Fauna Series No. 5

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

CHAPTER FOUR:
CARIBOU (continued)

Calf Crop

At times it is difficult to get a good calf count. Large herds often travel so compactly that many of the calves remain hidden behind the cows. When the herd is lying down the calves are hard to see. Therefore satisfactory counts of resting herds were usually not obtained. In 1939, when I had an assistant, I used field glasses and called off the classification of each animal as it passed and my assistant kept the tally. In this way we classified a number of herds. But in 1940 and 1941 I was alone practically all the time and usually found it extremely difficult to classify the animals accurately. In 1941 when the herds moved westward after the calving period the animals were so massed that there was little opportunity to count calves. During the latter year one herd numbered roughly 4,000 adults, another 1,000, and another 2,000, and the animals traveled in compact groups.

1939 CALF CROP

The counts obtained in 1939 give a fairly accurate figure for the calf crop. On several occasions conditions were ideal for classifying the herds. On June 16, 17, and 18, from a ridge, we observed the caribou moving along slowly on the river bars, often in single file. All of the caribou passing were not counted because of the interruptions caused by other events such as a wolf chasing a caribou calf. In addition, many bands bunched to an extent that the individuals could not be counted. On July 13 another excellent count was secured of a single herd of 827 animals. I was able to classify this herd twice.

To show how the bands vary in calf percentages I have tabulated the classified bands for 1939. See Table 15 (p. 178).

Although the calf percentage in many herds does not vary far from the average, some herds do show extremes. The herd classified on May 24 had practically no calves, while one seen on June 12 had 75 cows and 62 calves, and another herd seen on July 7 had 46 cows and 43 calves. It is obvious that erroneous conclusions on the calf crop could be obtained by classifying only a few bands.

Of 2,493 cows in the herds classified, 1,231, or 49 percent of them were followed by a calf. Since, as stated, some young bulls and yearlings are included in the figure for cows, the calf crop can be considered as being fully 50 percent.

TABLE 15.—Classified. Caribou Counts, 1939

¹Includes unclassified yearlings and young bulls in some instances. The counts of cows were therefore somewhat larger than was representative.

²Bulls were not sufficiently represented in the counts because the main herds of males were missed.

³Young bulls often could not be identified from cows in the moving massed herds.

⁴Indicates that yearlings could not he distinguished from cows. In these cases yearlings were recorded in the column headed "Cows."

⁵Several bands.

1940 CALF CROP

The figures for the 1940 season are not extensive but they signify that the calf crop was about the same as that of 1939. Of the 735 cows classified, 379 were followed by calves, so that the calf-cow ratio was 51:100. Many counts of herds were in agreement with the figures listed in the table below.

TABLE 16.—Classified. Caribou Counts, 1940

¹Includes unclassified yearlings and young bulls in some instances. The counts of cows were therefore somewhat larger than was representative.

²Bulls were not sufficiently represented in the counts because the main herds of males were missed.

³Indicates that yearlings could not be distinguished from cows. In these cases the yearlings were recorded to the column headed "Cows."

1941 CALF CROP

In 1941 I obtained but few figures on the calf crop. Many counts were attempted but were not accurate enough to tabulate. On June 28 two herds were classified. One consisted of 258 cows and 127 calves, the other of 29 cows and 17 calves. The calf percentage in these two herds was 50. From several partial counts my impression was that the calf crop was about the same as in the 2 preceding years.

It is interesting to compare the calf-cow ratio with that of elk, another herd animal. In Teton National Forest, Wyo., in the summer of 1935 O. J. Murie found that 38 percent of the cows were followed by calves and in Yellowstone National Park in 1937 I found 41 percent of the cows followed by calves. Darling (1937) states that the fertility of the hinds of the red deer in Scotland is about 60 percent and says it is the same as given by Cameron (1923) for red deer in the island forest of Jura. It would seem, from these figures, that the calf crop found in the caribou herds was about as expected.

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