California ground squirrel | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Rodentia |
Family: | Sciuridae |
Genus: | Otospermophilus |
Species: | O. beecheyi |
Binomial name | |
Otospermophilus beecheyi (Richardson, 1829) [2] | |
Synonyms | |
Arctomys (Spermophilus) beecheyiRichardson, 1829 [3] Contents |
The California ground squirrel (Otospermophilus beecheyi), also known as the Beechey ground squirrel, [4] 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. [5] A full species account was published for this species in 2016. [6]
John Richardson, who originally described the species as Arctomys (Spermophilus) beecheyi, or "Beechey's marmot", named it after Frederick William Beechey, an early 19th-century British explorer and naval officer. [3]
The squirrel's upper parts are mottled, with the fur containing a mixture of gray, light brown and dusky hairs. The shoulders, neck and sides are a lighter gray. The fur around the eyes is whitish. The underside is lighter, buff or grayish yellow. Head and body are about 30 cm (12 in) long and the tail an additional 15 centimetres (5.9 in). They can weigh from 280 to 738 g (9.9 to 26.0 oz). [7] The tail is relatively bushy for a ground squirrel, and at a quick glance, the squirrel might be mistaken for a fox squirrel. [8]
As is typical for ground squirrels, California ground squirrels live in burrows, which they excavate themselves. Some burrows are occupied communally, but each squirrel has its own entrance. [8] [ dubious – discuss ] 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 (80 ft) of their burrows, and rarely go further than 50 m (160 ft) from it. [8]
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. [9]
California ground squirrels are often regarded as pests in gardens and parks, since they eat ornamental plants and trees. They commonly feed on seeds, such as oats, but also eat insects such as crickets and grasshoppers, as well as various fruits. [10] The dental formula of O. beecheyi is 1.0.2.31.0.1.3 × 2 = 22. [11]
California ground squirrels' mating season is early spring and tends to last only for a few weeks. The females are considered to be promiscuous, so the individuals of one litter can be from multiple mates. The California ground squirrel has one litter of five to eleven per year, with gestation around one month. The young open their eyes at about five weeks and reach sexual maturity around one year old.
The coloration of the young is slightly lighter than the adults, and molting occurs at about eight weeks of age – when the young leave the burrows. [12] California ground squirrels can live up to six years. [7]
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California ground squirrels use their cheek pouches to store more food than can be consumed in one sitting to store it for a later date. They are considered to be mostly herbivorous, with seeds, grains, nuts, fruits, and sometimes roots constituting most of their diet. [12]
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 have varying levels of resistance to rattlesnake venom as adults. Female squirrels with pups also chew on the skins shed by rattlesnakes and then lick themselves and their pups (that are never resistant to venom before one month of age) to disguise their scent. [13] 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. [14]
Another strategy is for a squirrel to super-heat and swish around its tail. [15] When hunting, rattlesnakes primarily rely on their pit organ, which detects infrared 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.
The swishing of the tail from side to side is called tail-waving, which helps the squirrel to deter a snake attack. The snakes attacked the squirrels that exhibited the tail-waving at a shorter distance than those that did not and majority of those tail-waving squirrels successfully dodged these attacks. This successful dodging, along with the fact that the adult squirrels are larger than the young ones, helps to deter the predators, as the rattlesnakes are 1.6 times more likely to be deterred from attacking an area after an encounter with an adult squirrel. In 30 out of 45 interactions with snakes, the tail-waving behavior of the squirrels stopped the snake in its tracks and the snake attempted to wait for the squirrel to leave before it would consider attacking again, showing that the behavior does deter predatory attacks by the rattlesnakes. [16] This is due to the adult squirrels being vigilant and looking more threatening and also that they are able to more successfully dodge attacks. They also can use their tail-waving to signal to other ground squirrels in the area that a rattlesnake or other predator has recently been spotted. Though the ground squirrels have been found to also exhibit this tail-waving behavior when no predator is present, they wave their tails faster and for a longer time when they spot a predator or in an area where a predator has recently been spotted. [17]
Vigilant behavior in squirrels is also a defense mechanism to avoid predation. In addition to the tail-waving, the squirrels have been found to be more vigilant and on alert if a predator had recently been in the area than they were if no predator had been detected. [17] If the ground squirrels are aware that they are in an area where the rattlesnakes have recently been, they devote more time to being alert and searching for the predators than to hunting and foraging than in an environment where they do not believe predators exist. [10] These vigilant squirrels were found to have a faster reaction time to a stimulus from a predator and jump higher and further away than a squirrel that was not as vigilant. In a simulated environment study, 60% of squirrels that were in an environment with a recent snake encounter exhibited an evasive leap behavior, which propels them farther away from their attackers; 20% of squirrels exhibited this behavior in a primary encounter with a snake and roughly 5% of squirrels exhibited this behavior when no snake was present and no threat was detected. This shows that the squirrels are more alert, vigilant, and ready for an attacker after one has been recently seen. [17]
Ground squirrels are rodents of the squirrel family (Sciuridae) that generally live on the ground or in burrows, rather than in trees like the tree squirrels. 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 bushy-tailed ground squirrels tend to be known as chipmunks.
Franklin's ground squirrel is a species of squirrel native to North America, and the only member of the genus Poliocitellus. Due to the destruction of prairie, the populations of Franklin's ground squirrel have dwindled, approaching levels of concern. Its decline in the eastern portion of its range is mostly attributed to habitat fragmentation.
Richardson's ground squirrel, also known as the dakrat or flickertail, is a North American ground squirrel in the genus Urocitellus. Like a number of other ground squirrels, they are sometimes called prairie dogs or gophers, though the latter name belongs more strictly to the pocket gophers of family Geomyidae, and the former to members of the genus Cynomys.
