California Ground Squirrel

Otospermophilus beecheyi

Summary 3

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.

Description 4

California Ground Squirrels prefer open, well-drained habitat, and are common along roadsides, on farms, especially where grain is grown, and in grassy fields. Adult squirrels are active only a few months of the year. Males usually retreat underground in early summer and remain there until the following spring. Females follow as soon as they finish nursing their young, usually in late summer or early fall. The aboveground fall and winter populations are composed almost entirely of young squirrels. Litter size correlates with climate: where average temperatures are warmer, litters are larger. In the warmest part of their range, in southern California, they average 8.4 young, whereas in the cooler parts of central Oregon, an average of 5.5 young is born. Predation pressure and time spent aboveground may influence litter size. The longer warm season in southern California allows the squirrels to spend a greater number of days awake and foraging, which likely increases the risk of being killed by a predator.

Links:
Mammal Species of the World

Morphology 5

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.

Range mass: 280 to 738 g.

Range length: 330 to 508 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Distribution 6

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.

Biogeographic Regions: nearctic (Native )

Range description 7

This species occurs in the western United States and adjoining north-western Mexico, from extreme south-central Washington and western Oregon, south-ward throughout most of California, and into north-western Baja California.

Habitat 8

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.

Range elevation: 0 to 2200 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: chaparral ; mountains

Other Habitat Features: urban ; suburban ; agricultural

Migration 9

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Life expectancy 10

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.

Range lifespan
Status: wild:
6 (high) years.

Range lifespan
Status: captivity:
10 (high) years.

Known predators 11

Spermophilus beecheyi is prey of:
Crotalus
Mustela
Buteo jamaicensis
Aquila chrysaetos
Taxidea taxus
Felis silvestris
Canis latrans
Canis lupus familiaris

This list may not be complete but is based on published studies.

Known prey organisms 12

Spermophilus beecheyi preys on:
Insecta

This list may not be complete but is based on published studies.

Management 13

Management Requirements: Control measures may be short-lived; recolonizes former colonies rapidly (within a few months) if adjacent colony is present.

Population 14

Population

In California and northern Baja California, this species is widespread and locally abundant in most habitats where found, including agricultural areas. In the central desert of Baja California and California it is rare.

Population Trend
Stable

Reproduction 15

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.

Mating System: polygynandrous (promiscuous)

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.

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.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

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.

Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

Size 16

Length: 50 cm

Weight: 738 grams

Size in north america 17

Sexual Dimorphism: Males are slightly larger than females.

Length:
Range: 357-500 mm

Weight:
Range: 250-885 g

Taxonomy 18

Comments: Recent molecular phylogenetic studies suggest that the traditionally recognized genera Marmota (marmots), Cynomys (prairie dogs), and Ammospermophilus (antelope ground squirrels) render Spermophilus paraphyletic, potentially suggesting that multiple generic-level lineages should be credited within Spermophilus (Helgen et al. 2009). As a result, ground squirrels formerly allocated to the genus Spermophilus (sensu Thorington and Hoffman, in Wilson and Reeder 2005) are now classified in 8 genera (Notocitellus, Otospermophilus, Callospermophilus, Ictidomys, Poliocitellus, Xerospermophilus, and Urocitellus). Spermophilus sensu stricto is restricted to Eurasia.

Associations 19

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.

Known Predators:

  • American badgers (Taxidea taxus)
  • weasels (Mustela)
  • rattlesnakes (Crotalus)
  • red-tailed hawks (Buteo jamaicensis)
  • golden eagles (Aquila chrysaetos)
  • coyotes (Canis latrans)
  • domestic dogs (Canis lupus familiaris)
  • domestic cats (Felis silvestris)
  • bobcats (Lynx rufus)
  • mountain lions (Puma concolor)
  • rattlesnakes (Crotalus)

Anti-predator Adaptations: cryptic

Behaviour 20

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.

Communication Channels: visual ; acoustic ; chemical

Perception Channels: visual ; tactile ; acoustic ; chemical

Central and southern cascades forests habitat 21

The Oregon slender salamander is endemic to the Central and Southern Cascades forests ecoregion. The Central and Southern Cascades forests span several physiographic provinces in Washington and Oregon, including the southern Cascades, the Western Cascades, and the High Cascades, all within the USA. This ecoregion extends from Snoqualmie Pass in Washington to slightly north of the California border. The region is characterized by accordant ridge crests separated by steep, deeply dissected valleys, strongly influenced by historic and recent volcanic events (e.g. Mount Saint Helens).

