Ensatina Eschschouzii Nests at a Managed Forest Site in Oregon

NORTHWESTERN NATURALIST 87:203-208 W~R2006

ENSATINA ESCHSCHOUZII NESTS AT A MANAGED FOREST SITE IN OREGON

DEANNAH OLSON, RICHARD S NAUMAN,LORETTA L ELLENBURG,BRUCE P HANSEN, AND SAMUEL S CHAN USDA Forest Service, Pacific Northwest Research Station, 3200 SW Je&son Way, Corpallis, Oregon 97331; Richard [email protected]

ABSTRAn-We sampled terrestrial salamanders in riparian and upland areas within a 40-y- old managed forest site in western Oregon. We found 303 ensatinas (0.015 anirnals/m2) and 14 nests (0.0007 nests/m2, 0.05 nests/ensatina) within 20,280 m2 of forested habitat surveyed. Clutch size averaged 8.3 eggs (range 3 to ll), comparable to previous reports from Washington but lower than reported for California. Of 14 nests found, 11 were in upland forest, >30 m from streams. Nests were typically on or under dawned wood. Limited downed wood recruitment was apparent from decay class distributions. Managed wood recruitment may be necessary in such young stands to maintain critical life history functions of the ensatina and other terrestrial salamanders.

Key words: ensatina, Ensatinn eschscholtzii, Plethodontidae, nests, reproduction, relative abundance, downed wood, Oregon

