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Spermophilus beecheyiCalifornia ground squirrel

By Marcie Lima

Geographic Range

Spermophilus beecheyi is found throughout most of California, most of Western Oregon and portions of Western Nevada. This species also occurs in portions of southwestern Washington, and Baja California. (MacClintock, 1970; Whitaker, Jr., 1980)

Habitat

Spermophilus beecheyi has successfully exploited many habitat types. California ground squirrels are terrestrial, and semifossorial, requiring habitats with some loose soil where they can excavate an appropriate burrow.

You may find them colonizing fields, pastures, grasslands and in open areas such as oak woodlands. The only habitat they do not use is deserts. You may find them down in valleys and up on rocky outcrops in the mountains, to an elevation of 2,200 m. They can be found in urban, suburban and agricultural areas. By and large this species is widely distributed within its range. (Evans and Holdenried, 1943; MacClintock, 1970; Whitaker, Jr., 1980)

  • Range elevation
    0 to 2200 m
    0.00 to 7217.85 ft

Physical Description

California ground squirrels have mottled fur, with gray, light and dark brown, and white present in their pelage. They typically have a darker mantle. The shoulders, neck and sides of this species are a lighter gray. The bushy tail is a combination of the colors that appear on the back. The underside is a lighter combination of light brown, gray and white. California ground squirrels have a white ring around each eye.

The body length can range from 330 to 508 mm and tail length from 127-229 mm. These animals range in weight from 280 to 738 g. The ears are > 10 mm and < 25.4 mm. The dental formula is 1/1 : 0/0 : 2/1 : 3/3 = 22. (Alden, et al., 1998; Ingles, 1947; Linsdale, 1946; MacClintock, 1970; Whitaker, Jr., 1980)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    280 to 738 g
    9.87 to 26.01 oz
  • Range length
    330 to 508 mm
    12.99 to 20.00 in

Reproduction

Females of this species are considered promiscuous. They will often mate with more than one male, either through force or selectivity, and therefore the offspring of a single litter may have multiple paternity. Males may also mate with several females. (Boellstorff, et al., 1994)

The mating season of S. beecheyi occurs in early spring, typically for a few weeks only. As with most ground-dwelling squirrels, breeding occurs just after the animals emerge from their winter burrows. This is highly dependent on the area and climate the squirrel inhabits, since the timing of hibernation varies geographically, with elevation, and with other ecological factors.

Males possess abdominal testes which drop into a temporary scrotum during the breeding season only.

Females produce one litter per year after of a gestation period of roughly one month. Litters range in size from five to eleven young. The sex ratio of young are about 1:1.

Young S. beecheyi may open their eyes at around 5 weeks of age. They first leave burrows at 5 to 8 weeks of age, and are wenaed between 6 and 8 weeks. The coloring of the young is somewhat lighter than that of adults. Molting for young begins a few weeks after they emerge from their burrows. Young may begin to burrow at 8 weeks of age. They reach sexual maturity no sooner than 1 year old. In the first year of life, some ground squirrels remain above ground and do not hibernate. (Cato, 2003; Evans and Holdenried, 1943; Whitaker, Jr., 1980)

  • Breeding season
    Breeding begins shortly after emergence from hibernation. Timing of the breeding seasons varies, depending upon when the animals end their hibernation.
  • Range number of offspring
    5 to 11
  • Average gestation period
    1 months
  • Range weaning age
    6 to 8 weeks
  • Range age at sexual or reproductive maturity (female)
    1 (low) years
  • Range age at sexual or reproductive maturity (male)
    1 (low) years

The only active parenting is provided by the mother. Females give birth to their pups in a burrow, and will move young into new burrows frequently to avoid predation. Young are helpless at birth, and their eyes do not open until they are about 5 weeks old. Shortly after their eyes open, the young pups leave the burrow and begin to explore their surroundings. (Alden, et al., 1998; Boellstorff, et al., 1994; Evans and Holdenried, 1943; Whitaker, Jr., 1980)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The lifespan of a California ground squirrel can be up to 6 years in the wild. They have lived as long as 10 years in captivity. (MacClintock, 1970)

  • Range lifespan
    Status: wild
    6 (high) years
  • Range lifespan
    Status: captivity
    10 (high) years

