Wildlife and the Cold

Our native wildlife has a number of adaptations that help them survive during the winter. Some animals, like many birds, simply fly south where warmer weather awaits them. Animals like groundhogs, bears, or snakes find a cozy burrow and either fall into a deep sleep or go into a state of hibernation. Some animals are not so lucky. How do they stay active and manage to survive until spring arrives?

Our year-round residents have a number of adaptations that help them stay alive until the weather breaks during spring. For starters, these animals are usually larger than their counterparts to the south. The larger size means that there is less surface area exposed to the elements, and they can retain more of their body’s heat. To understand the concept of surface area, think about how difficult a large log would be to light in a fireplace; but when you split it up into smaller pieces, you increase the surface area and make it easier to burn. So a larger animal would have less of its body exposed to the elements and be able to retain more warmth than a smaller animal. Another adaptation that animals to the north possess, is a dense winter coat which helps them trap more of their body’s heat. This coat usually has a somewhat coarse outer layer that can repel moisture, and a thick, softer inner layer of downy hair which traps more of their body heat. On average, an animal’s winter coat allows them to retain about 80% of their core temperature. These winter coats are often darker than summer fur, enabling more sun to be trapped than in the summer.

Deer eating liriope, the only green thing they can find

Many animals eat a lot in the fall to put on a layer of fat which provides two benefits: it helps with insulation, and it provides stored energy reserves in case food becomes scarce. Animals that live in the north, especially birds, have more blood vessels in their extremities, like their feet and legs, which help to keep these areas warm, especially when they are wading in cold water. Many northern species also have thicker layers of skin, beaks, claws, or toenails.

All these adaptations help our winter residents survive until the spring once again arrives. Despite these adaptations, the winter is the harshest season for most wildlife and mortality can be high, especially in smaller animals like mice, rabbits, and squirrels. It is not unusual to loose 80% of these populations, mostly due to starvation and being eaten by larger predators. These smaller animals have a higher reproductive rate to counterbalance their relatively short lifespan.

Article by FCFCDB

Photo credits: Jan Barrow, Myersville, MD

Nature note for 2/5/21