Monday, November 28, 2011

Adirondack Wildlife: Snowfall and the Varying Hare

The recent snowfall that allowed Whiteface Mountain to open this past Thanksgiving weekend proved to be a most welcome weather event for both our region’s alpine skiing community and the multitude of varying hares that reside in those areas of the Park impacted by this late November winter storm.

In early October, the varying hare, also known as the snowshoe rabbit, (Lepus americanus) starts to develop a new outer coat of white fur. These lengthy hairs contain numerous air chambers that increase their insulational value while also allowing them to more effectively reflect light, which gives them a brighter, bleached appearance. As this layer of guard hairs develops, it allows this small game animal to better retain its body heat while also gradually changing its appearance from a brownish-gray to an ivory white that closely matches snow.
Around the time of Columbus Day, only areas on this creature’s lengthy ears and around the lower part of its massive hind feet show the presence of these white hairs. As October progresses, white fur starts to appear on the hare’s legs and along its sides, and by early November, the head and back show the presence of these white, soft-textured fibers. By the time Thanksgiving arrives, most varying hares in the Adirondacks have their dense coat of brownish-gray underfur completely covered and totally concealed by this layer of longer white guard hairs.

The exact time of the start and completion of this change depends upon the location of the individual hares. Those animals that inhabit the dense spruce-fir forests covering the uppermost slopes just below the tree line are the first to experience this process of pelage color change, as do snowshoe rabbits that exist much further north. Individuals that reside in the lowland swamps and alder thickets near the periphery of the Park, or in places that lie outside the traditional snow belt areas, are often several weeks behind in this color transformation.

The relative length of daylight to darkness is the environmental factor primarily responsible for triggering this change in color of the varying hare during the autumn. Such an internal response to a specific length of day is known as photoperiodism, and this type of external stimulus is known to initiate or regulate numerous other events in various forms of wildlife.
Over centuries, the process of natural selection has allowed only those individuals that have developed a certain response to a change in the environment to survive, reproduce, and pass this genetic information along to their offspring. In the case of the varying hare, the fact that the ground typically develops a lasting cover of snow by early November at higher altitudes, and late November for most other sections of the Park has strongly favored those snowshoe rabbits that complete their color change at these corresponding times of year.

While there are always years when the snow arrives early, or fails to form on the forest floor until much later in the season, these occurrences tend to be weather anomalies and are usually followed by more normal snowfall patterns in subsequent years. A contrasting background places the varying hare at a much higher risk of being detected by one of its many natural enemies, however, this animal is extraordinarily adept at eluding predators and avoiding capture. Inevitably, enough individuals survive these periods of adverse weather to reproduce and pass along to their offspring the genetic information for changing color at the “normal” time in autumn.

The recent article by Mary Thill indicating a delay in the onset of the winter season may seem to be bad news for our varying hare population. However, it is impossible to say how much of an impact it will have on our snowshoe rabbits. Researchers have not yet studied how this rate of change in the prevailing weather patterns will affect a change in the photoperiodism of a member of the wildlife community. It is possible that the hare will, over generations, adapt to compensate.

Our currently warm autumn has been great on the heating bill, nice for putting up outside Christmas decorations, and ideal for doing those end-of-the-season yard chores, but it has not been welcome by skiers and hares.

Photo: A Snowshoe or Varying Hare in Winter (Courtesy Wikipedia).

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Tom Kalinowski

Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

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