Reindeer (Caribou)

In the wild, the caribou diet consists of lichens, grasses, shrubs, and other vegetation. They forage seasonally, seeking out young flowering buds and new leaves to maximize nutritional value. The winter diet mainly consists of lichen, which is high in carbohydrates and low in protein.

At the zoo, our reindeer receive grain, alfalfa, hay, and browse as their regular diet. They sometimes will receive beet pulp or other novel foods when training.

Caribou have a widespread distribution spanning the northern parts of North America and Eurasia. Although historically more widespread, in North America the reindeer can now be found in Alaska and Canada. In Europe and Asia, populations occur in Norway, Finland, Russia, Greenland, Iceland, and Mongolia.

Caribou inhabit several different habitats from coastal plains, mountain ranges, sub-Arctic tundra, and boreal coniferous forests.

Depending on the location and habitats gray wolves, wolverines, lynx, and dholes predate on caribou. Brown bears, ravens, and eagles may prey on calves.

Although the reindeer may not be globally threatened, overhunting and poaching have caused some populations to decline. Oil exploration, industrial development, logging activity, and recreation have also caused increased human encroachment on territories. In North America, habitat modification has led to white-tailed deer moving into the caribou ranges and spreading deadly parasites. In Finland, the reindeer may also be at risk of hybridization with semi-domesticated animals. All caribou may be affected by future climate change, which could increase the frequency of rain and subsequent icing over food sources, leading to starvation. Warmer weather could disrupt migration routes by affecting the break-up of sea ice and could also increase the number of parasites of reindeer.

Reindeer, like many domesticated hoof stock species, were bred to be much more compact and sturdier than their wild counterparts. Wild caribou tend to have longer legs and are much larger. The coat occurs in a variety of colors from dark brown to nearly white, with differences depending on the subspecies, region, sex, and season. The long hairs under the neck, the fur just above the hooves, and the region about the tail are almost white. As protection against the unforgiving climate in which they live, caribou are covered in hair from their nose to the bottom of their feet. They have two coat layers: an undercoat of fine, soft wool that stays right next to their skin, and a top layer of long, hollow guard hairs. The air trapped inside the guard hairs holds in body heat to keep the animal warm against wind and cold. The hollow hairs also help the reindeer float, allowing it to swim across a river if needed. Their hairy hooves give caribou a good grip when walking on frozen ground, ice, mud, or snow.

Spongy footpads help them walk in marshy fields, and in winter their hooves harden so they can dig into the ice or snow and keep from slipping. Being broad, flat, and having two toes, a caribou’s hooves also allow it to push water aside when the animal swims. The hooves are even used to scrape at snow while looking for food. A long dewclaw on each leg serves as an extra hoof to help the animal climb rugged terrain. When a caribou walks, the tendons in their legs produce a clicking sound. This gives the line from the classic Christmas song “Up on the Rooftop" a whole new meaning!

In comparison to body size, caribou have the largest and heaviest antlers of all living deer species. A male’s antlers can measure up to 51 inches long, and a female’s antlers can reach 20 inches. Just as a tree has a trunk, all antlers have a main beam and several branches or tines that grow from the frontal bones of the skull. The tip of each antler is called a point. Unlike horns, antlers fall off and grow back larger every year. As new antlers grow, the caribou is said to be “in velvet”, because skin, blood vessels, and soft fur cover the developing antlers. When the velvet dries up, the caribou rubs it off against rocks or trees, revealing the hardened, bony core. This is the only breed of deer that both males and females grow antlers. Males begin to grow antlers in February and females in May. They both finish growing their antlers at the same time but cast off their antlers at different times of the year. A male drops his in November, leaving him without antlers until the following spring, while female caribou keep their antlers through the winter until their calves are born in May.

Caribou are the only deer species to have hair completely covering their nose. This specialized nose helps to warm incoming cold air before it enters the lungs and releases as little body heat as possible when exhaling. Caribou have a superb sense of smell, which is important for finding food hidden under snow, locating danger, and recognizing direction in the sometimes-featureless tundra.

Researchers have discovered that the ultraviolet (UV) light that causes the temporary but painful condition of snow blindness in humans is life-saving for caribou in the Arctic. Caribou can not only see ultraviolet light, but they can also make sense of the image to find food and stay safe.

Male caribou enter a " rut " phase during the breeding season, where they fiercely compete for the chance to mate. To prepare themselves for this they aggressively rub the velvet off their hardened antlers and put on weight. Additionally, their necks swell and the fur around the throat grows longer. This is a stressful time for the males, and they lose up to 25% of their body weight. The winners choose 5 to 15 females to be in his “harem”, or breeding group.

Pregnant females leave the herd in the spring and travel to a traditional calving ground. Here, they give birth within 10 days of each other, usually in May and June. Females usually give birth to a single calf, although there may be twins or more. The calf is not spotted like other deer species. Newborns can stand just one hour after birth, follow their mother at five to seven hours old, and outrun a human when only one day old! A caribou calf drinks its mother’s rich milk and begins to add solid food to its diet at one week old. By two weeks, it has doubled its birth weight. The calf is weaned about six months later. Antlers first appear as little hairy buds when the reindeer is in its second year.

Vocalizations include snorts, grunts, and hoarse calls, especially during the breeding season or rut. Calves bleat to call to their mother.

Caribou travel, feed, and rest together throughout the day in herds of 10 to a few hundred. During the spring, they may form super herds of 50,000 to 500,000 animals. The herds generally follow food sources, traveling south (up to 1,000 miles) when food is hard to find in winter. A healthy adult caribou is usually safe from predators, especially in a large herd where many individuals can watch for danger. It is the youngest calves that are most susceptible to predation. Old, weak, ill, and injured caribou are also vulnerable. After the breeding season, many bulls are exhausted or injured, and they are also at risk.