Despite being the second largest species of deer on Earth, many of us know little more about reindeer than what Christmas stories have conveyed. Indeed, in his 2002 book Fauna Britannica, Stefan Buczacki wrote that:
“Outside the month of December, most people in Britain never give the Reindeer a second thought, which is a pity because it is a remarkable beast.”
Buzacki's quite right and, from being the only species in which females routinely grow antlers to clicking when they walk, reindeer are a fascinating addition to the deer family.
That which follows is a summary of Reindeer natural history. The detailed article for this species will follow in due course.
The Reindeer at a glance
Evolved in Europe 5-6 million years ago and crossed into North America at some point during the early Pleistocene (250,000 years ago). Fossil evidence suggests reindeer in Britain at least 750,000 years ago, with remains from at least 30 archaeological sites in Britain and 22 in Ireland. Dating analysis suggests reindeer died out in Ireland around 10,250 years ago, but later in Britain; youngest remains, from a site in Sutherland in the Scottish Highlands, date to 8,300 years ago.
Size: Second largest deer species, after the moose (Alces alces). Males stand 100-130cm/3–4ft at shoulder and weigh 110-220kg/242-485 lbs; females are smaller, standing 95-115cm at shoulder and weighing 65-150kg/143-331 lbs. Domestication appears to suppress growth by 20-40%, males being more strongly affected than females.
Appearance: Unspotted grey-brown coat with lighter ash-grey belly, darker flanks and legs, white rump, short tail, white feet and, in males, a white mane. Winter coat lighter colour than summer one; composed of dense underfur covered by thick, hollow outer guard hairs. Reindeer have broad hooves that spread their weight, reducing sinking in boggy and snowy ground, and adapt to season: foam-like pads expand in the summer to provide grip when the tundra soft/wet, and contract during the winter, exposing the rim of the hoof to facilitate ice-walking and snow-scraping. Feet are furred, helping insulate and provide grip in icy conditions. Seasonal antlers present in both sexes.
Distribution: Small population of introduced animals exists in Britain, introduced from Sweden to Cairngorms by Michael Utsi and Ethel Lindgrenand in 1952. Found throughout much of the northern hemisphere, though populations highly fragmented and genetic purity of the few remaining wild herds recently questioned (significant mixing of wild and domestic/semi-domestic populations in Europe). Found from Norway across Eurasia to east coast of Russia, but IUCN notes that wild populations are only in Norway, Finland and Russia. Also found in parts of North America, specifically Alaska, Canada, Washington, and Idaho, where they're called caribou, and in Greenland.
Longevity, Mortality & Predators: Females typically outlive males; may survive for 17 years in good habitat, while males seldom exceed 14 years. Oldest of the Cairngorm herd was 19 years old; oldest on record died aged nearly 22 years. Harvested for meat. Reindeer have few predators although globally, particularly North America, primary predator is the grey wolf, packs of which will take down adult and young deer. Brown and polar bears occasionally take deer of all ages, with polar bears recorded swimming after adult deer to catch and drag them back to shore to kill and eat them. Bears will also scavenge carcasses. Wolverines take calves and very occasionally birthing or infirm individuals, while golden eagles will take calves.
Sexing: Males called bulls; females called cows; young are calves. Very similar in appearance, although males larger and grow mane during breeding season. Both sexes routinely grow antlers; males grow larger set than females and irrespective of habitat. Antlers in females corresponds closely with snowfall—more snow results in higher percentage of females growing antlers and vice versa. In habitats where winters are less harsh, like mountain forests, fewer females grow antlers, and those that do often grow smaller or asymmetrical ones. Small percentage of females never grow antlers.
