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.

Bringing back the buzz

Post by Jen Berlinghof

All summer long, swaths of wild bergamot (Monarda fistulosa) quake in the presence of thousands of native bumble bee wings beating away. These pollination dynamos use a technique called buzz pollination, vibrating their bodies to trigger nearby flowers to release pollen. At the Lake County Forest Preserves in northern Illinois, a similar buzz of excitement arrived in summer 2020 when staff spotted the federally endangered rusty patched bumble bee (Bombus affinis) at Greenbelt in North Chicago.

Fast forward to summer 2021. The hum continues to reverberate after multiple sightings of this keystone species were documented across the county from Flint Creek to Wadsworth Savanna in Wadsworth. While summer’s the height of hive activity, the shoulder seasons—usually defined as May, June, September and October—might be key to the success of the rusty patched bumble bee. This is partly due to the timing, or phenology, of the species’ lifecycle. It’s one of the first bees to emerge in spring and the last to enter hibernation in fall.

A worker, or male, rusty patched bumble bee (Bombus affinis) sits atop mountain mint. Photo © Dan Mullen.
A rusty patched bumble bee (Bombus affinis) sits atop mountain mint. Photo © Dan Mullen.
Continue reading

A thousand-mile journey on two-inch wings

Post by Jen Berlinghof

I’ve spent many days this summer living the “lake life,” from the sandy dunes of the Great Lakes to the cattail-studded coves of inland waters. The waterways found within the Lake County Forest Preserves in northern Illinois have been especially rewarding. Each shoreline has provided unique glimpses of wildlife, including an osprey (Pandion haliaetus) diving full throttle to catch a fish at dawn, and a red fox (Vulpes vulpes) pouncing on prey hidden among the beach grass at dusk.

Also present at every waterway this summer has been the jewel-hued, common green darner dragonfly (Anax junius). These ubiquitous insects effortlessly nab multitudes of mosquitoes on the wing. While the monarch butterfly (Danaus plexippus) reigns in our minds when it comes to insect migrations, recent research reveals the green darner takes a multi-generational, miles-long journey of its own each year.

Common green darner dragonflies (Anax junius) are found in the forest preserves. Stock photo.
Common green darner dragonflies (Anax junius) are found in the forest preserves. Stock photo.
Continue reading

A native garden to call your own

Guest post by Eileen Davis

What is your earliest gardening memory? Was it planting a seed in a paper cup at school, and watching it sprout and grow on the classroom windowsill? Perhaps you gathered dandelion flowers and presented your mom with a beautiful, yellow bouquet. Or did you rake up a giant pile of leaves to jump in on a crisp fall day? You might even have visited the native garden at Independence Grove in Libertyville, part of the Lake County Forest Preserves in northern Illinois.

My earliest gardening memory is helping my aunt and uncle in their garden. I was only about four or five years old, but I clearly remember the prickly feeling of the cucumber vines scratching my forearm as I helped pull weeds. No matter the memory, we are all doing the same thing—tending to our little piece of the Earth. It’s something humans have done for thousands and thousands of years. We are and always have been dependent on our environment for survival.

The author's daughters playing in a backyard leaf pile. Photo © Eileen Davis.
The author’s daughters playing in a backyard leaf pile. Photo © Eileen Davis.
Continue reading

Milkweed. It’s not just for the monarchs.

Post by Jen Berlinghof

Being home more these past months has allowed my family copious time to observe the common milkweed (Asclepias syriaca) in our garden go through its life cycle day by day. We’ve witnessed the transformation from wily little sprouts in early summer to blooming beasts, with pompoms of eraser-pink flowers wafting perfume across the yard—even threatening to take over the footpath—by Fourth of July. Now in the sweet days of September, our milkweed is laden with swelling seed pods, ready to burst with floating seeds like so many little white parachutes scattered in the autumnal sky. The situation is similar in many of the Lake County Forest Preserves in northern Illinois.

The beautiful flowerhead of common milkweed (Asclepias syriaca). Photo © Lake County Forest Preserves.
The beautiful flowerhead of common milkweed (Asclepias syriaca). Photo © Lake County Forest Preserves.
Continue reading

The moth and the moon

Post by Jen Berlinghof

A full moon rises, a screen door slams shut, a katydid’s creaking calls echo, and a Luna moth (Actias luna) flutters in circles around the back porch light. We’re captivated by this green ghost of summer, concealed by broad leaves and seen rarely during the day, emerging at night only to mate for its few fleeting days of adulthood. How lucky it is that Luna moths live in the Lake County Forest Preserves in northern Illinois.

The bright green wings of the Luna moth (Actias luna) are instantly recognizable. Stock photo.
The bright green wings of the Luna moth (Actias luna) are instantly recognizable. Stock photo.
Continue reading

A different kind of autumn apple

Post by Jen Berlinghof

Fall is the time of harvest here in the Midwest. Golden stacks of hay bales, farmer’s markets teeming with end-of-season produce, and above all, apples. But step away from the orchard and into an oak woodland and you’ll find a different kind of autumn apple: an oak apple gall. What looks like a small, lime-green, spotted apple dangling from an oak leaf is not a fruit at all, but rather a secret abode for a tiny wasp.

There are more than 50 species of oak apple gall wasps in North America. Each one creates a unique fruit-like structure that protects and feeds its eggs and larvae as they develop. Lately, I’ve been finding many dried, spent brown husks created by the larger empty oak apple wasp (Amphibolips quercusinanis) around the Lake County Forest Preserves in northern Illinois.

Continue reading

The din of the dog days

Post by Jen Berlinghof

The dog days of summer are a bounty for the senses. We see the lemon-yellow of whorled sunflower blooms, taste the ripe flavor of a homegrown tomato, smell the spicy sweetness of bee balm flowers, feel the heat of the day and the cool of the evening. Yet the most quintessential sensation of these end-of-summer days is hearing the overwhelming cacophony of cicada songs around the Lake County Forest Preserves in northern Illinois.

Continue reading

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.

Continue reading

Summer “buzz kill”

Post by Jen Berlinghof

The sun had set, the campfire was doused, and the food was stashed away for the night as my sons and I tucked ourselves into our sleeping bag cocoons, thoroughly exhausted in a way one can only be from a day spent entirely outdoors. Still, sleep would not come easily. The whirling drone of thousands of annual cicadas buzzed through the nylon walls of our tent loud enough to overpower our fatigue. I lay awake, thinking it odd the cicadas would be calling after dark, when I caught a hint of the rising full moon through the ceiling screen and realized they were staying up late to party with the extra light. One of my boys groaned, “Isn’t there anything that can stop these CICADAS?” As a matter of fact, the next day we found just the thing: a cicada killer wasp (Sphecius speciosus).

The author holds a dead cicada killer wasp in her palm. Photo © Lake County Forest Preserves.

Continue reading