Digging burrows in the ground, hibernating and breathing underwater, or huddling together to stay warm are some of the surprising strategies that help animals survive the cold winter months.
While we can simply put on extra sweaters or crank up the thermostat to stay warm, wild animals have their own unique ways of surviving the cold months.
Here are some unique techniques:
Soil-burrowing spiders
Many ground-dwelling spiders in North America, such as wolf spiders, survive the winter by burrowing in the ground, under leaf litter, or inside logs.
Ecologist George Uetz, a spider expert at the University of Cincinnati in Ohio, says, “The temperature difference between the frozen surface and just a few inches below it is often surprising.”
Sure! Here’s a rewritten version of the sentence:
“Numerous spiders and insects remain active in this ‘subfreezing’ environment, or occasionally in conditions just a few degrees above freezing.”
Since spiders are poikilothermic and don’t generate body heat, their metabolism slows down as temperatures drop. “That said, it’s not uncommon to see spiders and insects active on warm days,” Uetz says.
Many spiders “weave” egg sacs with multiple layers of silk insulation to protect their eggs throughout the winter. For example, black and yellow garden spiders hatch their eggs in the fall, so the young spiders congregate in the egg sacs all winter, only to emerge en masse in the spring.
Uetz says some spiders also have a “secret weapon”: On cool fall nights, they produce special compounds that act like antifreeze to prevent ice crystals from forming inside their bodies. This is a useful “trick” to survive until spring without freezing.
Turtles Hibernate and Breathe Underwater
Tortoises are slow in all seasons, and as winter approaches, they really slow down.
Some species, like the eastern box turtle, simply burrow underground, withdraw into their shells, and go into a state of inactivity called hibernation. They survive by burning stored fat.
Painted turtles spend the winter “dwelling” at the bottom of water, which helps them stay cool even when the surface freezes. Since these poikilotherms’ body temperatures match the temperature of the surrounding water, the cold isn’t a problem.
Normally, these reptiles breathe air, but in the winter, they’ve evolved the ability to take in oxygen from water and release carbon dioxide into it.
“When poikilotherms get cold, they don’t need as much O2,” says Jackie Litzgus, a biologist at Laurentian University in Ontario. “So what they can take in from water is usually enough to get them through the winter.”
Turtles exchange gases through “specialized” blood vessels near the surface of their skin, the lining of their mouths, and even their cloaca — a cavity that serves as both a waste disposal site and a breeding hole.
When oxygen is in very short supply, painted and snapping turtles can even switch to an anaerobic metabolism. This type of respiration leads to a harmful accumulation of lactic acid, but the turtles can absorb calcium from their shells to counteract the acid buildup.
Honeybees swarm and “generate heat”
When temperatures drop, European honeybees fly back to their nests, huddle together, and stay active during the long winter months.
“This is something special,” says Thomas Seeley, a biologist at Cornell University. “No other insect is capable of surviving the winter by maintaining its warmth.”
Worker bees gather around the queen, adjusting the composition of the “colonies” to match the temperature changes. Bees generate heat by simultaneously contracting and relaxing the two sets of muscles used to move their wings during flight.
“The energy they expend is not moving or doing anything other than generating heat,” Seely explains.
The queen’s nest in the middle of the hive is the warmest and most comfortable, but even the outermost bees don’t freeze. When it gets colder, they press inward, improving their insulation and compressing the area that needs to be kept warm.
“The dense outermost bees are there to keep the temperature above 50 degrees Fahrenheit,” Seely says. “That helps them survive.”
This “strategy” relies on months of “planning.” During the flower-rich summer months, bees produce and store 90 pounds of honey to sustain the hive through the winter. They also choose their location wisely, aiming for the top of a hollow tree, to create a warm environment.
Chipmunks “Build” Burrows
Chickens are members of the squirrel family, but unlike their bushy-tailed cousins, you won’t see them out and about all winter. Nor do they hibernate for the entire season, like groundhogs do before emerging to signal the arrival of spring.
Instead, these small mammals live in elaborate systems of burrows, tunnels, and “chambers” that they “build” to connect small holes filled with nuts, seeds, and other stored food.
Eastern chipmunks spend several days in a state of hibernation, during which their heart rate drops from about 350 beats to the “single digits,” and their body temperature drops from 94 degrees Fahrenheit (34 degrees Celsius) to the temperature of their burrow surroundings — as low as 40 degrees Fahrenheit (40 degrees Celsius). But they wake up every few days to eat and use certain “toilets.”
Snowbirds head for warmer climes
According to Jill Deppe, director of the National Audubon Society’s Migratory Bird Initiative, more than 70 percent of backyard birds in the U.S. and Canada are migratory, and many fly south for the winter.
“Even if people don’t know exactly what type of birds they are, they still notice that their backyards become quieter in the fall.”
Audubon’s Bird Migration Explorer maps the annual flights of more than 450 species of birds migrating to warmer climes — and some are “quite puzzling.”
The red-throated hummingbird weighs only about as much as a dime, but on its way to Central America, some of them have to fly across the Gulf of Mexico — as much as 500 miles (805km) — in a single day.
“They’re so light, they seem to ride the wind,” Deppe says. Meanwhile, some species of rufous hummingbirds in the western United States “break the mold of flying south.”
“Some birds will fly to places you don’t expect,” Deppe says. “There are quite a few that actually fly east, so you’ll see them in backyards in Louisiana or Florida in the winter.”
“If it gets cold where you live, raise a glass to the resilient animals that can make it through the harshest of seasons.”
