Highly adaptable, the various subspecies of white-tailed deer inhabit many different ecosystems, from arid grasslands to the Amazon and Orinoco basins; from the Pantanal and the Llanos to the high-elevation terrain of the Andes.

[3] Globally, the white-tailed deer has been introduced (primarily for sport hunting) to New Zealand, the Greater Antilles of the Caribbean (Cuba, Jamaica, Hispaniola, and Puerto Rico),[4] and some countries in Europe (mainly the Czech Republic, Finland, France, Germany, Romania and Serbia).

[5][6] In North America, the white-tailed deer is very common (even considered a nuisance in some areas) in states to the east and south of the Rocky Mountains, including southwestern Arizona, with the exception of the American West Coast and Baja California Peninsula, where its ecological niche is filled by the black-tailed (in the Pacific Northwest) or mule deer (Odocoileus hemionus) from that point west except for mixed deciduous riparian corridors, river valley bottomlands, and lower foothills of the northern Rocky Mountain region from Wyoming west to eastern Washington and eastern Oregon and north to northeastern British Columbia and southern Yukon, including in the Montana valley and foothill grasslands.

The westernmost population of the species, known as the Columbian white-tailed deer, was once widespread in the mixed forests along the Willamette and Cowlitz River valleys of western Oregon and southwestern Washington, but current numbers are considerably reduced, and it is classified as near-threatened by the IUCN.

[8] High populations of white-tailed deer are known to exist on the Edwards Plateau of Central Texas, as well as in Illinois, Maryland, Michigan, Minnesota, Indiana, Iowa, Mississippi, Missouri, New Jersey, New York, North Dakota, Ohio, and Wisconsin.

The conversion of land adjacent to the Canadian Rockies to agricultural use, and partial clear-cutting of coniferous trees (resulting in widespread deciduous vegetation), has been favorable to the white-tailed deer and has extended its distribution to as far northwest as the Yukon.

The Boone and Crockett or Pope and Young scoring systems also define relative degrees of typicality and atypicality by procedures to measure what proportion of the antlers is asymmetrical.

Populations of Arizona (O. v. couesi) and Carmen Mountains (O. v. carminis) white-tailed deer inhabit montane mixed oak and pine woodland communities.

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.

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.

[36] 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.

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.

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.

Records exist of American crows and common ravens attempting to prey on white-tailed deer fawns by pecking around their face and eyes, though no accounts of success are given.

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.

[51] 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.

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.

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.

[65] Several methods have been developed to curb the population of white-tailed deer in suburban areas where they are perceived as overabundant, and these can be separated into lethal and nonlethal strategies.

[69] 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.

[70] 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.

[73] 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,[74] (equivalent to $1.26 billion in 2023).

They are usually weaned after 8–10 weeks, but cases have been seen where mothers have continued to allow nursing long after the fawns have lost their spots (for several months, or until the end of fall) as seen by rehabilitators and other studies.

[99] Conservation practices have proved so successful, in parts of their range, the white-tailed deer populations currently far exceed their cultural carrying capacity and the animal may be considered a nuisance.

Timber harvesting and forest clearance have historically resulted in increased deer population densities,[102][103] which in turn have slowed the rate of reforestation following logging in some areas.

They are a good business venture because they have a high fertility rate and long reproductive life, can tolerate all weather, can be raised on land that is not suitable for agriculture and offer many by-products that can be sold.

[111] An essential procedure in understanding factors resulting in accidents is to quantify risks, which involves the driver's behavior in terms of safe speed and ability to observe the deer.

This data, confirmed by the National Veterinary Services Laboratory, alerted scientists to the possibility that white-tailed deer had become a natural reservoir for the coronavirus, serving as a potential "variant factory" for eventual retransmission back into humans.

[119] Infected deer can shed virus via nasal secretions and feces for five to six days and frequently engage in activities conductive to viral spread, such as sniffing food intermingled with waste, nuzzling noses, polygamy, and the sharing of salt licks.

Another study by Kennedy-Slaney, Bowman, Walpole, and Pond found that if current CO2 emissions remained the same, global warming resulting from the increased greenhouse gases in the atmosphere will allow white-tailed deer to survive further and further north by 2100.