California Ground Squirrel
Otospermophius beecheyi
Named for Frederick William Beechey, who explored much of Northern California in 1826-28 as captain of his majesty’s ship Blossom, this squirrel is also sometimes called the Beechey Ground Squirrel.
Otospermophius in Greek means seed-loving squirrel with prominent ears.
Characteristics
Gray, light brown and dusky fur is mixed to give the California ground squirrel’s upperparts a mottled appearance. A band of slightly darker fur, flecked with light gray, extends from the head over the middle of the back. Gray fur forms a cape over the sides of the head and shoulders. This gray cape may have a protective function, breaking up the animal’s body outline and making it more difficult for a predator to spot. Light buff or gray yellow fur covers the undersides.
Whitish fur rings the eyes and perhaps protects the squirrel’s eyes from too intense sunlight. Black fur edges the outer rims of the ears. The tail, 5 to 7 inches long and more than half the length of the head and body, is covered with mixed yellowish gray and black hairs and is lighter on the underside. Generally, California ground squirrels measure between 16 and 19 inches total length.
Habitat
California ground squirrels live in burrows. Hillsides or low earth banks are preferred sites because the burrows can be excavated horizontally, although many burrows are dug down vertically several feet to assure protection. Burrows, which are about 4 to 5 inches in diameter, may vary in length from 5 feet to more than 35 feet and may be used by many generations of ground squirrels. Some burrows house single squirrel occupants, while others may be colonial homes for several squirrels. Short burrows may have a single opening, but longer branched burrows often have 2 or more openings. In studying California ground squirrels, one group of scientists found a squirrel home with 6 females and 5 males which consisted of tunnels totaling 741 feet in length and had 33 openings. The deepest tunnel was 28 feet below ground. Although most tunnel excavation work is done in the spring, digging and burrow improvement is a continuing process.
Entering a nest burrow, a squirrel would have found cool, moist passageways opening into nurseries, food storage rooms, and spacious sleeping chambers, as well as side tunnels that ran upward and ended just below the surface. If a predator came in the “front door,” the squirrel would have raced up one of these side tunnels and burst through a thin layer of soil to escape.
Generally, ground squirrels spend most of their life within a fairly small area. In fact, most of their time is spent within about 100 feet of their burrow and rarely does a ground squirrel go beyond a 150 yard radius of its burrow.
Diet
Nuts & Seeds: Acorns, Calif. black walnuts, grass seeds, seeds of elderberry, jimson weed, nightshade, tarweed, poison oak, mallow, poppies and more.
Fruits: Manzanita berries, coffeeberries, gooseberries, prickly pears and others.
They also like insects such as grasshoppers, beetles, crickets, caterpillars and others. They like the eggs from Calif. Quail, Calif. Towhees, spotted towhees and other ground nesting birds.
Finally they like fungi, roots, bulbs and carrion.
Behavior
The California ground squirrel is diurnal, which means it is most active in the daytime. It lives in colonies, but the squirrels tend not to socialize with each other. They often spend their time feeding, sunning, dust-bathing, and grooming. In one of their favorite sun bathing positions the squirrels lies with its belly on the ground, elbows on the ground with forearms extended and head raised. They also like to sit straight up, motionless, with their arms hanging down across their chest and their paws resting one upon the other. From this position they love to look about. In fact, their vision is thought to be about equivalent to a human’s.
California ground squirrels loosen and aerate soil and bring seeds to the surface, contributing to plant growth and diversity. They cache seeds that may germinate if they are never retrieved for eating. They provide “pre-dug” dens and nests or owls, foxes and coyotes. They also play host to uninvited lodgers, including salamanders, western toads and amphibians. Mice and voles go in and out of squirrel burrow to raid the pantries, and spiders and insects live in the tunnel walls.
California ground squirrels are ever vigilant and ready to sound an alarm if danger is perceived. If frightened, a squirrel often makes long leaps and emits a sharp, metallic alarm cry several times in rapid succession. The squirrel may pause near its burrow and clink at intervals, or it may drop down into its tunnel system.
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.
Breeding
The breeding season in southern California starts in December, later in colder climates, depending on when they emerge from hibernation, which may be as late as mid-spring. Mating chases are common, with males chasing females until she is ready to accept one. Females may mate with more than one male and often mate more than one time. After about a month long gestation period, a mother squirrel may give birth from 3 to as many as 11 babies, with from 5 to 6 being an average. Mothers care for the young, moving them frequently to avoid predation. The babies remain underground with the mother. Their eyes open at about 5 weeks, leave burrows at 5 to 8 weeks, are weaned at 6 to8 weeks. At first the youngsters will play and feed very near the burrow entrance under the mother’s close and attentive supervision. They begin to burrow as early as 8 weeks and reach sexual maturity at one year or more.
California ground squirrels may live as long as 6 years, but 3 to 4 years is probably their average life span in the wild.
Predators and survival techniques
California ground squirrels are frequently preyed on by rattlesnakes. They are also preyed on by eagles, raccoons, foxes, and weasels. Since the 1970s, interdisciplinary research at the University of California Davis, has shown that the squirrels use a variety of techniques to reduce rattlesnake predation. Some populations of California ground squirrels have varying levels of immunity to rattlesnake venom as adults. Female squirrels with pups either roll on or chew on the skins shed by rattlesnakes and then lick themselves and their pups (who are never immune to venom before one month of age) to disguise their scent.
Another strategy is for a squirrel to swish around its tail from side to side. The tail-swishing appears to convey the message “I’m alert and ready to fight! Approach at your own risk!” These two confrontational techniques also distract the snake from any nearby squirrel burrows containing pups.
If an undaunted rattlesnake approaches a California ground squirrel, however, the squirrel pulls another trick out of its bag: it floods its moving tail with extra blood, causing it to heat up. The infrared-sensing pits on the sides of the rattlesnake’s head detect the heat, apparently causing the snake to perceive a larger animal than the one it is actually facing.
If the rattlesnake is really hungry, it may still decide to go after pups. First it searches for an adult female, hoping that she has young in a nearby burrow. As the snake glides past a mother squirrel, she stands stock-still to avoid revealing the location of her young. But when the snake gets close to the entrance of her nest burrow, she erupts into action, using her front feet to bombard the rattler with sand and pebbles, and biting or scratching its tail, which can cause a serious infection. The sandstorm may provoke the snake to rattle, a deliberately induced response that enables the squirrel to assess the degree of threat the snake poses based on its size and metabolic activity level. Other squirrels may come to her aid at this point, biting and harassing the snake. If the rattlesnake manages to slide into a tunnel, the mother squirrel may race into the burrow through a different opening and block the snake’s progress with dirt.
In spring, California ground squirrel pups make up about 70 percent of the diet of northern Pacific rattlesnakes.
Other Predators:
Birds – eagles, hawks, falcons, owls, roadrunners
Mammals – black bears, badgers, raccoons, foxes, coyotes, bobcats, mountains, weasels, domestic dogs & cats
Snakes – other rattlesnakes, gopher snakes, possibly other large snakes
References
California ground squirrel, from Wikipedia, the free encyclopedia
California Ground Squirrels, Otospermophilus beecheyi; www.mary.cc/squirrels/cgs.htm
California Ground Squirrel, Spermophilus beecheyi; NatureWorks, New Hampshire Public Television, Durham, NH 03824
Secrets of the Oak Woodlands – Plants & Animals Among California’s Oaks by Kate Marianchild
