Deer

I

Introduction

Deer, common name for certain hoofed, artiodactyl (even-toed) mammals, usually characterized by bony, often branching antlers that are shed and regenerated annually. Deer range through the Americas, Europe, Asia, and North Africa. The largest populations occur in mixed wooded and open land, although deer also live in swamps, on mountains, and on northern tundras. Deer species range in size from the European elk, or moose, which may reach a shoulder height of 2.35 m (7.7 ft), to the South American pudu, which can be as little as 25 cm (10 in) high at the shoulder. The first deer appeared in the early Oligocene epoch in Asia, about 38 million years ago.

II

Characteristics

Deer commonly have lithe, compact bodies and long, powerful legs suited for rugged woodland terrain. They are also excellent swimmers. Their lower cheek teeth have crescent ridges of enamel, which enable them to grind a wide variety of vegetation. The animals are ruminants, or cud chewers, and have a four-chambered stomach. Nearly all deer have a facial gland, in front of each eye, which contains a strongly scented substance, or pheromone, used to mark its home range. The males of many species open these glands wide when angry or excited. All deer except the musk deer have a liver without a gall bladder. The musk deer, along with the Chinese water deer, also differs from other species in that it has no antlers and bears upper canines that have developed into tusks.

III

Antlers

Unlike the hollow, permanent horns of other ruminants, the antlers of deer are solid and bony. Except in reindeer, antlers form only on males and their growth is controlled by the male sex hormone. Antlers arise from the frontal bones and are nourished by a highly vascularized, fine-haired skin, called velvet. It requires large amounts of calcium for antlers to complete their growth, which happens within a few months. Circulation is then cut off, and the resulting dead skin is sloughed off as the animal rubs its antlers against trees. Antlers are used to slash territorial markings on trees or bushes, to make threatening displays, and to combat other males. Usually the fighting is stylized and harmless, but occasionally males of large species lock antlers and die of exhaustion or starvation. Moose antlers reach a width of 1.8 m (6 ft) and a weight of 20 kg (44 lb); those of an extinct giant fallow deer spread more than 3 m (10 ft). Antlers in a given species may vary in size from one population to another, depending on the quality and quantity of food. In overpopulated areas that are heavily browsed, the deer usually have small antlers.

IV

Behaviour

Many deer species group into families around the female, with the male often becoming solitary; others, such as the musk deer and Chinese water deer, live mainly in pairs. The red deer, which are gregarious, associate in small to large herds, each led by a mature female. Caribou and reindeer migrate between the forest and the treeless tundra in herds of a thousand or more.

Deer forage on twigs, leaves, bark, and buds of bushes and saplings, and on grasses and other plants, feeding most actively at twilight. The female gives birth once a year, usually to one or two fawns. The gestation period lasts from 160 days in musk deer to ten months in roe deer; this long gestation in roe deer is accounted for by a delayed implantation. Fawns are kept hidden in thickets, camouflaged by their usually dappled markings. In the United States, where deer now have few natural predators, they often overbrowse their territory and may die of starvation, especially during winters of deep snow.