For most people in California, the Western Gray Squirrel (Sciurus griseus) is a rare sighting. Non-native Eastern Gray Squirrels and Fox Squirrels are common all over the state, and are much more comfortable living near people. Western Grays prefer quiet wooded habitat, which we in Humboldt county have plenty of! Unfortunately, their habitat is decreasing in much of the state, which has contributed to their steep decline in numbers.
You can identify a Western Gray by their silvery coat, white belly, and silver-black tail. They are much shyer than their Eastern cousins, and may be difficult to spot. Eastern Grays are far less common in Humboldt County, and can be distinguished by their brown/gray color.
Photo Credit: Jon Sullivan on Flickr
Sources: Wikipedia – Western Gray Squirrel