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You are here >1Up Info > Wildlife, Animals, and Plants > Wildlife Species > Mammals > Wildlife Species: Spermophilus townsendii | Townsend's Ground Squirrel
 

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BIOLOGICAL DATA AND HABITAT REQUIREMENTS

WILDLIFE SPECIES: Spermophilus townsendii | Townsend's Ground Squirrel
TIMING OF MAJOR LIFE HISTORY EVENTS : Aestivation - Townsend's ground squirrels become dormant in late spring or early summer, after grasses cure. They emerge from dormancy in late winter. Dormancy lasts 7.5 to 9 continuous months [1,24]. The aestivation period is shorter wet years, when green forage is available later in summer, than in dry years [1,27]. Breeding - Females breed as yearlings. Most males also breed as yearlings, although male Snake Valley ground squirrels breed at 2 years of age [24,27]. Most breeding occurs in late January or early February [27], just after dormancy ends. Piute ground squirrels breed from mid-February to early March, somewhat later than other subspecies [23,24]. Gestation - about 24 days [1] Litter size - One litter is produced per year, with 6 to 10 pups per litter [25]. Development - Pups are born hairless and with eyes closed. Early postnatal development of Townsend's ground squirrels is relatively slow compared to development of other Spermophilus species. Pups open their eyes at 19 to 22 days of age, and are weaned shortly thereafter [25]. PREFERRED HABITAT : Although Townsend's ground squirrels occur in arid environments, within those environments they are most common around desert springs and irrigated fields [10]. They also occupy ridgetops, hillsides, and valley bottoms [25], canal and railroad embankments, and old fields [5]. As a burrowing species, Townsend's ground squirrels select sites with deep, friable, well-drained soils [21,25]. In southeastern Idaho, 68 percent of Townsend's ground squirrel burrows were in sand, 28 percent in silt, and 4 percent in clay [19]. Home range and density: Smith and Johnson [27] reported a mean home range of 1,357 square meters (+/- 189.7 sq m) for 14 Snake Valley ground squirrels. Townsend's ground squirrel density can fluctuate greatly from year to year. Estimated population density of Snake Valley ground squirrels ranged from 3 to 32 individuals per hectare [27]. Densities of 296 to 331 individuals per hectare have been reported for Piute ground squirrels [1]. COVER REQUIREMENTS : Townsend's ground squirrels occupy open habitats and use burrows for shelter, protection from predators, and food storage. Burrows are often grouped into colonies, but some Townsend's ground squirrels are solitary [25]. Except when mothers have pups, there is only one Townsend's ground squirrel per burrow. Burrows have one to many openings and may have numerous auxiliary burrows in addition to the "home" or nest burrow [28]. Burrow dimensions of Townsend's ground squirrels in southeastern Idaho ranged from 2.6 to 3.8 inches (6.5-9.6 cm) horizontally and from 1.7 to 2.5 inches (4.3-6.3 cm) vertically [19]. Townsend's ground squirrels have been observed climbing shrubs while foraging, apparently for cover and to spot palatable vegetation [25]. FOOD HABITS : Townsend's ground squirrels consume mainly green vegetation and some seeds and insects [4,13]. Dietary studies on the Townsend's ground squirrel are few, but green grasses are apparently a staple from late winter until just prior to grass senescence and Townsend ground squirrel aestivation, when seeds become the primary diet item. Seeds are an imortant source of calories just prior to aestivation [23]. Where present, winterfat is browsed heavily [8], but only light browsing of other shrubs has been reported. From March through May on the Arid Land Ecology Reserve in eastern Washington, the Townsend's ground squirrel diet was 49 percent Sandberg bluegrass, 11 percent western yarrow (Achillea millefolium var. occidentalis), 8 percent pinnate tansymustard (Descurania pinnata) seed, 31 percent other plant species (mostly forbs), and 1 percent insects [13]. On a big sagebrush-crested wheatgrass community in southeastern Idaho, 80 percent of Townsend's ground squirrels trapped in June had consumed crested wheatgrass, and Townsend's ground squirrels became dormant after the crested wheatgrass senesced [17]. Cheatgrass (Bromus tectorum) is an important food item in some years. As an annual with wide year-to-year swings in productivity, however, it is not a reliable food source. Yensen and others [28] found that on the SRBPSA, Townsend's ground squirrel burrow densities declined over a 7-year period in areas dominated by cheatgrass or other exotic annuals. Adult cannabalism of unweaned young has been observed in the Townsend's ground squirrel [3]. PREDATORS : Townsend's ground squirrels are the primary prey of ferruginous hawks (Buteo regalis) in the Great Basin and Columbia Plateau [15]. They are also a major and often primary diet item of prairie falcons (Falco mexicanus) [21,22]. The Townsend's ground squirrel has been rated one of the two most important prey species on the SRBPSA because of its importance to ferruginous hawks and prairie falcons. (The other important prey species is the black-tailed jackrabbit [Lepus californicus]) [21]. Other important predators of Townsend's ground squirrels include other hawks (Accipiter and Buteo spp.) and falcons (Falco spp.), common crows (Corvus corax), badgers (Taxidea taxus), coyotes (Canis latrans), long-tailed weasels (Mestrela frenata), western rattlesnakes (Crotalus viridis), and gopher snakes (Pituophis melanoleucus) [1,12,25,27]. MANAGEMENT CONSIDERATIONS : Grazing effects: Effects of cattle grazing on Towsend's ground squirrels vary. In a small mammal population study on riparian sites in Nevada, Townsend's ground squirrels were trapped only in areas where cattle had been excluded [20]. In sagebrush steppe in southeastern Idaho, however, Townsend's ground squirrel density did not significantly vary between ungrazed sites and sites grazed by cattle [16]. Census: Because a given burrow may have one to many entrances, trapping is a more reliable method of Townsend's ground squirrel census than counting burrow entrances [16]. Predator-prey relationships: In areas where exotic annuals are increasing, Townsend's ground squirrel predators will probably face an increasingly unstable prey base [28]. REFERENCES : NO-ENTRY

Related categories for Wildlife Species: Spermophilus townsendii | Townsend's Ground Squirrel

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Information Courtesy: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Fire Effects Information System

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