How does extreme winter weather affect wildlife?

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Opossums like the Virginia opossum are prone to frostbite on their hairless tails. Photo: Chris Helzer/The Nature Conservancy

By Matthew L. Miller

Many animals, of course, are well adapted to thrive in even the coldest of temperatures. Creatures like Arctic foxes, with frostbite-proof feet, are exquisitely adapted for Arctic environments.

Other wild animals have evolved ingenious ways of conserving energy, including hibernation, torpor and other physiological changes. Some simply migrate to warmer climes. Others have thick layers of fat or lush fur that helps them stay warm and dry.

Birds will seek out a variety of unconventional shelters – both natural and human-made – to stay warm on bitterly cold nights. Naturalist Bernd Heinrich reports flying squirrels cramming into small tree holes, huddling together in a tight mass for warmth. (Heinrich’s book Winter World is a treasure trove of stories of how animals survive the cold).

There are species, though, that have recently expanded their range due to climate change or other factors. When a cold snap occurs, they’re ill prepared for it.

While it’s difficult to know how this latest bout of frigid weather will impact wildlife in parts of the United States, here are some species that may not fare well.

Virginia Opossum

The opossum has been expanding its range north for decades. It’s particularly well adapted to humanity, able to survive amidst farms, city parks and suburbs.

It’s much less well adapted to winter weather.

Unlike some other mid-sized mammals that thrive in the presence of humans – think raccoons, red foxes, coyotes – opossums don’t have furry, protective tails. In fact, their tails (and ears) are hairless, making them particularly susceptible to frostbite and even hypothermia.

Many opossums bear physical evidence of surviving harsh winters – damaged ears and tails. Their tails often appear stumpy or as if something had bitten them off, but these are signs that their tails suffered frostbite.

Opossums will den for a few days to escape the cold, but they don’t hibernate. They have to feed periodically. Sometimes they’ll change their nocturnal habits and feed in daylight hours during the winter, to take advantage of warmer temperatures.

That doesn’t make much difference, though, when it’s -20 degrees Fahrenheit (as it was in parts of their range this week).

Expect to see a lot of tail-challenged opossums this spring.

Bobwhite Quail

The northern bobwhite can survive harsh winters quite well – provided it has ample habitat.

This quail species was once a common farmland and grassland bird, and a celebrated game species over much of its range. Since 1966, its populations have declined by 85 percent. While the reasons for this decline remain contested, nearly all biologists agree that habitat loss plays a major factor.

Thick cover along fields provides many benefits for quail, among them protection from inclement weather. Bobwhites, like many species, need to burn more energy to stay warm in winter. Even a few degrees temperature can have a tremendous impact on survival. The conservation group Quail Forever has found that “the temperature inside a high-quality shelterbelt – ideal cover from the cold – can be 5°F warmer.”

Those 5 degrees can be the difference between life and death. Recent research found that a severe winter weather event can have long-lasting impacts on northern bobwhite populations. A healthy quail population could bounce back from this decline, but a population in peril – with inadequate habitat – may take years to recover, if it ever does.

New England Cottontail

The New England cottontail has faced numerous challenges to its survival – lack of young forest habitat, invasive plant species and competition from introduced eastern cottontails (a similar but separate species). And yet conservation efforts, including improved forest management and captive breeding, offer hope.

Will a harsh winter harm these “Yankee cottontails”? It would seem that a rabbit that lives in New England would be well suited to winter. And that’s probably often the case. With excellent habitat and a thriving population, the rabbits would likely do just fine. But a population on the brink without access to food may be wiped out by a heavy and persistent snow.

Researchers in 2015 found a 60 percent reduction in New England cottontail sites in Maine following a harsh winter. Every radio-collared rabbit in New Hampshire perished in that same winter. Plants like blackberry and raspberry bushes become buried with snow, making it harder for the rabbits to feed. The brown rabbits may also stick out more for predators (unlike snowshoe hares which turn white).

 

Matthew L. Miller is director of science communications for The Nature Conservancy and editor of the Cool Green Science blog.