California ground squirrel

California ground squirrel
California ground squirrel
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Otospermophilus
Species: O. beecheyi
Binomial name
Otospermophilus beecheyi
(Richardson, 1829)
Synonyms

Spermophilus beecheyi
Citellus beecheyi

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.[2]

Contents

Description

California ground squirrel at Point Lobos

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.[3]

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.[3]

In the colder parts of their range, California ground squirrels hibernate for several months, but where winters are mild some squirrels are active year round. In those parts where the summers are hot they may also estivate for periods of a few days.[4]

California ground squirrels are often regarded as a pest in gardens and parks, since they will feed off ornamental plants and trees.

Predators

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.[5] 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.[6]

Another strategy is for a squirrel to super-heat and swish around its tail.[7] 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.

Name

John Richardson, who originally described the species, named Otospermophilus beecheyi after Frederick William Beechey, an early 19th century British explorer and naval officer.[8]

References

  1. ^ 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. Downloaded on 8 January 2009.
  2. ^ 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. http://www.webcitation.org/62dP5i1JK. 
  3. ^ a b Animal Diversity Web
  4. ^ Linsdale, J. 1946. The California ground squirrel. Berkeley and Los Angeles: University of California press.
  5. ^ Squirrels Use Old Snake Skins To Mask Their Scent From Predators
  6. ^ California squirrels yank rattlesnakes' tails
  7. ^ "Squirrel Has Hot Tail to Tell Snakes". Scientific American. http://www.sciam.com/article.cfm?chanID=sa003&articleID=611BD788-E7F2-99DF-3997E1F762684A26&ref=rss. Retrieved 2007-09-29. 
  8. ^ Fauna Boreali-Americana or the Zoology or the Northern Parts of British American, page 170. http://books.google.com/books?id=NzxkAAAAMAAJ&printsec=frontcover&dq=Fauna+boreali-americana%3B+or+the+zoology+of+the+northern+parts+of+British+America#PPA170,M1. Retrieved 2009-01-11. 

External links


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