A common, easily-observed denizen of the Southwest, the rock squirrel has been variously classified as Sciurus variegatus, Citellus variegatus, Spermophilus variegatus, and Otospermophilus variegatus. This taxonomic indecision doesn't seem to have resulted in any identity crisis for the squirrels; they're quite confident to be themselves.
In fact, where acclimated to people, they are cheeky little beggars, approaching people quite closely. (At one point, while I was lying on my belly for a better angle, a squirrel I was trying to photograph spotted me, ran directly toward me, and climbed across my back.)
This can be problematic, as plague—Yersinia pestis, the Black Death itself—is firmly established in parts of the Southwest, and frequently carried by fleas on rock squirrels.
Apart from any disease risk, handouts of junk food tend to be bad for individual squirrels. Their normal diet includes fruit, nuts, and seeds, but also meat and eggs when they can get them. Many of the squirrels we observed were gorging themselves on juniper berries—check out the bulging cheek pouches in the second photo below.
In some ways, rock squirrels appear to be intermediate between tree squirrels and the other ground squirrels. Their tails, for example, are far bushier than those of most other ground squirrels, and while it's not something they do frequently, they can climb trees quite well. On the other hand, their "checkerboard" pelage, with fine barring or spotting on the mantle, is a trait shared by some other ground squirrel species, notably the California and Arctic ground squirrels.
Rock squirrels will retreat to their underground dens during cold snaps, but most likely do not hibernate. They are not colonial in the fashion of prairie dogs or some other ground squirrels, but do emit an alarm call (a loud chirp) upon spotting predators. These include coyotes, rattlesnakes, and several species of diurnal raptor, most notably red-tailed hawks, ferruginous hawks, and golden eagles. Even human-acclimated squirrels are wary of potential threats, actively scanning their surroundings in the midst of daily activities such as grooming and foraging.
Just in case you haven't seen enough yet, here follows a gallery—a rogue's gallery, if you will, for there is something roguish about these critters—of rock squirrel photos. (All photos in this essay were made by yours truly, and if this seems like a lot, trust me when I say that I'm going easy on you people. There are dozens more where these came from.)