanik 1969, Thompson et al. 1987). The We surveyed 40 km of the Snake River purpose of this study was to determine habitat riparian corridor within Grand Teton National use at Ruffed Grouse drumming sites and Park in northwestern Wyoming, from Jackson compare it to random logs and surrounding Lake dam downstream to Moose, Wyoming.

1Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Box 3166, Laramie, WY 82071. Present address: 13620 SW Beef Bend Rd #107, Tigard, OR 97224. 2United States Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Box 3166, Laramie, WY 82071.

236 2001] RUFFED GROUSE DRUMMING SITES 237

The width of the riparian corridor ranges from Habitat adjacent to the logs was sampled 0.25 to 2.6 km (mean = 1.4 km). Elevation using a 0.04-ha circular vegetation plot cen- varies from 1968 m to 2066 m. The upper 10 tered on the log as described by James and km of the study site consists of mature stands Shugart (1970) and Noon (1981). The same of closed-canopy lodgepole pine and Engel- individual conducted all vegetation sampling mann spruce that are contiguous with sur- to decrease variability from observer bias. rounding forest (Mattson and Despain 1985). Transect lines, which were established through The lower 30 km is isolated from forest habitat the center point (logs), ran in each cardinal and is dominated by big sagebrush (Artemisia direction (north–south and east–west) to divide tridentata) and silver sagebrush (Artemisia the circle into quarters for vegetation sam- cana). Understory along the entire 40 km is pling. We determined vertical foliage with a dominated by russet buffaloberry (Shepherdia density board placed at each of the 4 points canadensis), grouse whortleberry (Vaccinium where transect lines intersected the edge of scoparium), common juniper ( Juniperus com- the 0.04-ha circle. The density board was munis), red baneberry (Actaea rubra), wild divided into 4 heights of 0.0–0.3, 0.3–1.0, rose (Rosa woodsii), quaking aspen, Engel- 1.0–2.0, and 2.0–3.0 m, corresponding to low mann spruce, and subalpine fir. and high ground cover and low and high shrub cover, respectively. Values were aver- METHODS aged for each height. Dominant shrub and ground species <1 m tall and <3 cm dbh were We placed 7 transects each in the middle of recorded from most numerous to least in the lodgepole pine, Engelmann spruce, and mixed entire plot. Nearest tree and largest log within cottonwood/conifer cover types throughout each quarter were determined as to distance, the 40-km study area. Transects originated at diameter, and species of closest living tree (≥3 the river’s edge, running perpendicular to the inch dbh) and largest fallen log to the center channel within the cover type. Transects were point. We selected 5 representative trees from 100 m in length and were marked at 10-m the 0.04-ha plot, determined their height with intervals as well as 50 m to each side for a total a clinometer, and averaged the results. Both search area of 10,000 m2 (1 ha). Surveys were ground cover and canopy cover were estimated conducted in early morning (0530–1030) and with an ocular tube with crosshairs at one end. evening (1900–2200) hours between 20 May The observer peered through the tube at the and 30 June 1996 and 15 May and 30 June ground and at the canopy at 10 locations 1997. The observer listened 30 minutes for spaced 1 m apart along each transect. The drumming males and then located the logs. number of “hits” was recorded. A hit occurred Only males that were drumming within the 1- when the crosshairs intersected vegetation. To ha search area were used for habitat analysis. determine total percent cover, we divided the Using a stratified random design, we selected number of hits by 20. Shrub density was 30 random logs. Of 15 drumming logs identi- determined as the observer proceeded along fied, 8 were in lodgepole pine, 5 in Engel- each transect and counted the number of mann spruce, and 2 in mixed cottonwood/ woody stems <3 cm dbh that intersected the conifer. We therefore randomly selected 16 body and outstretched arms at breast height. sites in lodgepole pine, 10 in Engelmann The total number of shrub stems per hectare spruce, and 4 in mixed cottonwood/conifer. was estimated by multiplying the total number Randomly generated numbers for length along of stems encountered from both transects by and distance from the transect determined a 125. Deciduous and coniferous shrubs were point of inspection. At that point the closest recorded separately. Tree diameter of all tree log was used as the random log. Drumming species ≥3 cm dbh was recorded within the logs were measured as follows: diameter at entire circular plot. We also recorded total drumming position, length, number of limbs, number and species of snags >3 cm dbh with- percent bark remaining, and height above in the 0.04-ha plot. ground at drumming position. Random logs Statistical analysis of log use and adjacent were measured for similar variables, with log habitat (0.04-ha circle) varied and was consid- diameter and height off ground being mea- ered significant at P ≤ 0.05. We performed sured at the largest end. univariate comparisons with Mann-Whitney U 238 WESTERN NORTH AMERICAN NATURALIST [Volume 61 and 1-way analysis of variance (ANOVA) most marked difference between drumming through paired t tests by comparison of and random logs was the degree of decompo- means, as some variables were nonparametric sition. On average, only 8 limbs and 12% of (Minitab Inc. 1996). Two-sample t tests were the bark remained on drumming logs, indicat- used for variables that were found to have nor- ing advanced stage of decomposition (Masen mal distributions (Wilk Shapiro > 0.95). Logis- et al. 1979). Past research indicated that drum- tic regression was used to compare tree-diam- ming logs were not different from random logs eter classes between drumming and random but that Ruffed Grouse were using areas with sites. Trees were broken down into species greater vegetation cover (Boag and Sumanik and divided into 9 classes (3–8, 8–15, 15–23, 1969, Stauffer and Peterson 1985a). However, 23–38, 38–53, 53–69, 69–84, 84–102, and we found Ruffed Grouse using specific logs >102 cm), with the 10th class being total that were relatively free of bark and limbs for number of trees found in the plot. Logistic drumming. regression analysis revealed which diameter Analysis of adjacent habitat showed several class of tree species dominated the habitat differences between drumming and random surrounding the drumming log. log sites (Table 2). Drumming sites were typi- cally located within mature stands of lodge- RESULTS pole pine and Engelmann spruce with thick understory of saplings and shrubs. Drumming Compared with random logs, drumming sites were found only within the upper portion logs had fewer remaining limbs (8 ± 4.6 s; P = of the river that is surrounded by contiguous 0.003) and a smaller percentage of bark re- conifer forest. Large-diameter lodgepole pine maining (12% ± 8.2 s; P = 0.0001). They were and Engelmann spruce provided increased in advanced stages of decomposition as evi- conifer and total canopy cover as well as taller- denced by remaining bark and fewer limbs than-average canopy height. Lodgepole pine (Table 1). and quaking aspen snag diameter and stem Habitat composition surrounding drum- densities were greater for drumming sites, ming logs was significantly different from ran- indicating use of sites from middle- to late- dom locations (Table 2). Of 15 drumming logs, successional forest stages. Additionally, large- 8 were located in lodgepole pine, 5 in Engel- diameter logs on the forest floor indicated mann spruce, and 2 in mixed cottonwood/ mature stands. The subcanopy consisted pri- conifer. Of 30 random logs, 16 were in lodge- marily of quaking aspen of all size classes pole pine, 10 in Engelmann spruce, and 4 in ranging from saplings to mature trees (>48 mixed cottonwood/conifer. Lodgepole pine and cm). Engelmann spruce and subalpine fir sap- Engelmann spruce dominated the canopy and lings were also found in greater abundance. provided increased total and conifer canopy Quaking aspen has been determined to be cover, average canopy height, total number and important to Ruffed Grouse as cover and a size of Engelmann spruce and lodgepole pine. food source (Boag and Sumanik 1969, Gullion Subalpine fir and quaking aspen tree stems 1977, Stauffer and Peterson 1985a, 1985b). We dominated the subcanopy. Lodgepole pine and found Ruffed Grouse in close association with quaking aspen snags were in greater abun- quaking aspen in all forms from saplings to dance. Ground cover variables that were signif- mature trees. Drumming locations were typi- icantly greater were largest log dbh and verti- cally located either within or close to quaking cal foliage between 0.3 m and 3.0 m in height. aspen stands. Ground cover was dominated by russet Discussion buffaloberry, grouse whortleberry, wild rose, Ruffed Grouse drumming logs were signifi- and red baneberry. The combination of large cantly different from random logs, suggesting quantities of shrubs, saplings, and tree species that particular logs were used for courtship produced greater-than-average amounts of ver- displays (Table 1). Drumming logs were typi- tical foliage between 0.3 m and 3.0 m high. cally found close to clearings with large amounts While searching for drumming males, we had of undergrowth. On average, they had larger to get close to the birds before we could locate diameters (84 cm) than random logs, with the them. Higher density of ground and sub- top of the log 42.5 cm off the ground. The canopy vegetation cover has been shown to be 2001] RUFFED GROUSE DRUMMING SITES 239

