California Ground Squirrel
Encyclopedia
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.
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 (11.8 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 burrow
s 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 (164 ft) from it.
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.
California ground squirrels are often regarded as a pest
in gardens and parks, since they will feed off ornamental plants and trees.
s. 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.
, who originally described the species, named Otospermophilus beecheyi after Frederick William Beechey
, an early 19th century British explorer and naval officer.
Ground squirrel
The ground squirrels are members of the squirrel family of rodents which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots or prairie dogs, while the smaller and less...
of the western United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and the Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
; it is common in Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
and California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and its range has relatively recently extended into Washington and northwestern Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
. Formerly placed in Spermophilus
Spermophilus
Spermophilus is a genus of ground squirrels in the family Sciuridae. The majority of ground squirrel species, over 40 in total, are usually placed in this genus...
, as Spermophilus beecheyi, it was reclassified in Otospermophilus
Otospermophilus
Otospermophilus is a genus of ground squirrels in the family Sciuridae, containing three species. Otospermophilus was formerly placed in the large ground squirrel genus Spermophilus, as a subgenus or species group...
in 2009 as it became clear that Spermophilus as previously defined was not a natural (monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
) group.
Description
The squirrel's upper parts are mottled, the furFur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
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 (11.8 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
Fox Squirrel
The fox squirrel is the largest species of tree squirrel native to North America...
.
As is typical for ground squirrels, California ground squirrels live in burrow
Burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s 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 (164 ft) from it.
In the colder parts of their range, California ground squirrels hibernate
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
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
Estivation
Aestivation is a state of animal dormancy, characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions...
for periods of a few days.
California ground squirrels are often regarded as a pest
Pest (animal)
A pest is an animal which is detrimental to humans or human concerns. It is a loosely defined term, often overlapping with the related terms vermin, weeds, parasites and pathogens...
in gardens and parks, since they will feed off ornamental plants and trees.
Predators
California ground squirrels are frequently preyed on by rattlesnakeRattlesnake
Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...
s. They are also preyed on by eagles, raccoons, foxes, badgers, and weasels. Interdisciplinary research at the University of California, Davis
University of California, Davis
The University of California, Davis is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over , the campus is the largest within the University of California system and third largest by enrollment...
, 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
Snake venom
Snake venom is highly modified saliva that is produced by special glands of certain species of snakes. The glands which secrete the zootoxin are a modification of the parotid salivary gland of other vertebrates, and are usually situated on each side of the head below and behind the eye,...
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
Projectile use by living systems
Although projectiles are commonly used in human conflict, projectile use by living systems other than humans is relatively rare.-Liquid projectiles:...
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.
Name
John RichardsonJohn Richardson (naturalist)
Sir John Richardson was a Scottish naval surgeon, naturalist and arctic explorer.Richardson was born at Dumfries. He studied medicine at Edinburgh University, and became a surgeon in the navy in 1807. He traveled with John Franklin in search of the Northwest Passage on the Coppermine Expedition of...
, who originally described the species, named Otospermophilus beecheyi after Frederick William Beechey
Frederick William Beechey
Frederick William Beechey was an English naval officer and geographer. He was the son of Sir William Beechey, RA., and was born in London.-Career:...
, an early 19th century British explorer and naval officer.
External links
- Etc. California ground squirrel page
- 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