One Tough Winter: Winter Is Over But Its Effect On Wildlife Lingers

One Tough Winter: Winter Is Over But Its Effect On Wildlife Lingers

Frank Thompson, of the U.S. Forest Service, holds one of the bear cubs born this past winter. Many sows entered the dens in less than prime conditions and consequently gave birth to single cubs.

This past winter's deep, fluffy snow and subzero temperatures combined to make life difficult for much of Vermont's wildlife, including whitetail deer, wild turkeys, and a number of predators, particularly bobcats and barred owls. But often found the two feet of snow much to their liking.

Biologists with the Vermont Department of Fish & Wildlife have been compiling data each winter since the 60s to measure the winter's severity. Modeled after one created in Wisconsin, Vermont's winter severity index works on a point system: any day between December 1 and April 30 in which the low temperature is below zero gets one point; likewise, any day in which at least 18 inches of snow covers the ground also gets a point.

So it's not only a matter of opinion that the winter of 1993-94 was a tough one. The data show it to have been much harsher than average, and the worst in the last eight years in all but one region of the state. Take a look at the map on the next page to see which region has bragging rights for the toughest winter.

Generally speaking, whitetail deer are well-prepared for winter. The dense hollow hairs of their winter coats serve them well, combining with a layer of backfat produced in the summer and fall to insulate them against the cold. When winter kicks in, they'll migrate to a deeryard where a thick conifer canopy creates a hospitable micro-climate with less wind, less snow on the ground, and slightly warmer temperatures. While northern Vermont is within a few degrees of latitude from the northern edge of the whitetail's range, they can normally withstand almost anything that our winters can throw at them. In the short term, that is.

Prolonged stretches of tough winter weather weaken the deer, and the cumulative effect of deep snow and sub-zero temperatures can rapidly deplete their stored energy. The winter severity index is a good means of measuring long-term conditions.

Ron Regan, Fish & Wildlife's deer project leader, says that in years when the index has been much higher than average there has been substantial mortality. Often, the deer survive the winter m the deer yards using up very little energy, but don't survive the last hurdle of early spring, when temperatures have warmed up but food is scarce, and when travel on the slowly receding snow cover is still difficult.

In the spring, the deer fall victim to predation by domestic dogs and collisions with vehicles, both of which took a very heavy toll this year. Fish & Wildlife spokesman John Hall attributes the heavy roadkill to winter-weakened deer slipping down into the valleys in search of food. While the valleys hold the season's first green vegetation, they also hold the majority of the highways.

While the winter severity index was created with deer in mind, the same conditions that killed substantial numbers of deer may also have been devastating to what had been a burgeoning population of wild turkeys. By last summer the thirty-one turkeys captured in New York and transplanted in Rutland County in 1969 and 1970 had multiplied to an estimated 15,000 birds.

They are particularly plentiful in the lake plains, the western foothills, the Connecticut River Valley, and the eastern foothills. By establishing themselves in Orange County, they have exceeded the northern limit of their range at the time of the European settlement of Vermont.

Turkeys rely on acorns and soft mast for food, and they spend much of their feeding time scratching through the leaf litter. Unfortunately, they don't do much scratching through two feet of snow. And when the snow is fluffy, they don't do much walking on it either, so they spend more time roosting than feeding.

Savvy flocks will get some help from farmers and will pick through the grain in manure piles or fields that have been spread with manure.

Doug Blodgett, Fish & Wildlife's turkey project leader, estimates that turkey mortality went as high as twenty to thirty percent, with juveniles being particularly hard hit. Mortality hit individual birds as well as entire flocks that held as many as twenty birds. Fish & Wildlife officials were so concerned at the winter's toll on turkey that they took immediate action and requested that the governor, by proclamation, reduce the bag limit in the spring hunting season from two to a single gobbler.

Blodgett said that the effects of winter could be only a temporary setback if they experience good nesting conditions. Turkeys bounce back well, partly because they are prolific breeders, with hens laying as many as fifteen eggs. Most of the breeding is done by dominant, older males that are in prime condition and less likely to have been affected by the tough winter.

Some like it cold

The same conditions that were so devastating for turkeys and so difficult for deer were ideal for the denning animals, the ruffed grouse, and the small mammals who live under the snow.

The woodchuck, chipmunk, and a variety of bats, along with the meadow jumping mouse and the woodland jumping mouse, are the only true hibernators in Vermont. A hibernator's respiration and heart rate slow dramatically, and its body temperature plummets. Hibernators den underground, and for them, winter is a big snooze.

The black bear is the animal most people associate with hibernation, but black bears don't actually hibernate. Instead, they spend the winter cycling in and out of a deep sleep. Their respiration slows down to a few breaths per minute, but their body temperature remains at a nearly normal level, and they can be alert instantly if their den is disturbed.

Beech nuts and blackberries, staples of the bear's diet, were scarce last fall, according to Forrest Hammond, who heads a study of bears for Fish & Wildlife in the Stratton Mountain area. Consequently, they had to travel out of their traditional range in search of the more abundant acorns and apples. This movement made them more vulnerable to hunting pressure.

In addition, many of them entered the den in less than prime condition. Hammond said that, as a result, a number of their radio-collared sows gave birth to single cubs. Following a bountiful autumn, a sow is likely to produce twins or even triplets.

The thick insulating blanket of snow kept the bears snug and comfortable in their dens until April. Deep snow is such an effective insulator that, despite the many sub-zero nights, the ground in many parts of Vermont did not freeze. However, the snow took so long to melt, that when the bears emerged, they were even more desperate for the green-up of spring than we humans were.

Other species, like beavers in their lodges, live in dens in the winter and eat from caches. The skunk, raccoon, and porcupine are not often stressed by harsh winter conditions. While turkeys were hard hit, Vermont's other non-migrating gamebird, the ruffed grouse, should have made out well. Grouse (or partridge) burrow into deep, fluffy snow for their warmth.

They feed on almost anything, but their favorite food, aspen buds, is readily available all winter long. For grouse, a tough winter is an open winter or one in which the snow immediately develops a crust. It is fortunate that the winter was to the grouse's liking because 1993 was a low point in their population cycle. Judging from the amount of drumming heard this spring, the population will rebound as it inevitably does.

Other species that benefit from the snow include the small mammals that burrow underground and under the snow. Mice, rats, voles, moles and lemmings were safe from predators from late December through early April.

The pendulum, of course, swings both ways, and the predators who rely on these small mammjs went hungry. Margaret Fowle, of the Raptor Center at the Vermont Institute of Natural Science, said that they received numerous reports of owl carcasses, particularly barredowk.

If you hear the “Who cooks for you?” call of a barred owl this spring, it's a bird that survived the winter and is strengthening the species. They, along with sharp-shinned hawks, were spotted hanging around bird feeders; it was not the sunflower seeds that drew them but the chickadees and the rodents that come looking for seeds spilled onto the ground.

In the absence of prey animals, the bobcat was similarly hungry. Ron Regan said that he found a bobcat carcass and that he heard anecdotal evidence of others.

"Something I've never seen before but which wardens have mentioned in the past is that bobcats were showing up around farms and urban areas looking for meals. In fact, a bobcat was trapped alive in downtown Barre. The people didn't know it was a bobcat. It was small and they thought it was just a hungry feral cat. Well, they caught it in a box trap and it was all claws and teeth. It was pretty scrawny, so we released it over a deer carcass, but I don't know how he did," Regan said.

There is a general supposition that foxes and coyotes were also hit hard, not only because small mammals were well protected but because travel on the deep fluffy snow was difficult at best.

 
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