California ground squirrel
|California ground squirrel|
The California ground squirrel (Otospermophilus beecheyi), is a common and easily observed ground squirrel of the western United States and the Baja California peninsula; it is common in Oregon and California and its range has relatively recently extended into Washington and northwestern Nevada. Formerly placed in Spermophilus, as Spermophilus beecheyi, it was reclassified in Otospermophilus in 2009 as it became clear that Spermophilus as previously defined was not a natural (monophyletic) group.
The squirrel's upper parts are mottled, the fur containing a mixture of gray, light brown and dusky hairs; the underside is lighter, buff or grayish yellow. The fur around the eyes is whitish, while that around the ears is black. Head and body are about 30 cm (12 in) long and the tail an additional 15 cm (5.9 in). The tail is relatively bushy for a ground squirrel, and at a quick glance the squirrel might be mistaken for a fox squirrel.
As is typical for ground squirrels, California ground squirrels live in burrows which they excavate themselves. Some burrows are occupied communally but each individual squirrel has its own entrance. Although they readily become tame in areas used by humans, and quickly learn to take food left or offered by picnickers, they spend most of their time within 25 m (82 ft) of their burrow, and rarely go further than 50 m (160 ft) from it.
In the colder parts of their range, California ground squirrels hibernate for several months, but in areas where winters have no snow, most squirrels are active year round. In those parts where the summers are hot they may also estivate for periods of a few days.
California ground squirrels are often regarded as a pest in gardens and parks, since they will feed off ornamental plants and trees.
California ground squirrels are frequently preyed on by rattlesnakes. They are also preyed on by eagles, raccoons, foxes, badgers, and weasels. Interdisciplinary research at the University of California, Davis, since the 1970s has shown that the squirrels use a variety of techniques to reduce rattlesnake predation. Some populations of California ground squirrels have varying levels of immunity to rattlesnake venom as adults. Female squirrels with pups also chew on the skins shed by rattlesnakes and then lick themselves and their pups (who are never immune to venom before one month of age) to disguise their scent. Sand-kicking and other forms of harassment provoke the snake to rattle its tail, which allows a squirrel to assess the size and activity level (dependent on blood temperature) of the snake.
Another strategy is for a squirrel to super-heat and swish around its tail. When hunting, rattlesnakes primarily rely on their pit organ, which detects infra-red radiation. The hot-tail-swishing appears to convey the message "I am not a threat, but I am too big and swift-moving for it to be worth trying to hunt me." These two confrontational techniques also distract the snake from any nearby squirrel burrows containing pups.
- Linzey, A. V., Timm, R., Álvarez-Castañeda, S. T., Castro-Arellano, I. & Lacher, T. (2008). Spermophilus beecheyi. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 8 January 2009.
- Helgen, Kristofer M.; Cole, F. Russel; Helgen, Lauren E.; and Wilson, Don E (2009). "Generic revision in the Holarctic ground squirrel genus Spermophilus". Journal of Mammalogy 90 (2): 270–305. doi:10.1644/07-MAMM-A-309.1. Archived from the original on 22 October 2011.
- Animal Diversity Web
- Linsdale, J. 1946. The California ground squirrel. Berkeley and Los Angeles: University of California press.
- Squirrels Use Old Snake Skins To Mask Their Scent From Predators
- California squirrels yank rattlesnakes' tails
- "Squirrel Has Hot Tail to Tell Snakes". Scientific American. Retrieved 2007-09-29.
- Fauna Boreali-Americana or the Zoology or the Northern Parts of British American, page 170. Retrieved 2009-01-11.
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|Wikispecies has information related to: California ground squirrel|
- Measures for controlling California ground squirrels
- Squirrels disguise their scent by chewing on rattlesnake skin
- The Best of Enemies (Rattlesnakes and California ground squirrels)
- Prof. Donald Owings photographs of California ground squirrels under study at UC Davis
- Smithsonian article on California ground squirrel
- Original Description of the Species