White-tailed Deer – Background

Along the forest edge a small group of deer grazes quietly. Always alert for danger, the deer frequently lift their heads to sniff the wind. Suddenly a white tail goes up and they bound away, melting into the trees. The speed, grace, and agility we so admire in the white-tailed deer are the result of their place as prey animals in the forest food web. Though shy and elusive, these large herbivores leave tracks and signs that tell us about their lives, their connections to other woodland inhabitants, and their impact on the forest itself.

White-tailed deer are among the largest herbivores in our forests, and they consume a lot of vegetation. An adult deer might eat two tons of food in a year. In spring and summer, deer often feed at the edges of fields, eating leaves, grasses, berries, fungi, and farm crops. In autumn, they forage for fruits and for oil-rich nuts like acorns, beechnuts, and hickory nuts to store up energy for lean days ahead. In winter, they rely on a diet of bark, buds, twigs, and evergreen needles, for little else is available. Familiar signs of deer in our winter woods are their heart-shaped prints and their droppings, small oval pellets that fertilize the soil and plant seeds of the future forest.

Feeding mostly at dawn and dusk, deer eat furtively, always keeping an eye out for danger. Like cows, deer are ruminants, with four-chambered stomachs. They swallow food quickly and store it in the first chamber, the rumen, until they can find a safe place to rest. Later, the food is regurgitated as the cud, re-chewed, and swallowed again. It then goes through the remaining chambers where microbes assist with digestion, allowing deer to eat a diet of tough, woody foods. Lacking upper front teeth, deer tear off twigs and buds by working their lower incisors against their hard upper palates. They crush and grind foods with their serrated molars and strip off bark from young trees by scraping upwards with their lower incisors. The ragged twig-ends of deer-browsed plants, quite different from neatly snipped rabbit browse, tell us what they’ve been eating.

The forest understory provides food and cover for many kinds of birds and small animals, as well as the seedlings for the next generation of trees. In forests where deer are overcrowded, you often see a browse line about six feet high, below which all the vegetation has been eaten. When other food is scarce, deer will eat tree seedlings, starting with preferred species like maples and oaks. This can alter the composition of the future forest. When hungry deer eat all the shrubs and seedlings, the health of the entire ecosystem is affected.

It’s rare to come upon a deer in the woods, for the deer’s keen senses of hearing, sight, and smell alert it to our presence long before we get close. A deer’s long ears can swivel around to pick up sounds. Its large eyes, located on the sides of its head, allow for good peripheral vision and help it to see at dawn and dusk in the dimly lit forest. Bony ridges around the eye sockets protect the eyes from branches and twigs, and large tear ducts wash away dust and debris. A deer has trouble seeing something that is still, but the slightest movement sends it fleeing. Deer rely most heavily on their keen sense of smell to detect predators and to learn about other deer in the area.

The deer’s predators in the Northeast include humans, coyotes, bears, and bobcats. A predator must be fast, strong, and wily to catch the fleet-footed deer. By weeding out the slower, weaker individuals, predators have helped to shape deer into the swift and wary creature we know. With thin, strong legs, deer are agile runners and jumpers. A deer can travel at thirty-five miles an hour, jump twenty-five feet in a single bound, and clear an eight-foot fence. When fleeing, deer leap over uneven ground or brushy areas rather than navigating through them. Still, thin legs and small hoofs on such a large animal can be a disadvantage in deep snow or on thin ice. Deer walk on two toes, on hoofs that are hard and sharp, with leathery pads that help them grip rocks. In a conflict, their sharp hoofs can strike a dangerous blow.

Deer spend much of their time in the company of other deer, males and females generally in separate herds. Females are solitary in the spring, seeking out hiding places for their fawns in brushy areas or wetlands. A doe usually has one fawn in her first season and then twins after that. Fawns are hidden separately and left for several hours at a time while the doe feeds. Lying still, they wait for their mother to return, concealed by their almost total lack of scent and by spotted coats that blend in with the dappled forest floor. The doe comes to nurse only two to four times a day. In this way, she is less likely to lead a predator to her young. Fawns grow quickly, nourished by milk rich in protein. As the spring progresses, the mother and her fawns forage together, later joining with other groups of does and young, perhaps her sisters or cousins.

