The most similar species to White-tailed Deer is the Mule Deer, but there are clear external distinguishing traits. The most obvious are the rump patch and tail. In White-tailed Deer, the tail is longer and the upper (outer) surface of the tail is almost always the same brown colour as the rest of the body, not white or dark brown as in the Mule Deer. Only the white outer edges of the rump patch are visible when the tail is down in the resting position, so there is no large white rump patch always visible as in Rocky Mountain Mule Deer. When alarmed, White-tailed Deer raise the tail and the white hairs along its edge and underneath on the rump, making the tail area appear much larger. They will also bound off waving the raised tail – called flagging, this is another unique characteristic of the species. The ears lack the dark rim and are also proportionately smaller than those of Mule Deer. White-tailed Deer also lack the dark patch on the forehead that Mule and Fallow deer have. In summer coat, White-tailed Deer generally have a more reddish tinge than the Mule Deer. The metatarsal gland on the outside of the lower hind leg is also smaller, has white hairs in the centre, and is located towards the distal (lower) end of the metatarsal region rather than in the middle or at the proximal (upper) end, as in Mule Deer. For adult males, the non-forking tines of the antlers also separate them from Mule Deer.
Like the Mule Deer, White-tailed Deer skulls can be separated from other similar-sized species such as Fallow Deer by the vomer dividing the posterior nares. Unlike Mule Deer, the antorbital depression of the White-tailed Deer’s skull is shallow. While the vomer also divides the posterior nares in Caribou, White-tailed Deer lack upper canines and do not have the angled dorsal profile of the premaxilla.
Neither tracks nor faeces can be separated easily from those of the Mule Deer, but the clearly pointed hooves of all Odocoilid deer can be distinguished from the similar-sized but blunter tracks of the Bighorn Sheep and Mountain Goat.
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Gestation is 200 to 210 days. Twins are common when conditions are good, but triplets are rare. Young White-tailed Deer are born in early June and weigh 2 to 4 kg. With their spotted coats providing camouflage, they use the hider strategy in their first few weeks of life, lying hidden in thick vegetation during the day while their mothers go off to feed.
Under good conditions, female White-tailed Deer can give birth around their first birthday, but in most populations it takes place a year later. Females complete most of their body growth around 3 to 4 years of age, and males by about 4 to 6 years of age.
| There has been no detailed study of diets of White-tailed Deer in B.C., but probably like elsewhere, the species feeds on a range of vegetation, eating mainly forbs and browse, with lesser amounts of grasses, mushrooms and the bark of young deciduous trees. In winter in the East Kootenay, Douglas-fir and Kinnikinnick were found to be important foods. |
The age of a White-tailed Deer can be determined by tooth eruption sequence up to about 3.5 years old, and by counting cementum annuli of either incisors or molars for older animals. Tooth wear does not seem to be a reliable year-specific technique. White-tailed Deer probably live for 8 to 10 years, although there are no data for populations in British Columbia. A White-tail Deer skeleton lacking a skull, can be sexed by examining the pelvis. In males 2 years and older, a bump, called a suspensory tuberosity, projects from the anterior edge of each pelvic ilium just above their junction.
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The main predators in B.C. are probably Cougars and Coyotes, although Wolves, Lynxes and Bobcats are also known to prey on them in other areas. Bears sometimes prey on the young during the hider stage. White-tailed Deer prefer to avoid predators by hiding in dense vegetation, but if surprised, they will often snort and stamp a forefoot to give an alarm to others; they also behave this way in response to humans. When moved to flight, White-tailed Deer bound away majestically, tail raised and waving from side to side (flagging), exposing the erect white hairs underneath.
Diseases and parasites may have significant effects on White-tailed Deer populations. For example, outbreaks of epizootic haemorrhagic disease (EHD), an orbivirus closely related to Bluetongue, causes acute but sporadic mortality in White-tailed Deer. Such an EHD outbreak was reported in southeastern B.C. and the Okanagan Valley in the 1980s. The virus is transmitted by Biting Gnats that also transmit the Bluetongue virus. High mortality rates during EHD outbreaks may devastate small populations. Other deer species and domestic animals generally show mild to no clinical effects from EHD infection, although deaths have been reported in Mule Deer. We do not know how this virus persists in the environment. Domestic Cattle are not carriers of EHD.
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Adult male and female White-tailed Deer live apart for most of the year. The basic social unit is a family group comprised of an adult female with one or two of her yearlings and young of the year. Young males leave their family when about a year old. Males are usually solitary around the rutting period but otherwise may live in small all-male groups. White-tailed Deer will often form larger temporary aggregations when attracted to choice food sources, especially in open areas.
The necks of adult male White-tailed Deer swell just before rut, and with their hard antlers, they spar with each other as well as with bushes and small trees. In serious fights between similar-sized individuals, rival adult males approach and circle each other in a slight crouch, ears back and the hair on their body raised. The hairs of their tarsal glands are flared, and they seem to avoid eye-contact with each other. Then, they may suddenly lunge at each other and lock antlers, rapidly pushing and twisting with their heads close to the ground, trying to throw their opponent off balance. When one male slips or breaks away, the other tries to gore him in the rear as he flees. The winner will chase the loser for a short distance uttering a loud coughing bark, sometimes slapping his forefeet on the ground. Like most other deer, female White-tailed Deer, and males without hard antlers, fight with ears back and head held high, using their forefeet, either from a standing position or raised up on their hind legs.
In British Columbia, White-tailed Deer mate in November and early December (and their courtship is quite different than that of Mule Deer). Males vigorously rub their antlers against bushes and small trees, first to remove the velvet in August, and later in the fall, perhaps as visual, auditory and olfactory signals. The noise of a male thrashing a bush travels some distance; the scratches he makes on the bark are clearly visible, and the odour he leaves behind on the vegetation, possibly from his frontal glands, is powerful. Male White-tailed Deer also scrape small patches of ground with their forefeet, and then mark the depression with urine and tarsal gland secretions using the hock-rub. They often defend these scrapes against other males, and females are sometimes attracted to them and may also urinate in them. Both sexes urinate while rubbing their tarsal glands together, but in the rut it is mainly males that do this. Both the tarsal and the metatarsal glands secrete a musky odour.
When a female starts to come into heat, she is usually courted by a single male; but sometimes, several males will pursue her, often running in large circles. A courting male approaches the female with head low like a young trying to suckle, then rushes towards her, hits the ground with his hooves, barks a few times and chases after her if she runs away. Close to oestrus, the female becomes more tolerant and the male moves towards her in a crouch, sometimes bleating, and then stands alongside and guards her from other males. There are few pre-copulatory mounts, and copulation itself is quick, with the male performing a copulatory jump during ejaculation.
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