January-March 2008

Lord of the Burrows
The Incredible, Edible Ground Squirrel

A keystone species for the state's grasslands, the California ground squirrel provides food and shelter to numerous other species. Golden eagles, coyotes, and rattlesnakes depend on squirrels for food, while rare amphibians like the California tiger salamander spend most of their lives in the squirrels' burrows. Illustration by Tim Gunther.

by Kathleen M. Wong

A red-tailed hawk looming over its kill—a California ground squirrel. Squirrels are a very dependable food source for many raptors. In fact, the thriving squirrel populations around Sunol Regional Wilderness support the densest concentration of nesting golden eagles anywhere in the world. Photo by Rick Lewis.

They're a familiar sight to hikers, from the Bay shoreline to Sunol Regional Wilderness. Clad in sepia-brown fur and a mantle dappled with white, California ground squirrels (Spermophilus beecheyi) can be seen scampering across trails, chirruping to their neighbors, or lolling on the crumbling dirt piled before their front doors. One of the most abundant mammals in California, and well adapted to the presence of humans, these gopher-size rodents can be found just about everywhere in the state's extensive grasslands and oak savannas.

They may not seem worth a second glance, but California ground squirrels are the thread that binds state grassland ecosystems together. "Ground squirrels are a keystone species," says Joe DiDonato, stewardship manager of the East Bay Regional Park District. For predators like weasels and gopher snakes, badgers and golden eagles, ground squirrels are an extraordinarily reliable and abundant source of sustenance. To fend off these predators, squirrels have evolved a remarkable array of defensive strategies. In particular, California ground squirrels and the northern Pacific rattlesnake have been locked in a relationship that is a prime example of coevolution in action. But ground squirrels are more than just dinner—they are engineers whose digging turns soil and moves seed, and whose burrows provide subterranean homes for all manner of beasts, from burrowing owls to endangered frogs and salamanders.

Faced with a rattler, this ground squirrel is "tail-flagging," waving and heating its tail in a show of aggression unmistakable to the heat-sensitive snake. Photo by Richard G. Coss.

Wherever the grass is short, the vistas broad, and the forage plentiful, these eminently adaptable animals will dig themselves a home. California ground squirrels inhabit open fields from northern Mexico to southern Washington and east to the Sierra foothills. They gather in loose colonies or kinship groups of about a dozen animals, though some aggregations can contain several hundred.

You will find the rest of this article and additional features in the January-March 2008 issue of Bay Nature, available through our online store or by calling (888)4-BAYNAT or (888)422-9628. You may also purchase the current issue at bookstores and other retailers in the San Francisco Bay Area.

Kathleen M. Wong is a freelance writer specializing in science and the environment.

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