White-tailed deer are generalists and can adapt to a wide variety of
habitats. The largest deer occur in the temperate regions of North America. The northern white-tailed deer (
O. v. borealis), Dakota white-tailed deer (
O. v. dacotensis), and northwest white-tailed deer (
O. v. ochrourus) are some of the largest animals, with large antlers. The smallest deer occur in the Florida Keys and in partially wooded lowlands in the
Neotropics. Although most often thought of as forest animals depending on relatively small openings and edges, white-tailed deer can equally adapt themselves to life in more open prairie, savanna woodlands, and sage communities as in the Southwestern United States and northern Mexico. These savanna-adapted deer have relatively large antlers in proportion to their body size and large tails. Also, a noticeable difference exists in size between male and female deer of the savannas. The Texas white-tailed deer (
O. v. texanus), of the prairies and oak savannas of Texas and parts of Mexico, are the largest savanna-adapted deer in the Southwest, with impressive antlers that might rival deer found in Canada and the northern United States. Populations of
Arizona (
O. v. couesi) and Carmen Mountains (
O. v. carminis) white-tailed deer inhabit montane mixed oak and pine woodland communities. The Arizona and Carmen Mountains deer are smaller, but may also have impressive antlers, considering their size. The white-tailed deer of the
Llanos region of Colombia and Venezuela (
O. v. apurensis and
O. v. gymnotis) have antler dimensions similar to the Arizona white-tailed deer. In some western regions of North America the white-tailed deer range overlaps with those of the
mule deer. White-tail incursions in the
Trans-Pecos region of Texas have resulted in some hybrids. In the extreme north of the range, their habitat is also used by
moose in some areas. White-tailed deer may occur in areas that are also exploited by
elk (wapiti) such as in mixed deciduous river valley bottomlands and formerly in the mixed deciduous forest of eastern United States. In places such as
Glacier National Park in Montana and several national parks in the Columbian Mountains (
Mount Revelstoke National Park) and Canadian Rocky Mountains, as well as in the Yukon Territory (
Yoho National Park and
Kootenay National Park), white-tailed deer are shy and more reclusive than the coexisting mule deer, elk and moose. Central American white-tailed deer prefer
tropical and subtropical dry broadleaf forests, seasonal mixed deciduous forests, savanna, and adjacent wetland habitats over dense
tropical and subtropical moist broadleaf forests. South American subspecies of white-tailed deer live in two types of environment. The first type, similar to the Central American deer, consists of savannas, dry deciduous forests, and riparian corridors that cover much of Venezuela and eastern Colombia. The other type is the higher elevation mountain grassland/mixed forest ecozones in the Andes Mountains, from Venezuela to Peru. The Andean white-tailed deer seem to retain gray coats due to the colder weather at high altitudes, whereas the lowland savanna forms retain the reddish brown coats. South American white-tailed deer, like those in Central America, also generally avoid dense moist broadleaf forests. Since the second half of the 19th century, white-tailed deer have been introduced to Europe. A population in the
Brdy area remains stable today. In 1935, white-tailed deer were introduced to
Finland. The introduction was successful, and the deer began spreading through northern
Scandinavia and southern
Karelia, competing with, and sometimes displacing, native species. The 2020 population of some 109,000 deer originated from four animals provided by
Finnish Americans from Minnesota.
