Take me outside: How deer keep warm in the cold months

Deer may retreat deeper into the woods in the cold months.

Deer hunting season continues through the end of December (depending on the type of firearm used). However, those animals which escape the arrows and bullets will still have plenty of challenges ahead. Deep snow and severe cold are hard on them, but they have various physical and behavioral adaptations that help them survive the harshest season.

In the fall, white-tailed deer shift their diet from green plants to nuts and woody plants. Look for shaggy branch ends or jagged scars on trees where deer have used their lower teeth to tear off branches or scrape the bark. They have no upper incisors, so they don't leave a clean bite as a rodent would. To build up their body fat, they must consume five to nine pounds of food each day. Deer will draw on this fat reserve through the winter to supplement their food consumption. They may lose up to 20 percent of their body weight by spring.

Consuming energy is one way to stay warm; conserving it is another. A deer's "winter coat" is made of hollow hairs that trap air. This provides an insulated outer layer that can keep them warm even when it gets to -30 degrees (F).

Deer gather in "yards" composed of evergreen trees, often on a south facing slopes. They take advantage of less wind and shallower snow, sharing paths, which reduces their energy exertion.

When groups of deer congregate they also provide protection for each other. It is common to see a group situated so that they are all looking in different directions, watching for predators. If a predator is spotted, a flash of the white under part of the tail serves as a warning sign to the rest of the herd.

These natural gatherings are kept to reasonable sizes by limitations of the habitat. When people set up feeding stations for deer, an artificial yard may be created. These can actually cause more harm than good to the deer.

Human-sourced food is not as easily digested; higher densities of deer attracted to feeding stations can lead to disease transmission, more aggression between individuals, and over-browsing of the natural vegetation. For these reasons (and more) biologists and wildlife managers advise against feeding deer in the winter.

Male deer (bucks) and female deer (does) often intermingle on the wintering grounds. They can be distinguished by size, because bucks are larger, weighing between 150 and 310 pounds, while does range between 90 and 210 pounds.

Bucks may have antlers, while the females rarely do. However, as the season progresses bucks will begin to drop their antlers.

This phenomenon is one of the most intriguing aspects of the deer life cycle. Antlers, which are made of bone, begin as tiny buds emerging from the top of the buck's skull in April.

They are covered with "velvet" which supplies the growing antlers with blood and nutrients. They grow during the spring and summer.

Antler size depends on nutritional levels more than on the age of the animals (though young and very old bucks tend to have fewer tines). When shorter day length triggers the "death" of the antlers, the velvet is rubbed off to reveal a hard boney rack. These are used during competitive "wrestling" matches when two bucks vie for the chance to pass on their genes. You'll have to wait until next year to listen for the sound of antlers clacking against each other though. November is the time for this display, during the "rut" or mating season.

Now is the time when those antlers, having served their function for this year, start to fall off. From late-December through February, antlers are shed, one at a time, reducing the weight on the buck's head, another adaptation for winter survival. Good luck finding one of these discarded appendages. Even though between 85,000 to 95,000 deer live in Massachusetts, and many are bucks with a pair of antlers each, rodents will consume them nearly as fast as they are dropped, recycling the calcium that is concentrated in those bones.

Nothing is wasted in nature. Even if a deer doesn't make it through the winter, it will become food for other animals who are also trying to survive in the circle of life.