The range of the Denali Caribou Herd is almost exclusively within the boundaries of Denali National Park and Preserve. The Denali Herd inhabits most of the park east of the Foraker River and north of the Alaska Range throughout most of the year. Some animals of the Denali Herd will occasionally travel south of the Alaska Range toward the vicinity of Cantwell during the calving season. Biologists place great value on the research conducted on the Denali Herd because it is the only barren-ground caribou herd in North America of such a large size class that is currently not hunted. It also shares its range with a natural complement of large predators and both predator and prey populations within Denali are naturally regulated.
During the summer the body of the caribou is generally covered by brown fur. Coloration is variable, ranging from pure white through tan to dark brownish gray, with lighter rump and undersides. In the winter the coat turns grayish to almost white in color and gets thicker and longer than the summer coat. The coat is made of two layers: a guard coat made of straight, tubular hairs and a wooly undercoat. Calves are brown and unspotted. Mature caribou stand approximately four feet tall at the shoulder, eight feet in length and weigh from 130 to over 350 pounds. Caribou hoofs are very large and form a nearly circular print - acting like snowshoes to keep the animal from sinking in the snow. Both males (bulls) and females (cows) grow antlers standing as high as three feet or more
The Caribou breeding season occurs during late September though October. Cows begin breeding when they are around 2.5 years old. After breeding the gestation period lasts 225-235 days with the calves usually born mid-May to early June. Like the other members of the deer family bulls spar with each other during the rut for breeding access to the females. During these fights the bulls will charge each other with their heads cocked downward. They run into each other antlers first, rear up, and on their hind legs and paw at each other with the front hooves. Injuries are rare, however, the bulls will occasionally get their antlers locked together, which can result in death for both animals.
In the spring the females will migrate towards areas known as calving grounds to give birth in safety. According to studies, the number of predators on the calving grounds is less than the caribou encounter on their winter range. Instincts to reach these areas are so strong with the caribou that they are able to travel through adverse conditions like deep snow, steep mountains and icy rivers. The young are born shortly after the females arrive on the grounds.
The size of the Denali Caribou Herd has fluctuated greatly over the last 80 years. It once numbered over 20,000 caribou during the 1920's and 1930's. During the 1940's through the 1960's, the herd declined to 10,000 animals but remained somewhat stable. Further declines occurred during the 1970's when numbers reached a low of approximately 1,000 animals. The herd was subject to harvest until the mid 1970's but all harvest was discontinued as a result of the precipitous population decline. Studies from the late 1970's indicated that early calf survival was very poor even though adult cows were in good condition and had adequate food resources. Predation on young calves was thought to be a major factor in the population decline. The Denali Caribou Herd has experienced some periods of growth during the last 20 years. It increased by approximately 10% per year between 1977 and 1990. By 1990, the herd numbered 3,700 animals. However, the winter of 1990-91 was very severe and set new snowfall records. The herd declined as much as 30% between 1990 and 1991, likely due to weather induced stresses and increased vulnerability to predation. Currently, there are approximately 1,760 caribou in Denali National Park and Preserve.