Within these groups a hierarchy develops where the more dominant individuals get the best foods because they chase others away. When food is scarce, those lower down in the hierarchy get less to eat, and some may not survive. There is no sharing of food in a deer herd, but there are more eyes, ears, and noses to notice danger, a crucial advantage. Deer alert others by snorting and stamping their hooves when they are uneasy, and when alarmed, they raise up their foot-long tails like flags, flashing the white under-fur as a signal to flee.

Males form small, loosely knit groups of three to five bucks, foraging together in spring and summer. In the fall, each buck strikes out on his own, for this is the season of the rut, when bucks compete for does. Fall is the time to look for fresh deer rubs, saplings where a buck has rubbed off the bark with his forehead and antlers while leaving his scent. These message boards tell other deer about their status.

A buck’s most notable feature is his set of antlers, unique structures made of extremely fast-growing bone. Unlike horns, which have a bony core covered in keratin and grow continuously throughout an animal’s life, deer antlers are entirely bone and are shed in winter, growing anew every year. In summer they are covered in velvet, a special skin rich in blood vessels that supply the growing bone; later this skin dries and falls away. In his first year, a young buck grows unbranched spikes, for he still needs most of his nutrition for his growing body. Mature bucks can grow larger antlers, their size and branching dependent on nutrition more than age. In the fall, bucks spar with antlers and hoofs, fighting for dominance and access to females. Only a well-nourished male can grow a big rack, so his dominance and mating success is directly connected to the richness of his habitat.

One sign of deer we don’t often find are shed antlers, though bucks lose them every winter. After the mating season, a layer of dead bone develops at the base of each antler, and they eventually fall off.  Gnawing rodents like squirrels, mice, and porcupines find and eat them. Rich in calcium and phosphorus, deer antlers provide important nutrients to other woodland animals.

Though finding antlers is rare, clumps of shed deer fur can often be found in spring. Deer grow a thick winter coat of grayish-brown fur that blends in with the bark of bare tree trunks. The under-layer of short, dense fur and outer layer of long, hollow, crinkled hairs, provides excellent insulation. The tiny spaces within and between the hairs trap warm air close to the deer’s body. In the spring, deer shed their winter coats and grow new ones of red-brown fur. Shed hair sometimes turns up as a warm lining in nests of birds and mice – another link with their woodland neighbors.

Winter is a harsh time for deer when food is scarce and weather severe. An average deer can survive the winter on two and a half pounds of food a day, though it may lose a third of its body weight on this meager diet. Many deer gather in deer yards, sheltered evergreen stands often on south-facing slopes. Here the snow is less deep, the trees block the wind, and sharing trails makes it easier to get around. Oval impressions in the snow where a group of deer has rested and many crisscrossing trails are signs of a deer yard. Both male and female herds congregate in deer yards, traveling up to fifteen miles to reach them, for deer need this protection to survive our northern winters.

White-tailed deer are part of the fabric of our forests, their lives interwoven with those of the other dwellers like threads in a tapestry. The patterns of their tracks and signs give us clues about their lives. As large plant-eaters, seed-planters, and sometimes prey to large predators, deer can have a profound impact on their habitat and on the many other inhabitants of the woodland ecosystem.

Suggested Reading

Feldhamer, George, Bruce Thompson, Joseph Chapman. Wild Mammals of North America: Biology, Management, and Conservation. The Johns Hopkins University Press, 2003.

Holland, Mary. Naturally Curious. North Pomfret, VT: Trafalgar Square Books, 2010.

http://www.esf.edu/aec/adks/mammals/wtd.htm

Rezendes, Paul. Tracking and the Art of Seeing. 2nd edition. New York: Harper Collins, 1999.

Rue, Leonard Lee III. The Deer of North America. New York: Crown Publishers, 1979.

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