This ecoregion contains one of the highest levels of endemic amphibians (five of eleven ecoregion endemics are amphibians) of any ecoregion within its major habitat type. The threatened Northern spotted owl has been used as an indicator species in environmental impact assessments, since its range overlaps with 39 listed or proposed species (ten of which are late-seral associates) and 1116 total species associated with late-seral forests. Late-seral forests in general are of national and global importance because they provide some of the last refugia for dependent species, and perform vital ecological services, including sequestration of carbon, cleansing of atmospheric pollutants, and maintenance of hydrological regimes.

There are a number ofl amphibian taxa present in the Central and Southern Cascades ecoregion; the totality of these amphibian taxa are: the Rough-skinned newt (Taricha granulosa); the endemic and Vulnerable Shasta salamander (Hydromantes shastae);  the endemic and Vulnerable Oregon slender salamander (Batrachoseps wrighti); the Endangered Dunn's salamander (Bolitoglossa dunni); the Northwestern salamander (Ambystoma gracile); the Near Threatened western toad (Anaxyrus boreas); the Vulnerable Oregon spotted frog (Rana pretiosa); the Near Threatened Cascades frog (Rana cascadae); Coastal tailed frog (Ascaphus truei); Near Threatened Larch Mountain salamander (Plethodon larselli); California newt (Taricha torosa); Pacific giant salamander (Dicamptodon ensatus); Cope's giant salamander (Dicamptodon copei); Monterey ensatina (Ensatina eschscholtzii); the Near Threatened Foothill yellow-legged frog (Rana boylii); Northern Red-legged frog (Rana aurora); Pacific chorus frog (Pseudacris regilla); Van Dyke's salamander (Plethodon vandykei), an endemic of the State of Washington, USA; Long-toed salamander (Ambystoma macrodactylum); and the Olympic torrent salamander (Rhyacotriton olympicus).

There are a moderate number of reptilian species present in the ecoregion, namely in total they are: Western pond turtle (Emys marmorata); Western fence lizard (Sceloporus occidentalis); Sharp-tailed snake (Contia tenuis); Ringed-neck snake (Diadophis punctatus); Rubber boa (Charina bottae); California mountain kingsnake (Lampropeltis zonata); Yellow-bellied racer (Coluber constrictor); Western rattlesnake (Crotalus viridis); Western gopher snake (Pituophis catenifer); Common garter snake (Thanophis sirtalis); Northwestern garter snake (Thamnophis ordinoides); Western skink (Megascops kennicottii); Southern alligator lizard (Elgaria multicarinata); and the  Northern alligator lizard (Elgaria coerulea).

There is a considerable number of avifauna within the Central and Southern Cascades ecoregion; representative species being: Flammulated owl (Otus flammeolus); Western screech owl (Megascops kennicottii); White-tailed ptarmigan (Picoides albolarvatus); and White-headed woodpecker (Picoides albolarvatus).

There are a large number of mammalian taxa in the ecoregion, including: Bobcat (Lynx rufus); Wolverine (Gulo gulo); California ground squirrel (Spermophilus beecheyi); Yellow-bellied marmot (Marmota flaviventris); Ermine (Mustela erminea); Fog shrew (Sorex sonomae), an endemic mammal to the far western USA; Hoary marmot (Marmota caligata); Mountain beaver (Aplodontia rufa); and the Near Threatened red tree vole (Arborimus longicaudus); Yellow pine chipmunk (Tamias amoenus); and the American water shrew (Sorex palustris).

Conservation status 22

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.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Sources and Credits

  1. (c) Kim A. Cabrera, all rights reserved, uploaded by Kim Cabrera, www.bear-tracker.com
  2. (c) Howard Cheng, some rights reserved (CC BY-SA), http://www.flickr.com/photos/93183689@N00/3171348519
  3. Adapted by Kim Cabrera from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Otospermophilus_beecheyi
  4. (c) Smithsonian Institution, some rights reserved (CC BY), http://eol.org/data_objects/6625660
  5. Adapted by Kim Cabrera from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423446
  6. Adapted by Kim Cabrera from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423444
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  8. Adapted by Kim Cabrera from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423445
  9. Adapted by Kim Cabrera from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28915867
  10. Adapted by Kim Cabrera from a work by (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423448
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  12. Adapted by Kim Cabrera from a work by (c) SPIRE project, some rights reserved (CC BY), http://eol.org/data_objects/10543448
  13. Adapted by Kim Cabrera from a work by (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28915864
  14. Adapted by Kim Cabrera from a work by (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31267946
  15. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423447
  16. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28915871
  17. (c) Smithsonian Institution, some rights reserved (CC BY), http://eol.org/data_objects/6625661
  18. (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28915855
  19. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423451
  20. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423449
  21. (c) C. Michael Hogan & World Wildlife Fund, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/32153781
  22. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31423454

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