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Fauna Series No. 4






Population and Mortality







Other Larger Mammals

Small Mammals


Misc. Diet



Fauna of the National Parks — No. 4
Ecology of the Coyote in the Yellowstone
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coyote song
Figure 56— Coyote song.
Swan Lake Flat, April 14, 1938.

IN EARLIER DAYS of conservation effort on a new continent we were handicapped by lack of precise knowledge, and, in order to meet new problems brought about by the invasion of man's interests into original wildlife habitats, direct methods were necessary and often there was no time to discover ecological facts, at that time considered obscure, or to develop preventive methods. Consequently a decided viewpoint on the question of predation was developed and, with modification, it has persisted.

We often deplore an apparent lack of foresight in earlier viewpoints and methods of handling our wildlife resources, but we need to consider the fact that each succeeding generation has greater facilities and opportunities.

Since the advent of the modern conception of wildlife management a new attitude toward the question of predation is growing. One of its precepts is that control of potentially harmful or suspected species of birds and mammals should await precise data based on research.

The results of the present study are, of course, not complete from the ecological standpoint. At least one or two more years would have been a welcome addition to the program in order to cover more annual variables. However, it is felt that the information obtained is sufficiently significant for present purposes. It is hoped that studies may be continued, as other duties permit, and that the coyote situation may be kept under constant surveillance.

Analysis of more than 5,000 coyote droppings from within Yellowstone National Park, containing nearly 9,000 individual items, reveals that, during spring, summer, and fall, rodents constitute by far the most important part of coyote diet, the majority of these being field mice and pocket gophers. The percentage of birds taken is relatively small and there is much evidence to show that many of the birds were obtained in the form of carrion. As a matter of fact the percentage of insects, particularly grasshoppers and crickets, computed on the basis of occurrence, is more than double the percentage of birds in the diet. Considering these items, together with a long list of miscellaneous species and materials, we must conclude that the role of the coyote in the fauna is not a harmful one during these seasons of the year.

In winter the examination of droppings was supplemented with intensive field observations and it became clear that the big game herds furnish most of the coyote's food. This is chiefly in the form of carrion, and, particularly in the case of deer, of weakened animals fated to succumb before spring.

In some categories it was found difficult to distinguish the proportion of carrion, as in the case of newborn elk calves, although it was definitely determined that some such carrion is available.

Special emphasis was given to the task of determining the effect of coyote pressure on prey species. The facts show that in the case of elk this is negligible, and that no appreciable inroads on the populations of deer, antelope, and bighorn are taking place.

On the other hand it became clear that the big game species are seriously handicapped by a poor, crowded range. Several big game species are competing with the bighorn and this situation requires continued attention.

The problem of the big game species in Yellowstone is not one of predation, but of inadequate winter range, a problem shared by many districts throughout the Western States. To remedy the plight of some of these animals it is recommended that additional winter range be provided for antelope in the Yellowstone Valley north of Yellowstone National Park. This would not be an addition to the park, but part of Absaroka National Forest. Antelope need the range if they are to continue in satisfactory numbers. Providing adequate winter range down the Yellowstone for this species and some of the elk would tend to relieve the competition with the bighorn.

Special attention was given to the status of the trumpeter swan, since it is the policy of the National Park Service to safeguard threatened species. The coyote has been suspected as a destructive factor limiting the increase of the species. However, no evidence was found that the coyote preys upon the swans. On the other hand, positive evidence points to lead poisoning and starvation, among other possible factors. It is probable that food limitations in winter may be potent in preventing greater increase of the trumpeter swans.

It has been feared that Yellowstone National Park serves as a reservoir from which coyotes may spread and populate distant areas where they are not wanted. There are few precise data in support of this, but, on the other hand, observations indicate that coyotes would rarely travel any great distance and that the majority remain with the game herds in the vicinity of the park boundaries. Forested areas adjacent to the park already carry a permanent coyote population. Trappers along the north side of Yellowstone National Park welcome the appearance of coyotes outside of the boundaries.

Apparently the Yellowstone coyote population does not increase indefinitely. Facts enumerated above show that the population level is kept down by disease, possibly in some cases by starvation, and that this species is subject to natural controls.

In the present study every effort was made to study the coyote in its interactions with all elements of the fauna and its relation to human interests. In consideration of these findings and the absence of facts to show that the coyote is an undesirable element of the wildlife in Yellowstone, it is concluded that artificial control is not advisable under present conditions.

The National Park Service is charged with the responsibility of preserving designated areas, selected samples of primitive America, in their natural condition for the enjoyment and study of present and future Americans. In line with this high purpose the flora and fauna should be subjected to a minimum of disturbance. The natural interactions of the members of the fauna and flora and the environment have a place in such a scheme and serve to furnish significance and greater interest in the animal life. Study of early records shows that, with a few exceptions, the general faunal pattern of the Yellowstone has persisted to the present time. A desirable member of the assembly of animals, the coyote contributes to the interest and variety of this fauna.

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