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.

Go take a hike

Post by Nan Buckardt

Everyone has one! At least, anyone who regularly hikes in the Lake County Forest Preserves in northern Illinois has one: a favorite trail. It might be the trail near your home or the one that reminds you of a secret only-I-know-about-this spot growing up. Maybe it holds a special memory. Whatever the reason, something about it always sparks joy in your heart.

I’ve been thinking about trails a lot this fall as I’ve hiked those selected for this year’s Hike Lake County (HLC) program. HLC has encouraged folks for 20-plus years to explore seven of 12 designated trails between mid-August and November 30. More than 200 miles of trails thread through dozens of preserves countywide, so the diversity of choices isn’t necessarily a big surprise, but it is a big benefit to residents and visitors.

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Leopards and tigers and bears!

Post by Jen Berlinghof

Around the first frost is the best time for spotting bears in the Lake County Forest Preserves in northern Illinois…woolly bears, that is! These fuzzy caterpillars succumb to a late fall wanderlust and can often be found traversing trails and roads, as well as climbing vegetation and nibbling a last few bites before winter sets in. They belong to the subfamily Arctiinae, commonly known as tiger moths. Their scientific name stems from the ancient Greek word arktos (“bear”), for the appearance of their hairy larvae.

A woolly bear caterpillar (Pyrrharctia isabella) found along the Des Plaines River Trail. Photo © Lake County Forest Preserves.

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Happy New Year!

Video

Happy Winter from the Lake County Forest Preserves!

Video by Brett Peto

Whether venturing outside for fresh air and exercise, or finding a gorgeous spot to sit quietly and reflect on the past year, we find great peace in the Lake County Forest Preserves.

Thank you all for following along on our adventures this year. We encourage you to find a quiet spot to just breathe—perhaps the still woodlands of Captain Daniel Wright Woods:

Cheers to a new winter and peaceful new year!

Snowflake anatomy

Post by Jen Berlinghof

My family and I spent the beginning of the new year in the Northwoods. We wanted quiet. We wanted nature. Most of all, we wanted snow. As we started out on a snowshoe trek to a nearby river, tiny snowflakes settled on my son’s navy blue parka. They seemed to freeze on contact for only a few seconds, forming miniature constellations, before melting into temporary teardrop stains. The filigree of each flake in those hushed, fleeting moments fascinated both of my boys.

snow-crystal1

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Nature at night

Post by Jen Berlinghof

This winter’s lack of snow has made enjoying the winter woods a little more difficult for me. So, when a scant few inches of snow fell last week I made my way to Old School Forest Preserve at dusk to explore one of the Lake County Forest Preserves solar-lit trails.

Inky black branches of old oaks played in contrast to the white-washed sky before the blush of an orange sherbet sunset took over. The woods were still and quiet as I searched for any signs of crepuscular creatures that capitalize on the twilight. Continue reading

Des Plaines River Trail—Route 22 to Lake-Cook Road

Post by Jen Berlinghof

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It was a new year and a new trail, as we completed the last leg of our Des Plaines River Trail journey to hike the entire length of Lake County, Illinois. We began this hike just south of Route 22, which led us south through the recently completed trail section and beyond to the southern border of the county. We left our tracks upon the trail, just as the animals do along this greenway. Along the way, we found fresh signs in the snow that mice, squirrels, small birds, raccoon, deer, fox and even some intrepid fat-tire cyclists had all traversed the trail before us, taking advantage of a balmy 40-degree day in January. Continue reading

Stories in the snow

Post by Jen Berlinghof

As the thermometer dipped to -8 degrees Fahrenheit this week, one thing was clear: the snow and cold are entrenched for a while longer. So are the stories of the animals, as told by the tracks etched in the frozen landscapes that sweep across the Lake County Forest Preserves. We may not see the animals themselves. However, each track, pile of scat, bit of hair clinging to a branch, hole in the snow and chewed acorn is an element of the tale from their winter excursions.

How do we decipher these stories? When trying to identify which animal made a particular track, it is important to look not only at the individual track but the overall pattern. Also, scan the surrounding habitat for clues.

Let’s see if you can figure out what happened in each of these nature vignettes:

mouse tracks

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Surviving in the subnivean

This winter has been harsh in Lake County, Illinois, causing many of us to wish we could migrate to South America like some birds do, or hibernate in a cozy underground den like the groundhog.  Alas, most of us just stick it out in the cold. It may offer consolation to know we are not the only animals active during these record-breaking cold, snowy days. It turns out there is a whole ecosystem teeming with life right under the snow.

Recently, scientists having been taking a closer look at life in the subnivean, which literally translates to “a place under the snow.” The space between the snow and the ground acts as a seasonal refuge for invertebrates, birds, and small mammals. Snow affords these small critters with remarkable insulation, and temperatures around 32 F regardless of the temperature above the snow. Biologist Bernd Heinrich explains the science underlying these insulating properties in the book Winter World: The Ingenuity of Animal Survival. “As long as both ice and water exist side by side, they constitute a thermostat keeping temperatures constant.” When water converts to ice crystals, heat releases. When ice turns into water, the process uses up heat.

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A snowy spark

Many years ago, while running along the Lake Michigan shoreline late on an evening in January, a feathered ghost appeared on top of a flag pole. It was the first time I had ever seen a snowy owl (Bubo scandiacus) and it stopped me in my tracks. This was the spark on that frozen night that lighted my fire of curiosity about birds. This winter, snowy owls have left their Arctic homes in record numbers, causing one of the largest irruptions (sudden increase) in northern Illinois in decades.

Although it seems natural to correlate the arrival of these boreal birds with the extremely cold, snowy winter northern Illinois is having, experts say the motivator is more likely linked to food. On their Arctic breeding grounds, snowy owls feast under 24-hour sunshine. Their food of choice is lemmings, small mammals with an extremely cyclical population. Bird expert Kenn Kaufman explains in a recent Audubon magazine article, that when the lemming population explodes, like it did last summer in northern Quebec, snowy owls have great breeding success, producing large broods of up to 11 chicks. As these chicks quickly grow into juvenile birds, the competition grows for the now dwindling numbers of lemmings. Thus, the young birds get nudged further and further away to find a meal, resulting in them moving to areas that mimic their treeless tundra home, such as the Lake Michigan shoreline. Continue reading