Published accounts of terrestrial salamander story of Douglas-fir (Pseudotsuga menziesio and nests are limited. Although ensatina (Ensatina western hemlock (Buga heterophyllla) and an un- eschscholtzii) is 1 of the more common terrestri- derstory of bryophytes, sword fern (hlystirhum al salamanders in the Pacific Northwest and is rnunitum), Oregon grape (Berberis msa), and described as both widespread and ubiquitous huckleberry (Vdnium pamifilium). In 1998, the (Leonard and others 1993), few nests have been stand was thinned from a pre-harvest tree den- reported. Published descriptions of nests are sity of about 121 trees/ha to a mosaic of tree- available mainly from California (n = 12, clutch retention densities ranging from 16 to 49 trees/ sizes 3 to 25; Van Denburgh 1898; Storer 1925, ha. Interspersed within the harvest units were 1929; Howard 1950; Stebbins 1954) and Wash- clearcut and forest "islands" of 1to 3 ha and un- ington (n = 5, clutch sizes 8 to 10; Norman and harvested buffer zones of 4 widths ranging from Norman 1980; Jones and Aubry 1985; Norman 6 to 146 m wide, along each side of stream chan- 1986). One nest has been described in Oregon nels. (12 eggs with female in attendance; Maser and Before and after harvest, we oriented am- Trappe 1984). We present descriptions of en- phibian surveys both perpendicular (upslope satina nests that were detected at a site in west- transects) and parallel (bank searches) to head- ern Oregon before and after a density manage- water stream channels. Upslope transects were ment timber harvest of a young forest stand. 2 m wide and 59 to 197 m long, with length dif- We report nest detections relative to search ef- fering with riparian buffer width. During the fort, salamander detection rates, and downed spring wet season (June to July)prior to harvest wood availability. in 1997, we sampled 9 stream reach locations by using 4 parallel uphill transects (4 m apart) per STUDY AREAAND METHODS stream reach location. After harvest and during The study site was a 146-ha managed forest the spring wet-season in 1999, we surveyed 4 stand, about 40 y old, that was naturally regen- adjacent parallel transects, each offset from a erated subsequent to clearcut timber harvest 1997 transect by 2 m. These transects were (Keel Mountain, Bureau of Land Management placed near the center of thinning treatments [BLM], Salem District; Linn Co., OR; 44"31141'T\T, mid-way along stream reaches buffered by al- 122°37'55"W). Vegetation consisted of an over- ternative buffer widths, avoiding harvested 204 NORTHWESTERN NATURALIST gaps or patch reserves. After harvest, these up- RESULTS AND D~SSION slope transects extended from unharvested h- The total survey area fmm combined up- parian buffer zones into the thinned forest. For slope and bank searches at Keel Mountain was the 59-m-10ng extended 20,280 m2, where we found 303 ensatinas (0.015 through the 9-m-wide buffer into a 50-m thinned upslope area, and the 197 m transect ensatinas/m2) and 14 ensatina nests (0.0007 nests/m2, 0.05 nests/ensatina). Clutch sizes extended through the 146-m-wide buffer into ranged from 3 to 11 (1= 8.3 eggs, s = 2.2 eggs; about a 50-m thinned upslope. Table 1; was Bank searches were time-constrained with in 3 cases clutch size estimated in the search area (m2)visually estimated at each order to avoid further disturbing the nest). In location (10 locations/reach, 5 min search on each case, an adult was coiled around or on top each bank/location, 14 reaches); 5 more reaches of the eggs, as reported previously (Jones and were sampled than those with upland tran- Aubry 1985). In addition to the ensatina, only 1 sects. Bank locations were determined by a other salamander species, the Oregon slender stratified, random, systematic approach (Han- salamander (Batrachoseps wrigkfi), was regular- kin and Reeves 1988). Strata corresponded to ly encountered on upslope transects (252 cap- in-stream habitat units, pools, and riffles, tures total, 0.012 captures/m2, no nest detec- based on in-channel surveys not reported here. tions). Bank captures included the Dunn's sal- We conducted pre-harvest bank searches in the amander (Plethodon dunni; 0.02 captures/m2, 1 spring and s-er of 1995 and in the spring nest detected; Nauman and others 1999). of 1997, and post-harvest searches in the spring Ensatina nest detection rates (nests/m2 of 1999. Both upslope and bank sUZITeysin- searched) were extremely low (Table 2)- It is un- volved comparable search effort and moderate likely that the timing of Our missed the levels of disturbance. We Iifted and replaced period because only gravid cover objects, opened decayed logs in layers by among capmes and the timing hand or with a hand tool, and raked litter. We of our surveys coincided with the reported in- minimized disturbance whenever a nest was cubation period (Nussbaum and others 1983). detected. We captured all amphibians encoun- Our Survey efforts near the ground surface tered for identification and then released likely detect a larger subsurface pop- We estimated the number of eggs and approx- ulation of ensatinas and nests- hhssbaum and hate size of the attending adult (snout-vent (1983) reported ensatina nestsup to 0.8 length, SVL, or total length, TL, as possible the surface in undergr-d cavities. from the animal's position) and recorded mi- nests were primarily found in up- crohabitat cover. In 1999 only, we recorded the land forest areas beedistance from stream in diameter of logs where nests were found. Table 1); 10 of the 14 were found within upslo- In 1997, prior to harvest, we measured pe transectsl during bank searches* and downed wood cover within 140 circular plots during O~~orwtic in (6-m diameter, 28.3 m2) arrayed along addi- an UP~~OP~area- These observations suggest tional transects parallel to our animal sampling nests not usually occur at the ground tramects, 1 wood tr-ect per stream location surface in near-riparian areas. However, it is and set of 4 animal tr-ects (n = 9 wood kan- possible that subsurface nests went undetect- sects total). We recorded percent cover of ed. downed wood for 3 diameter categories, <0.05 An apparent clustering of nests was appar- m, 0.05 to 0.30 m, and >0.30 m. Decay classwas ent in 2 cases: we found 3 nests about 40 m from recorded for wood in the largest size category a small wetland on a relatively flattened topo- (>0.30 m, Maser and others 1979). We corn- graphic bench and 2 nests 20 an apart in a ro- pared downed wood availability at the Keel dent tunnel under a single log (diameter about Mountain site with a companion study site at 30 cm). Green Peak, which also is a riparian area with Thirteen of the 14 nests were associated with forest age about 40 y (BLM Salem District; Ben- downed wood and 10 of those were assodated ton Co., OR; 44°22'00"N, 123"27'3OWW).At with logs (Table 1). Although we did not rou- Green Peak we used similar methods to sample tinely collect log diameter information, in 1999, downed wood (n = 133 plots) and amphibians. 4 log diameters with nests were r0.4 m (Table WINTER2006 OLSON AND OTHERS: ENSATINA NESTSIN OREGON 205

