Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [38]
I hit the tree with an ax. One flying squirrel with huge black eyes and soft gray pelage popped its head out of the birdbox. After I started to climb the tree I saw three heads looking out. No—it was four! Coming near the nest box itself, I saw several more squirrels climb out and scamper up ahead of me. Definitely more than five. I counted again—four, five, six—and when I was up under to the box itself I saw even more climb up to the very tip top of the maple. They lined up one behind the other, like a queue of planes taxiing down the runway waiting for takeoff. A couple were still close enough for me to touch. One jumped off, flying toward the field, then veering in midair, changing direction while still airborne and gliding to the right. It made a perfect landing at the base of another maple at the edge of the field. I counted again—there were nine more squirrels on the tree with me. Ten squirrels in all! I reached into the birdbox and felt a flimsy structure of shredded plant material that was warm to the touch. No more squirrels. Not wanting to disturb the animals on the tree just feet above my head, which had pressed themselves immobile onto the tree trunk, I quickly climbed down and then watched as one after the other of the nine squirrels ran headfirst back down the maple trunk to rush back into their birdbox. The tenth that had jumped stayed away for the time being. All the squirrels were adult, and it was close to mating time. I had even seen enlarged testicles on one who’d been inches from my face.
I learned later that the winter sleeping aggregations of flying squirrels had been described, although the northern flying squirrel had not been reported to bunch up to the same extent as the southern species. Curiously, the communal aggregations are sex-specific (Osgood 1935; Maser, Anderson, and Bull 1981). The squirrels huddle for warmth, but why should males not huddle with females, or vice versa?
When I revisited the birdbox in early May right after the snow had melted in the woods, it was empty, at least of squirrels. When I reached in to pull the flimsy nest structure out to examine it more closely, my hand encountered a deep, foul layer of slimy material that was all to easy to identify. Apparently the squirrels had used the nest box not only as a sleeping place. There was not a bit of lichen in the nest, although lichens are a significant portion of the winter diet of flying squirrels, and lichens were a main component of some of their tree nests that I had found. Thus, although some flying squirrels in winter in effect live in a gingerbread house where they may find insulation, others opt for body-warmers and/or a convenient indoor toilet.
07
HIBERNATING SQUIRRELS (HEATING UP TO DREAM)
On several winter mornings in 2002 at dawn, when I sat at my desk looking out into the woods, I saw three gray squirrels emerge, one after the other, from the same leafy nest high in a pine tree. Within a few minutes the trio left unhurriedly, traveling on the bare winter branches of the maples. Like tightrope walkers they balanced on the slim branches and then acrobatically jumped from one tree to the next. They fed on the buds of broad-leafed trees after snipping off the terminal twigs (which they dropped), on sunflower seeds when they were available in the bird feeder, and on acorns on the trees or on the ground. In the spring, a red squirrel has a nest with young in one of my birdhouses. And these are not my only squirrel neighbors.
Within less than a hundred yards from my home in Vermont, and within a mile of my cabin in the Maine woods, live two more species of squirrels, in addition to the flying, gray, and red squirrels. All descended from a common ancestor more than 60 million years ago. They diverged and specialized on different kinds of food. They are what they eat and they hibernate depending on