Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [9]
Ruffed grouse that has tunneled into the snow to sit out the night or a snowstorm.
Snow also provides shelter at night for many kinds of birds, ranging from Siberian tits, ptarmigan, and ruffed grouse that burrow in and create igloolike snow caves. The birds leave tangible evidence that they sometimes tarry a long time in these snow shelters; I have found over seventy fecal pellets within a single ptarmigan snow cave near Barrow, Alaska, and in the Maine woods I routinely find over thirty where a ruffed grouse has spent the night. Often these birds also stay the day in their shelter, because on snowy, cold days I have flushed them out from underfoot under the snow even at noon.
From all appearance, many northern birds are excited by snow, especially that of the first snowstorm of the year. Both ravens and ptarmigan then become visibly animated, rolling, sliding, and bathing in the fluff when it is not yet packed. Owls, crows, finches, tits, and kinglets also bathe in snow (Thaler 1982).
Snow has been such a constant feature of their environment that many northern animals have become well adapted to it and now depend on it. Perhaps none depends on snow more than the snowshoe hare. The size of this hare’s tracks are all out of proportion to the animal’s size. As a result of its low foot-loading, the hare can walk, hop, and run very near the top of the fluffiest snow. As a consequence, the more that snow accumulates throughout the winter, the more easily the hare can reach its food, the fresh twigs of small trees and brush. Thus, the twigs feed the hares, who are in turn reincarnated into fox, bobcat, lynx, fisher, weasel, great horned owl, goshawk, and red-tailed hawk. Yet despite the hares’ rapid recycling into other lives, their populations persist because of tricks of individual survival coupled with a legendary reproductive potential. (A female hare may have four litters per year, with up to eight young per litter. The young are furred when born and almost ready to run and soon ready to reproduce.)
Regardless of how fast the hares reproduce, it would not take long for the predators to deplete them if it were not for their camouflage. The snowshoe, also called varying hare, changes from brown to a coat of pure white fur in winter. However, the more effective the camouflage is for one season, the less effective for another, and a hare’s trick to survival requires getting the timing just right. It is hard to be exact in when it is best to become white or brown, because the coat change requires a month or more, and a snowstorm can transform a landscape in minutes. Proximally the hare’s timing is determined by day length, but ultimately it must be dictated by the average time that the ground is snow-covered; the timing of the genetically fixed color change of locally adapted hares necessarily reflects the historic patterns of when there was snow cover because off-color hares are the first to be eaten and have their meat be reconverted into the next life, that of predators.
In the woods in western Maine the hares are almost all white by the end of November, the most usual time that there is continuous snow cover. However, in some years when the first snowfall is late, the hares show up for the whole duration of that lateness as if they had been marked in hunter’s fluorescent orange. Within a few minutes after it snows, however, they become practically invisible. I doubt that a hare knows whether or not it is invisible because the totally white hares I’ve seen on brown background made no apparent effort to hide. Nevertheless, they could still have some change in behavior that compensates for their inability to accurately time the molt with