Lay aside, for a while, your negative thoughts regarding raiders of backyard bird feeders and terrorizers of backyard birds like the gray squirrel. Let’s accentuate the positive. The most delightful physical attribute of a gray squirrel is its agility. They are the acrobats of the bird world.
Not long ago, I followed one as it made its way for several hundred yards from limb to branch to vine to branch to limb, seeming at times to walk on air. Using its feathery tail as a rudder and a parachute, it was completely at home in that nether world between the earth and the sky.
In the summer, gray squirrels construct "cooling beds" or loafing platforms" high in the treetops, where they while away the sultry midday hours far from the madding crowd.
But for the most part, gray squirrels are industrious critters. During the morning and early evening hours from late summer into late fall, they're constantly on the go, collecting and burying nuts for the coming winter.
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Biologists call this storage habit "cache economy." Various mammals and birds store surplus food items away for use in leaner times. Most food-storing mammals choose a single larder site or smaller caches spread out over a well-defined area.
The chipmunk, for instance, has a main underground storage bin in its burrow, with several backup surface pits scattered away from the burrow.
How do they remember where the nuts are?
The gray squirrel "scatter-hoards" — that is, it buries each nut separately. For over a century, biologists have been wondering: Can a gray squirrel remember where it buries its food or does it just relocate nuts by chance like a blind pig searching for an ear of corn?
Lucia Jacobs, a graduate student at Princeton University in the late 1980s set out to answer that burning question. (See her delightful article in the October 1989 issue of Natural History magazine.)
Like the objects of her attention, Jacobs was nothing if not industrious. By studying the tooth patterns on 4,000 nuts, she determined that hickory nuts were the gray squirrel food of choice, having "twice the calories of an average acorn."
So for a specific study site, she singled out a hickory grove, which she mapped, assigning each tree therein a number. Needing to be able to identify her gray squirrels individually, she "baited wire traps, putting peanut butter on the treadle and sprinkling a trail of sunflower seeds leading into the trap." In all, she trapped and either tagged or placed radio transmitters on 80 squirrels.
She observed that squirrels always remove the fragrant husks of hickory nuts prior to burial to "reduce the risk of discovery by a competitor." They seek spots that aren't too moist so that the nuts won't rot. After digging a hole 1-2 inches deep with its front paws, the nut is laid in and rammed securely in place with a sharp blow from the rodents front teeth. The site is then filled in with soil and carefully camouflaged with leaves.
Jacobs determined that gray squirrels rely on a combination of memory and smell to relocate individually cached nuts.
Memory was especially important when the ground was covered with a deep layer of snow. Just like you and I do when we place all of our eggs in one basket, a gray squirrel would invite disaster by putting all of its nuts in one hole.
George Ellison is an award-winning naturalist and writer. His wife, Elizabeth Ellison, is a watercolor artist and paper-maker who has a gallery-studio in Bryson City. Contact them at [email protected] or [email protected] or write to P.O. Box 1262, Bryson City, NC 28713