Antlers: Antler buds, which develop into pedicles, evident from ~3 weeks old in both sexes. Unlike other cervids, castrated reindeer or those with their ovaries removed grow, clean and cast their first antlers. Covered in velvet while growing; velvet shed in September. Mature males cast antlers during November and remain antlerless until February. Non-pregnant females tend to cast around the same time as the immature males (late winter or early spring), although some young males may retain antlers until April. Pregnant females won't cast until May, casting shortly after giving birth. Observation that antler growth in females correlates positively with snowfall indicates antlers are resource-driven. Most females are pregnant during period of greatest snow cover and retain antlers to allow access to best feeding patches and help clear snow. Antler size tails off in females by about 3yrs old; in males they grow in size and complexity until about 5yrs.
Territory/Range: In Britain spend most of the year well above the treeline in heather moorland on the slopes of the Cairngorms at 400-1,300 m/1,300-4,230 ft. before being brought down to lower pastures to give birth during summer. Reindeer typically inhabit open tundra, although some populations, particularly in Finland, have adapted to mountain forests. Herds living on tundra may migrate vast distances between inland winter feeding grounds and coastal summer feeding ones—journeys of 5,000 km/3,100 miles are known, with herds moving up to 150 km/93 miles per day. Excellent swimmers readily crossing rivers during migrations. Can sustain 6.5 km per hour/3.5 knots in the water and can reach 9.6 kmph/5 knots when followed by a speedboat
Diet: Ruminants with majority of diet soft, easily digested plant material. Lichens, particularly cup lichens(Cladonia), significant part of the diet, especially for domestic/semi-domestic deer, eaten throughout the year, but of particular importance in winter. Diet may also include young grasses, birch shoots, flower buds and leaves during the spring and summer; fungi during the autumn. Will take shrubs, particularly cowberry and bilberry, and sedges according to availability, and can feed on plants that are toxic to other mammals, including wolf's bane (Aconitum), hellebores (Veratrum) and broomrape (Pedicularis). Primarily herbivorous, but will supplement diet with animal protein including fish and birds' eggs; will take chicks from nests and reports of hunting lemmings in USA.
Reproduction: Rut during late September and October, males antler-clashing for access to mates. Bulls attempt to keep the females together in a single herd (harem) to protect them from interloping males. Females may stay in harem for most of the breeding season but become choosier around estrus, when they call more and visit 'satellite' bulls outside herd. Gestate for about 7 after which a 4.5-7 kg/10-15 lbs calf is born, typically from May into early summer. Typically have a single calf, very occasionally twins. Calf born with significant deposits of fat around heart, kidneys, groin and shoulders, allowing thermoregulation. In most populations calf is up and following the mother within a couple of hours and dam returns to main herd 20-30 hours after the birth. Woodland caribou hide calves in vegetation. Calf feeds almost exclusively on mother's milk for the first month or so then begins to take solid food. Reindeer milk is very rich, highest solid content (proteins, fats, minerals and carbohydrates) of any deer milk, enabling calf to grow quickly. The calf will stay with its mother for its first winter; independent by the following autumn.
Behaviour & Sociality: A gregarious species found in mix-sex herds outside rutting season; sexual segregation during rut. Will form herds of several thousand animals. Females less aggressive/more gregarious than males with female-only groups larger than either male-only or mixed-sex groups. Dominant bulls stabilise population during rut, herding females and controlling sociality. When females have choice, they opt to socialise with family members, but during the rut they're often constrained by dominant bull.
Can see UV light and may use it both to locate plants in the snow and avoid overhead power lines, which give off a corona of irregular flashes of UV. Make a clicking noise when they walk, caused when tendons in the legs rub over bony protuberances (sesamoid bones) in ankle. Clicking can be heard up to 40m/131 ft away on a still day and believed to help keep the herd together in conditions of poor visibility.
Threats: Worldwide population currently unknown, but thought to be ca. 3.5 million in North America and 3 million in Europe. Local population surveys suggest numbers are declining, particularly in North America. Additionally, warmer winters mean more storms and rain, which turns the snow surface to ice and makes it very difficult to get at their normal lichen. Reports of reindeer on Russian tundra starving to death as a consequence, with some estimates suggesting 80,000 having succumbed between 2006 and 2013.
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