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Washington Ground Squirrels

Washington Ground SquirrelThese little rodents will make you smile as they run between burrow entrances, survey their territories on hind feet, and whistle their alarm calls. The young are exceedingly cute and busy.

Small mammals are important to all ecosystems, and the shrub-steppe is no exception. Ground squirrels and other burrowing small mammals serve important ecological functions, such as reducing soil compaction by aerating the land with their burrows, fertilizing the soil with droppings and old vegetation within caved-in burrows, and improving seed dispersal. They are also important in the food chain and are a dietary staple for a host of avian and mammalian predators. Salamanders, toads and other creatures seeking cool, moist conditions take refuge in unoccupied gopher burrows. Lizards use abandoned gopher burrows for quick escape cover.

Description. The Washington ground squirrel (Spermophilus washingtoni) is a small-bodied ground squirrel with a short tail and spotted back. Similar to other ground squirrel species, Washington ground squirrels have short legs and small, rounded ears. The tail is short (1.3 to 2.5 inches long), and the rounded eyes are set high on the head and surrounded by a white eye-ring. Greyish-white splotches dot the smoky-grey base color on their backs. The underside is grayish-white and extends up the sides of the body to a line connecting the shoulder and thigh. Weight varies seasonally between 1/4-1/3 pound. The squirrels are about 6 to 7 inches long, with males being slightly larger than females.

Burrows. Ground squirrels construct and live in extensive underground burrows, sometimes up to 6-feet deep, with many entrances. They also use and improve on the abandoned burrows of other mammals, such as pocket gophers. Most return to their nests of dried vegetation within the burrows at night, during the warmest parts of the day, and when they are threatened by predators, such as snakes, coyotes, weasels, badgers and raptors.

 

If you're saying to yourself, "Okay, the photo above is just too cute. Got anything cuter?" Yup, we do; read on to learn about baby ground squirrels.

Washington Ground Squirrel Family

Reproduction & Dispersal

Breeding takes place immediately after emergence from their long sleep (next page). These endearing ground squirrels produce only one litter of young per year due to their limited period of activity. Washington ground squirrels have litters of about eight young after a four- to five-week gestation period. Pups are born in late winter and emerge from their burrows about a month after the adults. A visitor to a ground squirrel colony around the beginning of April is treated to the sight of playful young on all sides, while the adults go about the business of serious eating.

Juveniles grow to adult weight in two months after leaving the burrow. All individuals begin to deposit fat 6-8 weeks after emerging and end up with lipids comprising about 65% of their body weight when they go into the burrow for good. They then live through the summer, fall and winter on the fat deposited during the spring.

As with many wildlife species, many Washington ground squirrel young leave their parents to disperse from their birthplace. It's been reported that 72% percent of juvenile males dispersed in April. Dispersal distances ranged from 40 yards to 2 miles, and the median dispersal distance is 1/2 mile.

 

Sounds like Washington ground squirrels are fairly prolific. So, why don't you see them? One reason is that they sleep away most of the year. Let's learn about that.

Washington Ground Squirrel & Den

The Long Sleep

It's hard to conceive of a species spending most of its life asleep, but that's the case for certain ground squirrels.

Some ground squirrels, including the ones on and around Columbia National Wildlife Refuge, live in arid country in which lush, growing vegetation is present only during the spring. Washington ground squirrels are active during the time the grasses are green—only about a third of the year! During the few months of activity, with an abundance of fresh salads on the daily menu, the squirrels prepare for their sleeping months by eating . . . and eating . . . and eating. When the green grasses have dried up, they switch to dried seeds for a short while. The fat content in seeds helps layer fat on the small squirrels to enable them to sleep through the summer, fall and the long, cold winter.

The longest an individual of these species spends above ground is about four months. First, the adults retire back into their burrows in late May to early June. The juveniles return about a month later. They all spend the rest of the summer in a state of torpor called estivation. Estivation then grades into the usual winter hibernation. These little creatures sleep soundly, with a dramatically lowered metabolism, until awakened in spring. Adults emerge from hibernation between January and early March, depending on elevation and habitat conditions, with males emerging before females.

Estivation, which is from the Latin "aestas," which translates to "summer," is a state of animal dormancy—similar to hibernation and characterized by inactivity and a lowered metabolic rate—that is entered in response to high temperatures and arid conditions. Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo estivation. Hibernation, from the Latin "hibernus," meaning "winter," is similar to estivation and  refers to a season that is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate.

 

Much of the above was "burrowed" from Dennis Paulson, Northwest Nature Notes Blog, Slater Museum of Natural History.

Page Photo Credits — Washington Ground Squirrel - Jane Abel, Washington Ground Squirrel Family - Gordon Warrick, Washington Ground Squirrel and Den - Dennis Paulson
Last Updated: Nov 19, 2014
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