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Townsend's ground squirrel

April 14, 2024

Townsend's ground squirrel (Urocitellus townsendii) is a species of rodent in the family Sciuridae. It is found in high desert shrublands in several areas of the United States.

Townsend's ground squirrel
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Urocitellus
Species:
U. townsendii
Binomial name
Urocitellus townsendii
(Bachman, 1839)
Synonyms

Spermophilus townsendii Bachman, 1839

Distribution edit

Townsend's ground squirrel is found in the Great Basin and the Columbia Plateau. Its range includes south-central Washington, eastern Oregon, southern Idaho, western Utah, most of Nevada, and extreme eastern California.[2] The subspecies are distributed as follows:[3]

  • Urocitellus townsendii artemesiae – south-central Idaho
  • U. t. canus (Merriam's ground squirrel) – eastern Oregon; northeastern corner of California; northwestern corner of Nevada
  • U. t. idahoensis – southwestern Idaho
  • U. t. mollis (Piute ground squirrel) – eastern California; southeastern Oregon; southern Idaho; western Utah; Nevada; most widely distributed subspecies
  • U. t. nancyae – south-central Washington
  • U. t. townsendii – south-central Washington
  • U. t. vigilis – Snake River Canyon bottomlands of east-central Oregon and west-central Idaho

Townsend's ground squirrels typically inhabit arid grasslands and shrub-grasslands. Malheur ground squirrels, however, inhabit the relatively mesic and fertile Snake River Plain.[2] Plant communities in which Townsend's ground squirrels occur include crested wheatgrass (Agropyron cristatum), big sagebrush (Artemisia tridentata) wheatgrass,[4] rabbitbrush (Chrysothamnus spp.), shadscale (Atriplex confertifolia), and winterfat (Kraschenninikovia lanata) grasslands.[5]

In southeastern Idaho, the density of Townsend's ground squirrel burrows is highest on winterfat-Sandberg bluegrass (Poa secunda), intermediate in big sagebrush-Thurber needlegrass (Stipa thurberiana), and lowest in shadscale-Indian ricegrass (Oryzopsis hymenoides) and thread grass (Stipa comata) . Burrow densities were highly variable in mixed exotic annual communities, and negatively correlated with cheatgrass (Bromus tectorum) . They increase with increasing native grass cover, but the populations are unstable when native grass cover is overly high.[6][7]

Preferred habitat edit

Although Townsend's ground squirrels occur in arid environments, within those environments they are most common around desert springs and irrigated fields.[8] They also occupy ridgetops, hillsides, and valley bottoms,[2] canal and railroad embankments, and old fields.[9] As a burrowing species, Townsend's ground squirrels select sites with deep, friable, well-drained soils.[2][5] In southeastern Idaho, 68% of Townsend's ground squirrel burrows were in sand, 28% in silt, and 4% in clay.[10]

Smith and Johnson reported a mean home range of 1,357 square meters for 14 Snake Valley ground squirrels.[11] 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.[11] Densities of 296 to 331 individuals per hectare have been reported for Piute ground squirrels.[12]

Timing of major life events edit

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.[12][13] It is shorter in wet years, when green forage is available later in summer, than in dry years.[11][12]

Females breed as yearlings. Most males also breed as yearlings, although male Snake Valley ground squirrels breed at 2 years of age.[11][13] Most breeding occurs in late January or early February,[11] just after dormancy ends. Piute ground squirrels breed from mid-February to early March, somewhat later than other subspecies.[13][14] Gestation is about 24 days.[12] One litter is produced per year, with 6 to 10 pups per litter.[2] 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.[2]

Cover requirements edit

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.[2] 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.[7] 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.[10]

Townsend's ground squirrels have been observed climbing shrubs while foraging, apparently for cover and to spot palatable vegetation.[2]

