This is the season when some of our native critters are sound asleep. If you were a Canadian Grizzly Bear, you would have spent your time in late autumn preparing for a lengthy winter rest, trying to consume as many as 30,000 calories a day. From bears to bats, many of Canada’s wildlife species spend the winter in some form of hibernation. How they hibernate, and for how long, depends on the species and their habitat.

There are three types of hibernation – true hibernation, brumation and torpor.

• True hibernation is characterized by low body temperature, slow breathing, low heart rate, and a low metabolic rate. In this reduced state of activity, animals conserve energy during the long, cold winter months when there is little food available. During true hibernation, animals will not wake up if there is a loud noise or if they are moved or touched.
• Brumation is the hibernation-like state that cold-blooded animals (reptiles and amphibians) enter during very cold weather. It is triggered by the onset of colder temperatures and shorter daylight hours and can last for months. Animals in brumation typically wake up to drink water and might shift before returning to sleep.
• Torpor, or light hibernation, helps species survive the harsh winter months. Unlike true hibernation, torpor lasts only for short periods of time, allowing the animals to wake up during warmer winter days.

Here are some examples of species that hibernate during winter.

• Little Brown Bats hibernate in humid caves or abandoned mines that remain above freezing. Found across most of Canada, they do not feed or drink while hibernating.
• Groundhogs (Woodchucks) are one of Canada’s largest true hibernators, going into a deep, comatose sleep. They survive on accumulated body fat, dropping their temperature to 3 degrees C and their heart beat from 80 beats per minute to only four or five.
• Blanding’s Turtles and Northern Leopard Frogs are brumating species. The turtles remain underwater until the beginning of Spring, and the frogs spend their winters under the ice of rivers, creeks or ponds. A high concentration of glucose in the vital organs of Leopard Frogs prevents freezing. Once the weather warms and the ice melts, the frog will thaw and its heart and lungs resume normal activities.
• Grizzly Bears and Richardson’s Ground Squirrels are light hibernators. So are Eastern Chipmunks and Striped Skunks. Bears are not true hibernators. They only go into a torpor, during which their heart rate is extremely low but their body temperature remains high. The Ground Squirrels – an important part of the prairie ecosystem – can be in the torpor state for four to nine months a year, waking up for short periods of time. The chipmunks don’t sleep all the way through the season but wake up every few days to feed on their stored food. Unlike many rodents and birds, which hoard food for the cold months, the skunks have spent the autumn eating as much as possible. Once settled into its den, the mammal goes into a torpor, waking from time to time.

Of course, some species – including most carnivores and members of the deer family – don’t hibernate at all. Some of them are specially adapted to hunting or foraging in the deep snow and chilly temperatures of Canada’s north. Nature is teaming with wildlife in winter, it is just difficult to see. Here are some examples:

• Arctic Foxes are sub-zero specialists, well adapted to cold climates. Their compact body, short legs and ears reduce exposure and conserve heat, and their large, furry paws allow them to walk on top of snowdrifts. They can withstand temperatures as low as -50 degrees by sheltering behind rocks or windbreaks and wrapping their long, bushy tails around their heads.
• Beavers take advantage of the insulating snow and their waterproof coats get thicker in winter.
• Chickadees live in Ontario year-round. Throughout the year, they store food in cracks of tree bark. Their hippocampus – the part of the brain responsible for memory – expands in the fall and winter to help it recall where it stored food. Most amazing of all is the bird’s ability to go into regulated hypothermia. During the day, Chickadees gorge on their stockpiled food supplies. When dusk comes, they lower their internal body temperature and shiver through the night to keep warm. When daylight breaks, they begin feasting again to replenish the spent calories.
• Moose store up large quantities of fat in autumn, relying on their stored energy and conserving it by moving as little as possible. Gray Wolves have two layers of fur that help them stay warm during the cold winter.
• The Canada Lynx, one of our country’s biggest cats, has no problem trekking in deep snow, thanks to its large, furred paws, which act like snowshoes. Keen eyesight and their sharp, feline senses connect them to their environment and make them great hunters.

Nature is all around us, even in winter. Get outside, enjoy it, and discover a world of winter wildlife activities.  Remember that nature is not noisy; animals and plants go about their efforts for survival quietly. Happy hiking!

Sources: Canadian Wildlife Federation, Ontario Nature, Nature Conservancy of Canada, Bird Studies Canada, and field notes.