Great Basin Naturalist

Volume 50 | Number 2 Article 7

6-30-1990 Observations on the dwarf ( nanus) in northern Howard J. Berna Arizona State University, Tempe

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Recommended Citation Berna, Howard J. (1990) "Observations on the dwarf shrew (Sorex nanus) in northern Arizona," Great Basin Naturalist: Vol. 50 : No. 2 , Article 7. Available at: https://scholarsarchive.byu.edu/gbn/vol50/iss2/7

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OBSERVATIONS ON THE DWARF SHREW (SOREX NANUS) IN NORTHERN ARIZONA

Howard]. Bernal

ABS'I'RACT.-Qbservations of 23 dwarf (Sorex nanus) at Fracas Lake in Arizona extend the range of this uncommon shrew northward on the Kaibab Plateau and prOVide further information reganling the ecology and habitat requirements ofthis species. Shrews were captured in a previously unreported habitat type (Rocky Mountain montane conifer forest; Brown 1982). This study illustrates the usefulne~s of intensive, long~tel'm studies and faultal surveys llsingpitfall traps.

Since Merriam discovered the dwarfshrew 1982). Another specimen of the dwarf shrew in 1895, it has been considered a rare species. was reported from the Kaibab Plateau by For 70 years after it was named, Sore:< nanus Hoffmeister (1955). Itwas found in the Kaibab was known from only 18 specimens (Hoff­ Lodge, VT Ranch, when the lodge was mann and Owen 1980). With the recent use of opened in April 1944. The lodge is sur­ pitfall traps this number has increased greatly rounded by extensive grassy meadows to the (e.g., 81 S. nanus in [Armstrong et east and subalpine conifer forest to the west. al. 1973J, 48 in [Brown 1967], and A single specimen was collected on 14 16 in Arizona [Marshall and Weisenberger August 1959 in the White Mountains of 1971]). Greenlee Co., near Hannagan Meadows, in The dwarf shrew is one of many spruce-fir forest habitat (suhalpine conifer species inhabiting an archipelago of forested furest; Brown 1982), at an elevation of 2,805 montane islands in the western m, extending the range into the second area of (Lomolino et al. 1989). The species is cur­ ti,e state (Bradshaw 1961). To my knowledge, rently known from , Wyoming, there have been no recent records of Sorex , Colorado, , , nanus from this area. and Arizona (Hoffmann and Owen 1980). Marshall and Weisenberger (1971) trapped Sore>: nanus is known from reports ofonly 20 Sorex nanus in Arizona in a third area, near specimens from three areas in Arizona (Fig. 1; Flagstaff, in the Inner Basin of the San Fran­ Hoffmeister 1986); no new Arizona localities cisco Mountains at elevations between 2,865 have been reported for 15 years. and 3,293 m. During the summer of 1969 The first Sore>: nanus in Arizona was eight specimens were taken in rocky talus collected on 17 September 1937 from the and eight from mesic subalpine meadows and Kaibab Plateau, Coconino Co., 14.5 kIn east surrounding spruce-fir forest. The specimens of Swamp Point within the Grand Canyon reported in this article extend the known National Park (GCNP, North Rim) at an ele­ range ofSorex nanus in Arizona northward on vation of about 2,439 m (Schellbach 1948). the Kaibab Plateau and describe a newhabitat On 28 August 1973 another specimen was for this species in Ariwna. taken 5.6 kIn from the first record, near Kan­ abownits Springs within the GCNP (Ruffner STUDY AREA and Carothers 1975). Both areas typically con­ tain mixed-conifer forest, Picea pungens, The study area was Fracas Lake, Coconino Picea engelmannii, Abies Iasiocarpa, Abies Co., 9.6 km south-southwest of Jacob Lake concolor, Pseudotsuga menziesii, and Populus (36"37'52"N, 1l2°14'2O"W, elev. 2,514 m). tremuloides (subalpine conifer forest; Brown Fracas Lake is a permanent, natural limestone

lDepartmerlt ofZooklgy, AriMl'lz State Unhoen:ity. Tempe, AriWlla 85287-1501. Present address:: Ulliversity of ~ Franklill College of Arts and Science, ~partmentofZoology. 724 BiologiaJ ScIences Bvilding, Athens, G~rgla3Q602.

