White-tailed Deer

Odocoileus virginianus

Maine is near the northern extent of the white-tailed deer range, and they live in many habitats here, from deep woods to farmland to suburban backyards.

Habitat

Major habitats that provide food and cover for white-tailed deer in Maine are forest lands, wetlands, reverting farmlands, and active farmlands. Forest stands containing little or no canopy closure, wetlands, and reverting and active farmland yield the largest and best forage within reach of deer. However, stands made up of mature conifers with tree height greater than 30 feet, crown closure of greater than 60%, and interspersed or adjacent hardwoods for browsing provide critical winter habitat for deer. Ideal deer wintering habitat is connected by other usable habitat to aid deer in moving between them. Currently, 94% of Maine is considered deer habitat; this excludes developed parts of the state. In practice, even a portion of Maine's developed land is currently occupied by deer. Wintering habitat is more limited in availability, comprising only 2 to 25% of the land base in various parts of the state.

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Diet

Deer are highly selective herbivores, concentrating on whatever plants or plant parts are currently most nutritious. Finicky eaters, deer opt for variety over quantity, when feeding along in the woods and fields. Deer consume grasses, sedges, ferns, lichens, mushrooms, weeds, aquatics, leaves (green and fallen), fruits, hard mast (acorns, beech nuts, etc.), grains, and twigs and buds of woody plants. Contrary to popular belief, deer consume twigs and buds of dormant trees and shrubs only when more nutritious foods are unavailable. When restricted to woody browse, deer inevitably lose weight. During the course of the year, deer may browse several hundred species of plants. A few are highly preferred; many others are consumed only when the best forages have been depleted. Overabundant deer populations can reduce the abundance of preferred forages, while causing less-desirable plants to become more common. Extremely abundant deer can literally eat themselves out of house and home. At these times, hungry deer are underweight, prone to starvation and disease, produce fewer fawns, grow smaller antlers, and create increased conflicts with homeowners, gardeners, farmers, forest landowners, and motorists.

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Distinctive Characteristics

Maine is home to one of the largest of the 30 recognized subspecies of white-tailed deer. After attaining maturity at age five, our bucks can reach record live weights of nearly 400 lbs. Most adult bucks, however will range from 200 to 300 pounds live weight and will stand 36 to 40" at the shoulder. Does are considerably smaller; they normally weigh 120 to 175 pounds live weight. Newborn fawns begin life at 4 to 10 pounds but grow to approximately 85 pounds live weight in their first six months of life.

Whitetails have reddish brown fur in the summer switching to a grayish brown in winter. Their trademark white tail, when erected, flashes a danger signal to other deer in the vicinity. Whitetails have keen hearing, made possible by large ears that can rotate toward suspicious sounds. They have wide-set eyes, enabling them to focus on subtle movements while maintaining an excellent sense of depth perception. Whitetails have a very keen sense of smell enabling them to sense danger, even when visibility is poor. They have long graceful legs, enabling them to cover ground quickly by leaping, bounding, turning and outright running at speeds up to 40 miles per hour.

White-tailed deer communicate using a variety of sounds, ranging from explosive "whooshes" when startled, to the barely audible mews and grunts a doe uses to tend to her fawns. Deer are very expressive; they employ a large repertoire of signals using facial expressions and body language. These postures help to maintain the dominance hierarchy within all deer groups. Deer also communicate using odors, which emanate from a number of scent glands.

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Nocturnal/Diurnal

White-tailed deer are crepuscular animals, meaning they are typically most active around dawn and dusk. This does not mean that deer are not at all active during the day. Deer activity may also be influenced by weather, seasonality, and human activity. During hot summer days, for example, deer are less active during the daytime and more active at night when it’s cooler. Conversely, deer may be more active than usual during cooler weather. Deer activity may increase throughout the day during the breeding season while bucks are actively searching for does that are receptive to breeding. Areas with a lot of daytime human activity – which may include in the woods during the hunting season if hunter densities are high- may see little daytime deer activity and increased nocturnality of resident deer.

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Seasonal Changes

Summer home ranges (area that an animal lives within) for deer in Maine are generally 500-600 acres but can vary from 150 to more than 2,000 acres. Movement by deer from summer to winter range can vary from less than a mile to more than 25 miles depending on availability and suitability of the winter range. Deer are not generally territorial (defend their home range against intrusion of other deer). However, pregnant does will defend a small birthing area (less than 20 acres) against intrusion by all other deer, for about a month.

