How Wildlife Survive Winter

Squirrel eating nut in snow.

It’s hard to imagine spending the entire winter outside. As humans, we’re lucky we can keep warm indoors. Wildlife must either migrate, adapt or enter a state known as dormancy during the cold winter months.

Dormancy is when an organism’s metabolism slows down for a period of time. It’s triggered by environmental conditions like cold weather, reduced light and lack of food. Normal activities like running, eating and breathing use up large amounts of energy which are hard to recover in winter. It’s a useful strategy to conserve energy.

There are several types of animal dormancy including diapause, brumation and hibernation.

Diapause 

Diapause is a type of dormancy used by insects and other arthropods like spiders. The ability to enter diapause allows insects to temporarily stop their development until environmental conditions improve. This is often in the spring or summer. Diapause can happen at any time during their life cycle, however, it’s most common during the pupa life stage such as moths in their cocoon. When the weather gets cold, these animals seek shelter in a variety of places like under logs, bark, or soil.

Spider
Cross orbweaver. Photo credit: Jon Clayton

Brumation  

Brumation is a type of dormancy used by cold-blooded animals like reptiles and amphibians. They depend on their environment to regulate their body temperature. When temperatures and daylight hours drop, there is less heat in their environment. As a result, they must slow down and seek refuge in areas that remain ice-free to prevent their bodies from freezing. They move into underground crevices, deeper underwater or bury themselves in mud.

Animals in brumation generally do not eat, but on warmer days they may wake up to move or drink water. In the Credit River Watershed, this includes species like the eastern garter snake and northern map turtle.

Group snakes
Eastern garter snake mating ball. Photo credit: Sara Labrie

Hibernation 

Hibernation refers to any animal that goes dormant during the winter. This type of dormancy only applies to warm-blooded animals, usually mammals. They can control their internal temperatures using their energy reserves. This is why you often see mammals fattening up or storing food in the fall. It’s so they have enough energy to get through the winter. They will seek refuge in areas like dens or burrows.

Hibernating mammals include true hibernators and light hibernators. True hibernators, like woodchucks, enter deep sleep and have a very low body temperature, a little bit above freezing. In contrast, light hibernators have a higher body temperature and can periodically wake up on warmer days to move or eat, including racoons, and eastern chipmunks.

Raccoon in tree
Raccoon. Photo credit: Jon Clayton

Learn more about the animals in the Credit River Watershed.

By CVC’s Christina Kovacs, Specialist, Natural Heritage Management

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