161 - )105 162 H. J. BERNA [Volume 50

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Fig. 1. Collection sites ofSora nanU$ in Arizona. Boxed area ofstateenlarged. Contourline outlines Kaibab Plateau at elevation 2,195 m; A, this study; B, Hoffmeister 1955; C, Schellbacb 1948; D, Ruffner and Carothers 1975; E, San Francisco Peaks (Marshall and Weisenberger 1971); F. Hannagan Meadows (Bradshaw 1961). 1990] SOREX NANUS IN AJuzoNA 163 sinkhole basinless than 1 ha in area, varying in TABl.E 1. Monthly captures of Sorcx nanus at Fracas depth !Tom 0.5 to 1.5 m. Lake, Coconino Co., Arizona, in 1988 and 1989. The terrestrial habitat surrounding Fracas Month 19S8 1989 Lake is dominated by ponderosa pine (Pinus April o ponderosa) and a few aspen (Populus tremu­ May o o loide.) about 15-25 m from the edge of the June I 3 lake (Rocky Mountain montane conifer forest; July I 3 Brown 1982). There are a few small patches of August 6 6 September 3 o mixed-conifer forest within 1 km of the lake; October o o however, Pinus ponderosa is the dominant November o conifer for several square kilometers around the lake. Atground level there is little vegeta­ tion in the understory. Common shrub spe­ Standard measurements ofspecimens were cies include Juniperus communis, Ceanothus taken, and shrews were aged by tooth wear fendler;, Rosa fendleri, and Ribes inebrians. (Diersing and Hoffmeister 1977) and placed Short grasses occur in the open area around into two categories. the lake. Only a few fullen trees and woody Minimum and maximum temperatures and debris piles exist near the lake. precipitation were monitored daily through­ Mammal species (excluding bats) that r out the study periods. Air temperatures have collected or observed in association with varied !Tom -9 to 42 C, and sbrews were Sore>: namlS at this locality include: Spet·­ caught on evenings wben minimum tempera­ mophilus la.teralis, Eutamias umbrinus, Eu­ tures varied £i·om 1 to 10 C. The total number tamias minirnus. Tmniasciunl.8 hudsonicus. ofdays with rain during the study in 1988 was Sciurus ahem kaibahensis, Tlwmomys tal­ 58, with a total rainfall of 249 mm. H rained poUles, PeromysCU$ maniculatus, Microtus during 34 study days in 1989, witb a total longicaudus, Erethizon dorsatum, Odocoile­ rainfall of130.5 mm. us hemionus, and an occasional Sylvilllgus nuttalli, Canis la.traus, Mustela frenata, and RESULTS AND DISCUSSION Mustela. errninea (Bema 1990). r collected 23 Sorex nanus dUring this study METHODS (Table 1). Specimens were positively identi­ fied as Sorex nanus based on small body size Sorex nanus was captured at Fracas Lake Oess than 52 mm), upper third unicuspid during a two-year study of the Arizona tiger smaller than fuurtb, and presence of medial salamander (Ambystoma tigrinum nebulo­ tines on first incisor Ounge and Hoffmann sum). Fracas Lake was completely sur­ 1981, Hoffmeister 1986). One specimen was rounded by an aluminum drift fence 214.6 m kept as found in a mummified state, six were in circumference. The 40-cm-high feuce was captured alive and released, seven were pre­ buried 7-10 em below ground level. Two 4.5­ served as skins plus skolls, and nine were gallon buckets were buried as pitfall traps at fixed in 10% formalin and later stored in 65% each of 27 stations, approximately 7 m apart. ethanol. Specimens bave been deposited in The pitfall traps were adjacent to the fence, the mammal collection at Ariwna State Uill­ with one bucket on each side ofthe fence per versity. station. The average distance ofthe drift fence Standard body measurements, sex, and to the water was 8 m. Pitfall traps were age of several dwarf shrews are reported in checked daily !Tom 17 May to 15 September Table 2. Some shrews were partiallyeaten by 1988. They were checked every two weeks carrion beetles in pitfall traps, making sex from 15 September until 19 November 1988 determination impossible. Mean body mea­ and then daily from 27 April 1989 until surements (in mm, range in parentheses) 14 September 1989. After 14 September they were as follows (n = 16): total length 75 were checked once every week until 18 Octo­ (71-77), tail length 36 (34-39), hindfoot 9 ber 1989. Therefure, trapping occurred fur (8-10), ear !Tom notch 6 (4-7). Mean body 186 days in 1988 (10,044 trap nights) and 174 mass was equal to 2 g (n = 12). Reproductive days in 1989 (9,396 trap nights). condition was unambiguous for only oneoftbe 164 H J. BERNA [Volume 50

