Cold weather months prove challenging for wildlife in the Great Smoky Mountains—including one special deer

Winters in the Smokies can be harsh. The lush green mountainsides of spring and summer turn gray and brown and bare. There are no more tender shoots to browse, no more luscious leaves to nibble and no more juicy berries to slurp.

The myriad of creatures that call the Smokies home have developed different strategies for dealing with the wintertime blues. Birds can simply fly south to warmer climes. Other animals like black bears and groundhogs find winter a big bore and just sleep it off. But for many animals, the only alternative is to tough it out.

The white-tailed deer, an icon of southern forests, is one of those animals that is active year-round in the Smokies. To get an idea of how whitetails cope with winter in the Smokies, wildlife researchers spend a “virtual” winter with Doe X, a healthy three-year-old white-tailed doe. 

In late August or early September, Doe X begins to shed her reddish summer coat for a thicker, grayer winter coat. According to David Osborn, wildlife research coordinator at the University of Georgia’s D.B. Warnell School of Forest Resources, the change in fur is triggered by the longer nights. 

“Increased levels of melatonin, which are produced by longer periods of darkness, appear to be instrumental in initiating the fall molt,” Osborn says. “Conversely, lengthening days in the spring lessen melatonin levels, initiating spring molt.”

Doe X’s sporty new winter parka differs from her summer blazer. The reddish summer coat is composed of thin, solid hairs about an inch long, and there is no “underfur.” Winter coat hairs are about twice as long and hollow, allowing them to trap warm air. There is also a dense, wooly underfur that serves as an excellent insulator. As Doe X’s outward appearance begins to change there are also physiological changes. 

“Deer are ruminants and have a four-chambered stomach,” explains Lisa Miller, associate professor of wildlife at the University of Tennessee. “The rumen is the largest chamber [of the stomach], and it hosts different organisms like protozoa and bacteria that help break down plant material.”

In late September and October, Doe X still finds some succulent maple, sassafras, and buckthorn leaves to browse, but she also begins to supplement her diet with acorns, black cherry seeds and other hard mast. As she does, the insides of her stomach begin to change. 

“It’s like survival of the fittest in the stomach,” Osborn says. “The shift in diet favors some microbes over others.” According to Osborn, those microbes best suited for breaking down hard mast and woody twigs and roughage begin to supplant the ones best adapted to digesting green herbs and forage. “This allows the deer to utilize the less nutritious types of food it is likely to encounter in the winter,” Osborn says.

The change of microbes in Doe X’s stomach can actually put her at risk from well-meaning humans. 

“It’s a huge problem in more northern climes,” Miller says. “People think they are helping deer in areas where there is heavy snowfall by putting out foods like high-quality alfalfa and corn. But they are actually endangering the deer because the microbes in the deer’s stomach can’t adjust quickly enough, resulting in acidosis, which can cause death.”

By November, Doe X is in heat. A couple of randy bucks are locked in head-to-head combat trying to impress her. To the victor go the spoils, and Doe X accepts the advances of the prince of the forest.

A white-tailed doe time in heat is short-lived. The window when she can mate often lasts only 24 hours. If she doesn’t find a mate, there is generally a second heat about a month later. But white-tailed bucks are quite attentive during rut (the male deer’s period for sexual excitement), which generally lasts from October through December in the Smokies. Males herd does into harems and follow them for days at a time to insure a high breeding rate. One study in Texas determined that 90 out of every 100 does sampled across the state after rut were pregnant.

Doe X is a healthy three-year-old. This is her second year to breed. She is living in a decent habitat and is carrying two fetuses. That is the norm according to Osborn. Healthy does in good habitats generally bear twins, while healthy does in marginal habitats bear a single fawn. If food is too scarce, the placenta will be re-absorbed and no fawns will be born.

There are accounts of triplets being born. Osborn says the phenomenon of triplets is a genetic factor. Deer predisposed to having three fawns are few and far between but can produce three in a good habitat. 

Doe X, like most white-tails in a good habitat, is content to live her life within an area of about one-half a square mile. 

“And there is a core area within that home range,” says Osborn, “where a deer will spend 90 percent of its time.”

That core area is crisscrossed with trails, and Doe X knows them all. She awakens from her shallow sleep around 5 a.m. and strikes out for the ridge where acorns are abundant. She doesn’t take the most direct route but settles on one that will keep her head and nose pointed into a slight breeze. Her big eyes and ears are alert, and she walks slowly, stopping frequently to test the wind with her sensitive nose. Rounding a bend, she stops abruptly, breathing in great draughts. She detects the scent of a bobcat, stands motionless and listens as the bobcat prowls in the underbrush. A bobcat would readily take on a fawn or an old or sick deer, but a healthy white-tailed deer is a different story. It’s not unheard of for a bobcat to have a go at a healthy deer—especially if it’s hungry—but this cat is more interested in a communal nest of deer mice it has discovered.

Doe X continues her journey. As she approaches the ridge, once again she hears rustlings. This time it’s a raccoon that has come to share the bounty of acorns.

