Otospermophilus beecheyi (Richardson, 1829)
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publication ID |
https://doi.org/ 10.5281/zenodo.6840226 |
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DOI |
https://doi.org/10.5281/zenodo.6840672 |
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persistent identifier |
https://treatment.plazi.org/id/064D0660-FFAF-ED53-FA63-FCC4FD21F2AC |
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treatment provided by |
Diego |
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scientific name |
Otospermophilus beecheyi |
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218. View On
California Ground Squirrel
Otospermophilus beecheyi View in CoL
French: Spermophile de Californie / German: Kalifornien-Ziesel / Spanish: Ardilla terrestre de California
Other common names: Beechey's Ground Squirrel, Gray Digger
Taxonomy. Arctomys beecheyi Richardson, 1829 ,
“neighborhood of San Francisco
and Monterey, in California.”
Subspecies douglasii has been proposed as a unique species (0. douglasii) based on molecular genetic studies. Eight subspecies recognized.
Subspecies and Distribution.
O.b.beechey:Richardson,1829—WCCalifornia(USA).
O.b.douglasiiRichardson,1829—WashingtonandStoSanFranciscoBayinCalifornia(USA).
O.b.nesioticusElliot,1904—SantaCatalinaIandSantaBarbaraI,California(USA).
O.b.nudipesHuey,1931—N&CBajaCalifornia(Mexico).
O.b.parvulusA.H.Howell,1931—ArgusRange,California(USA).
O.b.rupinarumHuey,1931—vicinityofCatavina,BajaCalifornia(Mexico).
O. b. sierrae A. H. Howell, 1938 — Lake Tahoe between EC California and WC Nevada (USA).
Descriptive notes. Head-body mean 273-2 mm (males) and 254-3 mm (females), tail mean 181-7 mm (males) and 171 mm (females); weight mean 621-3 g (males) and 508-5 g (females). The California Ground Squirrel is medium to large in size, with grayish brown dorsum speckled with white spots, often with whitish collar on neck, shoulders, and sides. Venteris whitish, suffused with yellow to brown. Ears are prominent, and tail is bushy relative to most ground squirrels—so it is sometimes mistaken for tree squirrels. Eye rings are white and conspicuous. Males are larger than females; latitudinal gradient occurs in body size, with subspecies smaller in the south. Subspecies douglasii has shoulder patch of dark brown to black. Subspecies fisheri is pale, with more silver-gray on sides of neck and shoulders. Subspecies nesioticus is darker, with black top of head and ears. Subspecies nudipes has silvery white mantle. Subspecies rupinarum has gray dorsum, with many light spots and pale white venter. Subspecies sierra is less buffy, with gray sides of head and white venter. Subspecies parvulus is pale and diminutive. Chromosomal complement is 2n = 38 and FN = 72.
Habitat. [.ow-elevation grasslands and chaparral to meadows and open forest woodlands from sea level to more than 3000 m. The California Ground Squirrel can thrive in human-disturbed habitats such as roadsides, parks, modest-density human housing, successional forests, and agricultural lands of nearly all types. Following forestfires, densities of California Ground Squirrels increase in an apparent positive response to ground cover reduction.
Food and Feeding. The California Ground Squirrel is an herbivore that feeds on grasses, legumes, and forbs including their leaves, stems, flowers, and tubers; it frequently includes seeds and nuts of trees (especially Quercus, Fagaceae) during autumn preparation for hibernation. Seeds are a preferred food source, but their highly seasonal availability and low water content make them less efficient selections at times. It also occasionally eats mosses, lichens, and insects and scavenges animal matter. It is known to feed on agricultural crops, particularly cereal crops.
Breeding. The California Ground Squirrel inhabits burrows with a nest chamber in which young are born. Males typically emerge before females in spring. Individuals mate soon after female emergence. Males and females appear capable of mating multiple times during a breeding season in a promiscuous mating system. Gestation lasts 25-30 days, and litters have 3-11 young, varying with elevation and latitude. Infanticide is common in the California Ground Squirrel and, where systematically studied, appears to be performed almost exclusively by neighboring mothers, who frequently cannibalize victims. Young disperse from natal areas and are able to reproduce in their first year.
Activity patterns. The California Ground Squirrel is diurnal and hibernates for c.6 months, depending on elevation, in relatively simple burrow systems. It is active aboveground beginning in spring, usually late March for males and 2-4 weeks later for females. Immergence begins in September for males and October for females; young remain aboveground sometimes until November.
Movements, Home range and Social organization. The California Ground Squirrel lives in loosely structured colonies and is abundant throughout their distribution.
Densities are 8-92 ind/ha. Individuals do not appearto be territorial, and home ranges overlap considerably. Females (means 616-902 m®) typically maintain larger home ranges than males (means 270-375 m?), and home ranges do not change appreciably in size during and after the breeding season. California Ground Squirrels have evolved a fascinating suite of behavioral and physiological adaptations to defend against snakes, including venomous rattlesnakes. These behaviors are noted early in life and continue to be developed such that young individuals completely avoid snakes and adults actively seek, harass, and warn of snakes. They create distraction displays by tail flicking and increase amount of blood flow to the tail only for rattlesnakes, which hunt primarily by infrared thermal detection. Individuals are able to assess predation risk by tone and pace of rattling and deliberately provoke snakes to garner information. They induce rattling by kicking sand to assess specific risk factors such as probability of a strike, body temperature, and body size of a snake—all of which are correlated with rates of rattling. They also possess physiological ability to detoxify venom with specific blood proteins that greatly reduce risk of interaction. Alarm calls are high-pitched and vary based upon differences in levels of predation risk.
Status and Conservation. Classified as Least Concern on The IUCN Red List. Population trend of the California Ground Squirrelis stable. Major conservation challenges might be degradation of grasslands and fragmentation of habitats due to residential development and agricultural crops. It is often considered a significant agricultural pest, and it is hunted, trapped, and poisoned, or burrows are ploughed. It is able to persist in human-modified landscapes such as pastures, roadsides, mowed parks, and lawns. Populations appear to be healthy throughoutthe distribution, but southern and more isolated populations are not well studied.
Bibliography. Anthony (1928), Atwill et al. (2004), Biardi, Chien & Coss (2006), Biardi, Coss & Smith (2000), Blois et al. (2008), Boellstorff & Owings (1995), Coss & Biardi (1997), Hanson & Coss (2001a, 2001b), Helgen et al. (2009), Kosoy et al. (2003), Linzey, Timm, Alvarez-Castaneda, Castro-Arellano & Lacher (2008t), Marsh (1994), McGrann et al. (2014), Phuong et al. (2014), Putman et al. (2015), Rabin et al. (2006), Roberts et al. (2015), Schitoskey & Woodmansee (1978), Swaisgood, Owings & Rowe (1999), Swaisgood, Rowe & Owings (1999), Thorington et al. (2012), Van Vuren et al. (1997).
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