Fauna Series No. 5

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

CHAPTER THREE:
DALL SHEEP (continued)

Classified Counts of the Mountain Sheep (continued)

CLASSIFICATIONS FOR 1939

Total count.—Between the latter part of May, when practically all lambs had been born, and late October 4,985 sheep were classified. There were many duplications, but the count probably included 90 percent or more of the sheep. Some sheep were undoubtedly counted oftener than others, so that in the total count there is some danger of the averages being unduly influenced by some of the duplications. However, the results are about the same as the selected counts where there was very little, if any, duplication. The figures for the total classification are as follows: Ewes, 2,055; lambs, 1,064; yearlings, 549; 2-year-olds, 163; rams 1,154. The lamb-ewe ratio is 51 per cent, that is 51 percent of the ewes had lambs. The yearling-ewe ratio is 26 percent. If the lamb crop in 1938 was about the same as in 1939, then one-half of the lambs had succumbed during the first year. This I would presume to be a normal, good survival. The 2-year-olds were not counted consistently, so the count of them is smaller than it should be. In most other counts 2-year-olds were not segregated, so it may be best here to place half of them with the ewes and half with the rams so as to make all the figures comparable. This would reduce the figure for the lamb-ewe ratio from 51 percent to 50 percent and the yearling-ewe ratio from 26 percent to 25 percent.

Spring Count.—In the total count there were more duplications in some parts of the range than in others and if they happened to fall in localities where the lamb and yearling numbers were especially high or low, the final figures for the lamb and yearling ratios would be too high or too low. One representative count has therefore been selected from the field record in each locality. These were made as soon after lambing as a good count could be obtained, in order to have a classification of most of the population with a minimum of duplications. Although the counts were not made on the same date (there is more than a month separating some of them) I am confident there is little duplication. Where there could have been duplication, judging from the localities and dates appearing in Table 8, the movements of the bands were well enough known during the critical period to eliminate largely any probability of it. A range-wide count closely following the completion of the lambing gives a lamb-ewe ratio before potential summer losses have occurred.

The selected early 1939 counts, totaling 1,141 animals, are given in Table 8. The lamb-ewe ratio is 53 percent and the yearling-ewe ratio is 30 percent. If one-half of the 2-year-olds are placed with the ewes, the lamb-ewe ratio becomes 49 percent, and the yearling-ewe ratio 28 percent. These ratios do not differ greatly from those derived from the total count.

In this particular early count a fairly accurate count of 2-year-olds was obtained, although it is perhaps a little lower than it should be, since it was not always possible to count this age group. However, the figure gives some indication of the survival of sheep to that age. Sixty-seven 2-year-olds were counted, giving a ratio of 2-year-olds to ewes of 15 percent. The size of the lamb crop from which these 2-year-olds came and the number of these lambs surviving to the yearling stage is not known, but if similar to the 1939 lamb and yearling ratios, one might guess that a little more than one-half the yearlings had survived to the 2-year-old class. However, there is too much conjecture involved to accept this figure for the yearling loss with any assurance.

Fall count.—In order to check the survival of lambs during the summer, I have listed the most comprehensive fall counts for 1939 in such a way as to avoid duplication. Counts are available from fewer localities than in the spring, but the figures seem large enough to be significant. This late 1939 count is given in Table 9. One-half (5) of the 2-year-olds listed are added to the ewe figures. The lamb-ewe ratio is 49 percent, the same as in the spring, and the yearling-ewe ratio is 32 percent, four points higher than in the spring. The figures indicate that there were few losses of lambs and yearlings during the summer months. This was also the impression I gained from general field observations, for no indications of disease were noted, and wolves, after the appearance of the caribou, did not molest the sheep.

CLASSIFICATIONS FOR 1940

Total Count.—In 1940 the total count—1,157—was small, but the various counts were well distributed according to locality. The results of the total classification are as follows: Ewes, 479; lambs, 93; yearlings, 78; 2-year-olds, 20; rams, 487. The lamb-ewe ratio is 19 percent, and the yearling-ewe ratio is 16 percent.

Spring Count.—The best early classified counts are given in Table 10. They do not include two important localities—Savage River Canyon and Sanctuary and Teklanika Canyons—which were classified a little too early to get the lamb counts. The count is as follows: Total, 291; ewes, 97; lambs, 11; yearlings, 19; 2-year-olds, 6; rams, 158. The lamb-ewe ratio is 11 percent; the yearling-ewe ratio is 19 percent.

Fall Count.—The fall count given in Table 11 is a good sample. It is as follows: Total, 421; ewes, 208; lambs, 35; yearlings, 31; rams, 147. The lamb-ewe ratio is 16 percent, and the yearling-ewe ratio is 15 percent.

It will be noted that the lamb-ewe ratio in the spring was 11 percent, while in the fall, when it would be expected to be the same or smaller, it was 16 percent. If three bands, which were classified in the fall, had been classified in the spring, the lamb-ewe ratio for the spring would be raised to about 17 percent. It just happened that the lamb-ewe ratio was higher than average in these particular bands. There were apparently few lamb losses during the summer.

The losses in the 1939 lamb crop were too large to maintain the herd. The 49 percent lamb-ewe ratio of the fall of 1939 had been reduced by the following spring to a yearling-ewe ratio of 19 percent or less.

CLASSIFICATIONS FOR 1941

Total Count.—In 1941 the total count was as follows: Total, 2,732; ewes, 1,331; lambs, 722; yearlings, 38; rams, 641. The lamb-ewe ratio is 54 percent; the yearling-ewe ratio is about 3 percent.

Spring Count.—In the spring of 1941 large counts from many localities are available as shown in Table 12. Some of the counts were made as early as May 26, but by this date most lambs had been born. The count is as follows: Total, 844; ewes, 386; lambs, 209; yearlings, 16; rams, 233. The lamb-ewe ratio is 54 percent; the yearling-ewe ratio is 4 percent.

Summer Count.—In 1941 I left the park in early August so could not make counts in the fall. Most of the counts included in Table 13 were made in July and early August. Counts made about the middle of June at Savage and Sanctuary River Canyons are used in order that these localities can be included to make this count more comparable with the spring count. The count is as follows: Total, 452; ewes, 195; lambs, 111; yearlings, 1; rams, 145. The lamb-ewe ratio is about 57 percent, slightly higher than the 54 percent obtained In the "total" and "spring" tabulations (Table 14). Indications are that few lambs were lost during the summer.

The yearling-ewe ratio is about 0.5 percent, only one yearling being recorded in this late count. If the yearling-ewe ratio in the fall had been the same as in the spring there would have been eight yearlings in the fall count. The number of yearlings involved is so small that one hesitates to conclude that there was a yearling loss during the summer. A band or two harboring a few odd yearlings would bring the fall yearling ratio up to the spring ratio.

All the counts in 1941 show a high lamb crop (more than 50 percent) and an extremely low number of yearlings. Very few of the 1940 lambs survived the winter.

Continued >>>

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