How Deer Survive Cold Winters

Deer have several adaptations that allow them to survive in winter.  Remember, Pennsylvania is not the northern most range of the whitetail.  Deer can be found as far north as southern Canada where temperatures are lower and snow is deeper for longer periods of time.

Biological Adaptations:

Fat Storage

Deer start to prepare for winter months before the temperatures begin to drop.  They do this by storing fat around internal organs and under their skin which insulates and provides energy reserves for the lean months ahead.

A Dense Coat

Their coat plays a major role in keeping them warm.  Coarse, hollow, dark guard hairs cover soft, woolly underfur.  Guard hairs can absorb solar energy but it’s the underfur that provides the most insulative value.  Half the length of guard hairs, underfur is 5 times as dense.  For comparison, sheep underfur is only 4 times as dense.  The underfur traps layers of air, with warmer layers closer to the skin.  The insulative value of underfur is increased when the hair stands on end (goose bumps for people) trapping more air.

Oil

Sebaceous glands in the skin produce a water-repellent oil that coats hair filaments as well.

Behavioral Changes

Decreased Activity

Deer decrease movement activity thereby lowering their metabolic rate and voluntarily reduce food intake.

Selective Shelter Choices

Deer also seek shelter in conifer stands.  These areas have reduced wind speeds and snow pack and provide overhead thermal cover which means higher night time temperatures.

Winter Survival Rate

From the studies that have been conducted in PA over the last dozen years, we know that winter survival is very high. In the grand scheme of things, deer should weather Pennsylvania’s snows and cold snaps just fine.

You might like to read Living on the Edge: How deer survive winter from Maine Department of Inland Fisheries & Wildlife as well as White-tailed Deer in Winter from Vermont Agency of Natural Resources.

-Jeannine Tardiff Fleegle

Wildlife Biologist, Deer & Elk Management Section

PA Game Commission