Tackling the elements
Wildlife adapts to winter to find shelter, food

By Tom Venesky tvenesky@timesleader.com
Sports Reporter

When the snow falls and the temperatures plummet, most people are driven indoors where a turned-up thermostat and a television set offer an escape from the harsh winter conditions.

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Whitetail deer utilize any food source they can during the winter, including the bark of a tree.

Rich Koval PHOTOS/For The Times Leader
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This opossum escaped the winter cold and wind in the confines of a hollow tree.
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But not everything can get away.

For those species of wildlife that don't hibernate, they have to face the elements of winter head on. Often times they do so with remarkable ease but sometimes, as winter drags on, survival can be a struggle.

So how do they do it?

One basic rule of thumb, according to Pennsylvania Game Commission wildlife biologist Kevin Wenner, is many animals rely on fat reserves built up from fall feeding and limit activity when a winter storm hits to preserve precious energy.

Simply put, wildlife does what we do during a snowstorm, bed down and wait it out. The only difference is wildlife has to wait things out without the comfort of a furnace and a refrigerator full of food.

Still, there are places in the outdoors that some animals utilize to keep warm. Take deer for example.

"During a cold winter they seek areas of dense conifers," Wenner said. "Not only do these areas provide them shelter from the wind, but it provides a thermal cover as well.

"In the summer if you walk through a stand of conifers it's cooler. It works the opposite way in the winter. The dense conifers provide thermal cover, and it acts as insulation."

One of the most efficient species at utilizing heat in the cold, winter environment actually lives in a place that is the icebox of the outdoors.

Beavers spend their winters swimming under the ice of a frozen lake, and they handle the frigid water with ease.

When it comes to winter survival, nothing impresses North Branch Land Trust naturalist Rick Koval more than the beaver.

And it all starts with the lodge.

"It's a very unique structure," Koval said. "Lodges are very well insulated with mud, sticks and grass and they do a great job at retaining the body heat generated from the beavers inside."

Beavers access their lodges through underwater entrances, which means they never have to leave the safety of the water. Inside the lodge beavers build a pedestal, which allows them to get out of the water and dry off.

And if you're wondering just how much heat beavers can generate, there is a clue at the top of every lodge.

"They have a vent hole at the top that acts like a chimney and allows the air to circulate inside," Koval said. "I've stood on a lodge and I've actually felt the heat coming out of the vent."

Not every wild animal is able to spend its winter inside a cozy lodge or under the thermal cover of conifers. Rodents such as mice and voles survive quite well burrowing under a rock or inside a hollow tree.

Sometimes they adapt to the shelters abandoned by other animals, such as a white-footed mouse that Koval encountered one winter.

While walking along a hedgerow, Koval spotted a catbird nest with a strange mound of snow on top. The nest was built in the thick branches of a multi-flora rose bush, and Koval decided to take a closer look at the mound of snow.

"I wiped the snow off and inside was a food cache of rose hips from the multi-flora rose berries, acorns and a white-footed mouse on the bottom," he said. "It was actually insulated by the snow on top."

And then there's the opossum that Koval encountered in the winter while running a trapline in Lackawanna County.

"It spent two weeks living inside the body cavity of a dead deer. It had all the food and shelter it needed right there," he said.

While shelter is a key ingredient for winter survival, so to is food. It's extremely important for all species, especially birds such as turkeys that don't have the ability to make a shelter.

When a deep snow covers the ground, turkeys will spend days at a time on their roost in the tree tops, Wenner said. While they wait for the snow to melt and open up patches of bare ground, turkeys live off their fat reserves and eat the buds growing on the limbs where they roost.

"There's really no incentive for them to fly down off their roost," Wenner said. "By walking through deep snow, they burn up energy and expose themselves to predators."

Rather than wait things out, other species of birds have the ability to call it quits for a while and seek a warmer home by migrating south for short periods.

This is often the case with barn owls, whose main food source of meadow voles and mice become impossible to catch in deep snow.

"Barn owls do try to winter here, but when they can't find voles and mice because of the snow they'll fly south temporarily where food is available," Wenner said.

And just like the barn owl takes a break from the winter by flying south, other species such as bears and bats sleep through the cold winter months.

But hibernation isn't as simple as taking a prolonged nap.

While in their dens and caves, bears and bats essentially live off their fat reserves for a hibernation period that can last as long as six months. They're able to do this, Wenner said, by slowing their metabolism and thus significantly reducing the amount of energy being used.

"It's an impressive feat to be able to shut down like that," Wenner said. "Especially with female bears when you consider that they give birth to cubs in January and still have enough fat reserves to survive until April."

So while the snowstorm that hit last week was likely viewed as a burden to many, is it really that bad for wildlife?

"I think it's going to be a short-term challenge and it does present some difficulties, but our snows generally don't last for months anymore," Wenner said. "Most wildlife will just wait for things to warm a bit and expose areas of bare ground where they can forage again. It's basically a one-time disruption."