265 THE CANADIAN FIELD -N ATURALIST Vol. 128

New Records of the Ogilvie Mountains Collared Lemming ( Dicrostonyx nunatakensis ) in central Yukon

THOMAS S. J UNG 1, 4 , B RIAN G. S LOUGH 2, D AVID W. N AGORSEN 3, AND PIIA M. K UKKA 1

1Yukon Department of Environment, Box 2703, Whitehorse, Yukon Y1A 2C6 Canada 235 Cronkhite Road, Whitehorse, Yukon Y1A 5S9 Canada 3Mammalia Biological Consulting, Victoria, British Columbia V9C 3Z4 Canada 4Corresponding author: [email protected]

Jung, Thomas S., Brian G. Slough, David W. Nagorsen, and Piia M. Kukka. 2014. New records of the Ogilvie Mountains Col - lared Lemming ( Dicrostonyx nunatakensis ) in central Yukon. Canadian Field-Naturalist 128(3): 265–268. The Ogilvie Mountain Collared Lemming ( Dicrostonyx nunatakensis Youngman, 1967), reported only from the Ogilvie Mountains of central Yukon, is among the least known mammals in Canada. It was first discovered in 1961 and, since then, only 13 specimens had been collected, all from one mountain, in central Yukon. We conducted a targeted survey to determine the distribution of the species by trapping areas of apparently suitable habitat on 12 mountains within 40 km of the known location. Many of our traps were disabled by other mammals; however, we captured three Ogilvie Mountain Collared Lem - mings on two mountains 25.9 km and 29.6 km from the original location. Our findings suggest that this lemming may be more widely distributed than indicated by earlier specimens. We suggest further surveys to delineate the range of the Ogilvie Mountain Collared Lemming. Key Words: Ogilvie Mountain Collared Lemming; Dicrostonyx nunatakensis ; distribution; Tombstone Territorial Park; Yukon Introduction ducted a targeted survey for the Ogilvie Mountain Col - The Ogilvie Mountain Collared Lemming ( Dicro - lared Lemming to determine whether it inhabits other stonyx nunatakensis Youngman, 1967) is known from nearby mountains. This information is essential for bet - only one mountain in central Yukon, Canada. Collared ter understanding the distribution and conservation sta - Lemmings in the Ogilvie Mountains are geographi - tus of this population. cally separated from populations of Nearctic Collared Lemming ( Dicrostonyx groenlandicus ) to the northeast Study Area by about 250 km of apparently unoccupied habitat. During 19–31 August 2011, we surveyed 12 moun - The nearest recorded population of Nearctic Collared tains in the southern Ogilvie Mountains, all located Lemming is in the Richardson Mountains, northeast of within Tombstone Territorial Park. Tombstone Territo - the Ogilvie Mountains. Youngman (1967) speculated rial Park is approximately 2,200 km 2, much of which that Collared Lemmings in the Ogilvie Mountains rep - lies above the tree line. Our sampling sites were distrib - resent a relic population of Dicrostonyx that became uted over five distinct mountain ranges (Table 1 and isolated on nunataks (unglaciated mountain tops) dur - Figure 1). The mountains we surveyed were distrib - ing the Last Glacial Maximum and that they may uted throughout the park to provide spatial coverage remain reproductively isolated. Although the Ogilvie of the alpine habitat within the park. We did not sam - Mountain Collared Lemming is afforded species status ple at Trapper Mountain because the species was al - by Wilson and Reeder (2005), the taxonomic status of ready known from there (Youngman 1964, 1967, 1975; Collared Lemmings in the Ogilvie Mountains is unre - Slough and Jung 2007). Survey sites were accessed solved (J. Eger, Royal Ontario Museum, personal com - by helicopter. munication). The Ogilvie Mountain Collared Lemming is one of Methods the least known terrestrial mammals in North America On each mountain surveyed, we selected a sampling (Nagorsen 1998). Only 13 museum specimens exist, all site in alpine tundra that was similar in elevation and collected from a single mountain, Trapper Mountain habitat characteristics (dry heath, gentle slope) to cap - (64.583°, -138.217°), located in Tombstone Territorial ture sites on Trapper Mountain (Youngman 1975; Jung Park, Yukon (Youngman 1964, 1967, 1975; Slough and et al ., unpublished data). At each sampling site, we set Jung 2007). The specimens were collected at 1625– snap-traps in variable-length trap lines that contained 1676 m above sea level in dry rocky alpine tundra 60 trapping stations (49 in 1 case) set 10–15 m apart. (heath) at the base of glacial cirques. At each trapping station, we set both a Museum Spe - Limited survey effort has hampered our ability to cial and a Victor snap-trap (Woodstream Corp., Lititz, assess accurately the distribution of this apparently Pennsylvania) 1–2 m apart. Traps were baited with range-restricted small mammal. Because surveys have peanut butter and rolled oats and left unattended for been constrained by the remote high-elevation habi - 9–11 days ( x– = 10.3 ± 0.3 standard deviation [SD]; tats in the Ogilvie Mountains, it is unknown whether Table 1). We recorded the number of specimens cap - this species is restricted to a single mountain. We con - tured per trap line and the number of traps that were 266 THE CANADIAN FIELD -N ATURALIST Vol. 128 - b e m n w o a e t T r 0 1 0 0 0 0 0 0 0 0 0 0

