Deer - Biology

Biology

Deer weights generally range from 30 to 300 kilograms (70 to 700 lb), though the smallest species, the Northern Pudú, averages 10 kilograms (20 lb) and the largest, the moose, averages 431 kilograms (1,000 lb). They generally have lithe, compact bodies and long, powerful legs suited for rugged woodland terrain. Deer are also excellent jumpers and swimmers. Deer are ruminants, or cud-chewers, and have a four-chambered stomach. The teeth of deer are adapted to feeding on vegetation, and like other ruminants, they lack upper incisors, instead having a tough pad at the front of their upper jaw. Some deer, such as those on the island of Rùm, do consume meat when it is available.

The Chinese water deer, tufted deer, and muntjac have enlarged upper canine teeth forming sharp tusks, while other species often lack upper canines altogether. The cheek teeth of deer have crescent ridges of enamel, which enable them to grind a wide variety of vegetation. The dental formula for deer is:

Nearly all deer have a facial gland in front of each eye. The gland contains a strongly scented pheromone, used to mark its home range. Bucks of a wide range of species open these glands wide when angry or excited. All deer have a liver without a gallbladder. Deer also have a tapetum lucidum, which gives them sufficiently good night vision.

Nearly all cervids are so-called uniparental species: the fawns are only cared for by the mother. A doe generally has one or two fawns at a time (triplets, while not unknown, are uncommon). The gestation period is anywhere up to ten months for the European roe deer. Most fawns are born with their fur covered with white spots, though in many species they lose these spots by the end of their first winter. In the first twenty minutes of a fawn's life, the fawn begins to take its first steps. Its mother licks it clean until it is almost free of scent, so predators will not find it. Its mother leaves often, and the fawn does not like to be left behind. Sometimes its mother must gently push it down with her foot. The fawn stays hidden in the grass for one week until it is strong enough to walk with its mother. The fawn and its mother stay together for about one year. A male usually never sees his mother again, but females sometimes come back with their own fawns and form small herds.

Deer are selective feeders. They are usually browsers, and primarily feed on leaves. They have small, unspecialized stomachs by ruminant standards, and high nutrition requirements. Rather than attempt to digest vast quantities of low-grade, fibrous food as, for example, sheep and cattle do, deer select easily digestible shoots, young leaves, fresh grasses, soft twigs, fruit, fungi, and lichens.