Adapted from Jim Conrad's
Naturalist Newsletter of July 27, 2007
issued from Sierra Gorda Biosphere Reserve,
QUERÉTARO, MÉXICO

ROCK SQUIRRELS

We have squirrels in the hot, arid Jalpan Valley, despite the absence there of oaks and tall forests. I got a good look at the valley species the other day inside the Reserve office compound. He was perched atop a big heap of old tires being collected by the tree-planting guys who place the tires on steep slopes for erosion-control.

So, atop the top tire in this tire-heap the squirrel perched upright on his haunches the way a gray squirrel might when he's looking around, except that this tire-squirrel was perfectly still. Facing me directly he didn't twitch his nose, didn't wiggle an ear, in fact was so still that at first I thought he was a beer bottle someone had left there. But, no, when I moved closer he dove into the tire labyrinth and disappeared.

He was a Rock Squirrel, SPERMOPHILUS VARIEGATUS. With his foot-long, gray-brown body and eight extra inches of bushy tail, from a distance he looked like a regular gray squirrel. The most obvious difference was that across his back his fur was pale gray mottled with brownish black, so he looked as if he wore a gray and black calico shawl. If you have Flash Player installed on your computer or are willing to download it for free, you can see a video of a Rock Squirrel with a calico shawl just like ours eating flowers at http://www.desertusa.com/video_pages/rock_squirrel1.html.

Rock Squirrels are fairly common in the US's southwestern desert, extending north as far as Utah, and south as far as central Mexico.

I had to laugh, imagining how our Rock Squirrel must have felt when he discovered that mountain of old tires. For, the way a dog obsesses over odors, a pig over rooting in the soil, and songbirds over singing, I think Rock Squirrels must be perpetually fascinated with tunnels. Just imagine this critter's glee when he saw that his whole tire-mountain consisted of one circular tunnel after another, each in which he could go round and round as much as he wanted.

Rock Squirrels are polygynous. You might wonder what the difference is between polygynous and polygamous. Polygamy is a general term applying both to males having several wives, and females having several husbands. Polygyny, in contrast, just refers to males mating with several females -- polyandry being mating with several males. Moreover, I think of polygamy in a human social framework, while the term polygyny has more biological associations.

Rock Squirrels are not the same thing as ground squirrels, though both Rock and ground squirrels belong to the Squirrel Family and the Marmot "Tribe," along with marmots. "Ground squirrel" is a general name applied to species distributed through about six genera. The name "Rock Squirrel," however, usually just applies to our Spermophilus variegatus, so that's why I capitalize Rock Squirrel, but not ground squirrel.