Monotypic Species - The Reindeer
The reindeer may be an example of a monotypic species depending on which authority you consult. Its scientific name is Rangifer tarandus. Although there are subspecies it is the only species in its genus. Other animals which are unique in this way include the black rhino, giraffe, okapi, moose and platypus.
Reindeer are sometimes classified into two groups: tundra reindeer and woodland reindeer. In America, the reindeer is also known as 'caribou'.
The reindeer is well-known as the power behind Santa's sleigh. As well as being used as a draught animal, reindeer have provided (and still provide) milk, meat, antlers and hides to several Arctic and Sub-arctic groups.
Reindeer are widespread and common through the northern Arctic regions with large numbers found in Canada, Alaska, Greenland, Finland, Norway and Siberia. The South Atlantic island of South Georgia also has a herd of some 2600 animals. These were introduced at the beginning of the 20th century but are under threat because of the damage they cause to the environment. Herd populations are in decline across their ranges. Migratory herds are threatened by climate change and non-migratory herds by industrial disturbance.
Domesticated reindeer are found in Scandinavian countries and Russia.
Reindeer vary in size and colour. Both sexes have antlers with the males typically having larger antlers. Females in some herds may lack antlers altogether. There are typically two sets of points with considerable variation between the subspecies. Relative to body size, the reindeer has the largest antlers of any deer species other than the moose, with a large bull's antlers reaching perhaps 39 inches in width and 53 inches in beam length.
The antlers grow each year. A layer of fur or velvet covers the antlers. This is eventually lost.
The nose of the reindeer has specialised nasal turbinate bones. These large, highly folded passages increase the surface area within the nostrils. Cold air is held and warmed before entering the lungs; expired air has moisture condensed before being exhaled. This condensation is used to moisten dry incoming air. Interestingly the Australian emu also has nasal turbinates which create condensation for reabsorption into the body.
The footpads of the reindeer's hooves become sponge-like in summer, giving better grip on the soft, wet tundra. In winter the pads shrink away from the rim of the hoof which then cut into the ice preventing the animal from slipping. Such adaptation of the hoof also enables the deer to dig for lichen or reindeer moss under the snow during winter, a process known as 'cratering'. The knees of some subspecies 'click' as they walk.
Reindeer can see ultraviolet light and are believed to be the only mammals which have this faculty. Reindeer can see light with wavelengths well below the human threshold. This ability gives better contrast of objects in the Arctic. Thus fur (of wolves), which might blend into the landscape, becomes sharply contrasted in ultraviolet.
Depending on the subspecies, reindeer range from 64 to 81 inches in length and weigh between 170 and 260 pound. Males or bulls are generally slightly larger than females of their own kind. Height at the shoulder varies from 33 to 59 inches.
The subspecies R.t.platyrhynchus from Svalbard island exhibit insular dwarfism. Males are about 63 inches long, 31 inches high and weigh between 140 and 200 pound depending on the season. They are also relatively short in the leg.Credit: Wikimedia
The pelage colour can vary widely too. Northern herds are generally smaller and paler with the northernmost species, the Peary caribou, being the whitest and smallest of the American subspecies. The woodland caribou is the darkest, largest and southernmost. The coat has a dense woolly undercoat and an outer coat of hollow, air-filled hairs. These two layers provide great insulation against the cold.
Migrating herds may travel between 12 and 34 miles daily. Reindeer can run at 37 to 50 mph. Spring migrations result in small groups forming huge herds but autumn migrations consist of smaller groups. They are good swimmers and have no hesitation tackling a broad expanse of water.
Reindeer are ruminants (cud-chewing animals) and have a four-chambered stomach. Their diet consists mainly of lichens, willow and birch leaves, sedges and grasses. They may eat bird eggs, mushrooms, lemmings and arctic char (a fish) sometimes.
Males fight for the right to mate with females, locking horns, pushing and shoving. The breeding season is from late September to early November. Males stop eating during the season and become gaunt and lean. Calves are born from May to June and suckle until the following autumn.
The reindeer has a number of predators, most of which prefer newborn calves or weak and/or infirm adults. Golden eagles, wolverines, brown bears and polar bears all keep a lookout for an opportune kill. The grey wolf is particularly effective at preying on adult reindeer whether infirm or not. Foxes, ravens and hawks feed on the carrion. Although not a predator, black flies and mosquitoes can create great stress, affecting feeding and calving behaviours.