Moose and caribou are the only members of the deer family found in Denali. Caribou are circumpolar animals, well adapted to life in the Arctic. Caribou have large concave hoofs that spread widely to support the animal in snow and soft tundra. The feet also function as paddles when caribou swim. Caribou are the only member of the deer family in which both sexes grow antlers. Antlers of adult bulls are large and massive while those of adult cows are much shorter and usually more slender and irregular. Newborn calves weigh an average of 13 pounds. Bulls can weigh up to 400 pounds, females up to 225 pounds.
Caribou is a Micmac Indian name meaning “shoveler” referring to their large, pliable hooves which are use to “shovel” through snow to uncover the lichen they depend on in winter. Caribou are Pleistocene survivors along with other Denali mammals including moose, wolf, grizzly bear, foxes, lemmings, squirrels and voles.
Single calves are born in May and weigh 11 to 20 pounds. They grow rapidly gaining a pound per day for the first 100 days of life.
Caribou, like moose, reduce their metabolic rate in winter. To prevent excessive heat loss from their long legs, caribou maintain two internal temperatures: a body temperature of 105 degrees F and a 30-degree-cooler leg temperature. Caribou have what is known as counter-current circulation.
Counter Current Circulation: The easiest way to reduce the amount of energy needed to heat a house is with good insulation. Arctic animals try to keep their temperature constant too, but their legs remain cold, while their head and body core remain warm. This seems like a difficult feat, but with an adaptation called countercurrent heat exchange it requires little energy. In this system of circulation arteries, which carry warm blood from the heart to the extremities, lie very close to the veins, which carry blood from the cold extremities of the body back to the heart. In this way, heat from the warm arterial blood is transferred to the colder blood in a vein, thereby cooling the blood in the artery and warming the venous blood. Thus, as blood from the body reaches the extremities, it is already cooled and loses very little additional heat to the environment. Conversely, cool blood from the extremities is warmed prior to reaching the body core and does not shock the heart or reduce internal body temperature. The countercurrent exchange system has been well studied in both the arctic fox and the caribou, which maintain their core temperature nearly 30°C higher than their appendages.
Caribou suffer from Warble flies: Eggs are laid on the hair of the caribou’s legs and lower body. Once the eggs hatch, the maggots penetrate the skin of the caribou and start a long migration toward the animal’s back. Through the winter and into the spring, they continue their migration up to the spine and rump of the animal where they cut a breathing hole through the skin. By early summer the warbles are about 1 inch and are ready to emerge from the back. They fall to the ground and pupate. From the pupae emerges the adult fly that lives long enough to mate and lay its eggs on another caribou.
The second larvae of interest are the throat or nose bot. Its life cycle starts with the female laying larvae on the face of the caribou around the nostrils. There are no eggs, just larvae (maggots). These larvae crawl into the mouth and in the nasal sinuses and back of the throat where they spend the winter. In extreme cases they can cause suffocation. In the spring, the larvae detach from the host and leave through the nostrils causing caribou to snort and sneeze. The fall to the ground and in the fall they swarm again and the cycle repeats.
Caribou feed on willows, dwarf birch, grasses, sedges and succulent plants in the summer and switch to lichens and dried sedges in the winter.
Alaskan Wildlife can be seen in Denali National Park. Kantishna Wilderness Trails provides Alaska Wildlife Day Tours while Kantishna Roadhouse offers Denali lodging and accommodations for Alaska Travel and Alaska Vacations deep into Denali National Park.