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Results and Discussion C y 4 4 4 4 4 4 4 4 4 4 4 4 ( o

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Overall the number of animals captured was small: i e o

d r k e e a 26 captures of small mammals of four species, includ - t u k i p c s Y p

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r n n n n n o o u n n d t t i y a o Lemming (Table 1). Ogilvie Mountains Collared Lem - o o o o a o e r c c t t t t t l a e P h y y t r s s s s s a R e e

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l d d i a n k k b b b p mings were collected from two of the 12 mountains p a a n n a m u u l l s s c c u F w r i a m m m

e e o o a a r o o c o e r m f l l l l e e r r o o surveyed, both in the Seela Range (Table 1). The two o f o h u t t T S C C S B T T P P M B M o i r

S r t o sites were 5.7 km apart and 25.9 km and 29.6 km west . r . e a e s N 1 t

T a : of previous collections on Trapper Mountain. Capture s

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L a n o o e B locations were among the most distant sampling sites r t o i A 2 0 N T N 1 t 1 T s S 1 * 2 3 4 5 † 6 ‡ 7 8 9 1 from Trapper Mountain, and they were separated from 1 2014 NOTES 267

Trapper Mountain by the Blackstone River, a potential capture sites was dominated by mountain avens ( Dryas barrier to dispersal (Figure 1). spp.), dwarf willow ( Salix spp.), mosses, lichens Two Ogilvie Mountains Collared Lemmings were (Tham nolia vermicularis , Flavocetraria nivalis ), and juvenile males and the other was a juvenile female. grasses (e.g., Anthoxanthum monticola ), along with They were collected in dry heath type habitat at ele - other ericaceous species (e.g., Arctous alpinus , Betula vations (1631–1709 m above sea level; Figure 2) typi - glandulosa , Empetrum nigrum , Cassiope tetragona , cal of previous captures at Trapper Mountain (Young - Vaccinium vitis-idaea ; Figure 2). Small mammal man 1967; Slough and Jung 2002). Vegetation at the species caught in association with the Ogilvie Moun -