TABLE 1. Comparison of variable means from 15 Ruffed Grouse drumming logs and 30 random logs in Grand Teton National Park, Wyoming. Drumming logs Random logs Variable x– (s) x– (s) P-value Log dbh (cm) 84.33 (16.3) 75.43 (8.9) 0.401 Log height (cm) 42.5 (19.4) 34.75 (12.9) 0.205 Log length (m) 33.5 (6.8) 28.5 (12.9) 0.495 Number of limbs 8.5 (4.6) 40.7 (14.1) 0.003 Percent bark remaining 12.6 (8.2) 77.4 (20.4) 0.0001

TABLE 2. Comparison of habitat variable means from 15 Ruffed Grouse drumming sites and 30 random sites. Drum- ming sites were 0.04-ha circular plots adjacent to and centered on drumming logs. Random sites were adjacent to and centered on random logs. Drumming sites Random sites Variable x– (s) x– (s) P-value Largest log dbh (cm) 84.33 (8.3) 45.89 (18.6) 0.048 Conifer canopy cover (%) 73 (12.2) 48 (6.9) 0.0001 Total canopy cover (%) 86 (4.3) 59 (25.8) 0.035 Vertical foliage 0.3–1.0 m (%) 95 (5.9) 65 (15.7) 0.003 Vertical foliage 1.0–2.0 m (%) 90 (12.2) 50 (19.4) 0.009 Vertical foliage 2.0–3.0 m (%) 90 (11.9) 35 (21.1) 0.0001 Average canopy height (m) 114.84 (27.5) 89.14 (19.9) 0.044 Subalpine fir total stems 18.5 (8.7) 2.3 (12.2) 0.003 Quaking aspen tree dbh (cm) 48.3 (14.8) 14.5 (5.9) 0.001 Lodgepole pine snag dbh (cm) 62.3 (5.8) 24.8 (7.1) 0.008 Quaking aspen snag dbh (cm) 38.6 (8.4) 10.2 (2.7) 0.018 Engelmann spruce total stems 39.4 (16.5) 5.5 (1.7) 0.029 Lodgepole pine total stems 41.6 (17.5) 22.6 (18.6) 0.001 Quaking aspen snag total stems 8.4 (2.3) 1.9 (1.5) 0.048 Lodgepole pine snag total stems 11.0 (6.5) 5.2 (3.2) 0.002 Quaking aspen total stems 14.2 (3.2) 2.5 (1.5) 0.0001 Lodgepole pine tree dbh (cm) 65.3 (13.3) 31.6 (15.7) 0.001 Engelmann spruce tree dbh (cm) 86.5 (8.3) 53.9 (11.7) 0.007

important for drumming locations (Boag and slipping silently into nearby shrubs. If pur- Sumanik 1969, Stauffer and Peterson 1985a). sued, the grouse would flush and fly to nearby Ruffed Grouse appeared to be using drum- trees. Marshall (1946) determined that Ruffed ming logs with greater-than-average amounts Grouse initially remain motionless and then of screening cover. fly to conifer tree species when flushed. Any Since mate attraction is accomplished approaching predators would be detected through auditory means, visual cues are prob- through noise or motions, making it hard for ably not as important (Thompson and Fritzell those predators to effectively take a drumming 1989, Gormley 1996). Because drumming makes male. Large amounts of vegetation, therefore, males more conspicuous to predators, large appear to decrease the potential of predation amounts of screening cover may be needed to and are an essential part of Ruffed Grouse avoid predation. Aerial predators such as the drumming habitat. Northern Goshawk may have trouble pin- Ruffed Grouse in Grand Teton National Park pointing a grouse’s location due to increased used drumming logs in areas with greater- canopy cover and tree density. Increased ver- than-average amounts of vegetation. Drumming tical foliage from ground cover, shrubs, sub- sites had more vertical and horizontal cover, canopy trees, and mature trees could also con- which appeared not only to more effectively ceal a male grouse from terrestrial predators. hide the drumming male, but to make it hard When we approached a drumming male, he for a predator to approach undetected. Although would remain motionless on the log before males significantly used logs with fewer limbs 240 WESTERN NORTH AMERICAN NATURALIST [Volume 61 and less remaining bark, large amounts of veg- MASEN, C., R.G. ANDERSON, K. KROMAT, JR., J.T. WILLIAMS, etation, both vertical and horizontal, sur- AND R.E. MARTIN. 1979. Dead and down woody material. Pages 78–85 in J.W. Thomas, editor, Habi- rounding the log appeared to be the most tats in managed forests: the Blue Mountains of important factors influencing use of drumming Washington and Oregon. USDA Forest Service Agri- positions. culture Handbook 5. MATTSON, D.J., AND D.G. DESPAIN. 1985. Grizzly bear habitat component mapping handbook for the Yel- ACKNOWLEDGMENTS lowstone Ecosystem. National Park Service and United States Forest Service. 37 pp. Financial support was provided by the MINITAB INC. 1996. Minitab™ for Windows™ release 11.21. National Park Service–Grand Teton National Prowers Printing Company, Lebanon, PA. Park and Wyoming Game and Fish Depart- NOON, B.R. 1981. Techniques for sampling avian habitats. ment. Logistic support and equipment were Pages 42–52 in D. Capen, editor, The use of multi- variate statistics in studies of wildlife habitat. USDA provided by the Wyoming Cooperative Fish Forest Service General Technical Report RM-87, and Wildlife Research Unit and University of Rocky Mountain Forest and Range Experiment Sta- Wyoming. We thank J. Lovvorn and B. Reiners tion, Fort Collins, CO. for constructive comments on early revisions. STAUFFER, D.F., AND S.R. PETERSON. 1985a. Seasonal micro- habitat relationships of Ruffed Grouse in southeast- ern Idaho. Journal of Wildlife Management 49: LITERATURE CITED 605–610. ______. 1985b. Ruffed and Blue Grouse habitat use in BACKS, S.E. 1984. Ruffed Grouse restoration in Indiana. southeastern Idaho. Journal of Wildlife Mangement Pages 37–58 in W.L. Robinson, editor, Ruffed Grouse 49:459–466. management: state-of-the-art in the early 1980’s. STOLL, R.J., JR., M.W. MCCLAIN, R.L. BOSTON, AND G.P. North Central Section of the Wildlife Society. HONCHUL. 1979. Ruffed Grouse drumming site BOAG, D.A., AND K.M. SUMANIK. 1969. Characteristics of characteristics in Ohio. Journal of Wildlife Manage- drumming sites selected by Ruffed Grouse in ment 43:324–333. Alberta. Journal of Wildlife Management 33:621–628. THOMPSON III, F.R., AND E.K. FRITZELL. 1989. Habitat GORMLEY, A. 1996. Cause of mortality and factors affect- use, home range, and survival of territorial male ing survival of Ruffed Grouse (Bonasa umbellus) in Ruffed Grouse. Journal of Wildlife Management northern Michigan. Master’s thesis, Michigan State 53:15–21. University, East Lansing. THOMPSON III, F.R., D.A. FREILING, AND E.K. FRITZELL. GULLION, G.W. 1977. Forest manipulation for Ruffed 1987. Drumming, nesting, and brood habitats of Grouse. Transactions of North American Wildlife Ruffed Grouse in an oak-hickory forest. Journal of Natural Resource Conference 42:449–458. Wildlife Management 51:568–575. HALE, P.E., A.S. JOHNSON, AND J.L. LANDERS. 1982. Char- WHITE, D., AND R.W. DIMMICK. 1979. Survival of habitat acteristics of Ruffed Grouse drumming sites in Geor- use of northern Ruffed Grouse introduced into west gia. Journal of Wildlife Management 46:115–123. Tennessee. Proceedings of the Annual Conference of JAMES, F.C., AND H.H. SHUGART, JR. 1970. A quantitative the Southeast Association of Fish and Wildlife Agen- method of habitat description. Audubon Field Notes cies 32:1–7. 24:727–736. MARSHALL, W.H. 1946. Cover preferences, seasonal move- Received 24 November 1999 ments, and food habits of Richardson’s Grouse and Accepted 27 April 2000 Ruffed Grouse in southern Idaho. Wilson Bulletin 58:42–52. Western North American Naturalist 61(1), © 2001, pp. 241–244

