Deer in Winter
—Jeni Vogel, Education & Program Coordinator
It looks like winter may actually be here. The holidays are behind us, daylight is short and even the temperature is getting colder. Most animals have migrated south or are hibernating for the winter. However, as you drive up the RNC driveway or take a walk through the woods, you will likely stumble upon a family of deer. As you watch these magnificent creatures, you might wonder: are they ready for the cold months ahead? I would say yes, they have geared up by putting on a new coat, a few extra pounds, and searching for an overwintering spot.
Each fall, white-tailed deer grow a brand new coat of fur. They leave behind their light red coat of summer and put on a new gray to dark brown one. This dark top layer, known as guard hair, helps absorb more solar energy and will grow five times denser for the winter months. It is completely hollow, trapping air and providing additional insulation. White-tailed deer will then grow a second layer of fur, underfur, which is not present during the summer. Underfur is much finer than the guard fur and provides the most insulation.
It doesn't stop there! These well adapted creatures will continue to increase their insulation by puffing out the fur in response to the cold, using their muscles to adjust the angle of the fur. This response is similar to when humans have goose bumps. As a last line of protection, their skin contains sebaceous glands which secrete an oil like substance called sebum to help repel water and keep their fur dry, ensuring a truly warm coat for the winter.
Even with the extensive layer of fur, these deer wouldn't be able to survive the winter without putting on a few extra pounds prior to the winter months. Typically they will store fat around their internal organs and under their skin. This is necessary because deer eat less through the winter months because most of the available food has less protein and takes more energy to digest. By limiting food intake, deer will work off their fat reserves throughout the winter, losing 20 to 30 percent of their body mass. As they reserve their energy, deer will remain mostly in one place throughout the winter months, particularly in a coniferous part of the forest. Conifers tend to have less wind and snow and increase thermal cover. As you can see, white-tailed deer need all these adaptations to survive the winter, allowing us to enjoy their presence even during the coldest months of the year.