Diet White-tailed deer eat large amounts of food, commonly eating
legumes and foraging on other plants, including
shoots, leaves,
cacti (in deserts), prairie forbs, and
grasses. They also eat acorns, fruit, and corn. Their multi-chambered stomachs allow them to eat some foods humans cannot, such as
mushrooms (even those that are toxic to humans) and
poison ivy. Their diets vary by season according to the availability of food sources. They also eat hay, grass, white clover, and other foods they can find in a farmyard. Though almost entirely herbivorous, white-tailed deer have been known to opportunistically feed on nesting songbirds, field mice, and birds trapped in
mist nets, if the need arises. When additional amounts of minerals such as calcium are needed in their diet, they can resort to
osteophagy, chewing on bones of dead animals. A grown deer can eat around of vegetable matter annually. A population of around can start to destroy the forest environment in their foraging area. Their diet consists mostly of woody shoots, stems, and leaves of woody plants as well as grasses, cultivated crops, nuts, berries, and wildflowers. The items they feed on are not generally abundant in mature forests and are mostly found at "edges". Edges are described as a "mosaic of vegetation types that create numerous interwoven 'edges' where their respective boundaries intersect" and provide optimum cover for browsers such as the white-tailed deer. White-tailed deer can easily thrive in suburban areas, as a combination of increased safety from some predators (including human hunting), high quality and abundance of foods in home gardens, city parks, open farmland, and other factors all create landscapes with an abundance of edge habitat. The white-tailed deer is a
ruminant, which means it has a four-chambered stomach. Each chamber has a different and specific function that allows the deer to eat a variety of different foods, digesting it at a later time in a safe area of cover. The stomach hosts a complex set of microbes that change as the deer's diet changes through the seasons. If the microbes necessary for digestion of a particular food (e.g., hay) are absent, it will not be digested. Utilizing
foregut fermentation, the fermented ingesta (known as
cud) is regurgitated and chewed again, to mix it with saliva and reduce the particle size. Smaller particle size allows for increased nutrient absorption and the saliva is important because it provides liquid for the microbial population, recirculates nitrogen and minerals, and acts as a buffer for the rumen pH.
Predators There are several natural predators of white-tailed deer, with
wolves,
cougars,
American alligators,
jaguars (in the American southwest, Mexico, and Central and South America) and humans being the most effective natural predators. Aside from humans, these predators frequently pick out easily caught young or infirm deer (which is believed to improve the genetic stock of a population), but can and do take healthy adults of any size.
Bobcats,
Canada lynx,
grizzly and
American black bears,
wolverines, and packs of
coyotes usually prey mainly on fawns. Bears may sometimes attack adult deer, while lynxes, coyotes, and wolverines are most likely to take adult deer when the ungulates are weakened by harsh winter weather. Occasionally, both
golden and
bald eagles may capture deer fawns with their talons. In one case, a golden eagle was filmed in
Illinois unsuccessfully trying to prey on a large mature white-tailed deer. White-tailed deer typically respond to the presence of potential predators by breathing very heavily (also called blowing) and fleeing. When they blow, the sound alerts other deer in the area. As they run, the flash of their white tails warns other deer. This especially serves to warn fawns when their mother is alarmed. Most natural predators of white-tailed deer hunt by ambush, although
canids may engage in an extended chase, hoping to exhaust the prey.
Felids typically try to suffocate the deer by biting the throat. Cougars and jaguars will initially knock the deer off balance with their powerful forelegs, whereas the smaller bobcats and lynxes will jump astride the deer to deliver a killing bite. In the case of canids and wolverines, the predators bite at the limbs and flanks, hobbling the deer, until they can reach vital organs and kill it through loss of blood. Bears, which usually target fawns, often simply knock down the prey and then start eating it while it is still alive. Alligators snatch deer as they try to drink from or cross bodies of water, grabbing them with their powerful jaws and dragging them into the water to drown. Most primary natural predators of white-tailed deer have been essentially
extirpated in eastern North America, with a very small number of reintroduced critically endangered
red wolves, around
North Carolina and a small remnant population of
Florida panthers, a subspecies of the cougar.
Gray wolves, the leading cause of deer mortality where they overlap, co-occur with whitetails in northern Minnesota, Wisconsin, Michigan, and most of Canada. Coyotes, widespread and with a rapidly expanding population, are often the only major nonhuman predator of the species in the Eastern U.S., besides an occasional
domestic dog. Bobcats, still fairly widespread, usually only exploit deer as prey when smaller prey is scarce. Discussions have occurred regarding the possible reintroduction of gray wolves and cougars to sections of the eastern United States, largely because of the apparent controlling effect they have through deer predation on local ecosystems, as has been illustrated in the reintroduction of wolves to
Yellowstone National Park and their controlling effect on previously overpopulated
elk. However, due to the heavy urban development in much of the Eastern U.S., and fear for livestock and human lives, such ideas have ultimately been rejected by local communities and/or by government services and have not been carried through. White-tailed deer can run faster than their predators and have been recorded sprinting at speeds of per hour and sustaining speeds of per hour over distances of ; this ranks them amongst the fastest of all deer, alongside the Eurasian
roe deer. They can also jump high and up to forward. When shot at, a white-tailed deer will run at high speeds with its tail down. If frightened, the deer will hop in a zig-zag with its tail straight up. If the deer feels extremely threatened, however, it may choose to attack, charging the person or predator posing the threat, using its antlers or, if none are present, its head to fight off its target.