SUBNIVEAN ROOT CACHING BY A MONTANE VOLE (MICROTUS MONTANUS NANUS), COLORADO FRONT RANGE, USA

James B. Benedict1 and Audrey D. Benedict2

Key words: montane vole, Microtus montanus, pygmy bitterroot, Oreobroma pygmaea, caching behavior, snow, Colo- rado Rocky Mountains.

Food hoarding is a common winter-survival The meadow is at an altitude of 3410 m in strategy of cold-climate animals (Smith and the forest-tundra ecotone of Fourth of July val- Reichman 1984), including many microtines. ley. Beginning at the base of a low cliff, it Voles store grasses, leafy vegetation, and twigs slopes gently southeastward to the North Fork primarily in piles on the ground surface. They of Middle Boulder Creek. Snow blankets the store epiphytic lichens in tree cavities and bird meadow from October until early or mid-July nests above the level of the snow. And they of most years, supplying moisture that encour- store roots, rhizomes, and tubers belowground ages lush plant growth. Caching activities or in subnivean chambers, where the food reported in this paper occurred in a plant remains fresh for months (Vander Wall 1990). community dominated by sibbaldia (Sibbaldia Subnivean caches are among the least-studied procumbens) and fern-leaved lovage (Ligus- storage facilities due to the difficulty of observ- ticum tenuifolium). Other species include ing activities that occur entirely beneath the Deschampsia cespitosa, Bistorta bistortoides, snow. Caches are established after snow blan- Erigeron peregrinus, Viola labradorica, Castille- kets the ground. Their contents are ordinarily ja rhexifolia, Vaccinium myrtillus, Vaccinium consumed before meltout, and the chambers scoparium, Gaultheria humifusa, Phleum com- themselves are transient features. To our knowl- mutatum, Carex nigricans, and Juncus drum- edge the only published observations of sub- mondii. Of special interest is the locally high nivean caching by microtines are those of For- density of pygmy bitterroot (Oreobroma pyg- mozov (1966) in northern Kazakhstan and Gates maea [Gray] Howell, formerly Lewisia pyg- and Gates (1980) in western Maryland. maea), a species that elsewhere in the Front Snow arrived early in the mountains of Range reaches greatest percentage cover where western Boulder County, Colorado, during the maximum winter snow depths average 2 to 3 autumn of 1996. Heavy upslope snowstorms m (Walker et al. 1993). and downslope redistribution events between Two grass ball nests were present in the 17 and 27 September created a snowpack that meadow (Fig. 1), only one of which had been gave every indication it would remain for the recently occupied. The other was faded and duration of winter. Conditions then turned partially flattened, as though it had been built warm and dry. By 9 October an elaborate sys- during the preceding winter. We identified the tem of root caches, runways, foraging trenches, builder of the younger nest as a montane vole and surface ball nests had begun to emerge (Microtus montanus nanus), based on the char- from beneath the snow in a meadow above acteristics of dorsal guard hairs shed in its timberline in Indian Peaks Wilderness Area. nesting chamber. The hairs have brown to By 12 October the entire meadow had become black tips, yellowish ivory bands confined to exposed, providing a snapshot of what a vole the central portions of shields, and black lower can accomplish in unfrozen soil beneath a shields that terminate in subshield strictures. continuous snowpack in about 3 weeks’ time. Restriction of the color band to the central

1Center for Mountain Archeology, 8297 Overland Road, Ward, CO 80481. 2Cloud Ridge Naturalists, 8297 Overland Road, Ward, CO 80481.

241 242 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Fig. 1. Tape-and-compass map of runways, tunnel entrances, ball nests, and root caches. portion of the shield (as opposed to extending Ball nests at the study site were connected downward to the subshield stricture) distin- to root caches and subsurface tunnels by a guishes the dorsal guard hairs of M. montanus network of branching runways and foraging from those of M. longicaudus, Phenacomys trenches with an aggregate length of about 60 intermedius, and Clethrionomys gapperi (Moore m (Fig. 1). Runways and trenches were 2.5 to et al. 1974)—other vole species that occur 4.0 cm wide and up to 3.0 cm deep. Foraging above timberline in western Boulder County. trenches were flanked with levees of earth and Supporting this identification is the vole’s of cut rootlets, stems, and leaves piled to the choice of habitats. During 10 years of trapping side during the harvesting process. Five small- in a tundra saddle 8 km northeast of the valley, diameter (2.5 to 3.5 cm) holes near a boulder M. montanus was the only vole species cap- at the southwest end of the runway network tured in snowbed communities dominated by (Fig. 1) appeared to be tunnel entrances, such Sibbaldia procumbens, and the most numerous as might lead to a summer nesting chamber. A vole species in moist-meadow communities 6th entrance occurred nearby, at the edge of a dominated by Deschampsia cespitosa (Arm- smaller boulder. The older of the 2 ball nests, strong et al. in press). the tunnels, and several runways are thought The ball nest was made from stems and to predate the 1996 caching event. leaves of D. cespitosa, clipped to lengths of 7 Four root caches were present in the cm or less. Leaves of Carex nigricans and meadow, each linked to the trench network by leaves and twigs of Gaultheria humifusa, still a short runway (Fig. 1). Caches consisted of fresh and green, were present in trace quanti- roots that had been heaped on the ground sur- ties. The nest was globular in shape, with a face in chambers beneath the snow, forming height of about 8 cm. Its exterior diameter (19 circular mounds or irregularly elongated ridges. cm) was larger than has been generally reported Table 1 summarizes cache dimensions and for M. montanus, but extra-thick insulative contents. Tuberous roots of pygmy bitterroot walls may be required in such a low-tempera- (Oreobroma pygmaea) were the only food ture environment. Two entrances led to a snug, items represented. Roots of this species grow central chamber barely large enough for a sin- in the meadow at depths of 0.6 to 3.4 cm, the gle individual. Field and laboratory studies approximate depth range explored by the for- (Jannett 1982, McGuire and Novak 1986) in- aging vole. Fleshy rhizomes of Bistorta bistor- dicate that adult montane voles nest individu- toides, another potential food source, begin ally rather than in pairs or colonies. below the bases of the trenches, at depths of 2001] NOTES 243