Raccoons are also active year-round. This masked omnivore becomes a bit gluttonous around the end of summer into fall as it accumulates fat stores to see it through the harshest winter weather. The raccoon’s range increases during the winter as food becomes scarcer, but it has staked out several dens across that range and with the surplus fat, if things get too severe it will just hole up until things get better.

Neither Doe X nor the raccoon pay much attention as a shadowy silhouette glides in through the dark, hits the side of a white oak, and scrambles quickly around to the other side. A southern flying squirrel decided on one last snack before denning for the day. The scramble around the tree is a precautionary tactic, just in case an owl spied it coming in for a landing. 

“Southern flying squirrels and northern flying squirrels den communally to help offset heat loss in the winter,” says Chris Kelly, a biologist with the North Carolina Wildlife Resources Commission. “Because of their smaller body size, we sometimes see a dozen or more southern flying squirrels in a single nest box during the winter, compared to three or four of the larger northern flying squirrels.”

Kelly says that while neither the northern nor the southern flying squirrel experience any kind of torpor or dormancy during the winter, the northern flying squirrel can slow its metabolism and drop its body temperature slightly to help cope with caloric reductions during winter.

“The southern flying squirrel’s metabolism doesn’t slow during the winter, and it relies on food caches to insure a ready source of energy,” Kelly adds.

On a cold night, this flying squirrel was content to feast before taking any acorns to stash. Doe X was busy too. She spent only about 40 minutes gulping down slightly chewed acorns, which would be stored in her stomach. When you’re prey, the less time you spend preoccupied, the less vulnerable you are. She headed back to a favorite resting place where she curled up, regurgitated a cud full of acorns and silently chewed away while watching the sun rise over the Smokies.

Doe X’s routine won’t change much for the winter. Her cousins across the northern tier of the U.S. and into Canada usually have a seasonal migration and congregate on wintering grounds known as yards. Doe X will most likely find everything she needs within that half-square-mile of home territory in the Smokies. If it’s a tough winter, she may have to get out of her comfort zone to forage. And according to Miller, in cases of extended bad weather, Doe X’s metabolism may slow a little, curbing her appetite and allowing her to stay bedded in the best shelter she can find. 

By spring, Doe X will be most active around sunrise and sunset. As the hours of daylight begin to change once again and days grow longer and nights shorter, Doe X’s melatonin levels change again, and she starts to shed her long gray, warm winter coat. It will last a few weeks. As green shoots and leaves appear, Doe X will sample these delicacies. Her diet shifts slowly, and so does the micro flora in her stomach. By the time her diet transforms from acorns and woody twigs to green leaves and herbs, her stomach will be acclimated to the change.

Over the coming months, Doe X will begin to show a swollen belly, and she will look for a safe place in her home range to give birth to fawns and keep them away from predators. If she is successful and the twins survive, next winter three deer will haunt the trails through the Smokies that Doe X calls home. 

Common mammals that hibernate

Groundhogs – Body temperature falls from around 97 degrees Fahrenheit to 40 degrees Fahrenheit. Heartbeat slows from more than 100 beats per minute to as few as four. They may take only 10 breaths per hour, and sleeps curled in a grassy nest, deep in a winter burrow.

Bats – Little brown bat, tricolored bat, Indiana bat, big brown bat, Rafinesque’s big-eared bat, Virginia big-eared bat, evening bat, and the gray bat hibernate in caves. Body temperature drops to 35 to 50 degrees Fahrenheit. Heart rate drops to 20 beats per minute.

Jumping mice – Meadow and woodland jumping mice hibernate in underground burrows.

Black bear – Often classified as “not true hibernators” because their body temperature only drops 10 to 12 degrees, and they can rouse quickly if disturbed. Heart rate can drop to 8 to 10 beats per minute, and they may slumber for 90 days or more without eating or eliminating waste. Females give birth during hibernation.

Chipmunk – Another animal often classified as “not a true hibernator” because it will become active during winter warm spells. But when it is asleep or in torpor, its heart rate drops to four beats per minute and its body temperature can drop as low as 38 degrees Fahrenheit.

Common mammals that tough it out

White-tailed deer – Molts to thicker winter coat. May lower its metabolic rate slightly during extremely harsh conditions. Change in gut microbes allows it to digest hard mass and woody stems and twigs.

Eastern cottontail rabbit – Eats buds, stems, twigs and bark during winter. On cold days it may take advantage of groundhog burrows to keep warm.

Appalachian cottontail – Habits similar to eastern cottontail rabbit.

Fox – Red and gray foxes molt to thicker winter coats. Diet changes to almost exclusively small mammals in winter. Will eat carrion. Caches food. Gray foxes are good tree climbers.

Bobcat – More diurnal during winter. Breeds during winter. Home range often increases during winter.

Raccoon – Home range increases. Mates in late winter. Consumes more acorns and other hard mast. May hole up for days, living off stored fat.

Opossum – May den for a day or two during harshest weather to avoid frostbite on ears, feet and tail. Opossums are unable to accumulate fat stores like a raccoon, therefore they must forage regularly.

Coyote – A Thick winter coat. May hunt in packs more in the winter and may target larger prey more, like white-tailed deer.