Forest alteration In certain parts of eastern North America, high deer densities have caused large reductions in plant biomass, including the density and heights of certain forest wildflowers, tree seedlings, and shrubs. Although they can be seen as a nuisance species, white-tailed deer also play an important role in biodiversity. At the same time, increases in browse-tolerant grasses and sedges and unpalatable ferns have often accompanied intensive deer herbivory. Changes to the structure of forest understories have, in turn, altered the composition and abundance of forest bird communities in some areas. In regions of intermediate density, deer activity has also been shown to increase herbaceous plant diversity, particularly in disturbed areas, by reducing competitively dominant plants; and to increase the growth rates of important canopy trees, perhaps by increased nutrient inputs into the soil. In northeastern hardwood forests, high-density deer populations affect plant succession, particularly following clear-cuts and patch cuts. In succession without deer, annual herbs and woody plants are followed by commercially valuable, shade-tolerant oak and maple. The shade-tolerant trees prevent the invasion of less commercial cherry and American beech, which are stronger nutrient competitors, but not as shade tolerant. Although deer eat shade-tolerant plants and acorns, this is not the only way deer can shift the balance in favor of nutrient competitors. Deer consuming earlier-succession plants allows in enough light for nutrient competitors to invade. Since slow-growing oaks need several decades to develop root systems sufficient to compete with faster-growing species, removal of the canopy prior to that point amplifies the effect of deer on succession. High-density deer populations possibly could browse eastern hemlock seedlings out of existence in northern hardwood forests; however, this scenario seems unlikely, given that deer browsing is not considered the critical factor preventing hemlock re-establishment at large scales. Ecologists have also expressed concern over the facilitative effect high deer populations have on invasions of exotic plant species. In a study of eastern hemlock forests, browsing by white-tailed deer caused populations of three exotic plants to rise faster than they do in the areas which are absent of deer. Seedlings of the three invading species rose exponentially with deer density, while the most common native species fell exponentially with deer density, because deer were preferentially eating the native species. The effects of deer on the invasive and native plants were magnified in cases of canopy disturbance.
Population and controls The white-tailed deer population in North America has declined by several million since 2000, but as of 2017 is considered healthy and is approximately equal to the historical pre-colonization white-tailed population on the continent. The species has rebounded considerably after being overhunted nearly to extinction in the late 1800s and very early 1900s. In Maryland and many other states, a state agency sets regulations on bag limits and hunting in the area depending on the deer population levels assessed. Hunting seasons may fluctuate in duration, or restrictions may be set to affect how many deer or what type of deer can be hunted in certain regions. For the 2015–2016 white-tailed deer-hunting season, some areas allowed only the hunting of antlerless white-tailed deer. These included young bucks and females, which encouraged the culling of does, aiding in population control. removal strategy than public hunting is a method referred to as sharpshooting. Sharpshooting can be an option when the area inhabited by the deer is unfit for public hunting. This strategy may work in areas close to human populations, since it is done by professional marksmen, and requires a submitted plan of action to the city with details of the time and location of the action, as well as number of deer to be culled. While lethal methods have municipal support as being the most effective in the short term, some opponents of this view suggest that extermination has no significant impact on deer populations. Opponents of contraceptive methods point out that fertility control cannot provide meat and proves ineffective over time as populations in open-field systems move about. Concerns are voiced that the contraceptives have not been adequately researched for the effect they could have on humans. Fertility control also does nothing to affect the current population and the effects their grazing may be having on the forest plant make-up. Translocation has been considered overly costly for the little benefit it provides. Deer experience high stress and are at high risk of dying in the process, putting into question its humaneness. Another concern regarding translocation is the possible spreading of
chronic wasting disease to unaffected deer populations and concerns about exposure to human populations. In addition to the danger of
deer-vehicle collisions the
National Agricultural Statistics Service (NASS) reported that the estimated loss in field crops, nuts, fruits, and vegetables in 2001 was near $765 million (equivalent to $ in ). ==Behavior==