TABLE 1. Dimensions and contents of root caches. Number of Aggregate Cache Length (cm) Width (cm) roots weight (g)a A 9 8 139 17.0 B 24 18 432 70.4 C 37 18 290 45.9 D 5 4 26 7.4 TOTALS 887 140.7 aField-moisture content, 12 October 1996

4.7 to 8.7 cm. They were not represented in oven-dry weight of 0.31 kg. Rhizomes of the caches, although their upturned tips some- Potentilla canadensis were especially numer- times penetrate the foraging zone from below. ous, but underground parts of 3 other plant Rather than selecting for robust plants with species were also represented. The authors large roots, the vole appears to have stored all calculated that the cache could support a sin- O. pygmaea roots it encountered, regardless of gle average-sized vole for 86.8 days. On a per- size. Rootlets, stems, and foliage were trimmed animal basis, weights reported by these authors and discarded before caching. Altogether, are at least 3 times the oven-dry weight of caches contained 887 roots ranging from 5 to roots in Fourth of July valley caches. The ani- 27 mm in maximum dimension, with an aggre- mal may have intended to continue harvesting gate fresh weight of 140.7 g. Assuming that until the ground froze or a winter’s food sup- roots from the caches were similar in caloric ply had been stashed away, or the caches may value and macronutrient content to a sample have been meant merely to supplement other of fresh roots dug at the site in late August diet items available beneath the snow. Small 1998 and analyzed by Warren Analytical Labs hoards, reserved for times of great need, can (Greeley, Colorado), the caches represented make critical contributions to winter survival, 395 kcal of stored energy. They contained 40.4 even though they fall far short of meeting total g of moisture, 95.1 g of carbohydrate, 3.5 g of nutritional requirements (Hitchcock and Hou- protein, 0.1 g of fat, and 1.6 g of ash. ston 1994). How many roots would the vole have col- lected if snowmelt had not interrupted its We thank David Armstrong and Jameson activities? Wolff (1984) found that underground Chace for their encouragement and advice. food caches of taiga voles (Microtus xanthogna- David Armstrong provided reference hairs thus) in central Alaska held up to 3.6 kg dry from study skins housed at the University of weight (about one bushel) of horsetail (Equise- Colorado Museum. Peter Marchand, Carron tum sp.) and fireweed (Epilobium angusti- Meaney, Jerry Scrivner, and an anonymous folium) rhizomes, but these were communal reviewer made helpful suggestions for improv- caches made in late summer by 5 to 10 indi- ing the manuscript. viduals. Formozov (1966) reported that Micro- tus brandti, a field vole of the Mongolian LITERATURE CITED steppes, stored up to 30 kg of stems, leaves, and whole plants, including their roots. Plants ARMSTRONG, D.M., J.C. HALFPENNY, AND C.H. SOUTHWICK. 2001. Vertebrates. Pages 128–156 in W.D. Bowman were collected in autumn, usually by 10 to 12 and T.R. Seastedt, editors, Structure and function of voles, and were stored in underground cham- an alpine ecosystem: Niwot Ridge, Colorado. Oxford bers, where they provided food for a wintering University Press, New York. colony of up to 20 individuals. Formozov (1966) FORMOZOV, A.N. 1966. Adaptive modifications of behavior described caches of rhizomes made by mole- in mammals of the Eurasian steppes. Journal of Mam- malogy 47:208–223. voles (Ellobius sp.) in snow passageways, but GATES, J.E., AND D.M. GATES. 1980. A winter food cache of gave no details concerning their weights or Microtus pennsylvanicus. American Midland Natu- numbers. Gates and Gates (1980) studied the ralist 103:407–408. subnivean food cache of a meadow vole (Micro- HITCHCOCK, C.L., and A.I. HOUSTON. 1994. The value of a tus pennsylvanicus) in western Maryland. hoard: not just energy. Behavioral Ecology 5:202–205. JANNETT, F.J., JR. 1982. Nesting patterns of adult voles, Exposed by springtime snowmelt, the cache Microtus montanus, in field populations. Journal of contained 1655 food items with an aggregate Mammalogy 63:495–498. 244 WESTERN NORTH AMERICAN NATURALIST [Volume 61

MCGUIRE, B., AND M. NOVAK. 1986. Parental care and its WALKER, D.A., J.C. HALFPENNY, M.D. WALKER, AND C.A. relationship to social organization in the montane WESSMAN. 1993. Long-term studies of snow-vegeta- vole (Microtus montanus). Journal of Mammalogy tion interactions. BioScience 43:287–301. 67:305–311. WOLFF, J.O. 1984. Overwintering behavioral strategies in MOORE, T.D., L.E. SPENCE, AND C.E. DUGNOLLE. 1974. taiga voles (Microtus xanthognathus). Pages 315–318 Identification of the dorsal guard hairs of some mam- in J.F. Merritt, editor, Winter ecology of small mam- mals of Wyoming. Wyoming Game and Fish Depart- mals. Special Publication of Carnegie Museum of ment Bulletin 14: 1–177. Natural History 10. SMITH, C.C., AND O.J. REICHMAN. 1984. The evolution of food caching by birds and mammals. Annual Review Received 31 August 1999 of Ecology and Systematics 15:329–351. Accepted 14 March 2000 VANDER WALL, S.B. 1990. Food hoarding in animals. Uni- versity of Chicago Press, Chicago and London. 445 pp. Western North American Naturalist 61(2), © 2001, pp. 245–247

THE MONOGENEAN HAPLOCLEIDUS FURCATUS MUELLER, 1937 (PHYLUM PLATYHELMINTHES) ON LEPOMIS CYANELLUS RAFINESQUE, 1819 FROM UTAH: A RANGE EXTENSION

Michael N. McGee1, Michael J. Whitney2, and Richard A. Heckmann2,3

Key words: Haplocleidus furcatus, monogenean, range extension, Lepomis cyanellus.

The green sunfish, Lepomis cyanellus the opisthaptor (attachment organ; Fig. 1) and Rafinesque, 1819, is native to the central east- the type II copulatory complex (Beverly-Bur- ern United States but has been widely intro- ton and Suriano 1980, Beverly-Burton 1984). duced throughout the United States (Sigler Adults of this genus and other monogeneans and Miller 1963, Sigler and Sigler 1987). In lay eggs while on the gills, which can remain 1890 the species was introduced into Utah, on the same host or be flushed out via gill ven- where many self-sustaining populations occur. tilation. Eggs then incubate in the substrate Utah populations of L. cyanellus are generally before developing into free-swimming onco- stunted, and few individuals exceed 150 mm miracidia (Cope and Burt 1981, 1982, 1985, in length (Sigler and Miller 1963). This species Stoskopf 1993, Woo 1995). of sunfish is host to many ecto- and endopara- Green sunfish are a documented host of H. sites (Hoffman 1999). furcatus in other regions of North America We collected green sunfish from Red Lake, (Hoffman, 1999); however, this is the first pub- Utah County, Utah, during September 1997 lished record of H. furcatus in Utah. There- using angling equipment. Seven fish were fore, the range of Haplocleidus furcatus has weighed (g), measured (mm; Table 1), and been extended to Red Lake, Utah County, then examined for the presence of ectopara- Utah. We suspect that this monogenean was introduced to Red Lake with stocking of in- sites. We found a total of 162 monogeneans. fested green sunfish in the late 1907s. Accord- These flatworms were collected, fixed, and ing to the Utah Division of Wildlife Resources stained by standard methods (Stoskopf 1993) (C. Thompson personal communication), this and identified as Haplocleidus furcatus was done by a group of local Boy Scouts. Mueller, 1937. Stained specimens were sent to Haplocleidus furcatus in Red Lake infests Delane Kritsky, Idaho State University, for the green sunfish, which is the dominant fish generic confirmation. Slides deposited in the species in that body of water. Other resident Manter Collection at the University of Nebraska fish species may also be infested with this par- were given the accession number HWML asite, suggesting the need for further research 39822. The prevalence of H. furcatus was 100% at Red Lake and nearby lakes and streams to for the examined fish, with a mean intensity of learn more about host preference for H. furca- 23.1 worms per fish (range = 6 to 43 worms tus. This is the first known record for H. furca- per fish; Table 1). tus in Utah and the Rocky Mountain region. Haplocleidus furactus is a parasitic fluke on the gills of many species of fish including Lep- Taxonomic Summary omis cyanellus (Hoffman 1999). The genus Parasite: Haplocleidus furcatus Mueller 1937 Haplocleidus is characterized by a large set Utah host: Green sunfish, Lepomis cyanellus and a small set of anchoring hooks located on Rafinesque, 1819

