Spermophilus beecheyi

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.

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Mammal Species of the World

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: South-central Washington south through California and extreme west-central Nevada to Baja California, Mexico.

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.

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 )

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

Length: 50 cm

Weight: 738 grams

Sexual Dimorphism: Males are slightly larger than females.

Length:
Range: 357-500 mm

Weight:
Range: 250-885 g

Comments: Found in a wide variety of habitats. Usually in open areas in many plant communities in all life zones up to the Hudsonian. Sleeps and rears young in underground burrow. Digs deep burrow usually under protective object (log, rock, building, bush) if available, or in open.

Habitat and Ecology

Systems

• Terrestrial

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

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.

Comments: Omnivorous. During spring and summer, feeds primarily on green vegetation: leaves, flowers, bulbs, roots, etc. In late summer and fall, may eat more seeds, berries, and nuts. Also eats insects and occasional small vertebrates, including young conspecifics (done mainly by breeding adult females).

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.

Animal Foods: eggs; insects

Plant Foods: roots and tubers; seeds, grains, and nuts; fruit

Foraging Behavior: stores or caches food

Primary Diet: herbivore (Granivore ); omnivore

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.

Ecosystem Impact: disperses seeds; creates habitat; soil aeration

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

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.

Spermophilus beecheyi preys on:
Insecta

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

Usually in loose colonies. About 1/3 to 3/4 of a population consists of yearlings (see Boellstorff and Owings 1995). May carry fleas that transmit sylvatic plague. Predators include dogs, coyotes, and large hawks. Home range usually is less than 50 m across (Burt and Grossenheider 1964). In west-central California, mean home range size was 300-400 sq m in males, 600-900 sq m in females; home ranges overlapped (Boellstorff and Owings 1995).

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 ; acoustic

Comments: May hibernate in some areas; winter inactivity is more pronounced at higher latitudes and elevations (Dobson and Davis 1986). Active throughout the day during warmer months and in good weather.

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.

Breeding occurs soon after hibernation. Gestation lasts 25-30 days. Litter size averages about 6-7. In the lowlands, females usually produce one litter per year. The young are born hairless and their eyes are closed; they remain underground for about 8 weeks. In central Calfornia, young began to emerge from burrows in late April or early May (Boellstorff and Owings 1995).

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); 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)

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 6
Species With Barcodes: 1

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern

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

Population

Population Trend

Major Threats

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

Conservation Actions

Comments: May be locally destructive to nut, fruit, and cereal crops.

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.

Negative Impacts: injures humans (carries human disease); crop pest; causes or carries domestic animal disease