Biking back from my hike in El Dorado National Forest, on a small, paved road along which homes clustered about as densely as possible without being referred to as an urban zone, I came upon seven gray squirrels bounding up the middle of the road, one after the other. At first my approach on the bike didn't seem to register to them. Finally when I was about ten feet away the lead squirrel stood up and stared at me, looked confused, then scurried to the side of the road, with the others following and showing just as much indecision.
Well, I don't understand this whole event. Field guides speak of Western Gray Squirrel litter size as being 3-5, and of populations varying from two squirrels per acre to one squirrel for ten acres, so seven squirrels in the middle of a road makes no sense. I've heard of mass migrations of Eastern Gray Squirrels, so there's clearly repertory in the squirrel-behavior closet field guides and websites don't refer to.
In fact, I'm not absolutely certain that they were Western Gray Squirrels. They struck me as a bit larger than Eastern Gray Squirrels, and the Western species is indeed larger than its Eastern cousin, but sizes are hard to determine, especially while riding a bike. The problem is that Eastern Gray Squirrels have been introduced in certain places in California, as well as Eastern Fox Squirrels. The fox squirrels I've seen back East were reddish in color, but gray forms do exist and if these were fox squirrels they might have been of that gray form.
You might be interested in a website in Washington State profiling several western squirrels, including introduced species, and showing their pictures, at http://wdfw.wa.gov/wlm/diversty/soc/wgraysquirrels/.
The Washington-State site focuses on the decline of the Western Gray Squirrel. Though that species looks very much like the Eastern one, Western Gray Squirrels produce just one litter a year, while the Eastern produces two. Also our Western species seems to be more retiring and more strictly arboreal, and thus less adaptable to human changes in the environment. During the 1920s Western Grays were one of the most abundant mammals in the Northwest, but during the 1930s an epidemic of mange caused a tremendous die-off.
If anyone out there has an idea about what was going on with those seven gray squirrels that day, I'd like to hear from you