Behavior

California ground squirrels live in burrow systems that can house many generations, forming a sort of colony. Each individual has an entrance of their own. They tend to stay within 150 yards of their burrow system and retreat, usually only to their entrance of that burrow system. They frequently spend time sunning themselves. Depending on the climate, they may hibernate, or aestivate to escape undesirable temperatures. Males are more aggressive than females and sometimes appear territorial. (Alden, et al., 1998; Evans and Holdenried, 1943; Linsdale, 1946; MacClintock, 1970; Whitaker, Jr., 1980)

Communication and Perception

California ground squirrels use a variety of sounds, tail signals and scent production as means of communication. For example, glandular folds anterior to the tail region are used for individual identification. When finding a mate or mates, females may approach or males may approach, but scent cues are important in identifying reproductive condition. (Evans and Holdenried, 1943; Linsdale, 1946)

Food Habits

California ground squirrels use cheek pouches while they are foraging to collect more food than would otherwise be possible in one sitting. They are also known to cache or store food. They exploit a variety of food sources, which probably contributes to their success as a species.

The diet of these animals, as their genus name would suggest, is primarily seed-based. California ground squirrels consume seeds, barley, oats, and acorns (Quercus): valley oak, blue oak, coast oak). They also eat fruits, like gooseberries and pears, and quail (Callipepla) eggs. They include insects in their diets when they are available, and have been known to eat grasshoppers, crickets, beetles and caterpillars. They also eat roots, bulbs, and fungi, such as mushrooms. (Linsdale, 1946; MacClintock, 1970; Whitaker, Jr., 1980)

  • Animal Foods
  • eggs
  • insects
  • Plant Foods
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

These ground squirrels are highly vulnerable to predation due to their diurnal habits, open habitat, and the concentrations of conspecifics found in any particular colony. They are known to be preyed upon by red-tailed hawks, golden eagles, coyotes, foxes, badgers, weasels, house cats, dogs, and wild cats such as bobcats and pumas. In addition, large snakes may prey upon them.

Spermophilus beecheyi individuals probably avoid predation mainly through the use of burrow systems and vigilance. They are also cryptically colored. Also, they have skin glands on their back, just posterior to the shoulders, which secrete an odorous oil which could deter predators. (Alden, et al., 1998; Linsdale, 1946)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Due to their diet, California ground squirrels could play a role in regulating some insect populations. They may aid in seed dispersal when a cache is forgotten. they help to aerate the soil through their excavation of burrows, and create habitat for many other animals, such as other rodents and snakes, which occupy empty burrows. (Linsdale, 1946)

Economic Importance for Humans: Negative

This species may threaten agricultural crops, such as grain fields and orchards, through their foraging activities. They are potential carriers of diseases, such as tularemia, bubonic plague, and sylvatic plague. The two latter diseases are from fleas the squirrels carry. (Alden, et al., 1998; Boellstorff, et al., 1994; MacClintock, 1970)

Conservation Status

There are no special conservation practices currently for S. beecheyi. Some control of their numbers has been attempted, costing several hundred thousand dollars. These are generally targeted responses to crop damage or disease outbreaks. (Boellstorff, et al., 1994; MacClintock, 1970)

Other Comments

Spermophilus beecheyi was named for Frederick William Beechey, who spent time exploring Northern California from 1826-1828. This species used to be known as Otospermophilus beecheyi.

Contributors

Marcie Lima (author), Humboldt State University, Brian Arbogast (editor), Humboldt State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Alden, P., F. Heath, R. Keen, A. Leventer, W. Zomlefer. 1998. National Audubon society field guide to California. New York: Alfred A. Knopf.

Boellstorff, D., D. Owings, M. Penedo, M. Hersek. 1994. Reproductive behaviour and multiple paternity of California ground squirrels. Animal Behaviour, 47(5): 1057-1064.

Cato, F. 2003. "San Diego Natural history Museum Field Guide: Spermophilus beecheyi " (On-line). Accessed June 17, 2003 at http://www.sdnhm.org/fieldguide/mammals/sper-bee.html.

Evans, F., R. Holdenried. 1943. A population study of the Beechey ground squirrel in Central California. Journal of Mammalogy, 24(2): 231-260.

Ingles, L. 1947. Mammals of the Pacific States. Stanford, California: Stanford University Press.

Linsdale, J. 1946. The California ground squirrel. Berkeley and Los Angeles: University of California press.

MacClintock, D. 1970. Squirrels of North America. New York and Toronto: Van Nostrand Reinhold Company.

Whitaker, Jr., J. 1980. National Audubon society field guide to North American mammals. New York: Alfred A. Knopf.

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