The female varies in weight between 60 and 170 kg (130 and 370 lb) and measures 162–205 cm (64–81 in) long. The male (or "bull") is typically larger (although the extent to which varies in the different subspecies), weighing 100–318 kg (220–700 lb) and measuring 180–214 cm (71–84 in) in head-and-body length. Shoulder height can measure from 80–150 cm (31–59 in) and the tail adds 14–20 cm (5.5–7.9 in). Both sexes grow antlers, which (in the Scandinavian variety) for old males fall off in December, for young males in the early spring, and for females, summer. The antlers typically have two separate groups of points (see image), a lower and upper. Domesticated reindeer are shorter-legged and heavier than their wild counterparts. The bull reindeer's antlers are the second largest of any extant deer, after the moose, and can range up to 100 cm (39 in) in width and 135 cm (53 in) in beam length.
Reindeer have specialized noses featuring nasal turbinate bones that dramatically increase the surface area within the nostrils. Incoming cold air is warmed by the animal's body heat before entering the lungs, and water is condensed from the expired air and captured before the deer's breath is exhaled, used to moisten dry incoming air and possibly absorbed into the blood through the mucous membranes.
Reindeer hooves adapt to the season: in the summer, when the tundra is soft and wet, the footpads become sponge-like and provide extra traction. In the winter, the pads shrink and tighten, exposing the rim of the hoof which cuts into the ice and crusted snow to keep it from slipping. This also enables them to dig down (an activity known as "cratering")through the snow to their favorite food, a lichen known as reindeer moss. The knees of many species of reindeer are adapted to produce a clicking sound as they walk. The reindeer coat has two layers of fur, a dense woolly undercoat and longer-haired overcoat consisting of hollow, air-filled hairs.
Diet
Reindeer are ruminants, having a four-chambered stomach. They mainly eat lichens in winter, especially reindeer moss. However, they also eat the leaves of willows and birches, as well as sedges and grasses. There is some evidence to suggest that on occasion they will also feed on lemmings, arctic char, and bird eggs. Reindeer herded by the Chukchis have been known to enthusiastically devour mushrooms in late summer.
Reproduction Mating occurs from late September to early November. Males battle for access to females. Two males will lock each other’s antlers together and try to push each other away. The most dominant males can collect as many as 15-20 females to mate with. A male will stop eating during this time and lose much of its body reserves. Calves may be born the following May or June. After 45 days, the calves are able to graze and forage but continue suckling until the following fall and become independent from their mothers.
Migration
The reindeer travels the furthest of any terrestrial mammal. The caribou of North America can run at speeds up to 80 km/h (50 mph) and can travel as much as 5,000 km (3,100 mi) a year. Migrations can number in the thousands. The most extensive migrations occur in spring and fall. During fall migrations, the groups become smaller and the reindeer begin to mate. During the winter, reindeer travel to forested areas to forage under the snow. By spring, groups leave their winter grounds to go to the calving grounds. A reindeer can swim easily and quickly; migrating herds will not hesitate to swim across a large lake or broad river.
Predators
There are a variety of predators that prey heavily on reindeer. Golden Eagles prey on calves and are the most prolific hunter on calving grounds. Wolverine will take newborn calves or birthing cows, as well as (less commonly) infirm adults. Brown Bears and (in the rare cases where they encounter each other) Polar bears prey on reindeer of all ages, but (as with the wolverine) are mostly likely to attack calves or sickly animals. The Gray Wolf is the most effective natural predator of adult reindeer, especially during the winter. As carrion, caribou are fed on by foxes, ravens and hawks. Blood-sucking insects, such as black flies and mosquitoes are a plague to reindeer during the summer and can cause enough stress to inhibit feeding and calving behaviors. In one case, the entire body of a reindeer was found in a Greenland shark, the only shark typically found near the North Pole.[14] The population numbers of some of these predators is influenced by the migration of reindeer.