Food habits edit

Townsend's ground squirrels consume mainly green vegetation and some seeds and insects.[15][16] Green grasses are apparently a staple from late winter until just prior to grass senescence and Townsend ground squirrel estivation, when seeds become the primary diet item. Seeds are an important source of calories just prior to estivation.[14] Where present, winterfat is browsed heavily,[17] 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 is 49% Sandberg bluegrass, 11% western yarrow (Achillea millefolium var. occidentalis), 8% pinnate tansymustard (Descurania pinnata) seed, 31% other plant species (mostly forbs), and 1% insects.[16] On a big sagebrush-crested wheatgrass community in southeastern Idaho, 80% of Townsend's ground squirrels trapped in June had consumed crested wheatgrass, and Townsend's ground squirrels became dormant after the crested wheatgrass senesced.[18] 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.[7]

Adult cannibalism of unweaned young has been observed in the Townsend's ground squirrel.[19]

Predators edit

Townsend's ground squirrels are the primary prey of ferruginous hawks (Buteo regalis) in the Great Basin and Columbia Plateau.[4] They are also a major and often primary diet item of prairie falcons (Falco mexicanus).[5][20] The Townsend's ground squirrel has been rated one of the two most important prey species in southeastern Idaho because of its importance to ferruginous hawks and prairie falcons.[5] 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).[2][11][12][21]

References edit

  This article incorporates public domain material from Spermophilus townsendii. United States Department of Agriculture.

  1. ^ NatureServe. (2016). Urocitellus townsendii (errata version published in 2017). The IUCN Red List of Threatened Species. doi:10.2305/IUCN.UK.2016-3.RLTS.T20476A22266682.en
  2. ^ a b c d e f g h i Rickart, Eric A. (1987). "Spermophilus townsendii" (PDF). Mammalian Species. 268: 1–6.
  3. ^ Hall, E. Raymond. (1981). The mammals of North America. 2nd ed. Vol. 2. New York: John Wiley and Sons ISBN 1-930665-31-8
  4. ^ a b Kindschy, Robert R. (1986). . Rangelands. 8 (4): 157–159. Archived from the original on 2014-07-29.
  5. ^ a b c d Nydegger, Nicholas C.; Smith, Graham W. (1986). "Prey populations in relation to Artemisia vegetation types in southwestern Idaho". In: McArthur, E. Durant; Welch, Bruce L., compilers. Proceedings – symposium on the biology of Artemisia and Chrysothamnus; 1984 July 9–13; Provo, UT. Gen. Tech. Rep. INT-200. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. pp. 152–156
  6. ^ Knick, Steven T. (1993). "Habitat classification & the ability of habitats to support populations of Townsend's ground squirrels and black-tailed jackrabbits". In: Steenhof, Karen, ed. Snake River Birds of Prey National Conservation Area research and monitoring annual report: 1993. [Boise, ID]: U.S. Department of the Interior, Bureau of Land Management, Boise District. pp. 237–263
