Fauna Series No. 4

Fauna of the National Parks — No. 4 Ecology of the Coyote in the Yellowstone

CHAPTER VI:
MULE DEER IN RELATION TO COYOTES

STATUS OF DEER

Official counts of deer in Yellowstone made by the rangers show a steady increase since 1934. (Coyote control was terminated in the spring of 1935.) The counts by years are as follows: 1934, 363; 1935, 610; 1936, 673; 1937, 843; and 1938, 850.

Estimates made during these years vary from 850 in 1934 to 900 in 1938. The numbers of deer during these years probably has not varied greatly. However, there may have been some decline after the winter of 1934—35 when a number of deer died around the Game Ranch and near Gardiner outside the park. A heavy loss was probable that spring over most of the winter range. In reviewing the report on the 1938 census I note that the recorded population is a little low in a few localities, doubtless because of unfavorable counting conditions on the particular days when the census was taken. For instance, only 13 deer were counted in the Cottonwood area. About a week before the official count I found 90 deer on the area; and 10 days after the official count at a time when bare slopes had brought the deer out in the open to feed, I found 143. The official count along the Yellowstone River below Blacktail Deer Creek is also low. In these two areas the actual count, if made under more favorable conditions, would probably be 200 higher than the number recorded. The estimated population in this wooded area where counting is difficult would of course be a still higher figure. The actual count of deer in the park in 1938 should, therefore, be in excess of 1,000.

It seems probable that for some years the deer population has been held in check by range conditions and that the cause of mortality has been chiefly malnutrition and certain diseases, with other diseases and predation as secondary causes.

The primary winter deer foods now present in Yellowstone National Park are Douglas fir, sagebrush (Artemisia tridentata), yellowbrush, and to a lesser extent, in some localities, red cedar. Some food species such as poplar, service berry and willow, now scarce, probably once formed an important part of the diet. Other foods of less importance, because of their scarcity or lower palatability, are fringed sagebrush, greasewood (Atriplex oblanceolata), willow poplar, and Russian thistle. Over most of the range sagebrush is perhaps the most important winter food, at least on the basis of abundance and general use. Sagebrush was found in 24 of 39 stomachs examined during the winter. In 13 of these, sagebrush made up more than 50 percent of the contents, and in 3 more than 90 percent. Deer feed regularly on sagebrush, beginning in November (on the eighteenth 11 deer were seen feeding steadily on it) and continue well into the spring long after a variety of other green foods become available. Sage is heavily overbrowsed in places, especially on parts of the range near the Game Ranch and on the slopes of both sides of the Gardiner River. On some of these deer ranges, antelope have contributed to the overbrowsed condition of the sagebrush. Along the Yellowstone River the occurrence of sagebrush is spotted, and near Deckers Flat it is much overbrowsed. The best sagebrush range is on Reese Creek, the lower part of which has until recently been hunted so extensively that there has not been a heavy concentration of deer for more than a short time.

Douglas fir, an important deer food, now affords very little browse. Deer were often seen reaching high for the twigs, and even standing with the forefeet on rocks to better reach the browse. A fawn stomach contained 100 percent Douglas fir and numerous other stomachs contained lesser amounts, but many analyses showed no fir since it was not readily available to most of the deer. Deer and elk both are responsible for overbrowsing the fir, but since elk are present in greater numbers, overbrowsing is largely due to them. Scarcity of Douglas fir is one of the worst defects of the deer range.

Yellowbrush is generally distributed over the winter range and is much eaten by deer, but does not rank as high in the deer diet as sagebrush and Douglas fir. Red cedar (Juniperus scopulorum) is important along the Yellowstone River because of the local scarcity of Douglas fir browse. In the fall and spring, when the deer are still consuming winter forage, on the winter range, green grass is eaten in large amounts. From its first appearance in spring it is closely cropped, and makes up an important supplement to the regular winter food supply. Dry grass was eaten sparingly on a few occasions. It is very unpalatable to the population as a whole.

Figure 30— The old doe managed to rise and walk to the Gardiner River, where she fell and could not rise.
March 7, 1938.

To summarize, the data indicate that the status of the deer is dependent upon the condition of the range, particularly the condition of sagebrush, Douglas fir, and, to a considerably less degree, of red cedar and yellowbrush. The condition of the deer range is dependent upon the number of deer and elk. If there were fewer elk there would probably be more deer. It seems certain that for several years the deer have been pressing the range, the population being as large as the condition of the range and competition of the elk permits. Some years rather heavy mortality of deer has been reported while in other years the mortality has been light, depending, no doubt, on winter conditions and deer concentrations. Some fawns are killed by coyotes in winter, but it appears that this predation largely affects the weak animals, many of which would die before summer. Judging from the rather high number of fawns that come to the winter range, apparently few are lost during fawning time.

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