13 C.R. 101, Hesperus, CO 81326. 2Department of Zoology, Brigham Young University, Provo, Utah. 3Corresponding author.

245 246 WESTERN NORTH AMERICAN NATURALIST [Volume 61

TABLE 1. Length (mm) and weight (g) of green sunfish (Lepomis cyanellus) and number of Monogenea found on each fish. Standard length Total length Weight Number of Fish number (mm) (mm) (g) Monogenea 1 115 140 48.3 31 2 128 158 76.8 20 3 110 128 52.0 6 4 138 168 89.5 7 5 121 149 66.4 21 6 90 114 34.2 43 7 105 130 42.1 34

Fig. 1. Photomicrograph of Haplocleidus furcatus (magnification 100X). Identifying structures are marked as follows: A = anchor, H = hooks, O = opisthaptor.

Type host: Largemouth bass, Micropterus Specimens deposited: HWML 39822, Univer- salmoides Lacepede, 1802 sity of Nebraska (Manter Collection) Other paratenic hosts: Spotted bass, Micro- Comments: First record for H. furcatus in pterus punctulatus Rafinesque, 1819; blue- Utah and Rocky Mountain area gill, Lepomis macrochirus Rafinesque, 1819; smallmouth bass, Micropterus dolomieui Lacepede, 1802 We thank Delane Kritsky of Idaho State Site of infection: Gills University for confirming the genus identifica- Type locality: Florida tion and for providing protocols regarding col- Other localities: Alabama, Arkansas, California, lecting and fixing specimens. We also thank Kansas, Louisiana, North Carolina, Ohio, Dennis Shiozawa of Brigham Young Univer- Tennessee, Texas, Virginia, Washington, sity for the use of his laboratory during this Wisconsin, West Virginia, Ontario (Canada) study. 2001] NOTES 247

LITERATURE CITED ______. 1985. Population biology of Urocleidus adspectus Meuller, 1936 (Monogenea) on Perca flavescens in BEVERLY-BURTON, M. 1984. Monogenea and Turbellaria. New Brunswick. Canadian Journal of Zoology 63: Part 1. In: L. Margolis and Z. Kabata, editors, Guide 272–277. to parasites of fishes in Canada. Department of HOFFMAN, G.L. 1999. Parasites of North American fresh- Fishes and Oceans, Fisheries Research Board Pacific water fishes. 2nd edition. Comstock Publishing Asso- Biological Station, Nanaimo, BC. 209 pp. ciates, Ithaca, NY. 539 pp. BEVERLY-BURTON, M., AND D.M. SURIANO. 1980. Haplo- SIGLER, W.F., AND R.R. MILLER. 1963. Fishes of Utah. cleidus dispar (Mueller, 1936) and Pterocleidus acer Utah State Department of Fish and Game, Salt Lake (Mueller, 1936) (Mongenea: Ancyrocephallinae) from City. 203 pp. Lepomis gibbosus L. (Pices: Centrarchidae) in Ontario SIGLER, W.F., AND J.W. SIGLER. 1987. Fishes of the Great Canada: anatomy and systematic position. Canadian Basin: a natural history. University of Nevada Press, Journal of Zoology 58: 661–669. Reno. 425 pp. COPE, D.K., AND M.D.B. BURT. 1981. The invasion route STOSKOPF, M.K. 1993. Fish medicine. W.B. Sanders Co., of the gill parasite Urocleidus adspectus Meuller, 1936 Philadephia, PA. 725 pp. (Monogenea: Ancyrocephalinae). Canadian Journal WOO, P.T.K. 1995. Fish diseases and disorders. Volume 1. of Zoology 59:2166–2171. Protozoan and metazoan infections. CAB Interna- ______. 1982. The behavior of Urocleidus adspectus tional, Wallingford, UK. 808 pp. Meuller, 1936 (Monogenea) on the gills of Perca flav- escens. Canadian Journal of Zoology 60:3237–3240. Received 14 October 1998 Accepted 11 April 2000 Western North American Naturalist 61(2), © 2001, pp. 248–251

HELMINTHS OF NORTHERN LEOPARD FROGS, RANA PIPIENS (RANIDAE), FROM NORTH DAKOTA AND SOUTH DAKOTA

Stephen R. Goldberg1, Charles R. Bursey2, Robert G. McKinnell3, and Irene S. Tan1

Key words: Rana pipiens, Ranidae, helminths, North Dakota, South Dakota.

The northern leopard frog, Rana pipiens National Parasite Collection, USDA, Beltsville, Schreber 1782, is widely distributed in North Maryland (Appendix). America from the northeast Atlantic coast We found gravid individuals representing 5 through Hudson Bay, Canada, to eastern Wash- species of Trematoda: Cephalogonimus ameri- ington, Oregon, and California, south to north- canus Stafford 1902; Glypthelmins quieta ern Virginia through Nebraska to New Mexico (Stafford 1902), Stafford 1905; Gorgoderina and central Arizona (Stebbins 1985). Trematodes attenuata (Stafford 1902), Stafford 1905; Haema- and cestodes of R. pipiens have been summa- toloechus varioplexus Stafford 1902; Mega- rized by Prudhoe and Bray (1982), nematodes lodiscus temperatus (Stafford 1905) Harwood by Baker (1987). Additional R. pipiens helminth 1932. We also found 5 species of Nematoda: records are included in Dyer (1991) and Cosmocercoides variabilis (Harwood 1930) McAlpine and Burt (1998). Because to date Travassos 1931; Falcaustra ranae (Walton 1941) there are no published records of helminths Chabaud and Golvan 1957; Oswaldocruzia for R. pipiens from North Dakota and South pipiens Walton 1929; Rhabdias ranae Walton Dakota, we undertook an investigation to 1929; Spinitectus gracilis Ward and Magath report helminths harbored by R. pipiens from 1917. In addition, metacercariae representing these states. 4 species of Trematoda (Apharyngostrigea pip- One hundred forty R. pipiens from 6 collec- ientis, Alaria sp., Fibricola sp., Ochetosomati- tion sites (2 in North Dakota and 4 in South dae gen. sp.), plerocercoids of 1 species of ces- Dakota) were examined (Appendix). The frogs toda (Proteocephalus sp.), and 3rd stage larvae were collected from 1995 to 1998 (collection of 2 species of Nematoda (Physaloptera sp., dates are in the Appendix), fixed in 10% for- Physocephalus sp.) were found. Prevalence malin, and preserved in 70% ethanol. After and mean intensity for each helminth species opening the body cavity, we removed the gas- are given in Table 1. trointestinal tract. The lungs, esophagus, stom- One hundred three of 140 (74%) frogs har- ach, small intestine, large intestine, bladder, bored helminths: 49 of 71 (69%) female frogs and body cavity of each frog were then exam- and 54 of 69 (78%) males. There was no signif- ined separately with a dissecting microscope icant difference in prevalence between female for helminths. Nematodes were cleared on a and male frogs (χ2 = 1.53, 1 df, P > 0.05). A glass slide in glycerol; selected cestodes and total of 2057 helminths were found (20.0 ± trematodes were stained with hematoxylin and 32.8 s helminths per infected frog). Of 103 mounted in balsam. We made identifications infected frogs, 48 harbored 1 species of hel- from these preparations. Frogs were deposited minth, 24 harbored 2 species, 24 harbored 3 in the herpetology collection of the Natural species, 5 harbored 4 species, and 2 harbored History Museum of Los Angeles County 5 species (1.9 ± 1.0 s helminth species per (LACM), Los Angeles, California (Appendix). infected frog). Representative specimens were placed in vials Helminths we found in this study fall into 3 of ethanol and deposited in the United States categories: phoresis (resting stages), anuran

