Abert’s squirrels (Sciurus aberti aberti), getting fat on gambel oak acorns, in the Coconino National Forest, Arizona.

These are tasseled squirrels, though all of these have shed their distinctive tufts of ear fur for the summer. Winter coats will begin to thicken in just a few weeks.

When I was at university I took a course in bio-geography with Robin Andrews, now Professor Emerita of Biological Sciences at Virginia Tech. Abert’s squirrels figured prominently in one of the key topics of that course. These squirrels are now estranged from their famous cousins, the Kaibab squirrels (S. aberti kaibabensis), found only on the northern Kaibab plateau in the Arizona strip. As the gap of of the Grand Canyon grew over millions of years it separated squirrels on the north and south canyon rims, and the isolated populations became morphologically distinct. For a time they were deemed separate species, now only subspecies, but the evolutionary process of divergent speciation due to isolation and habitat diversification is clearly taking place. 

The squirrel in the center photo is striking a languid (but alert) pose I have frequently observed when the squirrels first become aware of my presence. My guess is they are trying to disguise themselves as bumps on the tree limb. If I continue to approach they then climb to a higher branch. Without exaggeration, I have shot hundreds of blurry photos of them making escape to the treetops.

And a final note: It seems sadly unfair that evolution would provide these animals with a means of losing ear fur, when I am at an age when bushy coarse hairs (I call ‘em Brezhnev Brows) appear on my ears and eyebrows, seemingly overnight.