How animals survive the winter

Guest post by April Vaos

Living in Illinois, we’re lucky enough to enjoy a change of seasons. Though I often find it difficult to switch from the crunch of fall leaves to the crunch of snow, it can be a peaceful time to head outdoors. Recently, I went walking in Independence Grove in Libertyville, part of the Lake County Forest Preserves in northern Illinois. As I looked around in the quiet, contemplative landscape, I thought about the life that teemed all around me, and how it was now hidden from view or departed on a migration.

While leading winter walks, I’m often asked, “Where are all the animals?” It depends on the animal. Each employs different survival strategies that help it adapt and even thrive in winter. What, exactly, do animals do to make it through the challenges of cold temperatures and a lack of food? Well, I like to say they have MAD strategies: migrate, active and dormant.

When cool temperatures arrive in northern Illinois, so do dark-eyed juncos (Junco hyemalis). Not only do they visit Illinois, they migrate into all of the lower 48 states to spend a milder winter than where they’re from: Canada. Stock photo.
When cool temperatures arrive in northern Illinois, so do dark-eyed juncos (Junco hyemalis). Not only do they visit Illinois, they migrate into all of the lower 48 states to spend a milder winter than where they’re from: Canada. Stock photo.

Migrate: Many animals in Lake County migrate, or travel, from one place to another over short, medium or long distances to survive winter. It isn’t so much about the cold as the lack of food in winter. Food sources such as insects, plants and fish—which can’t be reached when waterbodies are frozen over—are largely unavailable.

Birds, butterflies and even bats are common migrators. Though we often think of animals migrating across hundreds or thousands of miles to different states or countries, they can also migrate short distances vertically. For example, some amphibians and insects burrow further down the soil horizon below the frost line to stay warm.

Lots of folks marvel over the long migration of monarch butterflies (Danaus plexippus), but hoary bats (Lasiurus cinereus) make extended flights, too. It’s believed that Illinois’ hoary bats migrate to southern California or Mexico for the winter, a 1,200-mile trip each way!

Hoary bats (Lasiurus cinereus) migrate to warm, southern locales for the winter. Photo © Merlin Tuttle.
Hoary bats (Lasiurus cinereus) migrate to warm, southern locales for the winter. Photo © Merlin Tuttle.

Active: Some animals remain active during winter. Doing so means they need to find food continuously to survive. To endure the weather, they may grow extra fur or build winter homes. Examples of animals that stay active include white-tailed deer (Odocoileus virginianus), coyotes (Canis latrans) and even channel catfish (Ictalurus punctatus).

Northern cardinals (Cardinalis cardinalis) are both the Illinois state bird and a great example of an active winter animal. Cardinals are permanent residents, forgoing southward migration. Due to the cardinal’s varied diet of seeds, fruits and insects, they can find enough food in Lake County year-round. While often called warm-blooded, a better term is endothermic, meaning cardinals can produce their own body heat.

Northern cardinals (Cardinalis cardinalis) are red year-round. They get their color from carotenoid pigments in the seeds and fruits they eat. Stock photo.
Northern cardinals (Cardinalis cardinalis) are red year-round. They get their color from carotenoid pigments in the seeds and fruits they eat. Stock photo.
During winter, red foxes (Vulpes vulpes) practice a hunting technique called mousing. Fox ears are sensitive to the quiet sounds that prey animals make as they chew or move around beneath the snow. When a fox locks on to a vole or mouse, it pounces, punching through the snow headfirst, trying to snap up its prey. Stock photo.
During winter, red foxes (Vulpes vulpes) practice a hunting technique called mousing. Fox ears are sensitive to the quiet sounds that prey animals make as they chew food or move around beneath the snow. When a fox locks on to a vole or mouse, it pounces, punching through the snow headfirst, trying to snap up its prey. Stock photo.

Dormant: Dormancy describes a period when an animal’s metabolic activity is minimal and development is temporarily suspended to conserve energy. This allows species to prosper in environments where they might not otherwise be able to survive.

There are varying degrees of dormancy. Hibernation is full winter dormancy, which can last all season and includes decreased body temperature, heart rate and metabolic rate. Groundhogs (Marmota monax) and thirteen-lined ground squirrels (Spermophilus tridecemlineatus) are hibernators. On the other hand, torpor, a deeper sleep than normal—as seen in black-capped chickadees (Parus atricapillus) and deer mice (Peromyscus maniculatus)—may only last a few hours. These animals are active in warmer weather but may enter torpor daily or during bouts of extreme cold.

Groundhogs (Marmota monax) are skilled at surviving winter through hibernation—but contrary to popular culture, they don't have the ability to predict weather or the severity of the winter. Stock photo.
Groundhogs (Marmota monax) are skilled at surviving winter through hibernation—but contrary to popular culture, they don’t have the ability to predict the severity of the winter. Stock photo.

