How native animals survive the colder months
Editor's note: April Vaos, environmental educator for the Lake County Forest Preserves, wrote this story.
In your forest preserves, winter is peaceful, the sounds softened by snowfall and an apparent drop in animal activity. When Environmental Educator April Vaos leads winter walks, participants commonly ask, "Where are all the animals?"
The answer depends on the species.
"Each employs survival strategies that help it adapt and even thrive in winter," Vaos said. "I like to say wildlife have 'MAD' strategies: migrate, active, dormant.
Migrate: On the move
Many native animals migrate over short, medium or long distances to survive winter. It's less about the cold and more the lack of food sources such as insects, plants and fish, which become inaccessible when bodies of water freeze over.
Birds, butterflies and bats are common migrators.
"You've probably heard about the migration of monarch butterflies, but hoary bats migrate 1,200 miles each way from Illinois to southern California or Mexico for the winter," Vaos said.
Dark-eyed juncos migrate to the lower forty-eight states from their Canadian breeding grounds. Recognize them by remembering the phrase "leaden skies above, snow below."
Not all wildlife travels to different states or countries. Some amphibians, such as American toads, and insects, such as June beetles, burrow into the soil below the frost line to stay warm.
Active: What cold?
Other animals remain active, including coyotes, great horned owls and channel catfish. Staying in the area requires wildlife to find food continuously. They may grow extra fur or build special homes to endure the weather.
Northern cardinals, the Illinois state bird, are permanent residents. Their diet of seeds, fruits and insects helps them find enough food year-round.
Like mammals, "cardinals are endothermic, meaning they produce their own body heat," Vaos said.
When snow is on the ground, red foxes practice a hunting technique called mousing. Prey animals such as white-footed mice and meadow voles make sounds as they chew food or move beneath snow. Fox ears are sensitive to these sounds. Once a fox hears prey, it pounces, punching through the snow headfirst to snap it up.
Dormant: An Epic Nap
Certain animals enter dormancy, a period when metabolic activity is minimal and physical development is suspended to conserve energy. Hibernation is full dormancy and can last all season.
Body temperature, heart rate and metabolic rate greatly decrease. Groundhogs and 13-lined ground squirrels are hibernators. Some animals are active in warmer weather but enter a deeper sleep, called torpor, daily or during bouts of extreme cold. Black-capped chickadees and deer mice do this.
In fall, a wood frog finds a safe spot under a log or leaf litter. When the temperature falls below 32 degrees, the frog starts to freeze. Its liver converts glycerol into glucose, forming a natural antifreeze that protects its body.
"If you found a frozen wood frog, there would be no heartbeat or breathing motion to show it was alive. But in spring, this hardy creature will thaw and hop away as if it never became a frog-cicle," Vaos said.
Many animals use multiple strategies to outlast the cold. Blanding's turtles are ectothermic, or coldblooded. Sunlight and air and water temperatures keep their bodies functioning.
For the winter, this species and other freshwater turtles migrate to the bottoms of wetlands, bury themselves in mud and enter dormancy.
• Kim Mikus is a communications specialist for the Lake County Forest Preserves. She writes a bimonthly column about various aspects of the preserves. Contact her with ideas or questions at kmikuscroke@LCFPD.org. Connect with the Lake County Forest Preserves on social media @LCFPD.