Basics - Nut? What Nut? The Squirrel Outwits to Survive - NYTimes.com
In the acuity of their visual system, the sensitivity and deftness with which they can manipulate objects, their sociability, chattiness and willingness to deceive, squirrels turn out to be surprisingly similar to primates. They nest communally as multigenerational, matrilineal clans, and at the end of a hard day’s forage, they greet each other with a mutual nuzzling of cheek and lip glands that looks decidedly like a kiss. Dr. Koprowski said that when he was growing up in Cleveland, squirrels were the only wild mammals to which he was exposed. “When I got to college, I thought I’d study polar bears or mountain lions,” he said. “Luckily I ended up doing my master’s and Ph.D. on squirrels instead.”
The Eastern gray is one of about 278 squirrelly species alive today, a lineage that split off from other rodents about 40 million years ago and that includes chipmunks, marmots, woodchucks — a k a groundhogs — and prairie dogs. Squirrels are found on all continents save Antarctica and Australia, and in some of the harshest settings: the Himalayan marmot, found at up to 18,000 feet above sea level, is among the highest-living mammals of the world.
A good part of a squirrel’s strength can be traced to its elaborately veined tail, which, among other things, serves as a thermoregulatory device, in winter helping to shunt warm blood toward the squirrel’s core and in summer to wick excess heat off into the air. Rodents like rats and mice are nocturnal and have poor vision, relying on whiskers to navigate their world. The gray squirrel is diurnal and has the keen eyesight to match. “Its primary visual cortex is huge,” said Jon H. Kaas, a comparative neuroscientist at Vanderbilt University, A squirrel’s peripheral vision is as sharp as its focal eyesight, which means it can see what’s above and beside it without moving its head. While its color vision may only be so-so, akin to a person with red-green colorblindness who can tell green and red from other colors but not from each other, a squirrel has the benefit of natural sunglasses, pale yellow lenses that cut down on glare.