TABLE 2. Standard measurements (length in mm, mass in g) ofbody size, sex, and age (Ad =- adult, Juv '= juvenile) of Sorex nanus captured at Fracas Lake during 1988 and 1989. TL = total length, T = tail length, HF = hindfoot length, E = length ofear from notch.

Date Age Sex TL T HF E Mass 19S8 23 June Ad male 82 3& 9 7 2.5 1& July Ad female 81 37 9 5 2.0 1 August Ad male 79 36 9 7 2.0 6 August Jvv female 74 36 9 & 2.0 17 Auguse ~ ? 21 August Juv male 73 34 7 6 2.0 23 August Juv male 72 38 9 6 1.8 30 August JlIV male 78 38 10 7 2.0 h 2 September ~ ?

7 September ~ ? (mummified specimen, no measurements) 19S9 8 June Ad ? 7& 37 10 6 - 10 June Ad female 74 38 10 7 HJune Ad ? 76 36 9 6 5 July Juv male 74 36 8 5 2.0 21 July Juv male 71 36 8 4 1.8 27 July Juv ? 71 35 9 7 10 August" ? 12 Augustb ? 21 August Juv male 72 38 10 6 2.0 25 August Juv male 77 39 10 6 1.8 26 August Juv male 72 36 10 6 1.8 "Cuptu('("-d alive and ldetl~ed ullha.'moo. l'1\'Vl) live ~pcdmmlS enu!dJt on this dute and released unharmed. three females captured. The female captured orthopterans, and a few hemipteran and ho~ on 16 July 1988 had three developing follicles mopteran species. greater than 2 mm in diameter. Observations ofthree live shrews caught in All shrews were collected in pitfall traps pitfull traps suggested that dwarfshrews avoid outside the drift fence, suggesting that the tenebrionid beetles. In two instances the shrews do not reside within the fenced area shrew and a few tenebrionid beetles were all but use the area only as a foraging site. Juve­ that remained alive in the pitfall trap. Shrews niles were caught in July and August (Table 2), seemed to favor carabid beetles, which they and this activity may correspond to the period attacked voraciously with bites to the head of juvenile dispersal. All shrews were col­ and thorax followed by a quick retreat, and lected in the morning, although pitfall traps then repeated until the heetle was subdued were checked twice daily, Shrews were more and consumed. 1 also observed a shrew feed­ frequently caught on days with measurable ing on ants while it was in a pitfall trap. rainfall (17 of23, or 74% caught on days with Shrews are known to take a variety of small rain). This may be due to increased foraging vertebrates as prey (Hoffmeister 1986). On range when the stress ofwater requirements two occasions in this study a Sorex nanus was of the shrew is lessened, or it may simply fonnd in the same pitfall trap as an adult tiger correspond to increased prey activity. salamander (Ambystoma tigrinum nebulo­ Potential prey for Sorex rnmus at this local­ sum). The salamanders (snout-vent length ity include spiders, which were abundant 85-90 mm) were unharmed on both occa­ early in the season (April-June); tenebrionid sions, but in one instance the shrewwas found beetles, common throughout the studyperiod dead. This may indicate an unwillingness to (May-September); and the following families consume these large vertebrates with toxic and orders of invertebrates that appeared in skin secretions, or it may suggest that adult pitfall traps at various times during the study: salamanders are much too large to be consid­ Formicidae, Carabidae, Scarabidae, Curculi­ ered part of the ordinary diet of even the onidae, Coccinelidae, larval lepidopterans, hungriest Sorex nanus. 1990] SOREX NANUSIN ARIZONA 165