FIGURE 2. Landscape (top) and micro-site (bottom) views of the high alpine heath habitat where the Ogilvie Mountains Col - lared Lemming ( Dicrostonyx nunatakensis ) was collected in central Yukon, Canada, August 2011. Scale shown in the bottom panel is approximate. Photos: Brian Slough (top) and Thomas Jung (bottom). 268 THE CANADIAN FIELD -N ATURALIST Vol. 128

tains Collared Lemming were the Northern Red-backed Acknowledgements Vole ( Myodes rutilus ), the Tundra Vole ( Microtus oeco - We thank D. Amos, C. Eckert, and T. Powell for nomus ), and the Montane Shrew ( Sorex monticolus ; facilitating this work and assisting with field logistics. Table 1). We thank L. Hughes, S. Hughes, M. Kienzler, and A. – Many traps ( x = 81.2% ± 3.7% SD) were prema - McCulley for field assistance. We thank J. Eger for turely sprung or missing when we returned to check discussions about collared lemmings and archiving our them (Table 1), which substantially reduced the sam - specimens at the Royal Ontario Museum. Two anony - pling effort. Based on earlier survey work using the mous reviewers provided thoughtful comments on an same trapping protocol in the study area (Jung et al ., earlier draft of this manuscript. unpublished data), we suspect that most traps were disabled early within the sampling period, resulting in the low number of small mammals captured. However, Literature Cited MacDonald, S. O. 2003. The small mammals of Alaska: a the time from deployment during which our traps were field handbook of the shrews and small rodents. Unpub - functional is unknown. Arctic Ground Squirrels ( Uro - lished manuscript. Accessed 20 September 2013. http:// citellus parryii ) were abundant at all sampling sites, science.nature.nps.gov/im/units/swan/assets/docs/reports and we suspect that they were responsible for the vast /inventories/MacDonaldS_2003_AKRO_SmallMammal majority of traps that were prematurely sprung or miss - HandbookCondensed_572288.pdf ing. For further surveys, means should be sought to Nagorsen , D. W . 1998. Dicrostonyx nunatakensis . Page 88 in reduce disturbance of traps by Arctic Ground Squir - North American Rodents: Status Survey and Conservation rels, such as placing a wire enclosure over the trap. Action Plan. Edited by D. J. Hafner, E. Yensen, and G. L. We confirm that Ogilvie Mountains Collared Lem - J. Kirkland. IUCN Publications, Gland, Switzerland. mings are more widely distributed than solely on Trap - Slough, B. G., and T. S. Jung. 2007. Diversity and distribu - per Mountain. We suspect that they were present on tion of the mammals of the Yukon Territory: a review. some of the 10 mountains we surveyed without detect - Canadian Field-Naturalist 121: 119–127. ing them. The habitat at all sites surveyed was similar. Wilson, D. E., and D. A. Reeder (editors). 2005. Mammal The functional loss of many traps likely resulted in a Species of the World. A Taxonomic and Geographic Ref - low sampling effort, hindering our ability to capture erence. Third edition. The Johns Hopkins University Press, collared lemmings at some survey sites. The occur - Baltimore, Maryland, USA. 2142 pages. rence of Ogilvie Mountains Collared Lemmings on Youngman, P. M. 1964. Range extensions of some mammals three mountains within the Ogilvie Mountains suggests from Northwestern Canada. Natural History Papers 23. National Museum of Canada, Ottawa, Ontario, Canada. that they may be somewhat widespread in suitable habi - Youngman , P. M. 1967. A new subspecies of varying lem - tats there. Moreover, Youngman (1975) speculated that ming, Dicrostonyx torquatus (Pallas), from Yukon Territo - the Ogilvie Mountains Collared Lemming likely also ry (Mammalia, Rodentia). Proceedings of the Biological occurs in the adjacent Wernecke and Selwyn Moun - Society of Washington 80: 31–34. tains of central Yukon, but there have been few (if any) Youngman , P. M. 1975. Mammals of the Yukon Territory. small mammal surveys in these ranges. Further sur - Publications in Zoology 10. National Museum of Canada, veys are needed to delineate the range of the Collared Ottawa, Ontario. 192 pages. Lemming within the Ogilvie Mountains and adjacent ranges. Received 2 October 2013 Accepted 3 February 2014