  7. ^ a b c Yensen, Eric; Quinney, Dana L.; Johnson, Kathrine (1992). "Fire, vegetation changes, and population fluctuations of Townsend's ground squirrels". The American Midland Naturalist. 128 (2): 299–312. doi:10.2307/2426464. JSTOR 2426464.
  8. ^ Hansen, Richard M. (1954). Ground squirrels (Citellus) of Utah. Salt Lake City, UT: University of Utah. Dissertation
  9. ^ Davis, William B. 1939. The recent mammals of Idaho. Contribution Museum of Vertebrate Zoology, Berkeley, CA. Caldwell, ID: The Caxton Printers, Ltd
  10. ^ a b Laundre, John W. (1989). "Horizontal and vertical diameter of burrows of five small mammal species in southeastern Idaho". The Great Basin Naturalist. 49 (4): 646–64.
  11. ^ a b c d e f Smith, Graham W.; Johnson, Donald R. (1985). "Demography of a Townsend ground squirrel population in southwestern Idaho". Ecology. 66 (1): 171–178. doi:10.2307/1941317. JSTOR 1941317.
  12. ^ a b c d e Alcorn, J. R. (1940). "Life history notes on the Piute ground squirrel". Journal of Mammalogy. 21 (2): 160–170. doi:10.2307/1374972. JSTOR 1374972.
  13. ^ a b c Rickart, Eric A. (1982). "Annual cycles of activity and body composition in Spermophilus townsendii mollis". Canadian Journal of Zoology. 60 (12): 3298–3306. doi:10.1139/z82-418.
  14. ^ a b Rickart, Eric Allan. (1982). The ecology of Townsend's ground squirrel, Spermophilus townsendii mollis. Salt Lake City, UT: University of Utah. Dissertation
  15. ^ Clary, Warren P.; Medin, Dean E. (1992). "Vegetation, breeding bird, and small mammal biomass in two high-elevation sagebrush riparian habitats". In: Clary, Warren P.; McArthur, E. Durant; Bedunah, Don; Wambolt, Carl L., compilers. Proceedings – symposium on ecology and management of riparian shrub communities; 1991 May 29–31; Sun Valley, ID. Gen. Tech. Rep. INT-289. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. pp. 100–110
  16. ^ a b Johnson, Mark K. (1977). "Food of Townsend ground squirrels on the Arid Land Ecology Reserve (Washington)". The Great Basin Naturalist. 37: 128.
  17. ^ Groves, Craig R.; Steenhof, Karen (1988). "Responses of small mammals and vegetation to wildfire in shadscale communities of southwestern Idaho". Northwest Science. 62 (5): 205–210. hdl:2376/1712.
  18. ^ Koehler, David K.; Anderson, Stanley H. (1991). "Habitat use and food selection of small mammals near a sagebrush/crested wheatgrass interface in southeastern Idaho". The Great Basin Naturalist. 51 (3): 249–255.
  19. ^ Callahan, J. R. (1993). "Squirrels as predators". The Great Basin Naturalist. 53 (2): 137–144.
  20. ^ Ogden, Verland T.; Hornocker, Maurice G. (1977). "Nesting density and success of prairie falcons in southwestern Idaho". Journal of Wildlife Management. 41 (1): 1–11. doi:10.2307/3800084. JSTOR 3800084.
  21. ^ Janes, Stewart W. (1985). "Habitat selection in raptorial birds". In: Cody, Martin L., ed. Habitat selection in birds. Academic Press Inc.: pp. 159–188 ISBN 0-12-178081-3

