December 27, 2007
By Susan Benson
Director of Education
Cable Natural History Museum
I saw the first white snowshoe hare of the season today. I was walking down near the Namekagon River when I noticed this white lump just inside the tree line along the road. There were still a few brown spots on the shoulder and back, but the hare had otherwise changed over to his beautiful, pure white winter coat that will eventually help it to disappear against the winter snow.
The change in fur color from brown to white in the fall and back again in the spring is just one difference between hares and rabbits, but it is the most easily observed. Because of this unique transition, the snowshoe hare is also known as the “varying hare.” Why do hares molt this way and rabbits do not? The answer is mostly related to climate.
The geographic ranges of hares and rabbits overlap here in Wisconsin, but hares are considered a northern species, while rabbits are a southern species. Farther north, the durations of summer and winter are more equal, so hares change colors to match their environment. The same is true of other far northern species, such as the weasels (which are also found in Wisconsin), ptarmigan, arctic fox, and collared lemmings. But the change in color has to also keep the hare warm, and white is typically known as a color that reflects sunlight. The answer to this riddle is that white in the natural world is not a color but is the absence of color, or pigment. The cells in white hairs are empty of pigment and are instead filled with air, which provides thermal insulation. The change from brown to white fur begins as the amount of daylight decreases. The ears and feet are the first to change, and the whole animal is white after about 10 weeks.
Snowshoe hares (waabooz in Ojibwemowin) are found in the northern half of Wisconsin where they prefer spruce and cedar swamps and other thickly-vegetated coniferous woodlands. Up to two litters of one to seven (usually two to four) hares are born each year between May and August. Hares primarily feed on grasses, tree buds, and other plant material, but they are also known to feed on the meat of dead animals, including other hares. They do not kill other animals, but they will scavenge carcasses whose insides have been exposed. Main predators of snowshoe hares in Wisconsin include weasels, gray and red foxes, coyotes, wolves, bobcats, and mink.
A popular topic of study for biologists has been the dramatic fluctuations of snowshoe hare populations. Hares are known to go from periods of great abundance (almost overabundance) to periods when there seem to be none left anywhere. The severity of the fluctuation varies geographically, and this is thought to be caused by the relative number of other species that occupy the same level as the hare in the food chain. In other words, if there are fewer links in the food chain (such as in far northern latitudes), and the hare is a main source of food for larger predators, than over-consumption by predators can cause the hare population to decline sharply, and the predator population will soon follow. On the other hand, if there are other animals (such as cottontail rabbits here in Wisconsin) for predators to feed on, then the hare population does not change so dramatically. It is estimated that as many as 85% of hares do not live for more than one year. The common life span for those that do survive is five years.
The change of seasons is upon us. The varying hare has shown that winter is indeed on the way, even if we do not see much snow yet. But the lack of snow makes it easier for us to see this fascinating animal if we look hard enough.
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility in Cable at 43570 Kavanaugh Street or on the web at www.cablemuseum.org to learn more about exhibits and programs.