Bucks annually produce antlers, which are made of bone. Triggered by day length and maintained by hormone production, antlers begin growing in April, and are nurtured by a velvety outer network of skin tissue and blood vessels. Velvet is shed when growth is complete in late August and September. The hardened, polished antlers remain until they are shed in late December to early March. In whitetails, antlers allow bucks to advertise and demonstrate their dominance; hence they play a role in reproduction. A buck's first true set of antlers normally is grown by age one. Buck fawns, however, begin growing the antler base at one month of age. This base develops into two or three-inch velvet-covered "nubbins" by early winter. White-tailed does sometimes produce antlers, but this is rare. Does that do sprout antlers typically are older (5 to 15 years old); their antlers are usually velvet-covered spikes. Most antlered does remain fertile.

Each year, deer produce two coats of hair, each adapted to seasonal climate. In late spring, deer grow a coat of fine, short reddish hair. This pelage allows ample air circulation and helps the deer to stay cool in summer's heat. During September, deer molt to a highly insulative coat which consists of a dense layer of fine woolly hair under a layer of long hollow brown, gray, and white guard hairs. The guard hairs can be erected to form a very thick insulative coat, which protects against the cold winds of winter. Fawns are born with a reddish-brown coat dappled with white spots. This affords excellent camouflage against detection by predators in the summer. By early autumn, fawns grow the typical winter coat.

Another adaptation for survival is the deer's habit of storing fat for the winter. In autumn, deer accumulate fat under the skin, in the viscera, between the muscles, and in the hollow bones of the legs. This fat layer can comprise 10 to 25% of a deer's body weight by late fall. In winter, fat is reabsorbed to provide much-needed energy to supplement inadequate diets of woody browse.

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Reproduction & Family Structure

The peak breeding season for deer in Maine occurs during mid-November, although some breeding may occur in October and as late as January. The onset of the rut in bucks and estrus in does is controlled primarily by decreasing day length. Does in estrus are receptive to breeding for roughly 24 hours, and if not successfully bred, they will come into heat every 28 days, until early winter. Bucks establish and maintain a dominance hierarchy; typically the majority of does in an area are bred by the most dominant bucks. Gestation period for deer is roughly 200 days, after which well-nourished adult does give birth to twins, triplets, and rarely, quadruplets. Fawn and yearling does typically produce one fawn, if they conceive at all. The peak fawning season in Maine is mid-June. In a typical year, each 100 Maine does will give birth to about 130 fawns. However, early fawn losses tend to be high; only 60 to 80 of these young deer typically survive their first five months of life.

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Survival & Threats

White-tailed deer can live to 18 years, but few deer in the wild live that long. Does typically live longer than bucks presumably because rutting behavior predisposes bucks to higher losses due to hunting, motor vehicle collisions, physical injuries, and depletion of fat reserves going into the winter. Deer populations subjected to high hunting mortality are comprised of predominantly young deer. Conversely, a greater proportion of deer annually survives to older age classes within lightly hunted herds.

Causes of mortality of while tailed deer vary throughout the state. In more developed areas, deer are commonly struck by vehicles, harvested by hunters, and killed by predators. In less developed areas, human-related deaths are relatively few, and adult deer are more commonly taken by predators, particularly coyotes, lynx, and bobcats. Young fawns may also be preyed upon by black bear, fisher, and fox. Deer of any age may succumb to malnourishment of other natural causes, particularly at the end of harsh winters and in the following spring. Presently, Maine’s deer are relatively disease-free, and there are no diseases with significant negative impacts on our deer populations at this time.

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Management & Conservation

Population and Distribution Trends

Maine’s white-tailed deer population has experienced periods of boom and bust, and circumstantial information suggests that the state’s deer population likely did not exist in high abundance prior to the arrival of European colonists in the early 1600’s. With a combination of harsh winters, a higher predator population, and perhaps a lack of young vegetative growth for forage, white tailed deer may have been restricted to the southern coast until the European colonization. With colonization, settlers began clearing the landscape through small-scale logging operations, triggering an increase in the growth of undergrowth, providing white tailed deer with an optimum mix of forage and cover. From then, deer expanded their range and became more common in central and northern Maine. After the extirpation of cougars and wolves from Maine, deer were able to farther expand and increase in numbers with virtually no predation. Still, deer numbers continued to fluctuate with winter severity and large-scale events that caused significant habitat changes such as fires or spruce bud worm outbreaks.