TABLE 1. Ensafinn eschscholtzii nests found at Keel Mountain in western Oregon. NA = not applicable. Log decay Female class (log Number size1 diameter, Distance from Date of eggs (mm) Microhabitat m) stream (m) 3 June 1999 10 80 TL hole in soil2 NA 161 (91 m from ephemeral stream) 3 June 1999 55 SVL in log 5 (0.4) 38 100 TL 4 June 1999 11 100 TL under soil on log 4 (0.5) 62 4 June 1999 10 100 TL under bark on soil2 NA 91 9 June 1999 ~3~ 40 SVL under bark in log 3 (0.48) 32 86 TL 9 June 1999 ~5~ 90 TL under bark on log 3 (0.6) 50 (9 m from ephemeral pond) 9 June 1999 8-10 80 TL in bark on soil2 NA 69 (46 m from ephemeral pond) 4 June 1997 8 48 SVL under log on soil 1 No data 4 June 1997 8 55 SVL under log on soil 1 No data 4 June 1997 8 62 SVL in lop" 4 23 93 TL 3 July 1997 8 48 SVL inlog 4 14 94 TL 17 Julv 1997 11 50 TL under bark on loe 4 50 18 JUG1997 8 60 TL under bark on loi 3 114 2 August 1995 7 90 TL under bark on soil NA 27 1 Depending upon female position and visibility, reliable estimates of both TL and SVL could not be obtained. Nest found post-harvest; all others found prior to experimental treatment. In some cases, the number of eggs was estimated to kduce disturbance to the nest.

I), suggesting that large logs might be pre- (n = 2; Norman and Norman 1980); between ferred; large logs were only about 10% of those fissured rock in a seepage area (n = 2; Stebbins available (Fig. 1). Aubry and others (1988) 1954); and inside a mountain beaver (Aplodontin thought that large, moderately decayed rufa) nest chamber (n = 1; Storer 1925). downed wood might be necessary for ensatina Disturbance accompanying timber harvest persistence; our small sample size of nests in activities may negatively affect salamander large logs supports their contention. populations (deMaynadier and Hunter 1995; Published accounts of ensatina nest locations Ash 1997; Herbeck and Larsen 1999; Welsh and include: on soil under logs (n = 4; Van Den- Droege 2001). Ha~estimpacts such as site xer- burgh 1898; Storer 1925; Stebbins 1954); under ification, ground compaction, and microhabitat loose bark on top of logs (n = 3; Howard 1950; cover disturbance may result in both direct Stebbins 1954); within logs (n = 6; Stebbins mortality and indirect effects on survival and 1954; Maser and Trappe 1984; Jones and Aubry reproduction through habitat degradation 1985; Norman 1986); under moss on top of logs (deMaynadier and Hunter 1995; Welsh and

TABLE 2. Area searched for salamanders by 2 different methods, and ensatina and nest detections. NA = not applicable. Area Ensatina Ensatina Number Nest Year Method searched lm2) ca~tures densitvl of nests2 densitv1c2 1995 bank 3046 38 0.012 1 0.0003 1997 bank 1343 32 0.024 1 0.0007 1999 bank 1993 13 0.006 0 NA 1997 upslope 6949 119 0.017 3 0.0004 1999 upslope 6949 101 0.014 7 0.0010 Total 20,280 303 0.015 12 0.0006 'Relative abundance (number detected/m2 seardmd). Dmnot include 2 nests discovered outside of bank searches and upslope tramects. 206 NORTHWESTERN NATURALIST

