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

FAWN SURVIVAL

An effort was made to determine the number of fawns which were surviving in order to learn: (1) The status of the deer population, that is, whether it appeared that enough fawns were surviving to maintain the species; and (2) if there were any correlation between the condition of a unit of the range and the number of fawns surviving on it.

After the deer had moved into the winter range in 1937—38 there was no noticeable shifting about from one unit of the range to another, even though there is continuous winter range between some of the units. On the contrary, the deer seemed restricted to relatively small areas. Approximately the same number of deer were always found in certain draws, and individual deer that I could recognize were found frequently in the same locality. For instance, a horned doe remained in the vicinity of Junction Butte the year round. She was seen there by Ranger Condon in the winter of 1936—37, and in the fall of 1937, early spring of 1938, and early spring of 1939 by myself. On February 5, 1938, near the mouth of Blacktail Deer Creek I saw a doe with the top half of both ears missing. Ranger Gammill saw this doe in the same area on March 28 almost 2 months later. Six counts of deer in the open areas below Deckers Flat between February 17 and April 1 varied from 40 to 48, indicating a stable population. These deer were usually concentrated around two draws a few hundred yards apart. During most of the winter the home range of some of the deer probably did not cover an area much more than a mile across, others possibly ranged more widely. The deer tabulated for the various units on the winter range were on the whole restricted to that particular unit all winter. Any movement that there might have been would not be sufficient to make an appreciable difference in the figures.

At first some attempt was made to segregate the yearlings but as differentiating them was difficult and often there was not time to classify them, they were finally grouped with does and bucks. All the animals were classified into three groups, does (including yearling does) bucks, and fawns. The fawns were usually readily distinguishable by a combination of characters, including small size, short rostrum, marked facial pattern, and general darker color, but by spring some of these characters were not so distinctive and occasionally a few animals were seen which had to be scrutinized carefully to determine their age. Size as a criterion is deceptive so that yearling does sometimes appeared to be adults and in the distance yearlings sometimes looked like fawns. After some experience with the difficulties involved the likelihood of errors in making fawn identifications became small.

Figure 23— Buck deer killed by another buck during the rut. It was wounded inside the hind leg and in the abdominal cavity where a tine apparently pierced an artery near the vertebrae.
Game Ranch, November 13, 1937.

Because some of the bucks spend the winter higher than the does, in the deeper snow and among the trees on the fringes of the winter range where they are not so easily counted, it is certain that the bucks are not represented in the counts in their true proportions. But even after making a most generous allowance for uncounted bucks there still seemed to be about twice as many females as males in the population. The lower number of bucks may be due in part to the fact that bucks enter the winter in poor condition from rutting activities. Fighting, resulting in a few casualties among the bucks and possibly a number of injuries which have some permanent weakening effect, may be a minor factor in reducing the buck population.

Since figures for the fawn-doe ratios on the different range units are comparable, percentage of fawn increase is given in terms of the doe counts. Buck counts are not included in these calculations because of their probable variability over the various range units. The tabulations made in the winter of 1937—38 are based on a sample which includes more than 800 of the 1,000 or more deer on the winter range. Because there is sometimes considerable variation in the fawn ratio in various bands, small samples are apt to be misleading.

Winter of 1936—37.—My data on the survival of fawns during the winter of 1936—37 are not extensive but bear out observations made by others. On May 7, 1937, before deer had begun to leave their winter ranges, I observed along the Yellowstone River between Hellroaring Creek and the mouth of Blacktail Deer Creek 10 does and 8 fawns. The percentage of fawns in the sample of the population seen may have been considerably higher than the true average but indicated a good winter survival. This was on poor range where, in the following hard winter of 1937—38, scarcely a fawn survived. Ranger Raymond West, who spent some time in the area during the winter, observed that nearly every doe was followed by a fawn. Ranger Dave Condon, who watched deer closely at Tower Falls, also reported a high fawn survival. During the entire winter of 1936—37 the snow was loose and crustless, a condition highly favorable to the deer, especially on the poor range along the Yellowstone River where the different species of food plants are quite scattered and so entail for the deer considerable moving about to obtain a balanced diet.

Winter of 1937—38.—The winter range was divided into a number of more or less natural units, between which there was very little movement of deer. Counts of deer on these units were made as opportunity offered throughout the winter. The classified counts and the fawn-doe ratio have been tabulated. The counts on each unit of range vary considerably because the deer were not always where they were visible to the same degree, and because it was not always possible to cover the entire unit. In some areas the number of deer seen differed considerably. Especially was this true along parts of the Yellowstone River where the numbers of deer seen in a stretch on different trips varied from 1 to more than 100. The great variation in counts on this range was due to the fact that most of the inhabited part of it was wooded so the deer were not readily seen but, as snow left the open areas, some deer came out on them to feed and were easily observed.

Classified Counts Made in 1937—38 in Different Range Units

Best late counts excerpted from classified counts

1 Adults.

Figure 24— Part of a band of deer which included 3 fawns, wintering near Norris.
April 29, 1938.

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