Biology Reference
In-Depth Information
more northern parts of their range normally have one litter a year. Farther south, two litters a year is
common. Breeding for the first litter is in January and February, with May and June the usual breeding
time if there's to be a second litter. The young are born blind and naked, usually two or three to a litter,
although there may occasionally be as many as five.
Red squirrels have somewhat larger litters, usually four or five, but sometimes as many as seven.
They, too, sometimes bear two litters a year, although one is more common.
If humans handle young squirrels in their den, the mother's exceptionally keen sense of smell detects
it. However, rather than abandoning her brood, she immediately moves her young to another den as a
precautionary measure.
As this behavior indicates, squirrels of both species are extremely good mothers. Despite the
care that they lavish on their broods, however, life is apt to be brief and hard for squirrels in the
wild—juveniles and adults alike. Eighty percent of young squirrels die during their first year, and adults
seldom live more than three or four years.
One major reason for such a high mortality rate is predation, for many hungry creatures are perfectly
happy to dine on squirrel. Foxes, coyotes, and bobcats sometimes catch an unwary squirrel on the
ground, but members of the weasel family are a much greater threat to tree squirrels (see chapter 14).
Although weasels themselves spend most of their time on the ground, they can climb trees to get into
squirrel dens, and these slender little predators can easily slip into any hole or burrow that a red squirrel
can enter. Two larger weasel cousins, the marten and the fisher—especially the former—can also pur-
sue and capture squirrels in the treetops.
Hawks and owls also take a heavy toll of squirrels, and I received a striking demonstration of that
fact within a few feet of our house. I had just opened the door and stepped out, when a movement
caught my eye. No more than fifteen feet away, a hawk—either a small Cooper's hawk or a large sharp-
shinned—had just seized Big Red (actually one of our many Big Reds) in its talons and was bearing
it away toward the nearby woods. And although barred owls, at least, seem generally to prefer mice to
squirrels (see chapter 11), a fellow naturalist told me of watching a barred owl in the forest seize a red
squirrel.
Predation is by no means the only danger faced by squirrels. A variety of parasites and diseases can
also prove fatal, and accidents happen, as well. Remarkably, however, in view of lives spent racing
around through the trees, leaping from slender branch to slender branch, squirrels are rarely injured in
falls. Partly this is because squirrels are so agile and adept in the trees that they seldom fall, and partly
it's due to their ability to survive a fall without serious injury.
My mother had a bird feeder at her upper-story bedroom window, and she frequently became in-
censed at the sight of hog-fat gray squirrels gobbling up the seeds she intended for the birds. At such
times she would shoo the grays off the feeder. They, without the slightest hesitation, would launch
themselves outward to fall two and a half stories onto the bare ground below. Not once did one of these
daredevils ever show any visible sign of injury. No doubt this ability is due to a combination of light
weight and substantial wind resistance, which, much in the manner of a parachute, slows the squirrel's