April 14, 2024
townsend, ground, squirrel, urocitellus, townsendii, species, rodent, family, sciuridae, found, high, desert, shrublands, several, areas, united, states, conservation, statusvulnerable, iucn, scientific, classificationdomain, eukaryotakingdom, animaliaphylum, . Townsend s ground squirrel Urocitellus townsendii is a species of rodent in the family Sciuridae It is found in high desert shrublands in several areas of the United States Townsend s ground squirrelConservation statusVulnerable IUCN 3 1 1 Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass MammaliaOrder RodentiaFamily SciuridaeGenus UrocitellusSpecies U townsendiiBinomial nameUrocitellus townsendii Bachman 1839 SynonymsSpermophilus townsendii Bachman 1839 Contents 1 Distribution 2 Preferred habitat 3 Timing of major life events 4 Cover requirements 5 Food habits 6 Predators 7 ReferencesDistribution editTownsend s ground squirrel is found in the Great Basin and the Columbia Plateau Its range includes south central Washington eastern Oregon southern Idaho western Utah most of Nevada and extreme eastern California 2 The subspecies are distributed as follows 3 Urocitellus townsendii artemesiae south central Idaho U t canus Merriam s ground squirrel eastern Oregon northeastern corner of California northwestern corner of Nevada U t idahoensis southwestern Idaho U t mollis Piute ground squirrel eastern California southeastern Oregon southern Idaho western Utah Nevada most widely distributed subspecies U t nancyae south central Washington U t townsendii south central Washington U t vigilis Snake River Canyon bottomlands of east central Oregon and west central IdahoTownsend s ground squirrels typically inhabit arid grasslands and shrub grasslands Malheur ground squirrels however inhabit the relatively mesic and fertile Snake River Plain 2 Plant communities in which Townsend s ground squirrels occur include crested wheatgrass Agropyron cristatum big sagebrush Artemisia tridentata wheatgrass 4 rabbitbrush Chrysothamnus spp shadscale Atriplex confertifolia and winterfat Kraschenninikovia lanata grasslands 5 In southeastern Idaho the density of Townsend s ground squirrel burrows is highest on winterfat Sandberg bluegrass Poa secunda intermediate in big sagebrush Thurber needlegrass Stipa thurberiana and lowest in shadscale Indian ricegrass Oryzopsis hymenoides and thread grass Stipa comata Burrow densities were highly variable in mixed exotic annual communities and negatively correlated with cheatgrass Bromus tectorum They increase with increasing native grass cover but the populations are unstable when native grass cover is overly high 6 7 Preferred habitat editAlthough Townsend s ground squirrels occur in arid environments within those environments they are most common around desert springs and irrigated fields 8 They also occupy ridgetops hillsides and valley bottoms 2 canal and railroad embankments and old fields 9 As a burrowing species Townsend s ground squirrels select sites with deep friable well drained soils 2 5 In southeastern Idaho 68 of Townsend s ground squirrel burrows were in sand 28 in silt and 4 in clay 10 Smith and Johnson reported a mean home range of 1 357 square meters for 14 Snake Valley ground squirrels 11 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 11 Densities of 296 to 331 individuals per hectare have been reported for Piute ground squirrels 12 Timing of major life events editTownsend 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 12 13 It is shorter in wet years when green forage is available later in summer than in dry years 11 12 Females breed as yearlings Most males also breed as yearlings although male Snake Valley ground squirrels breed at 2 years of age 11 13 Most breeding occurs in late January or early February 11 just after dormancy ends Piute ground squirrels breed from mid February to early March somewhat later than other subspecies 13 14 Gestation is about 24 days 12 One litter is produced per year with 6 to 10 pups per litter 2 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 2 Cover requirements editTownsend 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 2 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 7 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 10 Townsend s ground squirrels have been observed climbing shrubs while foraging apparently for cover and to spot palatable vegetation 2 Food habits editTownsend s ground squirrels consume mainly green vegetation and some seeds and insects 15 16 Green grasses are apparently a staple from late winter until just prior to grass senescence and Townsend ground squirrel estivation when seeds become the primary diet item Seeds are an important source of calories just prior to estivation 14 Where present winterfat is browsed heavily 17 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 is 49 Sandberg bluegrass 11 western yarrow Achillea millefolium var occidentalis 8 pinnate tansymustard Descurania pinnata seed 31 other plant species mostly forbs and 1 insects 16 On a big sagebrush