How suburban wild animals survive cold winters

While suburban residents have tried to stay indoors as much as possible during the recent subzero temperatures, most wild animals don't have that choice.

Fortunately for them, the frigid blast that sends us running for extra blankets or to turn up the heat is just part of another Chicago winter that, experts say, every creature from deer and ducks to frogs and fish has adapted to survive.

“They are built for this,” said Allison Frederick, environmental communications specialist with the Lake County Forest Preserve.

Their survival strategies are varied, but they're honed over generations of evolution and life in a cold climate.

“We wouldn't have the species we do in the forest preserves if they weren't able to live through harsh conditions,” said Jeff Rapp, director of the Crabtree Nature Center in Barrington Hills.

While some birds such as warblers or sparrows migrate as far south as Texas or South America, most animals native to the Chicago suburbs stay here year-round, Frederick said.

The ducks and geese that choose to stay have multiple layers of feathers that help them stay warm when the temperatures drop.

“That's why we use those cozy down comforters, because what ducks and geese have underneath is so warm,” Frederick said.

While humans complain about the cold temperatures that have canceled school days and broken records, some birds travel here to escape harsher weather up north.

“We are their winter home,” Frederick said of the ducks and geese that live in Canada in the summer. “But this is warm for them.”

The best way for animals who stay in the area to stay warm is to keep moving, she said.

“Even on the coldest days, they may slow down and strategize, but they still stay active,” Frederick said.

Most of that active time is spent looking for food and eating it.

“This time of year, the animals are eating quite a bit more than they do in spring, fall and summer because they spend a lot of energy trying to stay warm,” said Stefanie Fitzsimons, wildlife biologist with the Illinois Department of Natural Resources.

Animals that hibernate, such as the eastern chipmunk, ground hog or woodchuck, are the exception. They reduce their body temperatures to nearly freezing, drastically reduce their heart rates and sleep from late September until late March, Frederick said.

Some animals take hibernating to an extreme, such as a the gray tree frog that freezes solid during winter, Rapp said.

“They are dead and then they come back to life,” he said. “It's really interesting. You either hibernate through it, you leave or you tough it out.”

Toughing it out takes strategy, such as venturing out during the warmest part of the day, rather than waiting until night to hunt. That's why people may see more wildlife out in the middle of a cold day.

Deer, foxes and coyotes also grow a warmer, different coat of fur in the winter to help keep them warm, experts said. Each hair on a deer's fur is hollow like a straw, which helps maintain their body heat, Fitzsimons said.

When lakes and ponds freeze over, the fish just swim a little deeper to survive, Frederick said.

“But extreme cold can harm fish. The thicker the ice, the less oxygen they have,” she said. In winters with long or prolonged periods of ice, there can be a “fish kill,” or a localized die-off of a fish population.

Smaller mammals, such as vols or mice, are able to look for food by burrowing below the snow pack, experts said.

They build grass nests for insulation from the snow, and with their body heat, those nests can reach 50 degrees, Frederick said.

Hiding under the snow is a way to stay warm, but it doesn't always keep small mammals alive.

“Owls do very well listening for sounds in the snow and can go after prey down below,” Rapp said.

A coyote or red fox can also pinpoint its prey's location under the snow and collapse its escape tunnels with its nose or paws, he said.

Others such as squirrels or raccoons or even insects may hunker down in hollow logs as insulation until the weather warms up.

Turtles burrow down in the mud near bodies of water and let the snow pile up around them. Moths and butterflies are in the cocoon stage during winter, tucked under a piece of bark and waiting for spring.

“They don't need us to give them blankets or hand warmers or anything like that,” Frederick said.

While coyotes and other wild animals have built up a tolerance for cold weather, experts still advise keeping household pets inside as much as possible when the temperatures are below freezing.

“If your dog is used to a warm bed every night, then they haven't built up the fur that they need and they don't know how to access food outside. They aren't equipped for it,” Fitzsimons said.

With February ending this week, experts said the weather will hopefully start to warm up for animals and humans alike. “It's not going to be cold for too much longer,” Rapp said. “I've already heard birds calling.”

On the coldest of winter days, like when the high temperatures are in the single digits, animals are like people — they bear down and wait for it to pass.

“We've had two extremely cold winters in a row,” Fitzsimons said. “It goes to show that animals adapt to their surroundings and it really is survival of the fittest.”

But, the truth is, not every animal survives the winter.

“That's kind of how the ecosystem keeps itself in check,” Fitzsimons said. “If we didn't have winter die-off in some of each population, we'd have an overabundance of everything. It's all just a natural part of an active ecosystem.”