Wood frogs (Lithobates sylvaticus) have an almost zombie-like adaptation. In fall, a wood frog finds a safe spot under a log or leaf litter. When the temperature in its home falls below 32 degrees Fahrenheit, the frog starts to freeze. This prompts its liver to convert glycerol into glucose, forming a sort of antifreeze. If you were to find a frozen wood frog, there’d be no heartbeat or breathing motion to tell you it was alive. But come spring, this hardy critter will thaw and hop away as if it never became a frog-sicle.

It’s interesting to note that most animals don’t have just one, but multiple strategies for outlasting winter. Blanding’s turtles (Emydoidea blandingii) are cold-blooded—or ectothermic—so they depend on the sun’s rays, plus air and water temperature, to keep their body temp ideal. For the winter, a Blanding’s turtle migrates down to the bottom of a wetland and buries itself in mud. Once safe and sound, it enters dormancy.

Looking for a way to not just survive but thrive this winter? Venture out for a hike with our Animals in Winter program on January 15, 2022, 1-4 pm. Or learn to decipher animal tracks by taking our Winter Tracking and Wildlife Observation Workshop program on January 29, 2022, 9:30 am-12 pm.

Whatever you choose, I hope you get outside this winter and enjoy the serenity of the season, knowing that many animals are hunkered down for the time being—just waiting for spring to return.

Become a community scientist

Post by Jen Berlinghof

While the past year and a half has kept many of us mostly at home, nature in our backyards and beyond has provided a balm for these trying times. General use of the Lake County Forest Preserves in northern Illinois is trending 30% higher in 2021 than a typical pre-pandemic year. And in 2020, there was an astounding 70% surge in visitation. The number of folks delving into home gardening and backyard birding has skyrocketed as well, making headlines by leaving store shelves bare of birdseed and bird feeders. The COVID-19 pandemic has amplified our desire to connect to nature closer to home, and it has created space and time for local, daily observations. All of this translates to an environment ripe for community science, also called citizen science.

Community scientists flip over a cover board during a BioBlitz event held at Middlefork Savanna in Lake Forest in 2008. Photo © Carol Freeman.
Community scientists flip over a cover board during a BioBlitz event held at Middlefork Savanna in Lake Forest in 2008. Photo © Carol Freeman.
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Time to make a moment

This gallery contains 18 photos.

Post by Brett Peto

Time can never be stopped, sped up, or slowed down. It started long before now and will continue far after. But with photographs, we can pause time, pin it in front of us, and study reality. It’s like kneeling at a riverbank and scooping a handful of water. The current stops in your palm, but just a foot beneath it carries on. Photos take time to make a moment.

With nearly 31,000 acres to explore, many moments are possible in the Lake County Forest Preserves in northern Illinois. An eastern bluebird (Sialia sialis) landing with one foot, wings at sharp angles. A cluster of milkweed seeds hanging on to their pod by threads of floss. Sunflowers and sunbeams, two shades of honey mixing in the air. I’ve collected these special moments and more in a gallery below.

All photos featured were taken by the truly skillful photographers in our group Flickr pool. Each of these images, these presses of the pause button and scoops out of the river, were captured in 2018. Our sincere thanks go to every photographer who shares their time and talent documenting the flora, fauna, and natural areas of Lake County.

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“Toadally” awesome!

Post by Jen Berlinghof

Last week, our Wetland Explorers summer nature campers went wild…in a good way! We were hiking along the Des Plaines River Trail when we came upon a major toad hatch-out. Hundreds of dime-sized toadlets took over the trail, prompting shrieks of excitement from the campers. The kids scurried around, scooping up handfuls of toads, trying to save all the hopping and popping amphibians from potentially hazardous bike tires and hiking boots along the trail.

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Slippery spring saga

Post by Jen Berlinghof

It was late March, fourteen years ago, when I took my first hike at Ryerson Woods. The air felt heavy with thawing snow. The sun warmed my back for the first time in many months. Standing at the edge of a small, glistening pool of water in this oak flatwood forest, I saw my first blue-spotted salamander (Ambystoma laterale). About the length of a crayon, this inky black amphibian is adorned with tiny, blue confetti-like spots on a dewy body. Blue-spotted salamanders hide in abandoned mammal burrows or under logs most of their life. Each spring, warming temperatures and increased precipitation lure these creatures out of their covert caverns for a slow and steady march to their breeding ponds.

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Wood frogs found!

Discovery is often about being in the right place at the right time. This is exactly what happened recently when a wildlife biologist for the Lake County Forest Preserves was in the right woodland on the right spring day. While monitoring wildlife, a biologist heard sounds from the elusive wood frog (Rana sylvatica). The duck-like breeding calls made by male wood frogs had not been heard in Lake County, Illinois since the late 1980s. This discovery is the first sign of victory following extensive habitat restoration and recent species reintroduction efforts.

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Army of frogs

My young sons and I recently read a library book together about the names of animal groups. I was struck by how many of the group names match the animals’ behavior or movement: a parliament of owls, a flutter of butterflies, a walk of snails. The boys and I agreed our favorite group name was an army of frogs. Continue reading