Fauna Series No. 5

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

CHAPTER FOUR:
CARIBOU (continued)

Parasites

Two parasites—the warble fly (Oedemagena tarandi) and the nostril fly (Cephanomyia nasalis)—annoy the caribou considerably and at times, perhaps, are a serious drain on their vitality. O.J. Murie (1935, p. 10) writes as follows about these parasites:

The warble fly deposits its eggs on the hair of caribou; the larvae hatch, home through the skin, and migrate to the back region, where they develop just under the skin, until they finally work out and drop to the ground, producing the familiar perforated skin condition. in July and August, the active egg-laying time, these flies cause the caribou much uneasiness. Although the fly does not sting, the animals fear them and stand in a strained, alert attitude, stamping a foot or shaking the head when one hovers about. It would be interesting to know to what extent the animal is able to avoid these attacks by such vigilance. The writer has seen a caribou suddenly run for more than a quarter of a mile, then abruptly drop on a sand bar, in the shelter of a steep bank, and remain there quietly for a long time. Such flight is probably effective, if long enough and in the right quarter of the wind, for the flies probably hunt by scent.

On one occasion, while traveling overland with a companion, using several dogs as pack animals, the writer noticed a warble fly buzzing along behind the dogs, flying along until it caught up with the rear dog, but not alighting. Presently the fly seemed to become fatigued and lit on the ground. When the dogs were some distance ahead the fly again took up the chase and soon was hovering about the dog once more. This procedure continued for some time, leaving the impression that the fly was fatigued each time it dropped to the ground, and that after a period of rest it again followed the scent of the animals. In the absence of caribou, the fly probably was somewhat attracted by the scent of the dogs but not to the extent of laying eggs.

The nostril fly deposits its larvae in the nostrils of the caribou, and they finally lodge in the soft palate, in the posterior part of the mouth cavity. In spring they become very noticeable and appear as a tightly packed wad of larvae, the writer in one case having counted 125 in the throat of one animal. In April caribou were seen coughing repeatedly for some time, apparently as a result of such irritation. The larvae drop out probably in May.

On July 30, 1939, I watched a yearling for half an hour, alternately holding its head in a clump of willows and biting at flies. At times it cocked its ears and appeared to be watching a fly in front of it. It frequently licked its hind leg near the ankle, and several times a front foot and a hind foot. Occasionally it shook itself. Sometimes the nose was held almost touching the ground. This caribou seemed to be endeavoring to avoid warble flies and possibly nostril flies too. Such behavior was seen several times.

The animals would sometimes bunch up on the river bars. After reading what Sdobnikov (1935 p. 64) says about this habit in reindeer, it appears that the caribou may avoid warble flies by standing close together. He states that "in order to lessen the injury to the reindeer, caused by the gadfly [warble fly], the experienced herder puts the herd on 'tandara'." The term "tandara" means a place where the herd is kept closely together during the flight of the warble fly. There the herd stands sometimes for from 8 to 10 hours. The animals in the center of the band are scarcely molested.

If the caribou should become too abundant in a region these two parasites might become so numerous and infest the caribou to an extent that would greatly reduce their vitality. The shifting of the ranges and movement of the caribou probably reduces the degree to which they are affected by the parasites. Exceptionally heavily infested animals would presumably become weakened and more subject to predation and disease. Sdobnikov (1935) states that in Russia the warble fly may utterly exhaust the reindeer when the infestation is heavy. More than 1,000 larvae have been found on one animal.

The bladderworm (Taenia hydatigena) is found in the liver. Another tapeworm (T. echinococcus), becomes encysted in the lungs, and a hair lungworm has been found in the lung. The protozoan Sarcosporidia was found in one caribou by Hadwen and Palmer (1922). It produced a "pitted" appearance on the surface of various bones and tendons. The incidence of these parasites in caribou is not yet well known.

Disease

The Park Superintendent's report for January 1926 speaks of the presence of a disease among the caribou the previous year as follows: "No indications of disease have manifested themselves of late, and much to the relief of all concerned, there does not seem to be any further advancement of the ailment which killed a number of caribou last year." I have found no other mention of this "disease" so do not know its nature or how large the losses were.

Several skulls that were picked up showed severe necrosis and exostosis of the jawbones, especially around the teeth. Very likely the caribou are subject to a disease similar to necrotic stomatitis common among the elk in the States.

A cow found dead July 15, 1940, had probably succumbed from some kind of internal infection. Pus completely filled one lung and part of the other. On the tissue adjacent to one lung was a nodule of pus 2 inches in diameter.

Concerning disease of caribou, O. J. Murie (1935, p. 9) writes as follows:

No opportunity during this investigation was had to make a careful study of caribou diseases, but none of the observations made indicated that these animals are subject to disease to a serious degree. Seymour Hadwen and L. J. Palmer (1922) discuss various diseases and parasites found among the domestic reindeer, and some of these may occur in caribou. They found, however, that in a number of cases conditions were aggravated by close herding, and it is therefore probable that the caribou—scattered over a wide territory—are much less susceptible to disease than are the reindeer.

The caribou move about so much that losses would not be easy to discover, but so far as we know the losses from disease are not great.

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