1Department of Biology, Whittier College, Whittier, CA 90608. 2Department of Biology, Pennsylvania State University, Shenango Campus, Sharon, PA 16146. 3University of Minnesota, Department of Genetics and Cell Biology, 250 Biological Sciences Center, 1445 Gortner Avenue, St. Paul, MN 55108.

248 2001] NOTES 249 s 0.0 2.3 0.0 ± ± ± ± – x = 23) N P ______s 23.326.5 — 13 1.0 — 1.0 — — 1.9 30 2.6 2.3 — — ± ± ± ± ± ± – x = 26) ( N P s 15.4 16 22.3 9.8 — — — — 0.9 27 2.6 3.6 19 3.4 5.2 — — 7 4.0 ± ± ± ± ± ± – x = 31) ( N P s 27 — — 15 14.3 2.8 3 4 — — — — 1.79.9 —1.0 16 — 1.4 19 12.2 4 1 — — .— —— —— 4.2—— ± ± ± ± ± ± ± – x = 20) ( N P from North and South Dakota. s 26 50 21 .— —— —— —— 2.6—— 0.70.4 2081 3.3 95 8.6 15 2.0 ± ± ± ± ± ± – x = 20) ( Rana pipiens N P s North Dakota South Dakota 0.7 15 21 2.1 — — 60 3.6 .— ——0.5 3 14.1 —— 401.3—— —— 52 2.3 25 —— 1.2 —— 20 —— 65 ——1.3—— 1.0 5 6 — — 32 4.6 ± ± ± ± ± ± ± ± ± – x = 20) ( ) of helminths from 140 N s ( Barnes Co. Sargent Co. Beadle Co. Brown Co. Hamlin Co. Hand Co. ± 5 1 —— —— —— —— —— 40 3 25 1.4 3020 5.7 2.5 20 1.5 —— —— —— 295.7 —— —— —— 295.7 ——— —— —— — —— 4 2 —— — — — — 3 1 23 1.8 —— —— —— —— —— 4 2 —— —— 206.8 —— —— 206.8 ______– x ______sp. 30 2.0 sp. 10 1.5 sp. — — 25 5.8 sp. 55 55 p ——sp. 5 1 —— 3 2 —— —— Alaria Apharyngostrigea pipientis Fibricola Proteocephalus Physaloptera Physocephalus 1. Prevalence (P) and mean intensity ( ABLE metacercariae, Ochetosomatidae gen. sp. 5 1 5 20 5 24 16 16.0 larvae, Rhabdias ranae Spinitectus gracilis larvae, Falcaustra ranae Falcaustra Oswaldocruzia pipiens T Cephalogonimus americanus Glypthelmins quieta Gorgoderina attenuata Haematoloechus varioplexus Megalodiscus temperatus mesocercariae, plerocercoids, Cosmocercoides variabilis metacercariae, metacercariae, EMATODA ESTODA REMATODA C T N Helminth P 250 WESTERN NORTH AMERICAN NATURALIST [Volume 61 parasites, and dietary artifacts. Of 2057 hel- North Dakota Game and Fish Department to minths, 1575 (76%) were larvae of species that RGM; frogs from South Dakota were collected do not reach maturity in frogs (1531 metacer- under permit 25 issued by the Department of cariae, 12 plerocercoids, 29 larval nematodes Game, Fish and Parks of South Dakota to in cysts) and 3 were larval nematodes repre- RGM. Frogs were collected with support, in senting dietary artifacts. For these metacer- part, of grant 2675BR1 from the Council for cariae, mammals are definitive hosts for Alaria Tobacco Research–USA, Inc. to RGM. sp. and Fibricola spp., birds for Apharyn- gostrigea spp., and snakes for Ochetosomati- LITERATURE CITED dae gen. sp.; frogs serve as paratenic hosts (Schell 1985). Species of Proteocephalus are ANDERSON, R.C. 1992. Nematode parasites of vertebrates. Their development and transmission. CAB Interna- primarily parasites of fish with intermediate tional, Wallingford, Oxon, U.K. 578 pp. stages in microcrustaceans (Olsen 1974). BAKER, M.R. 1987. Synopsis of the Nematoda parasitic in Species of Physaloptera and Physocephalus amphibians and reptiles. Memorial University of require an insect intermediate host (Anderson Newfoundland, Miscellaneous Publications in Biol- 1992); and in anurans, larvae of Physocephalus ogy 11:1–325. DYER, W.G. 1991. Helminth parasites of amphibians from are most often found in cysts while larvae of Illinois and adjacent midwestern states. Transactions Physaloptera pass from the body without fur- of the Illinois State Academy of Science 84:125–143. ther development. JILEK, R., AND R. WOLFF. 1978. Occurrence of Spinitectus The remaining 482 helminths represent gracilis Ward and Magath 1916 (Nematoda: Spiru- roidea) in the toad (Bufo woodhousii fowleri) in Illi- species reaching maturity in anurans. Thirty- nois. Journal of Parasitology 64:619. nine (55%) female and 44 (64%) male frogs MCALPINE, D.F., AND M.D.B. BURT. 1998. Helminths of were infected. There was no significant differ- bullfrogs, Rana catesbeiana, green frogs, R. clamitans, ence in prevalence between female and male and leopard frogs, R. pipiens, in New Brunswick. frogs (χ2 = 1.13, 1 df, P > 0.05; 1.4 ± 0.6 s Canadian Field Naturalist 112:50–68. ± MUZZALL, P.M. 1991. Helminth infracommunities of the species per infected frog, 5.8 7.6 s helminths frogs Rana catesbeiana and Rana clamitans from per infected frog). Thus, anuran parasites rep- Turkey Marsh, Michigan. Journal of Parasitology resent 23% of the helminth load of these frogs. 77:366–371. With the exception of S. gracilis, these OLSEN, O.W. 1974. Animal parasites: their life cycles and ecology. University Park Press, Baltimore, MD. 562 helminths have been reported previously in R. pp. pipiens and are common parasites of amphib- PRUDHOE, S., AND R.A. BRAY. 1982. Platyhelminth parasites ians of the American Midwest (see Dyer of the Amphibia. Oxford University Press, Oxford, 1991). Spinitectus gracilis, a parasite of fish, U.K. 217 pp + 4 pp microfiche. has been reported from Bufo woodhousii from SCHELL, S.C. 1985. Handbook of trematodes of North America north of Mexico. University Press of Idaho, Illinois (Jilek and Wolff 1978) and Rana cates- Moscow. 263 pp. beiana from Michigan and Oklahoma (Trow- STEBBINS, R.C. 1985. A field guide to western reptiles and bridge and Hefley 1934, Muzzall 1991). amphibians. Houghton Mifflin Company, Boston. 336 Rana pipiens represents a new host record pp. TROWBRIDGE, A.H., AND H.M. HEFLEY. 1934. Preliminary for Spinitectus gracilis. North and South Dakota studies on the parasite fauna of Oklahoma anurans. are new locality records for each helminth Proceedings of the Oklahoma Academy of Science listed in Table 1. 14:16–19.