FIGURE 1. Percent ground cover (n, sz) of woody material in 3 size in survey plots at 2 managed stands in western Oregon. FIGURE 2. Percent ground cover (2, sf) of large woody material by decay class in survey plots at 2 managed stands in western Oregon. Decay class 1in- Droege 2001). Ensatina is thought to be the dicates the least decayed down wood, such as a re- most resilient of Pacific Northwest terrestrial- cently fallen tree (see Maser and others 1979). breeding salamanders relative to forest management: the salamanders range broadly impact on terrestrial salamanders than the me- across the region, occur in multiple forest types chanical disturbance of the harvest. and stand ages, and can be found in relatively An important cumulative effect of multiple dry conditions (Blaustein and others 1995; timber harvests over time at a site is the change Kuchta and Parks 2005; Kuchta and Wake 2005). in the downed wood component (for example, Interestingly, this study showed that ensati- Spies and others 1988; Rose and others 2001). na continued to occur and reproduce in the Managed recruitment of downed wood from spring following forest density management. current stands may be necessary to maintain The harvest design included a mosaic of re- critical life history functions of terrestrial sal- serve areas, such that about 106 ha of the 146 amanders. The Keel Mountain site exhibited an ha site was disturbed by a partial harvest and, abundance of large down logs relative to the in harvested areas, 10 to 46% of the trees were other study areas (pers. obs.; Fig. 1). a legacy retained. Not dlnests and captures occurred in of past harvest (D. Sneadecor, pers. comm.; the undisturbed portion of the site in 1999. Spies and others 1988; Rose and others 2001) Post-harvest detection rates were nearly iden- and had relatively much smaller levels of wood tical in thinned (0.011 ensatina/m2, upslope in the early decay classes (Fig. 2). These results transect sampling) and untreated areas (0.013 are consistent with U-shaped frequency distri- ensatina/m2). Additionally, 3 of 7 post-harvest butions of decaying wood inputs to managed nests were found in the thinned areas (Table 1; stands (y-axis) over time (x-axis; Spies and oth- total area sampled = 2775 m2: 31 ensatina cap- ers 1988), where the bottom of the U, low wood tured, 0.001 nests/m2, 0.10 nests/ensatina), inputs, is reached as legacy large wood dete- whereas the other 4 were found in untreated re- riorates and is not replaced. The legacy large served areas (6167 m2 sampled: 83 ensatina wood may have been a boon to salamanders in captured, 0.0006 nests/m2, 0.05 nests/ensati- this managed stand. This site contains about 3 na). to 4 times more large wood than occurs in sim- Although the harvest seemed to have little ilarly aged stands that we have studied in west- impact on ensatina initially, a longer-term re- em Oregon (see Fig. 1 for a comparison with sponse to management is possible. Our post- wood cover at the Green Peak site, a 40-y-old harvest sampling was conducted in the 1st stand in the Oregon Coast Range where we spring after harvest and prior to the disturbed found >I00 ensatina found in upslope tran- areas experiencing the summer dry season. The sects but no ensatina nests. These Green Peak potential site xerification during summer dry data (Fig. 1) also indicate limited large downed seasons after timber harvest may have a greater wood recruitment. While we did not conduct WINTER2006 OLSONAND OTHERS: ENSATINA NESTSIN OREGON 207 tallies post-treatment, we did not observe phibian ecology; a review of the North Amelrican downed wood to have been removed or de- literature. Environmental Rwiews 3:230-261. stroyed at the site due to harvest activities. HANKINDG, REEVESGH. 1988. Estimating total fish Conversely, additional recruitment of new abundance and total habitat area in small streams downed logs was not noticeable post-treatment based on visual estimation methods. Canadian Journal of Fisheries and Aquatic Sciences 45:834- in 1999, although subsequent blow-down or 844. ice-damaged down trees have been seen in HERBECKLA, LARSENDR. 1999. Plethodontid sala- some areas. Further study of ensatina densities mander response to silvicultural practices in Mis- in association with downed wood abundance souri Ozark forests. Conservation Biology 13: and character in managed forest stands are 623-632. warranted. Downed wood management at HOWARDWE. 1950. Eggs of the salamander Ensatitla young stands may be necessary for the main- eschscholtzii platmsis. Copeia 1950:236. tenance of life history functions of terrestrial JONESLLC, AWBRYKB. 1985. Ensatinn escscholtzii or- salamanders on the forest floor. egonensis (Oregon ensatina). Reproduction. 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