Fauna Series No. 5

Fauna of the National Parks — No. 5 The Wolves of Mount McKinley

CHAPTER FOUR:
CARIBOU (continued)

Food Habits of Caribou

The caribou is a grazing and browsing animal with a special fondness for lichens. The more important foods eaten in the Mount McKinley region consist of lichens, grasses, willows, and dwarf Arctic birch.

WINTER FOOD

Although lichens, and to a lesser extent mosses, are relished at all times of the year, they are especially sought during the period when the abundance of green foods of summer are not available. My summer observations in Mount McKinley National Park indicate that relatively few lichens are eaten. Perhaps more are eaten at this season farther westward where such food is in greater abundance. In September, when the green vegetation has largely disappeared, caribou seek out and feed extensively on lichens. Species of the genus Cladonia seem to be the favorite ones. Throughout the winter, the caribou paw through the snow for lichens as well as grasses. One of the requirements of a wintering ground seems to be the presence of lichens, even though they by no means form the exclusive diet.

Grasses, sedges, and willows are also eaten extensively in winter. Even patches of coarse sedge were closely grazed in some places. So far as I could tell, practically all species of grasses and sedges were utilized. The willow twigs are eaten and some of the dry leaves are picked off the ground. Willow was much utilized during the winter months.

SUMMER FOOD

The important summer foods are grasses and sedges, willows, and dwarf birch, supplemented by an assortment of herbs. In early spring the caribou near Wonder Lake were seeking the new green shoots of sedge and grass. Grasses and sedges form a large part of the summer food. When the willows and the dwarf birch leaf out in May they are eaten in large quantities. For a period in May and early June willow and dwarf birch seem to make up the bulk of the food. The leaves are stripped from the twigs, and some of the fine twigs are also eaten at this time of the year, perhaps more or less accidentally. Where large bands of caribou have fed, many of the willow twigs which have had the leaves removed are withered. Several kinds of willows are eaten, including two or three species of dwarf willow that are highly palatable. More than half the stomach contents of a cow which died July 15 consisted of two species of dwarf willow. Willows and dwarf Arctic birch are widely distributed and abundant in the park.

Various herbs such as Boykinia, Hedysarum, and Dryas are eaten in summer. Hedysarum, growing abundantly on the gravel bars, is eagerly sought, so that where herds of caribou have passed, hardly a plant has escaped a close grazing. Equisetum was especially sought on several occasions. (For a large list of food plants see O. J. Murie, 1935.)

When migrating a caribou may settle down for a period to feed, but much of the time it eats hurriedly as it travels. Often, before a willow twig is stripped of leaves, the caribou has moved forward and is reaching far back to complete the action. Even when the caribou has settled down to feed more leisurely, it faces in the direction it is going. This is so consistently true that one can almost always know the direction of the general migration of a herd by watching the movements of a single animal. When the animals are on the wintering grounds or on the calving grounds they feed more leisurely, although even then they are usually moving about a great deal.

Stomach contents of some dead caribou found on the range were as follows:

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Last Modified: Thurs, Dec 20 2001 10:00:00 pm PDT
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