Rana pipiens from North Dakota were col- Received 13 December 1999 Accepted 27 April 2000 lected under permit 102038938 issued by the 2001] NOTES 251

APPENDIX female, 11 male, Lake Poinsett, Hamlin County (44°35′N, 97°04′W, 502 m elevation), collected October 1995, MUSEUM ACCESSION NUMBERS LACM 143845–143870; N = 23, SVL = 59.5 mm ± 6.2 s, 10 female, 13 male, Jones Lake, Hand County (44°28′N, Collection data for Rana pipiens from North Dakota 98°56′ 494 m elevation), collected July 1996, LACM and South Dakota. NORTH DAKOTA: N = 20, snout- 143871– 143893. vent length (SVL) = 54.9 mm ± 9.8 s, 11 female, 9 male, Helminths from Rana pipiens deposited in the United Sheyenne River, Little Yellowstone State Park, Barnes States National Parasite Collection. Cephalogonimus County (46°38′N, 97°55′W, 381 m elevation), collected americanus USNPC 88784, Glypthelmins quieta USNPC September 1998, LACM 145306–145325; N = 20, SVL = 88785, Gorgoderina attenuata USNPC 88786, Haematolo- 64.5 mm ± 6.2 s, 11 female, 9 male, Silver Lake, Sargent echus varioplexus USNPC 88787, Megalodiscus temperatus County (46°01′N, 97°34′W, 372 m elevation), collected USNPC 88788, Alaria sp. (mesocercariae) USNPC 88789, September 1998, LACM 145326–145345. SOUTH Apharyngostrigea pipientis (metacercariae) USNPC 88790, DAKOTA: N = 20, SVL = 59.8 mm ± 9.9 s, 12 female, 8 Fibricola sp. (metacercariae) USNPC 88791, Oechetoso- male, Lake Cavour, Beadle County (44°24′N, 98°03′W, matidae gen. sp. (metacercariae) USNPC 88792, Proteo- 399 m elevation), collected July 1996, LACM 143822– cephalus sp. (plerocercoids) USNPC 88793, Cosmocer- 143841; N = 31, SVL = 61.4 mm ± 5.0 s, 11 female, 20 coides variabilis USNPC 88794, Oswaldocruzia pipiens male, Richmond Lake, Brown County (45°32′N, 98°35′W, USNPC 88795, Rhabdias ranae USNPC 88797, Spinitectus 414 m elevation), collected October 1995, LACM gracilis USNPC 88796, Physaloptera sp. (larvae) USNPC 143791–143821; N = 26, SVL = 55.7 mm ± 5.9 s, 15 88798, Physocephalus sp. (larvae) USNPC 88799. Western North American Naturalist 61(2), © 2001, pp. 252–254

FIRST REPORT OF TWO CONE AND SEED INSECTS ON PINUS FLEXILIS

A.W. Schoettle1 and J.F. Negron1

Key words: Coleoptera, cone and seed insects, Conophthorus contortae, Dioryctria auranticella, Hemiptera, Lepi- doptera, Leptoglossus occidentalis, limber pine, Pinus flexilis.

Limber pine (Pinus flexilis James) ranges in D. auranticella in ponderosa pine in north latitude from 33°N to 51°N and in elevation central Colorado. Dioryctria auranticella has from 870 m above sea level (asl) in North previously been reported on knobcone (Pinus Dakota to ~3400 m asl in Colorado (Burns attenuata Lemm.), ponderosa (Pinus ponderosa and Honkala 1990). In the central Rocky Dougl. ex Laws.), radiata (Pinus radiata D. Mountains, limber pine co-occurs with many Don), and Austrian (Pinus nigra Arnold) pines tree species due to its broad elevational range (Keen 1958); this is the 1st report of it on limber (Peet 1981). Limber pine seeds are large, gen- pine. Dioryctria auranticella has a broad dis- erally wingless, and dispersed by birds (Lan- tribution that includes most of the western U.S., ner and Vander Wall 1980). While it is known north into British Columbia, Canada, and south that seeds of limber pine in Colorado are into north central Mexico (Hedlin et al. 1981). eaten by animals such as Clark’s Nutcrackers The most severe infestation of D. auranti- (Nucifraga columbiana Wilson), black bears cella that we encountered was at Dave’s Draw (Ursus americanus; McCutchen 1996), and Research Natural Area (1630 m asl). This site small rodents, little information is available on is the southern end of an escarpment on the insect utilization of cones and seeds of limber Pawnee Grasslands in north central Colorado; pine for food and habitat. to the north the escarpment is occupied by a In July 1999 we encountered 2nd-year lim- mix of limber and ponderosa pines. We also ber pine cones that were host to lepidopteran observed limber pine cones of similar condi- larvae at several sites (Table 1). As a result of tion to those at Dave’s Draw at a 2652 m asl larval feeding, limber pine cones were brown, site in North Park, west of Walden, Colorado fragile, and full of coarse, reddish brown frass (Table 1). At this site, limber pine is growing pellets. The point of insect entry was fre- with quaking aspen (Populus tremuloides quently at the base of the appressed side of Michx.) on a knoll surrounded by dry sage- the cone. Upon incubation of cones at room lands and irrigated hay fields. temperature, a number of larvae completed Dioryctria auranticella may impact limber pupation, and a moth emerged after ca 10 pine seed availability for regeneration and days. The moth was identified as Dioryctria possibly food for rodents and birds at Dave’s auranticella (Grote) (Lepidoptera: Pyralidae), Draw Research Natural Area. It is currently the ponderosa pine coneworm, by its charac- unclear whether Clark’s Nutcrackers frequent teristic markings in the forewings and con- Dave’s Draw Research Natural Area; we have firmed by comparison with voucher speci- never seen nutcrackers at this site, and they mens from the entomology collection at Rocky are reported to be rare on the northeastern Mountain Research Station (Fort Collins, CO). plains of Colorado (Andrews and Righter 1992). During a subsequent field trip in late Septem- Inspection of more than 50 cone-bearing trees ber 1999, we found numerous cones that con- at this site in late July 1999 revealed that all of tained vacated pupae from D. auranticella. them exhibited lepidopteran damage. Of 96 Pupation inside cones is the common habit of limber pine cones collected that produced any

1Rocky Mountain Research Station, 240 West Prospect Road, Fort Collins, CO 80526.

