Spermophilus beecheyiCalifornia ground squirrel

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.