As temperatures in Madison dropped toward -50 degrees Fahrenheit during the Polar Vortex last week, few people ventured outside for even fifteen minutes. Imagine if you were one of the local cardinals, deer or fox who live outside year-round, including the chilling winter months. How would you keep warm while temperatures remained below zero Tuesday through Thursday?
Many have heard about bears’ ability to sleep the winter months away in hibernation—a classic example of how animals deal with the cold. But that's not the only way local wildlife stay warm.
“The animals that are here year-round and are active in the winter, they’ve evolved different defenses to kind of deal with cold,” said David Drake, Professor and Extension Wildlife Specialist in the Department of Forest and Wildlife Ecology.
Some animals ⸺ such as amphibians, bats, and woodchucks ⸺ hibernate through the winter like bears. Others can be seen out and about all winter long, including deer, foxes, cardinals and blue jays.
“If you think about a coyote or a fox, who are active year-round, they’ve got such a thick coat on them and that coat provides a great amount of insulation for them,” Drake said. “With a deer’s winter coat, the outer hairs are hollow and actually absorb and transfer heat from solar radiation into their body.”
While these animals’ fur acts as a winter coat, even with the best winter coat it’s hard to imagine surviving the Polar Vortex outside without somewhere to warm up. To solve this, local wildlife take advantage of what Drake describes as microclimates: places within our landscape with pockets of warmer air.
“A lot of times we see coyotes go into cattail marshes or thick grassland and bed down there because that grassland is not only blocking the wind but it’s providing a lot of thermal insulation, and other animals will get into evergreen trees because that evergreen tree doesn't lose its needles,” Drake explained. “There’s a lot of wind blockage and those evergreens kind of serve as an umbrella—nature’s umbrella.”
This is similar to the way humans use buildings to keep us out of the wind and the weather. In houses, for example, insulation lining the exterior walls keep in the heat generated by furnaces. These furnaces are fueled by natural gas or electricity. Lots of local wildlife active during the winter have a different type of furnace, a high metabolism, which they fuel by eating lots of food.
“With smaller animals, like a meadow vole or some of the mouse species, they eat more than double their weight every day in food because their metabolism is running so high that they’re burning a lot of calories,” Drake said. “There is a lot of vegetation available for them to eat and they’re just constantly piling food into their body to keep that engine, or that furnace, running.”
How do we know so much about what animals are doing during the winter, when most humans are indoors keeping warm? Researchers such as those running the UW Urban Canid Project, a team led by Drake, collect data on animals even during the frigid temperatures we had last week. Each winter, the group traps local fox and coyotes to put radio collars on them which track their movements.
“We’re collecting eight hourly locations a night on coyotes and four hourly on fox. Last week when it got down super cold, those animals they still moved quite a bit. Every single night, they were out moving around,” Drake said.
These coyotes and fox are traveling all over our urban landscape during the winter months, and some can cover quite a bit of ground, as Drake explained: “We’ve got a coyote now who is essentially covering the entire western part of Madison in the course of a week.”
Coyotes and foxes also trek across the frozen surface of Lake Mendota toward locations such as Governor Nelson State Park which sits on the north shore opposite from UW-Madison campus.
Drake added that foxes will be having kits by the end of the month, and as cute as a fox puppy sounds, these offspring must be tough enough to cope with late winter weather. The benefit to having kits this early is by the time other small mammals start having their young the kits will be old enough to hunt and “there is just a plethora of food out on the landscape for them to hunt.”
Animals have evolved a variety of adaptations which allow them to not only survive but thrive during the winter. Insulating fur, high metabolisms, and resourcefulness in finding warmer microclimates within evergreen trees or grasslands are some of the defenses animals active during the winter have developed to fight off the cold.
You may have been worried about local wildlife during the Polar Vortex last week but rest assured. These animals are just as innovative as humans in finding ways to keep warm through the winter. Their innovations just look a little different.