crested wheatgrass community in southeastern Idaho 80 of Townsend s ground squirrels trapped in June had consumed crested wheatgrass and Townsend s ground squirrels became dormant after the crested wheatgrass senesced 18 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 7 Adult cannibalism of unweaned young has been observed in the Townsend s ground squirrel 19 Predators editTownsend s ground squirrels are the primary prey of ferruginous hawks Buteo regalis in the Great Basin and Columbia Plateau 4 They are also a major and often primary diet item of prairie falcons Falco mexicanus 5 20 The Townsend s ground squirrel has been rated one of the two most important prey species in southeastern Idaho because of its importance to ferruginous hawks and prairie falcons 5 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 2 11 12 21 References edit nbsp This article incorporates public domain material from Spermophilus townsendii United States Department of Agriculture NatureServe 2016 Urocitellus townsendii errata version published in 2017 The IUCN Red List of Threatened Species doi 10 2305 IUCN UK 2016 3 RLTS T20476A22266682 en a b c d e f g h i Rickart Eric A 1987 Spermophilus townsendii PDF Mammalian Species 268 1 6 Hall E Raymond 1981 The mammals of North America 2nd ed Vol 2 New York John Wiley and Sons ISBN 1 930665 31 8 a b Kindschy Robert R 1986 Rangeland vegetative succession implications to wildlife Rangelands 8 4 157 159 Archived from the original on 2014 07 29 a b c d Nydegger Nicholas C Smith Graham W 1986 Prey populations in relation to Artemisia vegetation types in southwestern Idaho In McArthur E Durant Welch Bruce L compilers Proceedings symposium on the biology of Artemisia and Chrysothamnus 1984 July 9 13 Provo UT Gen Tech Rep INT 200 Ogden UT U S Department of Agriculture Forest Service Intermountain Research Station pp 152 156 Knick Steven T 1993 Habitat classification amp the ability of habitats to support populations of Townsend s ground squirrels and black tailed jackrabbits In Steenhof Karen ed Snake River Birds of Prey National Conservation Area research and monitoring annual report 1993 Boise ID U S Department of the Interior Bureau of Land Management Boise District pp 237 263 a b c Yensen Eric Quinney Dana L Johnson Kathrine 1992 Fire vegetation changes and population fluctuations of Townsend s ground squirrels The American Midland Naturalist 128 2 299 312 doi 10 2307 2426464 JSTOR 2426464 Hansen Richard M 1954 Ground squirrels Citellus of Utah Salt Lake City UT University of Utah Dissertation Davis William B 1939 The recent mammals of Idaho Contribution Museum of Vertebrate Zoology Berkeley CA Caldwell ID The Caxton Printers Ltd a b Laundre John W 1989 Horizontal and vertical diameter of burrows of five small mammal species in southeastern Idaho The Great Basin Naturalist 49 4 646 64 a b c d e f Smith Graham W Johnson Donald R 1985 Demography of a Townsend ground squirrel population in southwestern Idaho Ecology 66 1 171 178 doi 10 2307 1941317 JSTOR 1941317 a b c d e Alcorn J R 1940 Life history notes on the Piute ground squirrel Journal of Mammalogy 21 2 160 170 doi 10 2307 1374972 JSTOR 1374972 a b c Rickart Eric A 1982 Annual cycles of activity and body composition in Spermophilus townsendii mollis Canadian Journal of Zoology 60 12 3298 3306 doi 10 1139 z82 418 a b Rickart Eric Allan 1982 The ecology of Townsend s ground squirrel Spermophilus townsendii mollis Salt Lake City UT University of Utah Dissertation Clary Warren P Medin Dean E 1992 Vegetation breeding bird and small mammal biomass in two high elevation sagebrush riparian habitats In Clary Warren P McArthur E Durant Bedunah Don Wambolt Carl L compilers Proceedings symposium on ecology and management of riparian shrub communities 1991 May 29 31 Sun Valley ID Gen Tech Rep INT 289 Ogden UT U S Department of Agriculture Forest Service Intermountain Research Station pp 100 110 a b Johnson Mark K 1977 Food of Townsend ground squirrels on the Arid Land Ecology Reserve Washington The Great Basin Naturalist 37 128 Groves Craig R Steenhof Karen 1988 Responses of small mammals and vegetation to wildfire in shadscale communities of southwestern Idaho Northwest Science 62 5 205 210 hdl 2376 1712 Koehler David K Anderson Stanley H 1991 Habitat use and food selection of small mammals near a sagebrush crested wheatgrass interface in southeastern Idaho The Great Basin Naturalist 51 3 249 255 Callahan J R 1993 Squirrels as predators The Great Basin Naturalist 53 2 137 144 Ogden Verland T Hornocker Maurice G 1977 Nesting density and success of prairie falcons in southwestern Idaho Journal of Wildlife Management 41 1 1 11 doi 10 2307 3800084 JSTOR 3800084 Janes Stewart W 1985 Habitat selection in raptorial birds In Cody Martin L ed Habitat selection in birds Academic Press Inc pp 159 188 ISBN 0 12 178081 3 Retrieved from https en wikipedia org w index php title Townsend 27s ground squirrel amp oldid 1181873716, wikipedia, wiki, book, books, library,

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