I’m wrapping up the spring run of the California Ecology and Conservation class this week. That means a lot of sitting on the back deck of Blue Oak Ranch Reserve (BORR) barn while I answer questions from students and complete administrative tasks. My ever-present companions are the dozens of California ground squirrels (Otospermophilus beecheyi) that live in an enormous colony next to the barn. By now, I have accidentally accrued hundreds of hours of behavioral observations of these prairie-dog-like mammals. They are endlessly entertaining to watch as they scurry about the important business of eating seeds and chasing neighbors.

              Despite, or maybe because of their abundance, squirrels are under constant threat of being eaten by many species of birds, mammals, and snakes. Several times a day, a squirrel in the colony sounds an alarm. Ground squirrels actually have two types of alarms. The first is a single loud whistle, often given in response to an aerial predator like a hawk, which means “duck and cover”. At the call, squirrels will drop what they’re doing and run into the closest hole. The second type of alarm call is a descending chattering that often morphs into a high, regularly spaced beep. That one must mean “look around”, because when it’s sounded, everyone stands up on their back legs as surveils the field for a bobcat or fox. This time of year, you can only see their little heads poking up above the tall grass. Humans can cause the squirrels to make either type of alarm, especially in colonies far from the barn. When I hike up to the distant areas of the reserve that experience far fewer human intrusions, my presence is heralded with chatters and beeps from a half mile away. On the other hand, strolling directly through the colony by the barn will barely illicit a chirp from the jaded resident squirrels.

Amazingly rattlesnakes generate a different, third predator response in ground squirrels—the tail flag. I’ve watched a squirrel alert to a rattlesnake and then approach it quite aggressively, wagging its tail rapidly back and forth. The snake, apparently relying on a stealthy approach, gave up the hunt and retreated down a hole, despite the squirrel clearly being within striking range. I don’t fully understand why the tail flag works, but it’s a scientifically supported method. Researchers have simulated rattlesnake strikes and found tail-flagging squirrels are better able to leap away. They’ve also found that snakes are more likely to leave the area in response to an approaching flagging squirrel than a non-flagging one.

Despite all the alarming, squirrels get got. A lot. On the reserve. I’ve seen predation by bobcats, coyotes, Red-Tailed Hawks and a Golden Eagle. With all the predators around taking their toll, there’s lots of turnover in the individuals in the squirrel colony. Two notable squirrels that didn’t seem to make it through this past winter were Gordon and Blondie. Gordon was a squirrel particularly acclimated to humans. He developed a preference for dining on the food waste bucket, even scampering into the kitchen to steal treats. His healthy appetite had some serious health consequences—he was the fattest ground squirrel I’ve ever seen. When I showed back up this spring, all the squirrels were slim, trim, and relatively meek. Based on past behavior, by the end of fall, this year’s generation will learn the art of stealing human food and splooting their chonky bodies on the back deck before too long.

Blondie was another squirrel that lived next to the barn who had exceptionally light fur. Ever since I’ve been visiting BORR, a small number of squirrels in the barn colony have been blonde. Their color does blend in quite well once the grass dries out, but they stick out like sore thumbs in the spring when the grass is green and the pups are young and vulnerable. Presumably the genetic mutation in fur color was able to persist in the barn colony because all the human activity results in fewer predators locally. At least until this year. Despite searching for them this spring, I couldn’t find blondie or any other lighter-furred squirrels this spring. This year’s generation of pups are just emerging from their dens now. It will be interesting to see this summer if any of them are Blondie Juniors. I’ll definitely be looking out for them as I resume my squirrel watch five weeks from now.