Historical Management

MDIFW began estimating deer populations in the mid-1950’s, enabling the state to better understand the status of the populations and create a more informed management decision process. Between the mid-1950’s and early 1960’s, MDIFW estimated Maine’s deer population at 250,000. Eventually, habitat changes, severe winters, coyote colonization, and increased hunting pressure led to declining deer populations, and Maine’s deer population reached an estimated 141,000 deer in the 1960’s. Following this time and continuing through the late-1980’s, Maine’s deer population expressed slow growth, eventually causing a series of new management strategies and laws that attempted to expedite the growth of Maine’s deer population. Finally, Maine’s deer population grew prolifically through the 1990’s as a result of the regulatory system that limited doe harvest, plus a series of mild winters. During this time, Maine’s deer population grew to an estimated all time high of 331,000, however, much of the growth occurred within the southern tier of the state. Generally speaking, the Department has been successful in achieving deer population objectives in central and southern Maine, where wintering habitat and other factors were more favorable. Achieving meaningful herd increases has been less successful in eastern and northern Maine. Today, deer abundance ranges from one to five deer per square mile in the north, to 15 to 35 deer per square mile in central and southern areas. Some locations, in which access to recreational deer hunters has been limited or denied entirely, support higher deer populations that are above socially acceptable levels.  These latter areas are above desired population levels, and they are the focus of most deer/people conflicts in Maine today. 

Current Management

Prior to 1975, MDIFW did not set specific goals or quantified objectives for the deer population, harvest, or hunter success rates. Most regulatory actions were made by the Legislature and they were reactions to severe winters, or perceived regional declines in deer abundance. Between 1975 and 1985, MDIFW initiated strategic planning for deer, part of which involved setting publicly-supported goals and objectives. In some areas, this meant attempting to manage deer populations to specific deer densities.

With the more recent implementation of a new Big Game Management Plan, the Department no longer attempts to manage deer to specific deer densities. That approach did not adequately account for many other important aspects of deer population management such as maintaining animal health and social acceptance of deer levels and limiting negative impacts of overabundant deer. Deer management in Maine currently strives to maintain deer levels that are socially acceptable and in balance with available habitat. In areas where deer numbers are not socially acceptable or where deer are causing significant damage to habitat, the Department employs a variety of small-scale management options to try and alleviate the problems.

Each year, MDIFW staff and contractors examine roughly 6,000-8,000 hunter-killed white-tailed deer to collect data on population sex ratios, age structure, estimated mortality and recruitment rates, and body and antler size to provide a clearer picture of the size and health of both the population and habitat. From these examined deer, we also collect samples from roughly 500 deer annually to test for Chronic Wasting Disease, one of the greatest threats facing deer in this country. For more information on data collected in support of Maine deer management, please visit our Research & Management Report (PDF).

Improving deer populations in Maine's northern and eastern forestlands depends on protecting and increasing amounts of deer wintering habitat. Protection of deer wintering habitat is largely dependent on landowner cooperation and is not always possible. Many Mainers in areas of low deer density have begun artificially feeding whitetails, especially in the winter, which adds an important and relatively new dynamic to the deer wintering landscape in Maine. In Maine's heavily developed southern and coastal regions, MDIFW staff will continue to develop innovative approaches to safely manage deer harvests in order to maintain deer populations at levels that provide hunting and viewing opportunity while alleviating negative impacts from deer. In all of Maine, we will need to improve access to huntable land through proactive landowner relations programs in order to keep deer populations at tolerable levels.

Current Research in Maine

Maine Deer Winter Mortality Study

Since the early 1970’s, Maine has used a metric called the winter severity index (WSI) to describe how Maine winters impact winter mortality rates (WMR) in deer. WSI is one of the cornerstones of deer management in Maine and impacts the number of any-deer permits allocated for hunters each year (any-deer permits allow hunters to hunt antlerless deer and bucks with antlers). Because ecological relationships change over time, this metric needs to be periodically re-evaluated.

For that reason, in 2015, the Maine Department of Inland Fisheries and Wildlife (MDIFW) began a study to reassess the relationship between WSI and WMR. Doing so requires data on winter temperatures and snow conditions, which are used to determine WSI, and data on the survival rates of deer in the winter. Temperature data are provided by temperature loggers placed at 26 WSI monitoring stations throughout the state. Snow condition data are also recorded by biologists and volunteers at these monitoring stations. At the end of winter, in early April, data from temperature loggers and snow measurements are used to calculate a WSI value, which will inform ADP allocations for the upcoming deer season. 

Since 2015, MDIFW has been capturing white-tailed deer and fixing GPS collars to them to monitor their movements and survival rates. From early January to early April, MDIFW researchers are in the field capturing deer in wildlife management districts (WMDs) 1, 5, 6, and 17.

The fates of these deer in conjunction with data on the severity of the winters they encounter will help to re-evaluate the relationship between WSI and WMR and help shape deer management in Maine in the future.

The major goals of this study are to:

  1. Reevaluate the correlation between WSI and WMR for white-tailed deer
  2. Assess seasonal survival rates for the adult deer population
  3. Assess cause-specific mortality of our adult deer population
  4. Reassess the current winter severity index and try to identify a new and more simplistic metric

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