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Urocitellus brunneus 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Rodentia Sciuridae

Scientific Name: Urocitellus brunneus
Species Authority: A.H. Howell, 1928
Common Name(s):
English Idaho Ground Squirrel
Synonym(s):
Spermophilus brunneus (A.H. Howell, 1928)
Taxonomic Source(s): Helgen, K.M., Cole, F.R.,Helgen, L.E. and Wilson, D.E. 2009. Generic revision in the Holarctic ground squirrel genus Spermophilus. Journal of Mammalogy 90(2): 270-305.
Taxonomic Notes: Northern and southern subspecies (Urocitellus brunneus brunneus and U. b. endemicus) are well differentiated morphologically, and may be approaching species-level differentiation, according to Yensen (1991). Electrophoretic analyses yielded equivocal results regarding the species versus subspecies status of the northern and southern groups of populations (Gill and Yensen 1992). Thorington and Hoffmann (in Wilson and Reeder 2005) did not recognize endemicus even as a subspecies. This species is now recognized under a new genus, Urocitellus (Helgen et al. 2009).

Assessment Information [top]

Red List Category & Criteria: Vulnerable B1ab(iii,iv,v)c(iii,iv) ver 3.1
Year Published: 2016
Date Assessed: 2016-07-11
Assessor(s): Yensen, E. & NatureServe
Reviewer(s): Amori, G.
Contributor(s): Hammerson, G.A., Cannings, S. & Jefferson, J.
Justification:
Listed as Vulnerable because its extent of occurrence is less than 20,000 km², its range is severely fragmented, and there is an ongoing decline in the extent and quality of its habitat, as well as the number of locations and subpopulations and number of mature individuals due to persecution and other human disturbances. This species is also subject to extreme fluctuations in the number of locations and subpopulations and number of mature individuals. Further examination of this species' range and population may merit it an Endangered listing.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to a five-county area of west-central Idaho in the United States (Yensen and Sherman 1997). The northern subspecies (brunneus) presently is known only from Valley and Adams counties at elevations of 1,150-1,550 m asl; most populations are small and often isolated by several kilometres (Yensen 1991). The southern subspecies (endemicus) has a patchy distribution at lower elevations (670-975 m asl) north of the Payette River in Gem, Payette, and Washington counties. The species is apparently extirpated in the area between the extant populations of the northern and southern subspecies (Yensen 1984, 1991; Yensen et al. 1991; Yensen and Sherman 1997). Even within subspecies, populations are disjunct.
Countries occurrence:
Native:
United States (Idaho)
Additional data:
Lower elevation limit (metres):670
Upper elevation limit (metres):1550
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The total adult population size appears to be at least several thousand individuals (Yensen 2001, USFWS 2002). This species is only found at approximately 18 populations, with the largest population consisting of less than 300 individuals (May et al. 1997).

Current overall trend is uncertain but may be relatively stable. With regards to the long term trend, a significant decline has occurred in area of occupancy, number of subpopulations, and population size (USFWS 2002, 2004).
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:YesPopulation severely fragmented:Yes
Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:Yes

Habitat and Ecology [top]

Habitat and Ecology:This species occurs in mountain meadows surrounded by forests of Ponderosa Pine and Douglas Fir. The Idaho Ground Squirrel is found in areas originally covered with sagebrush and native bunchgrasses, but the current vegetation consists of annual grasslands composed of introduced grasses.

Mating occurs soon after spring emergence; males guard sexually receptive females from other males; after mating, female excludes male from female burrow; gestation lasts about three weeks; litter size is 2-10 (average around 6-7); young are weaned in three weeks (Yensen 1991, Spahr et al. 1991).

This species may be limited by competition from Columbian ground squirrel (Spahr et al. 1991). Badgers and prairie falcons are the primary predators. This species feeds on green vegetation and seeds. Southern populations emerge in late January or early February and cease above-ground activity in late June or early July; northern populations are active above ground from late March or early April until late July or early August (Yensen 1991). Activity is constrained by time of snow melt and vegetation desiccation.
Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes

Threats [top]

Major Threat(s): The primary threat to this species is loss and fragmentation of meadow habitat due to forest regrowth. Poisoning and replacement of native grasses by tall introduced grasses have also had large negative impacts on the species. Other threats include grazing by domestic livestock, off-road vehicle use (may destroy burrows), competition with Columbian ground squirrels (which may exclude the Idaho ground squirrel from deeper soils that provide more favourable conditions for hibernation), and some recreational shooting (USFWS 2002). Recreational housing developments in the near future could present a major conservation challenge.

The decline of this species has resulted from shrub-steppe habitat conversion to agriculture, poisoning, and degradation of remaining rangeland habitat, mainly by the invasion of exotic annual grasses such as Cheatgrass (Bromus tectorum) and Medusahead (Taeniatherum caput-medusae) and the loss of shrubs. This has changed the species composition of vegetation (reducing squirrel diet quality and reliability) and has altered the fire regime throughout much of the range. Recreational shooting and poisoning of ground squirrels historically were common activities, but recent regulatory changes and educational efforts probably have reduced this threat (USFWS 2004). In most areas, this squirrel faces threats associated with small population size (USFWS 2004).

Conservation Actions [top]

Conservation Actions: Subspecies brunneus was listed as threatened on 5 April 2000 under the United States Endangered Species Act. Subspecies endemicus was listed as a Candidate for listing by USFWS (2001).

The USFWS announced a 12-month finding on a resubmitted petition to list subspecies endemicus under the ESA, and found the petition does warrant listing, but is precluded by other higher priority listing actions. It is still considered a candidate for listing (Federal Register, 27 December 2004).

Translocation and habitat improvement measures by the United States Forest Service have resulted in population increases of S. b. brunneus in the past five years.

At least a few occurrences are adequately protected. The following is needed: survey colonies for precise population numbers; protect occurrences from agricultural development; maintain natural habitat; research life history and reproductive biology.

Citation: Yensen, E. & NatureServe. 2016. Urocitellus brunneus. The IUCN Red List of Threatened Species 2016: e.T20473A22266145. . Downloaded on 10 December 2016.
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