Deer Biology

Biology and Behavior

White-tailed buck Deer are found throughout Massachusetts-with occasional sightings in Boston and other cities. MassWildlife biologists estimate approximately 85,000 deer live in the state. The white-tailed deer, Odocoileus virginianus, has long, slender legs, large ears, and a tail that, when the deer is alarmed, flares erect to reveal the fluffy white underside for which the animal is named. White-tails belong to the Cervidae (deer) family, which includes elk, moose, caribou and mule deer.

White tailed deer are smaller than most people realize; attaining a total length of about 71 inches and a height of about 39 inches. Weight depends upon age, sex, and physical condition of the animal and upon the quality and quantity of food available to the deer. Bucks (male deer) generally range in weight from 100-250 lbs. whereas does (female deer) are somewhat lighter at 70-150 lbs. In addition to their larger size, bucks also are characterized by branched antlers that grow each year and are shed after the breeding season. On rare occasions, does grow antlers.

During summer, the upper parts of deer are reddish- brown and with short, thin, straight and wiry hairs. In winter, the coat changes to a grayish brown and with long, thick, hollow hairs which are slightly crinkled. The hollow hairs provide excellent insulation against the cold. The belly, throat, areas around the eyes, insides of the ears and the underside of the tail are white year round. Fawns (young deer) are a chestnut brown color with conspicuous white spots on their back and sides, mimicking the sunlight dappled forest floor and serving as camouflage from predators. Spots fade by 3-4 months of age.

Life History

Deer prefer forest-edge habitats or thickets intermixed with glades, wetlands, or abandoned pastures. They have readily adapted to the fragmented forests typical of most suburban residential areas. Agricultural lands located adjacent to woodlots or wooded wetlands also are favored by deer. From late January through early March, deer often congregate and seek shelter from wind, deep snow, and cold temperatures in stands of dense conifers, rhododendron, or mountain laurel.

White-tailed deer are crepuscular, meaning that they are most active at dawn and dusk. Deer may also be active at other times of the day, especially during the breeding season in late fall. Typically, an adult doe, her fawns, and in some cases, female offspring from the previous year, stay together on the maternal range, in a familiar habitat from 1 to 2 sq miles in size. Males leave the maternal range as yearlings to adopt either a solitary existence or, more commonly, form "buck groups" consisting of 2-5 individuals. Bucks traverse larger areas than females. Typically New England white-tails travel no more than 5-15 miles.

Breeding occurs from late October to early December in Massachusetts. After a gestation period of about 28 weeks, fawns are born from late May to early July. Depending upon age and physical condition, a doe may produce 1, 2 or, sometimes, 3 fawns weighing about 4-6 lbs. at birth and able to walk about within an hour of birth.

Food

The diet of white-tailed deer is highly variable; they consume a wide variety of herbaceous and woody plants. Deer lack incisors on the upper front jaw. Twigs browsed by deer will look as though it was partially clipped, with a trailing, ragged edge. By contrast, a twig neatly "snipped" off, with a clean, smooth cut, is an indication of a rabbit or woodchuck browsing.

Deer are ruminants, meaning they have a four-chambered stomach and frequently chew a "cud". Food preferences are largely dependent on the kinds of plants in an area and the season. Green leaves, herbaceous plants and new growth on woody plants are eaten in the spring and summer. In late summer, fall and early winter, both hard and soft fruits such as apples, pears and acorns are a major component of their diet. In winter, the deer feed on evergreen leaves, hard browse (twigs, shoots, leaves and buds), or bark from trees (during severe winters or when food supplies are limited). Good supplies of a variety of natural foods at all times of the year are essential to support healthy deer.

Population Management

The white-tailed deer is prized animal, both for its value to sportsmen and women who enjoy the opportunity to participate in a special outdoor and culinary experience as well as to other wildlife enthusiasts for its aesthetic appeal. Deer are a valuable natural resource. Their reproductive rate and adaptability to residential areas point to the need for be active population management. The key to managing deer is controlling their populations at levels suitable for both the needs of deer and people. Increases in crop and landscape damage as well as deer-vehicle collisions are all indicators of high deer population densities. Deer can strip their habitat of its life-supporting qualities negatively impacting many other wildlife and plant communities. Without adequate food sources and cover, deer work harder for daily nourishment and often cannot build up the energy reserves they need to survive the winter. Undernourished deer are also more vulnerable to exposure and disease. In addition, they are typically smaller, with smaller antlers and a lower reproductive capacity.

MassWildlife uses hunting as a deer population management tool, mostly through regulating the number of does taken by hunters. In regions of the state where there are high numbers of deer/square mile, a large number of antlerless (doe) deer permits are made available to hunters in an effort to decrease the number of deer that could be born the following spring. Conversely, in regions where there are few deer (sometimes resulting from poor habitat quality), few antlerless permits for that area are allocated for hunters. Public support of management programs are essential to maintaining deer as a public asset to be enjoyed in by Bay State citizens and visitors now and in the future.

Deer and Disease

Fortunately no significant, widespread health issues currently exist in our deer population; however, white-tailed deer populations are susceptible to diseases. MassWildlife has an active, ongoing disease surveillance program for chronic wasting disease (CWD). CWD is one of our biggest deer health concerns. Check here for additional information on CWD, or visit the Chronic Wasting Disease Alliance website.

Lyme disease, often associated with white-tailed deer, is a bacterial disease transmitted by the bite of infected lacklegged ticks. Although adult ticks often feed on deer, these deer do not become infected. Deer are nevertheless important in transporting ticks and maintaining tick populations. Check here for additional information on Lyme disease provided by the Massachusetts Department of Public Health or visit the Centers for Disease Control and Prevention website.

Leave Fawns (young deer) Alone!

The arrival of spring and summer also means the arrival of newborn deer. Every year, the lives of some fawns are upset by people who mean only to help. Deer often leave their fawns alone for hours in order to forage for food. If left alone most times the mother will return. Hovering or "checking in" on the fawn frequently will only delay the doe's (adult female) return. If you are concerned that something may have happened to the doe, note the location of the fawn and check the next day to see if it is there. Do not take a fawn from the wild and try to care for it. This is illegal, unwise and in the end, usually harmful to the fawn. Instead call your local MassWildlife office and report your sighting and concern.