How Wild Animals Survive Freezing Winter Weather

how wild animals survive winter

Story at-a-glance -

  • Birds that don’t migrate survive the winter by eating and building up a thick fat layer, then entering a state of hypothermia overnight and shivering to help stay warm
  • Fish typically enter a rest state during the winter, during which they have decreased demands for food and oxygen
  • Frogs, snakes and turtles enter a dormant state known as torpor when the weather gets cold
  • Certain mammals that don’t hibernate, including skunks, raccoons and opossums, may take naps that last for weeks during the coldest months, but will venture out to look for food when they’re able

By Dr. Karen Shaw Becker

Have you ever wondered how wild animals survive cold, harsh winter weather, even as temperatures and wind chills dip well below freezing? Different species have different survival methods, making them well-equipped to handle the cold, even as you feel you might freeze while running between your car and your house.

While some animals leave town entirely, migrating to warmer areas, other animals hibernate or brumate while still others find the warmest places they can to weather the winter and make it their mission to find as much food as possible.

Their very survival often depends on it. "These animals are well adapted to this environment," Mike Konrath, director of Sagawau Environmental Learning Center in Lemont, Illinois, told the Chicago Tribune. "They have lived in it for thousands and thousands of years."1

Birds Eat to Build up a Layer of Fat

Birds that don’t migrate survive the winter by eating and building up a thick fat layer, then entering a state of hypothermia overnight and shivering to help stay warm. Certain birds, including chickadees and kinglets, are able to enter “regulated hypothermia,” in which their body temperatures drop by up to 15 degrees Fahrenheit at night, which allows them to save significant amounts of energy.2

Birds like chickadees will also hide seeds they collect during the fall to eat later during the winter. Interestingly, the volume in their brain’s hippocampus actually increases by 30 percent in the winter months in order to help them remember where they put all their seeds, then shrinks back down to “normal” size come spring.3 Things get especially challenging for birds when snow covers up their food supply, which is why putting bird feeders (and a heated bird bath) in your backyard is so important.

"Finding food is the biggest thing for them," Konrath told the Tribune. "As long as they can find food, they do pretty good. But when snow is on the ground, a lot of their (natural) food is covered."4

Fish Slow Down for a ‘Winter Rest’

Fish are cold-blooded, so their metabolism slows when temperatures drop, as does their heart rate. Fish typically enter a rest state during the winter, during which they have decreased demands for food and oxygen.

Fish can generally survive in water as cold as 37 degrees F, although when snow covers a frozen pond it decreases sunlight entering the water, and therefore photosynthesis by algae, lowering the amount of oxygen in the water, which can be problematic for fish.5 Further, according to the U.S. National Ocean Service:6

“Because warm water sinks in very cold freshwater, fish in these water bodies often gather in groups near the bottom. Some species, like koi and gobies, may burrow into soft sediments and go dormant like frogs and other amphibians, but most fish simply school in the deepest pools and take a ‘winter rest.’”

Frogs, Snakes and Turtles Enter Torpor

Frogs, snakes and turtles enter a dormant state known as torpor when the weather gets cold. Many frogs spend the colder months buried in mud at the bottom of ponds (with the exception of tree frogs, which actually freeze and thaw out in the spring via an antifreeze-like compound in their blood).7 Snakes similarly take shelter in a crevice to ride out the winter.

Some turtles, on the other hand, depend on cloacal respiration during winter months, which is the ability to extract oxygen from the water via its cloaca — the hole in a turtle behind through which it excretes, urinates and lays eggs. The “butt-breathing” process efficiently absorbs oxygen without much exertion on the turtle’s part, which allows turtles to survive underwater even over a period of several months without having to come up to the surface for air.

Alligators Brumate During the Winter

When temperatures become too cold, alligators brumate, which is similar to hibernation in that their metabolic rate and other physiological processes slow down. Unlike hibernation, however, which entails animals falling into a deep hyper-slumber during which they are inactive and do not eat or drink, during brumation alligators become lethargic and stop eating but continue to drink and have periods of activity.

If temperatures reach freezing, alligators are known to stick their noses out of the water just as ice forms, allowing it to freeze around them and giving them a portal through which to breathe until spring.

Many Mammals Hibernate or Take Long Naps

Animals that hibernate through winter — fattening up in the late summer then going into a deep sleep until winter is over — include woodchucks, some bats, Franklin’s ground squirrels and meadow jumping mice. Other mammals, including skunks, raccoons and opossums, may take naps that last for weeks during the coldest months, but will venture out to look for food when they’re able. Some nocturnal mammals will even search for food during daylight hours to avoid cold night temperatures.8

Rabbits, however, must search for food daily then burrow under the snow to try and stay warm. As for shrews, which are among the smallest mammals, their braincases change in size seasonally, decreasing about 15 percent during the autumn and increasing by more than 9 percent in the spring.

In addition to their shrinking skull and brain, which helps them conserve energy in winter, shrews become less active during the winter months, and their body mass and liver shrinks as well, which means they need less food to survive.

Because of their small size and high metabolism, shrews must eat every two to three hours in order to survive. While it may seem like wildlife all but disappears during the winter, it’s a season that’s ideal for tracking and spotting animals. Jordi Raos, a naturalist at the Cape Girardeau Conservation Nature Center in Missouri, said in a news release, “[Winter] is a great time to take a hike or go out in your yard to look for tracks, scat and chew marks to see who’s been out and about.”9

With the exception of bird feeders, which can help many birds survive the winter, experts don’t recommend putting out food for wild animals. "All you're doing is inviting a nuisance to your property,” Konrath told the Tribune. “The food that's provided by nature is what they need to continuously eat and survive on.”10

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