Three species of tree squirrels live in the Bay Area: the Eastern Gray Squirrel (sciurus carolinensis), the Eastern Fox Squirrel (sciurus niger), and the Western Gray Squirrel (sciurus griseus). Of these three, only the Western Gray Squirrel is a California native, and its status is of concern to naturalists.

This is a beautiful squirrel, black from nose to tail with a grizzled charcoal gray fur on its back. Its eyes are outlined in a creamy white, which matches its chest. The tail is longer than its body and bushy, with black and white hairs mixed in with the gray. This squirrel is larger than the Eastern Gray and slightly smaller than the Eastern Fox Squirrel, with weight varying from 700 to 1000 grams (24.5 to 35 ounces).

Western Grays are found on the West Coast of the United States, from north-central Washington to southern California, and in a very small part of western Nevada. They now occupy only a small part of their former range.

The Western Gray was considered one of the most abundant mammals in the northwest in the 1920s, but by the 1930s an epidemic outbreak of mange decimated many populations in Washington. While the eastern gray and the eastern fox squirrels are capable of producing more offspring in times of abundance to compensate for population loss in lean times, the western gray appears unable to do so, thus limiting its ability to rebound from low populations. Additionally, unlike its eastern cousins, which breed twice a year, the Western Gray has one litter a year, with between three and five young per litter.

Western Grays appear to be less tolerant of people and development than their eastern cousins. They are shy squirrels, who are dependent upon older mixed forests with a variety of oak and pine or oak and fir trees with interconnected tree canopies for food, cover, nesting sites, and arboreal travel. These squirrels generally nest in the top third of larger trees, building leaf and twig nests called drays, which they line with lichen, moss and bark shavings. They often build more than one nest, and alternate among them.

Favorite foods are pine nuts, acorns, nuts, berries, fungi, green vegetation and insects. The animals are generally non-territorial, but show a dominance hierarchy at food sites.

Western Grays are a federal Species of Concern, but are not listed as threatened or endangered. Oregon considers them a State Sensitive Species, and Washington state considers them State Threatened. They are still hunted in California and Oregon. Conservation groups in Washington state have petitioned the federal government to provide an emergency listing for this species. Only time will tell whether these efforts will be sufficient to preserve this squirrel.

There are three species of tree squirrels found in this area: Western gray, eastern gray and eastern fox squirrel. Of these, only the western gray squirrel is native to California and is usually found in  mountainous regions. Eastern fox and eastern gray squirrels are commonly found in your backyard and suburban parks. Eastern gray squirrels are either a grayish tan with white on their tails and stomachs or solid black. Eastern fox squirrels are usually reddish in color with a red and black tipped tail. A full grown fox squirrel is larger in size, weighing about three pounds, while a gray squirrel only weighs one and a half pounds. A Tree squirrel’s diet consists of nuts, seeds, fruits, insects, greens, fungi and grains. Also, squirrels are not known to carry the rabies virus.

Tree squirrels will typically have two litters of three to six young each year. The first batch arrives around March and the second sometime in July. The babies are fully weaned at about three months and don’t leave their mother until they are almost full grown.

A mother squirrel will build her nest out of leaves and sticks and will sometimes strip the bark from trees. What may look like a pile of dead leaves to you is actually a home for a mother squirrel and her babies. Local squirrels have found that palm trees and their large fronds make good nesting sites but oak trees are the best. Squirrels make good mothers and are very good caretakers of their young. She will retrieve babies that have fallen out of the nest and will move her infants to an alternate site if she feels that they are in danger. If you happen to find a young squirrel, put it at the base of the tree where the nest resides, keep an eye out for cats, and most likely the mother will pick it up. If she does not, place it carefully in a ventilated shoebox with a soft t-shirt and bring it to the Wildlife Center.