The Arctic ground squirrel is a species of ground squirrel native to the Arctic and Subarctic of North America and Asia. People in Alaska, particularly around the Aleutians, refer to them as "parka" squirrels, most likely because their pelt is good for the ruff on parkas and for clothing.
Belding's ground squirrel, also called pot gut, sage rat or picket-pin, is a squirrel that lives on mountains in the western United States. In California, it often is found at 6,500 to 11,800 feet (2,000–3,600 m) in meadows between Lake Tahoe and Kings Canyon. This species is not of conservation concern, and its range includes some protected areas.
The thirteen-lined ground squirrel, also known as the striped gopher, leopard ground squirrel, and squinny, is a ground squirrel that is widely distributed over grasslands and prairies of North America.
The Cape ground squirrel or South African ground squirrel is found in most of the drier parts of southern Africa from South Africa, through to Botswana, and into Namibia, including Etosha National Park.
The round-tailed ground squirrel, known as "Ardillón cola redonda" in Spanish, live in the desert of the Southwestern United States and Northwestern Mexico. They are called "ground squirrels" because they burrow in loose soil, often under mesquite trees and creosote bushes.
The tropical ground squirrel is a species of rodent in the family Sciuridae. At one time the species was originally described as Spermophilus adocetus, but the genus Spermophilus was revised and subdivided in 2009 and it was placed in the genus Notocitellus. It is endemic to arid upland areas and deciduous woodland in Mexico. It is locally referred to as Cuinique.
The ring-tailed ground squirrel is a species of rodent in the family Sciuridae. It is endemic to the Pacific coast region of central Mexico. It is a common species and feeds mainly on fruits and nuts. The IUCN has assessed it as being of "least concern".
The Baja California rock squirrel is a species of rodent in the family Sciuridae. It is endemic to Baja California, Mexico.
The Columbian ground squirrel is a species of rodent common in certain regions of Canada and the northwestern United States. It is the second largest member of the genus Urocitellus, which is part of the tribe Marmotini, along with marmots, chipmunks, prairie dogs, and other holarctic ground squirrels. They are stout, with short dense fur, which is characteristically tawny across the bridge of the nose. Social encounters sometimes are initiated with kissing behavior and the most common activity above ground is standing at attention. Residing in mountainous terrain and high plains in northern latitudes, they hibernate for 8 to 9 months of the year in burrows, which may be used for many years. They are emaciated when emerging in the spring. The Columbian ground squirrel came to the attention of the scientific community through writings produced by Lewis and Clark, while 21st century molecular genetics has more finely illuminated its ties with other close relatives.
The Mexican ground squirrel is a species of rodent in the family Sciuridae. It is found in Mexico and the United States. One of its closest relatives is the thirteen-lined ground squirrel.
The speckled ground squirrel or spotted souslik is a species of rodent in the family Sciuridae from Eastern Europe. Spermophilus suslicus consists of three subspecies: S. s. boristhenicus, S. s. guttatus, and S. s. suslicus. It is threatened by habitat loss.
The rock squirrel is a species of rodent in the family Sciuridae. It is native to Mexico and the Southwestern United States, including southern Nevada, Utah, Colorado, Arizona, New Mexico, West Texas, and the panhandle of Oklahoma.
Otospermophilus is a genus of ground squirrels in the family Sciuridae, containing three species from Mexico and the United States. Otospermophilus was formerly placed in the large ground squirrel genus Spermophilus, as a subgenus or species group. Since DNA sequencing of the cytochrome b gene has shown Spermophilus to be paraphyletic to the prairie dogs and marmots, it is now separated, along with six other genera.
Pygmy ground squirrels are small ground squirrels in the genus Xerospermophilus, family Sciuridae, containing four species from Mexico and the United States. The members of this genus were formerly placed in the large ground squirrel genus Spermophilus. Since DNA sequencing of the cytochrome b gene showed that Spermophilus was paraphyletic to the prairie dogs and marmots, this group is now separated, along with six other genera. Within the genus, the Mohave ground squirrel and the round-tailed ground squirrel were thought to be close relatives, sometimes a subgenus Xerospermophilus, while the spotted ground squirrel and the Perote ground squirrel were formerly placed in the subgenus Ictidomys.
Robosquirrel refers to several versions of robotic squirrels developed by researchers at the University of California, Davis and San Diego State University. Robosquirrel is currently in use and development in an interdisciplinary research project that uses biorobotics to investigate how communication between prey and predators evolve in response to each other. It has received extensive science and popular media coverage. It stirred controversy when Senator Tom Coburn listed it in his Wastebook 2012 as a scientific research project that wastes United States federal tax dollars. Senator Coburn's release of Wastebook 2012 was quickly picked up by the popular media and the robosquirrel project was the headline of many media stories.
Donald H. Owings was a professor of psychology and faculty member of the Animal Behavior Graduate Group at the University of California, Davis. His research focused on ground squirrels, in particular, their interactions with predators such as rattlesnakes; and, more generally, on concepts of communication within and between species. In 1994, he was elected as a fellow of the animal behavior society and in 2010 he received the Exemplar Award for mentoring graduate students.
Tail vibration is a common behavior in some snakes where the tail is vibrated rapidly as a defensive response to a potential predator. Tail vibration is distinct from caudal luring, where the tail is twitched in order to attract prey. While rattlesnakes are perhaps the most famous group of snakes to exhibit tail vibration behavior, many other snake groups—particularly those in the Colubridae and Viperidae families—are known to vibrate their tails.