Appearance

Barren-ground caribou adult males stand about 110 cm high at the shoulder. They can weigh up to 140 kg in the fall when in their prime and drop down to about 100 kg in November after a month of mating activity. In winter, adult females weigh an average of 85 kg.

Caribou have long legs ending in large, broad, sharp-edged hooves. Their hooves help them dig craters through ice and snow to feed during the winter months and provide good support and traction when traveling over snow, ice or muskeg.

In winter, the fleshy pads between their hooves shrink and the hair between their toes forms tufts covering the pads and protecting them from contacting the frozen ground.

Caribou are one of the few mammals adapted to feed and digest lichens.

The caribou's coat varies in colour seasonally. After the summer moult, caribou are dark brown with a distinctive white belly and white mane. Throughout the summer months, white-tipped guard hairs are grown out and turn the caribou a more uniform light brown colour by fall.

The guard hairs are hollow and give the caribou buoyancy when swimming during the summer months. In the winter, the air cells in the guard hairs act as an insulating layer to conserve body heat.

During the winter, the caribou's coat fades to light beige.

Antlers

Caribou are the only species in which both males and females grow antlers. Females have antlers to defend their winter feeding craters from other caribou. Bulls have large antlers to advertise their strength to other bulls and to the cows.

Antlers are shed and regrown each year. As the bone bore of the antlers grows, it is covered with velvet. The velvet is skin richly supplied with nerves and blood vessels and densely covered by short hairs.

Caribou calves have short spikey antlers that increase in size and complexity each year until the animals are older. Older caribou have smaller antlers with fewer branches. Adult males may shed their antlers as early as November, just after the rut. Younger males and barren cows may retain their antlers until April. Pregnant females lose their antlers a few days after calving in June.

Annual cycle

Barren-ground caribou begin to migrate from their wintering areas northwards towards their calving grounds in March and April. Pregnant cows lead the way in their urgency to reach traditional calving grounds. These calving areas can be as far as 700 kms away and are often located in high, rocky areas with little shelter from wind and driving snow. Generally barren-ground caribou herds are named for a geographic feature in the calving area.

Bulls and immature caribou lag behind the cows and do not go all the way to the calving grounds. 

Most calves are born within a few days of each other during the first two weeks of June and temperatures are usually near the freezing point. Calves can stand and suckle within a few minutes of birth. In an hour, a calf can follow its mother.

After calving, cows and calves begin the long trek back toward the winter range. As spring turns into summer, the cows meet up with the bulls that have continued to drift north.

Caribou form dense groups or "post-calving aggregations" in an attempt to reduce the intense disturbance caused by mosquitoes, warble flies and nose-bot flies.  These groups can number in the tens of thousands of animals.

In August and September, insect disturbance decreases and allows caribou to focus on feeding. They break into smaller bands and slowly move across the tundra towards the treeline. They rapidly gain weight as they feed on mushrooms, lichens, shrubs and grasses. The cows, in particular, have to gain enough weight to be able to breed in the fall.

The rut occurs in October when the bulls are in their prime. The rut may last for two or three weeks but most cows are bred within a few days of each other.

The distribution of barren-ground caribou changes constantly during the winter as the herds search for places where the food is abundant and the snow is shallow. Caribou use their excellent sense of smell to lead them to lichens under the snow. Their broad hooves are designed for digging feeding craters through snow and ice. Lichens are the mainstay of their winter diet, but sedges and evergreen leaves are also eaten.

When spring arrives, the caribou once again begin their migration to the calving grounds.