How Wildlife Prepare for the Cold Winter Months: Aspen Valley Wildlife Sanctuary


Submitted by Aspen Valley Wildlife Sanctuary

There are many ways that wildlife prepare for the cold winter months. Some species, such as groundhogs and bears, engage in varying degrees of hibernation. Birds migrate, while wolves, foxes and moose use various forms of physical adaptation to get through the cold winter days.

Interestingly, although bears prepare for a long winter nap, they aren’t true hibernators. Instead, bears go into mild hibernation known as torpor, where heart and respiratory rates drop, body temperature drops slightly, and they don’t eat or release bodily waste.

After settling in their dens, bears will sleep for an extended period of time, but may be woken up by noise or warmer temperatures. Bears can even be seen outside during this time.

Cubs are born in the den in late January or February while their mothers are in hibernation. The cubs then stay with their mother in the den until spring. With a litter of one to four cubs, literally underfoot, the rest time is really “light”.

Chipmunks are also mild hibernators. These gatherers collect and hide (store) their food in underground dens. There they settle into a self-imposed lockdown, waking up every few days to feed on their caches of stored food. Once the reserves are depleted, they are thought to hibernate more completely.

On the other hand, groundhogs are one of Canada’s largest true hibernators. When a groundhog is down for the winter, it is almost impossible to wake up. While sleeping, a groundhog relies on its accumulated body fat to survive; coupled with a drop in body temperature and an astonishing drop in heart rate from 80 to just four or five beats per minute. In this state of reduced activity, energy is retained during the long, cold winter months when little food is available.

Regardless of the type of hibernation, it has little to do with the change in temperature. Rather, it is a survival tactic used by animals to overcome a food shortage. Essentially, wildlife prepares for the winter months by increasing body fat and reserves. After that, they slow down to save power.

Furley (one of our four bears in residence at the Sanctuary), for example, did not hibernate before settling forever here at Aspen Valley Wildlife Sanctuary (AVWS). Furley lived in a small cement enclosure located in a provincial park until it closed in 2013. There Furley was fed during the winter months, which overrode his natural instinct to hibernate. This has been done on behalf of the public all year round, which is what we oppose here at the Sanctuary.

In Aspen Valley, Furley has a large enclosure with its own pond in a cool, shady forest. Here we start supplementing her food intake in the fall, but stop feeding her in November.

(Photo: Aspen Valley Wildlife Sanctuary)

The AVWS is also home to a number of non-hibernating species. On the contrary, they adapt to the cold.

Our arctic fox, Mystic (pictured above), is a subzero specialist who adapts well to the winter months. Its compact body, short legs and small ears help retain heat, while its large, hairy legs allow it to walk on snowdrifts.

Able to withstand Muskoka’s colder temperatures, Mystic will often be seen sheltered in his enclosure, with his long, bushy tail wrapped around his head like a scarf. Mystic’s coat also changes color from gray to white. This adaptation allows the arctic fox to blend into the white canvas of winter and escape predators.

Wolves are largely carnivorous, and by targeting small to medium-sized prey in the wild, they do quite well on their own during the winter months. This is the time when sick, injured and weak prey are most vulnerable. This is the circle of good news / bad news in life. Wolves also depend on a plentiful diet in the fall and a thick coat, which keeps them warm on colder winter nights.

(Photo: Photograph of Ina)

In the wild, contemporaries of our beloved moose, Ella, store large amounts of fat that their bodies will use up through the winter months. Another adaptation is the significant thickening of their coat, which can be a problem in a mild winter. Heat stress and tick infestations are common in moose when lakes are frozen over and there is nowhere to cool off.

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