These recent observations extend the along a cross-sectional transect through the Ar­ known range ofSorex nanus northward on the kansas River watershed, Colorado. Southwestern Naturalist 17: 315-326. Kaibab Plateau in Arizona 25 km from the BERNA. H.). 1990. First record of the ermine (Mustela previous record of Hoffmeister (1955). The enninea) in Arizona. Southwestern Naturalist (in habitat at this locality is dominated by Pinus press). ponderosa, which is a new habitat type Bfu\DSHAW, C. V. 1961. New Ari.zona locality for the dwarf recorded for this species in Arizona. In this shrew. JoumaJ of Mammalogy 42: 96. BROWN, D. K 1982. Biotic communities ofthe American study Sorer nanus was collected within 8 m of Southwest-United States and Me;(ico. Desert water, unlike previous records for Arizona Plants 4: 1-342. (Hoffmeister 1986). BROWN, L. N. 1967. Ecological distribution of si;( species Future surveys using pitfall traps else­ ofshrews and compuison ofsampling methods in the central Rocky Mountains. Journal of Mammal­ where on the Kaibab Plateau, and on other ogy 48, 617-623. southwestern montane "islands," would be DIERSINC, v. E., AND D. F. HOFFMEISTER. 1977. Revision beneficial in determining the abundance and ofthe shrews Sorex meniamiand a description ofa distribution of Sorex nttnus in the southern new species of the subgenus Sorex. Journal of portions ofits range. They would also provide Mamm.logy 580 321-J33. HOFFMANN, R S., AND j. C. OWEN. 1980. SOf"n tenellus a clearer definition of tbe habitat require­ and Sorex nanlls. Mammalian Species 131: 1-4. ments ofthis species. HOFFMEJSTER, D. F. 1955, new to Grand Canyon National Park, Arizona. Plateau 18: 1-17. __. 1986. Mammals ofArizona. University of Arizona ACKNOWLEDGMENTS Press, Tucsoo. 602 pp. I thank T. Jones and B. Spicer for en­ JUNCE,j. A., AND R. S. HOFFMANN. 1981. An annotated key R. to tbe long~tailed Jihrews (genus Sorex) of the couraging this manuscript, and D. F. Hoff­ United States and Canada, with notes on middle meister for providing all researchers with an American Sore.'(. University afKansas Museum of excellent guide to mammals in Arizona. Many Natural History Occasional Papers 94: 1-48. thanks for field assistance go to C. A. Schmidt, LOMOUNO, M. V., J. H. BI\OWN, AND R DAVIS. 1989. Island biogeography of montane forest mammals in the S. J. Berna, and S. L. Steele. This article American Southwest. Ecology 70: 180-194. benefited from comments by J. P. Collins, MARSHALL. L. G., AND C. J. WEISENBERGER. 1971. A new C. A. Schmidt, S. George, and J. A. Junge. dwarf shrew locality for Arizona. Plateau 43: This research indirectly benefited from funds 132-137. provided by the Arizona State University De­ RUFFNER, G. A.. "-NO S W. CAR01llERS. 1975. Recent notes on the distribution ofsome mammals of the partment of Zoology Graduate Student Re­ Crand Canyon region. Plateau 47; 154-160. search Fund, and Sigma Xi, the Scientific Re­ SCHELLBACH, L.. III. 1948. A record of the shrew SQre:t search Society. nanus for Arizona. joumal ofMammalogy 29: 295.

LITERATURE CITED Received 16 November 1989 ARMSTRONG. D. M., B. H. BA.NTA, AND E. J. POKROPus. Revised 26January 1990 1973. Altitudinal distribution of small mammals Accepted15 Aprol990