How Hares Cope with Winter
I was thumbing through a recent issue of the journal Arctic the other day when I suddenly remembered a poem. No, the publication of the Arctic Institute of North America has not decided to add rhymes to its studies of far-northern matters. Rather, one of the articles answered a question posed in an early attempt at poetry from daughter #1: The snow does fall/The wind does blow/I wonder where the white hares go?
Probably all of us some time have thought about creatures who brave winter's worst without benefit of walls, roof, or windows, without even campfires or long underwear. How do they do it? Some of us have thought pretty seriously---hunters, trappers, long-distance mushers, for example---but most of us are happy to give a shiver of sympathy and let it go at that.
At least one scientist was unwilling to let it go at that. Thus the article that caught my eye: "Behavioral adaptations to arctic winter: shelter seeking by arctic hare (Lepus arcticus)" by David R. Gray. Gray spent portions of many years keeping an eye on the hares of the Canadian High Arctic, working mostly in what he called "late winter." April and May qualify as late winter in his study areas on Bathurst and Ellesmere islands; the temperature is still well below freezing, and often well below zero.
It's also windy country, and Gray thinks wind plays an important role in how hares cope with the winter weather. He'd find resting hares sitting atop snowdrifts on the lee side of boulders, for example. Measurements of wind speed showed that the drift tops encountered slightly slower rates of moving air than any other location apparently sheltered by the big stones. Even hollows at the base of the boulders showed higher wind speeds than the resting spots the hares selected.
Sometimes the hares burrowed into the snow for shelter. Generally the animals made shallow scrapes, digging or simply patting hare-sized pits in which they hunkered down. More rarely, they tunneled into snowdrifts, and sometimes even dug proper dens, with expanded chambers at their ends. The dens and tunnels also seemed to protect the animals from aerial predators.
Usually, though, Gray found that the preferred way for arctic hares to shelter themselves from the cold was to adjust their posture. A warm hare is a sprawled-out hare, and "warm" is a relative term for an animal of the High Arctic. Gray saw hares relaxing in this posture, lying on their sides with their legs sticking out, at temperatures down to -15 degrees centigrade.
A cold hare, on the other hand, looks rather like a bowling ball made out of white fur. The hare tucks all extremities in tightly, folding its ears snugly down against its back and pulling its feet in under its belly. Only the pads of it hind paws touch the snow beneath. The hare has minimized its external area, and thus reduced the amount of heat it loses to the atmosphere and the amount of energy it needs to keep itself warm. Gray calls this extreme-weather pose the resting sphere. As the weather eases, so does the hare's posture. A warmer hare will relax from the resting sphere to the sitting crouch, in which the animal looks more oval than spherical and its toes and eartips protrude. Given a bit warmer and calmer conditions, the hare extends still more into a lying crouch. Finally, when the hare decides spring is here, it will take its snooze breaks in a sprawl.
Interestingly, no matter how cold and windy the weather, adult hares will not huddle together for warmth. Hares of the High Arctic do herd up, but they keep their distance within the group. Coming closer than a couple of hare-lengths can lead to a fight.
So it looks as if research has answered the poetic question. The hares don't go anywhere. They just shape up.
