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.

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

Hordes of hummingbirds

Post by Jen Berlinghof

hummingbirds 003

For me, most days on the job consist of time in my “office” outdoors—a woodland, prairie or wetland in the Lake County Forest Preserves—with my “clients”—students, teachers, and families interested in learning more about local nature. On those rare days spent plunking away at a computer indoors, the photo above is my view. Recently, this view is bustling with activity, as hordes of ruby-throated hummingbirds buzz around the feeders, bulking up for a long flight south.

Screen Shot 2016-08-22 at 11.46.50 AM

Continue reading

Des Plaines River Trail—Route 60 to Route 22

Post by Jen Berlinghof

As the hours of daylight drastically shorten in November, the miles of our hike along the entire Des Plaines River Trail quickly stack up. The trek south along this stretch of the trail from Route 60 to Route 22 was summed up in the stillness of bare branches that were silhouetted against the sky and reflected back from mirrors of water in the surrounding floodplain forest. Continue reading

April Fools’ bird

Post by Jen Berlinghof

It was a windy, but bright, April 1 this year. I was on a trail at Ryerson Woods with a group of volunteers. Most of our heads were focused downward, inspecting the minutiae of a bloodroot bloom. Then, someone shouted, “EAGLES!” I truly thought the next thing shouted would be “APRIL FOOLS’!” but when we snapped our heads skyward, we saw two ivory-headed eagles swooping back and forth above the trees. No joke!

Continue reading

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

Heron highrise

This past weekend I had the pleasure of hearing Kenn Kaufman, a naturalist and bird expert, speak at the Smith Nature Symposium. He is somewhat of a “rock star” in the birding world. His novel, Kingbird Highway, chronicles a personal adventure hitchhiking around the country at the age of 16 on a quest to find birds—a story that has reached the status of folklore. Many years later, and surely a much longer “life list,” his keynote address at Ryerson Conservation Area focused on warbler migration: the phenomenon of these teeny tiny birds in every hue of the rainbow that travel thousands of miles across entire continents each spring and fall. He presented complicated doppler maps and in-depth scientific research on these migratory dynamos, but by the end of the discussion the focus had shifted to something more simple: the children from his young birders club.

guide-bookLate that evening, as I settled down with one of his many guide books, Field Guide to Advanced Birding, I was struck by this same theme of simplicity. Kaufman urges folks to slow down and focus not on looking for the birds, but instead to spend time looking at the birds. He stresses getting to know the common birds of an area very well. By doing so, we are well on our way to knowing when a rare bird may enter the scene. This concept brought to mind one of the best places to take a long look at one common bird of Lake County, Illinois: a great blue heron rookery.

Continue reading

Where do insects go in the winter?

Post by Allison

Earlier this week, my husband came in from the yard with a mosquito on his forehead. Had it been summer, that little tag-along would never have made it so far—but not in December. In the colder months, critters that are commonplace during the Midwestern summer are often the farthest things from our minds. It always amazes me when the weather has been cold for an extended period, then, at the first sign of warmth, insects seem to magically reappear. Where have they been hiding? How did they survive the frigid air that makes me shiver in my sweater when I’m outdoors longer than a few minutes?

Where do insects go in the winter?

Continue reading

Warbler fever

Birding fever hit a high this past weekend in natural areas throughout northern Illinois. Birders flocked in throngs with binoculars strung on their necks like potential Olympic medals and a hope of spotting some of the most coveted migratory birds— wood-warblers. Members of the family Parulidae, wood-warblers are the colorful jewels of migration from the sapphire blue of a cerulean warbler (Setophaga cerulea) to the amber orange of a Blackburnian warbler (Setophaga fusca). Yet, as these birds flit about in the treetops, no color is as visually striking as the lemony-yellow citrine that adorns so many warblers as they pass through our area on a flyway. Once these impish birds reach their destinations (as far as northern Canada for some species) and breed, they will molt their flamboyant plumage and become far less conspicuous, which is why seeing them in the spring is considered such a prize for birders.  Continue reading

Glimpses from the car window, bootprints on the trail

Like most of you reading this, my life is busy. Even though I work outdoors in the forest preserves, not all of my nature experiences occur there. Many days I have to take the glimpses of nature where I can get them. On my drive home from work last week, glancing at the “not-so-glamorous” retention pond next to the tollway, I spotted my first hooded merganser of the year. I knew the gang was back, although some of them not for long. This “gang” I’m referring to is the group of migratory waterfowl that show up here in the early spring during migration en route to their final destinations further north. With names like horned grebe, American wigeon, northern shoveler, and gadwall (just a few of the species seen in the past few days at Independence Grove Forest Preserve, here is the complete list), who wouldn’t want to meet this cast of characters?

This time of year is the perfect opportunity to take a peek at some fascinating birds close to home. Continue reading