When the going gets tough, the tough… adapt

While some wildlife migrate to warmer regions in winter, others hibernate, change their furs or freeze.

Many creatures — like chipmunks, hummingbirds, woodchucks, bees, snakes, bears, skunks and opossums — enter states of winter dormancy to conserve energy. This is typically called hibernation. Hibernation is a type of winter dormancy where body temperature, heart rate, metabolic rate, and/or breathing rate decline. But each species hibernates in its own special way.

Weasels, hares, and jackrabbits change their coats to white to blend in with their snowy surroundings. Fish congregate in deeper, warmer waters. Some amphibians freeze for the winter.

Some humans choose to stay inside. But we hope you, our loyal readers, stay active and discover the wonders of winter outdoor recreation and wildlife viewing (scroll down for insider tips from our park naturalists!).

Special gratitude and a shout-out to our friends in the Nongame Wildlife Program (of Eagle and Falcon Cam fame) who collaborated with us on content for this Trailblazer issue. 

Frozen

Amphibians and reptiles are famously cold-blooded or “ectotherms,” which means they depend on the environment to regulate body temperature.

On summer evenings, look for the gray treefrog by your window, feeding on bugs attracted to the light inside.

Spring peepers, some gray treefrogs (pictured) and wood frogs spend the winter in a partially frozen state under fallen leaves, rocks or logs. Their livers convert glycogen into glucose (wood frogs) or glycerol (spring peeper and gray treefrogs) to produce an antifreeze to keep liquids from freezing inside their cells, while allowing ice crystal to form between layers of skin and muscle. They stop breathing and their hearts stop beating.

More about wood frogs from the National Park Service.

Turtles adjust their body temperature to their surroundings and can drop it as low as 39 degrees Fahrenheit.

The snapping turtle is Minnesota’s largest turtle.

Many Minnesota turtles survive the winter underwater or mud. Within hours of being underwater, a turtle’s blood oxygen levels drop to near zero, when they rely on cloacal respiration. The blood vessels around the cloaca (butt) are able to take up oxygen directly from the water. If oxygen is depleted, snapping and painted turtles can switch to anaerobic respiration, which is a form of breathing that does not require oxygen. This can cause lactic acid build-up, which turtles neutralize with carbonate buffers… and plenty of basking in the springtime sun to increase metabolic rate and get rid of acidic by-products.

Source and more information: How do turtles survive the winter? from Carleton College Cowling Arboretum website.

Northern migrants

Many songbirds have migrated south of Minnesota for the winter. But some songbirds migrate south *to* Minnesota!

Snowy owls (pictured) nest in the Arctic tundra of northern Canada and Alaska during the summer. From early November to late March, some migrate south to Minnesota to hunt voles, mice, and other small animals. Look for them in northern Minnesota in large, open areas (like fields and airports), or perched on the ground, on buildings or on utility poles. Snow buntings have adapted to thrive in winter environments. Their dense white feathers, which cover them from bill to ankles, and a lower body temperature help them fend off hypothermia. They migrate from the Arctic to spend October through April wandering the northern Great Plains, looking for food by lake shores, grasslands and farm fields.

Click on the photo to read about golden eagles wintering in Minnesota on the Minnesota Conservation Volunteer magazine.

Golden eagles also migrate from Canada, some from as far north as the Arctic Circle, and spend November through March hunting turkeys and fox squirrels in central and southeast Minnesota. Golden eagles can be hard to distinguish from young bald eagles, but there are subtle differences.