Western Gray Squirrel

Critters in the Garden

Carol Lerew
RSABG Volunteer, Nature Interpreter

A delight to visitors of all ages, the tree squirrels at Rancho Santa Ana Botanic Garden provide entertainment as well as insights into nature. School children are often diverted from theme-lead tours by the squirrel’s acorn-hoarding activities or breathtaking treetop acrobatics. Nature Interpreters take advantage of these teachable moments to lead discussions about the habits and habitats of these engaging creatures.

One of the two tree squirrel species at the Garden is the western gray squirrel, Sciurus griseus. Indigenous to Washington, Oregon and California, its coat is silver-gunmetal gray and has a white underside. The tail is large and bushy. These squirrels are shy and likely to run up a tree and give a hoarse barking call when disturbed. It is the largest native tree squirrel in the western coastal states.

Western gray squirrels are forest dwellers. Their time on the ground is spent foraging, but they prefer to travel distances from tree to tree. They are strictly diurnal (active during the day), and feed mainly on nuts and seeds, particularly pine nuts and acorns. Scatter hoarders, they make numerous caches of food when it is abundant. Although they have relatively good relocation abilities, some food caches are never reclaimed, thus becoming seedlings in the spring. Though they don’t hibernate, they do become less active in the winter. Tree squirrels are prey for bobcats, hawks, mountain lions, coyotes, cats and humans.

Squirrel nests are called dreys (also spelled drays) and can be seen high in trees. They are built from sticks and leaves wrapped with strands of grass and lined with leaves, moss, lichens and shredded bark. The large round nests are used for shelter in winter, birthing and rearing young. A second smaller nest is used temporarily for sleeping. On warm sunny days younger squirrels can sometimes be seen balanced spread-eagled on a high tree limb taking a siesta.

Western gray squirrels may have two litters a year, depending on food supply, in early winter and late spring. Litter sizes range from one to five kits. Infant mortality rate is high. Kits are slow in development and will not leave the nest for six months or more. Females can be quite territorial, and will chase others away as well as have violent altercations between themselves. These mammals can unfortunately become serious pests in almond, walnut and filbert orchards as well as in residential neighborhoods where they receive human handouts.

Habitat loss, road-kill mortality and disease have taken a toll on the western gray squirrel. Populations have not recovered. Urbanization, catastrophic wild fires, forest degradation and overgrazing have pushed them further into the mountains and surrounding foothill communities. The introduction of the eastern fox squirrels (Sciurus niger) in the early 1900s in the Los Angeles area, and perhaps later introductions, have been the biggest cause of the more reclusive western gray squirrel’s retreat. These aggressive cousins appear to be the largest threat in the Southern California area.

The eastern fox squirrel is generally russet-colored with a bright yellowish-cream belly and long bushy tail. Gregarious and playful, they are often seen chasing each other up and down trees and across yards and clearings. Also present in the Garden is the California ground squirrel, a mottled brown with white patches on the shoulders. They dig burrows in the ground for shelter, food storage and to raise young.

Alan Muchlinski, professor emeritus at Cal State Los Angeles, has been conducting a Southern California research project to determine the current distribution of the western gray squirrel. He and his students have recently completed the third year count at RSABG. Results indicate that the number of western gray squirrels is down from two years ago and the number of red fox squirrels has increased. Professor Muchlinski invites area residents to participate in this study in their own neighborhoods. Visit the Cal State L.A. web page to get started.

Next time you are in the Garden, slow down, observe the tree squirrels and try to identify the western gray squirrels from the eastern fox squirrels. Perhaps one is digging numerous holes searching for a buried acorn or chasing another through the treetops lunging and scrabbling as if hanging on for dear life. I find myself laughing. Do you as well?