90.

Sagebrush Vole

Lemmiscus curtatus

French: Campagnol des armoises / German: BeifulR-Wiihimaus / Spanish: Topillo de artemisia

Taxonomy. Arvicola curtata [sic] Cope, 1868, Pigeon Spring, Mt. Magruder, Nevada, near boundary between Inyo County, California and Esmeralda County, Nevada, USA.

Six subspecies are recognized.

Subspecies and Distribution.

L.c.curtatusCope,1868—ECCaliforniaandSWNevada,USA.

L.c.intermediusW.P.Taylor,1911—NECalifornia,SEOregon,SIdaho,N&CNevada,andWUtah,USA.

L.c.levidensisGoldman,1941—WIdahoandSMontanaSEtoNEUtahandNColorado,USA.

L.c.orbitusDearden&Lee,1955—SCUtah,USA.

L.c.pallidusMerriam,1888—SSaskatchewanandSAlberta,Canada,andMontana,WNorthDakota,andNWSouthDakota,USA.

L. c. pauperrimus Cooper, 1868 — C Washington to S Oregon and extreme N California, USA.

Descriptive notes. Head—body 92-114 mm, tail 16-28 mm; weight 17-5-25 g. The Sagebrush Vole is small, with long and lax fur, and has substantial geographical variation in morphology across its distribution. Dorsum ranges from drab brown to ash gray. Ears and nose can have buffy tips. Sides are paler, and belly is silvery to buffy. Tail is not strongly bicolored, but it is lighter below than above. Feet are white or light gray to buffy. Skull is flattened and angular, with short rostrum and zygomatic arches that are heavy and wide. Molars are rootless and have closely enclosed triangles and wide intervening reentrant angles. Inner and outer reentrant angles have similar depths. Chromosomal complement is 2n = 54, FN = 58.

Habitat. Semiarid habitats dominated by sagebrush ( Artemisia spp.) and rabbitbrush ( Chrysothamnus spp., Ericameria), both Asteraceae (making it a bit unusual for arvicoline rodents) at elevations of 300-3800 m.

Food and Feeding. Sagebrush Voles eat a wide variety of green grasses (e.g. Bromus tectorum, Agropyron desertorum, Poa bulbosa, Holcus lanatus, Stipa spartea, and Elymus caputmedusae, all Poaceae), forbs (e.g. Eriogonum strictum, Polygonaceae and Medicago sativa, Fabaceae), shrubs, and other green vegetation. Food is generally not stored in caches, but Sagebrush Voles reportedly steal from caches of other rodents such as North American Deermice ( Peromyscus maniculatus).

Breeding. Sagebrush Voles breed year-round, but in northern parts of their distribution, breeding can be restricted to March-December. Pregnancy rates are bimodal, with highest levels in spring and autumn when green vegetation peaks, and relatively few litters are born in hot summer months. A female can have up to 3 litters/year. Gestation averages 25 days, with averages of 4-6 young/litter reported in separate studies. Newborns are pink, hairless, and blind, but they are fully weaned at 21 days old. Burrow systems have nests that are often lined with sagebrush bark.

Activity patterns. Sagebrush Voles are most active in evening and early morning, but they can be active at any time of day throughout the year. Wind reportedly decreases activity.

Movements, Home range and Social organization. Burrows of Sagebrush Voles were 8 cm to almost 0-5 m underground, although it is unclear if deepest burrows were actually abandoned pocket gopher ( Geomyidae) burrows that had become occupied and modified by Sagebrush Voles. Surface runways are less well-defined than in other voles. Sagebrush Voles often form colonies in burrows with up to 30 entrances, obscured by sagebrush or rock piles. In Idaho, these voles were not colonial in summer. Dramatic population fluctuations have been tied to rainfall and pulses of green vegetation.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Bradley, Ammerman et al. (2014), Carroll & Genoways (1980), Hafner et al. (1998), Hall (1981), Maser et al. (1974), Mullican & Keller (1987), Musser & Carleton (2005), Wilson & Ruff (1999), Wurster et al. (1971).