252 2001] NOTES 253

TABLE 1. Summary of cone and seed insects found on limber pine during the summer of 1999 along an elevational gradient east of the Continental Divide in northern Colorado and southern Wyoming. For a more complete description of each site, see Schoettle and Rochelle (2000). Presence is noted by +, absence by –. Dioryctria Leptoglossus Site Elevation (m) Female cones auranticella occidentalis Dave’s Draw RNA 1630 + + + Woods Landing (WY) 2609 + – – Jelm View (WY) 2646 + – – Lake John 2652 + + – Pond View 2963 + – – Lawn Lake 3084 – Crown Point 3133 – Mid-Rollins Pass 3170 + – – Jenny Lake 3328 + – –

seeds, 78% had some insect-caused damage We observed no signs of insects in matur- reducing seed yield. This is a conservative ing cones at 3 higher-elevation sites domi- description of the impact of the insect popula- nated by limber pine (2963, 3170, and 3328 m tion since numerous cones were destroyed asl); and we could not find any maturing cones completely and were not collected. at 2 other sites (3084, 3133 m asl; Table 1). During the September site visit to Dave’s Limber pine appears to be an alternate host Draw Research Natural Area, we also collected for several cone and seed insects that affect numerous specimens of the western conifer co-occurring species. Limber pine co-occurs seed bug, Leptoglossus occidentalis Heide- with ponderosa pine in its lower-elevation mann (Hemiptera: Coreidae). The seed bug range; in this area we report that it is host to was abundant on the tips of current-year nee- D. auranticella and L. occidentalis, which are dles and conelets (1st-year cones), predomi- commonly found on ponderosa pine. Where nantly on the south side of limber pine trees. limber pine grows with lodgepole pine, it is Leptoglossus occidentalis has a broad distribu- host to C. contortae, an insect that is often tion that includes all of the western U.S. into associated with lodgepole pine. southern Canada (Hedlin et al. 1981). It has These new records purport the need to fur- been reported on numerous species, but this ther investigate the arthropod fauna that is is the 1st report of it on limber pine. We have associated with cones and seeds of limber not observed the presence of L. occidentalis at pine. Voucher insect specimens collected have any of our other limber pine sites (Table 1). been placed in the entomological collection At 2 mid-elevation sites (2609 and 2646 m located at the Rocky Mountain Research Sta- asl), limber pine cones were host to beetles, tion, Fort Collins, Colorado. the impact of which was consistent with that caused by Conophthorus contortae Hopkins We thank Region 2 USFS Research Natural (Coleoptera: Scolytidae) previously reported Area Program for access to the Dave’s Draw on numerous western pines including limber, site and David Leatherman of the Colorado lodgepole (Pinus contorta Dougl. ssp. latifolia State Forest Service for helpful comments on Bailey), and ponderosa (Hedlin et al. 1981). an earlier version of this manuscript. The point of attack was the base of the cone. Infested cones were small and cone expansion LITERATURE CITED appeared to have been arrested after the 1st year of development. Infested cones produced ANDREWS, R., AND R. RIGHTER. 1992. Colorado birds: a reference to their distribution and habitat. Denver no seed. Several trees had a partially infested Museum of Natural History, Denver, CO. 480 pp. cone crop, but more frequently the damage was BURNS, R.M., AND B.H. HONKALA. 1990. Silvics of North isolated to individual trees that experienced America. Volume 1: Conifers. USDA Forest Service destruction of their entire cone crop. Both Agricultural Handbook 654. beetle-affected limber pine stands are within HEDLIN, A.F., H.O. YATES III, D.C. TOVAR, B.H. EBEL, T.W. K OERBER, AND E.P. MERKEL. 1981. Cone and an extensive forest dominated by lodgepole seed insects of North American conifers. Canadian pine. Forestry Service, United States Forest Service, and 254 WESTERN NORTH AMERICAN NATURALIST [Volume 61

Secretaria de Agricultura y Recursos Hidraulicos, PEET, R.K. 1981. Forest vegetation of the Colorado Front Mexico. 122 pp. Range: composition and dynamics. Vegetatio 43:3–75. KEEN, F.P. 1958. Cone and seed insects of western forest SCHOETTLE, A.W., AND S.G. ROCHELLE. 2000. Morpholog- trees. USDA Technical Bulletin 1169. ical variation of Pinus flexilis (Pinaceae), a bird-dis- LANNER, R.M., AND S.B. VANDER WALL. 1980. Dispersal persed pine, across a range of elevations. American of limber pine seed by Clark’s Nutcracker. Journal of Journal of Botany 87:1797–1806. Forestry 78:637–639. MCCUTCHEN, H.E. 1996. Limber pine and bears. Great Received 11 November 1999 Basin Naturalist 56:90–92. Accepted 19 April 2000 Sixth Biennial Scientific Conference on the Greater Yellowstone Ecosystem

YELLOWSTONE LAKE: HOTBED OF CHAOS OR RESERVOIR OF RESILIENCE? October 8–10, 2001 The greater Yellowstone conference series encourages the awareness and application of wide-ranging, high- caliber scientific work on the region’s natural and cul- tural resources. We encourage multidisciplinary pre- sentations and interdisciplinary discussions about the relationships between the regional landscape and its residents of many species.

This year’s conference will focus on a central feature of the ecosystem’s landscape, Yellowstone Lake—from its depths, where submerged hot springs and spires emerge atop the Yellowstone caldera, to its beaches, where rare plants and evidence of prehis- toric peoples erode at the mercy of wind, waves, and modern footsteps. Through scholarly papers and panel discussions, we will uncover and debate the following topics or others relating to the lake’s basin and history— ➛ hydrology, geology, geochemistry, and geophysics ➛ plants, fish, and other wildlife in or around the lake ➛ invertebrates and microfauna ➛ archaeology and human history of the lake basin ➛ socioeconomic values associated with Yellowstone Lake and its resources ➛ issues related to recreational use of or around Yellowstone Lake ➛ management of natural or cultural resources

REGISTRATION INFORMATION

The conference will be held October 8–10, 2001, at the Mammoth Hotel in Mam- moth Hot Springs, Wyoming (headquarters for Yellowstone National Park). Please contact Kevin Schneider at (307) 344-2233 for more information.

PLEASE NOTE

Although the deadline for submitting papers is past, we welcome your attendance and participation in the conference. ANNOUNCEMENT AND CALL FOR PAPERS

GICAL RESEA LO RC IO H B C N O GREAT BASIN BIOLOGICAL I N S F A E B R RESEARCH CONFERENCE T E A N E C R E October 11–13, 2001 G

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G Y N O U conference will feature contributed paper and poster sessions in a variety of disciplines, includ- ing biogeography, landscape ecology, fire and disturbance ecology, invasive species biology, and the biology and management of rare taxa for both terrestrial and aquatic ecosystems. Additional activities will include workshops, roundtable discussions, a plenary session, a banquet (included in registration price), open house at the Bean Museum and Shrub Sciences Laboratory, and a post-conference half-day field trip. Abstracts must be fewer than 250 words and submitted by July 13, 2001. Electronic submissions are encouraged via the conference website: bioag.byu.edu/mlbean/gbbrc. Papers will be allotted 12 minutes each, with an additional 3 minutes for questions (15 minutes total). Presentations may use a variety of media: 35-mm slides, overhead projector, and an LCD projector with laptop and PowerPoint 2000. Posters are allotted 5′× 6′ maximum size. Registration. Make registration checks payable to Great Basin Biological Research Conference. Credit card payments (VISA and MasterCard only) are also acceptable. Early registration (until August 17, 2001) $65 Late registration $85 Early student registration $40 Late student registration $55

Post-conference field trip to Antelope Island on the Great Salt Lake, with bag lunch and dutch oven cookout, Saturday, October 13, 12:30–9:00 p.m. $30. For further information, see the website above or contact Great Basin Biological Research Conference, 290 MLBM, Brigham Young University, Provo, UT 84602 (phone 801-378-5052, FAX 801-378-3733); also, Douglas C. Cox (801-378-6355 or e-mail: [email protected]).