Arctic Ground Squirrel

biology_ecology

ECOLOGY Population characteristics. — Urocitellus parryii is colonial, and aspects of its population biology have been studied in detail. Density of breeding adults varies with latitude and habitat; in northernmost Alaska, densities range from 0.2 to 1.7 adults / ha (Mayer 1953; Batzli and Sobaski 1980), although 5 – 8 adults / ha are typical farther south (Carl 1971; Donker and Krebs 2011). However, variation of equal or greater magnitude can occur between habitats in U. p. plesius, with <1 – 3 / ha documented in boreal forest habitats (Hubbs and Boonstra 1997; Byrom and Krebs 1999; Byrom et al. 2000; Hik et al. 2001; Donker and Krebs 2011; Werner et al. 2015) and 3 – 16 / ha documented in meadow or tundra habitats (Lacey et al. 1997; Hik et al. 2001; Donker and Krebs 2011; Werner et al. 2015). Population densities increase in summer before juvenile dispersal, and local densities can also be higher during hibernation than in the active season (Carl 1971). Significantly higher densities than those listed above are reported from experimental manipulations (Hubbs and Boonstra 1997; Byrom and Krebs 1999; Byrom et al. 2000). Colony size is relatively stable in tundra populations of U.

Urocitellus parryii (Rodentia: Sciuridae)

conservation

CONSERVATION Due to a relatively large geographic range and sometimes locally high abundance, Urocitellus parryii is not currently a conservation concern. It is currently classified as “ Least Concern ” by the International Union for Conservation of Nature and Natural Resources (Cassola 2016). Overhunting at local to regional scales may be the most significant conservation threat to U. parryii at present (Cassola 2016). Although once used more intensively as a food source and for pelts by indigenous peoples (e. g., Ross 1861; West et al. 2017), which may have resulted in reductions in local densities and abundance (Bee and Hall 1956), current impacts of hunting on range-wide stability are today likely minimal. However, evidence of this is still needed in areas where the species has been historically understudied and undersampled (e. g., Northwest Territories and Nunavut, Canada). Direct anthropogenic threats such as land use changes, conflicts with livestock, and pest management may impact some U. parryii populations (e. g., Davidson et al. 2012). The overall magnitude of these threats is probably lower in U. parryii than southern congeners; still, patchy distributions typical of t

Urocitellus parryii (Rodentia: Sciuridae)

description

FOSSIL RECORD The earliest fossils potentially assignable to Urocitellus parryii are from the Fish Creek fauna in northernmost Alaska and date to 2.4 million years ago or older (Repenning et al. 1987). Additional early records are available from the early to middle Pleistocene of Yukon and are dated at 1.5 – 1.7 million years ago (Fort Selkirk Local fauna — Storer 2003). However, the specific identity of both series of specimens is inconclusive, particularly given that U. undulatus likely arose from Nearctic stock (McLean et al. 2016) and must therefore have colonized Asia via Beringia. Material more confidently assignable to U. parryii is available from the middle to late Pleistocene of Yukon and Alaska (Sangamon interglacial and Illinoian glaciation — Guthrie and Matthews 1971; Jopling et al. 1981; Harington 2011). A relative abundance of material exists from the middle Wisconsin glaciation through Holocene (80,000 years ago to present — Graham and Lundelius 2010); much of that material comes from fossil ground squirrel middens, which themselves have contributed to understanding of Beringian late Quaternary paleoecology and paleoenvironments (Zazula et al. 2007). Mummified remain

Urocitellus parryii (Rodentia: Sciuridae)

description

GENERAL CHARACTERS Urocitellus parryii (Fig. 1) resembles other true ground squirrels in gross external morphology in having a semicylindrical body plan, dorsoventrally compressed cranium, shortened pinnae, relatively short but stout limbs, and relatively elongated manus, pes, and digits with sharp claws. The posture of U. parryii is plantigrade; forelimbs and hindlimbs possess 4 and 5 digits, respectively. Membranous cheek pouches are present. Tail length is typically 35 – 50 % of head – body length. Ranges of external measurements (mm) for mainland subspecies excluding U. p. plesius are as follows: total length, 340 – 495; tail length, 88 – 165; hind foot length, 52 – 68. Ranges of the same measurements (mm) from the more diminutive U. p. plesius are as follows: total length, 300 – 363; tail length, 85 – 105; hind foot length, 50 – 57. Ear length in U. parryii ranges from 10 to 21 mm. Adult weights from 450 to 1,000 g are possible, and average greater in northern than southern populations. Weights exceeding 1 kg have occasionally been reported in U. p. parryii, U. p. kennicottii, U. p. osgoodi, and U. p. leucostictus (Howell 1938; Batzli and Sobaski 1980; Buck and Barnes 1999 a;

Urocitellus parryii (Rodentia: Sciuridae)