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Fauna Series No. 1
Methods
Fauna of the National Parks
of the United States
PROBLEMS OF GEOGRAPHICAL ORIGIN
EXPOSURE OF NATIVE SPECIES TO
DISEASES AND INFLUENCES OF ALIEN FAUNAS (9)
One of the fundamental principles governing the distribution of animal life is that when the faunas of two different continents meet, the fauna of the larger continent will be the survivor. There is abundant paleontological as well as present-day evidence substantiating this fact. When we bring domestic stock, particularly sheep and cattle, in contact with native game, we are exposing the native game to members of the Asiatic fauna. This brings in new diseases and new conditions with which the native fauna has not had to cope before, and the results are apt to be disastrous.
All livestock and wild game are subject to many different diseases and parasites. If an outbreak occurs in domestic stock, there are chances of its being controlled. If it gets into the native wild life, it is apt to run its course, with irreparable damage. There is one important exception to the foregoing statement, and that is the control of the hoof-and-mouth epidemic among deer in California, 1924. The plague was stamped out by killing 22,214 deer. But it is obvious that any such remedy would be fatal to mountain sheep, mountain goats, antelope, elk, moose, or any other rare forms of animal life.
It is not actually necessary for domestic stock and native game to come in contact for the damage to be done. Even use of the same range may be just as effective, for some of the most viable disease germs may be carried in the soil for years to start a new outbreak.
Because of the above circumstances, it is clear that the only way to treat problems of this type is to prevent possibility of their occurrence. This can be accomplished for species occupying a restricted range by keeping domestic stock out of a neutral zone between the two. This would work with mountain sheep or antelope, but not so well for deer or elk. Fortunately, the rarer species are the ones to which it is most feasible to extend this sort of protection.
Where a disease has already been contracted by a park animal there is but little that management can do so far as is known at the present time. The first step is to adjust the park boundaries so as to prevent reinfection through the same avenue. The spread of disease may sometimes be checked by destroying carcasses of infected animals. In another case the disease might be eliminated by destroying the alternate host where that host was not a rare form and could be counted upon to reinvade the territory later on when the disease had been conquered.
Sheep scab in Rocky Mountain. – There is some dispute concerning whether the wild sheep of America were subject to sheep scab before the introduction of domestic sheep, but the evidence seems to point to the fact that they were not. Numerous accounts tell of heavy losses of mountain sheep from sheep scab in the pioneer days of the sheep industry in the West. Merritt Cary 16 says: "A danger which threatens mountain sheep in Colorado, as well as in other Western States, is the introduction of scab from domestic sheep allowed to graze on the higher mountain slopes." Warren 17 says: "C. F. Frey tells me they suffer much from scab in the West Elk Mountains, and that a party told him in 1902, at one place near the head of Sapinero Creek, 75 head were counted which had died of scab. Domestic sheep had been run in that locality, and the wild sheep doubtless contracted it from them."
Aside from the question of origin of the disease, the fact remains that whereas domestic sheep may be treated and cured of sheep scab, there is no known way of dealing with it in mountain sheep. When the survey party was in Rocky Mountain in 1930 and in 1931 the mountain sheep were scabby. Reports of local residents indicated that scab had been present for many years, being worse in some periods than others. Domestic sheep had been run in these mountains for so long that it was not possible to determine definitely that the wild sheep were not subject to an endemic form of sheep scab.
The sheep situation in Rocky Mountain should be investigated thoroughly. In the meantime reinfection should be prevented by removing the domestic sheep as far as possible from the mountain-sheep range. The Never Summer Mountains addition has already been an improvement in this regard.
16 A Biological Survey of Colorado, by Cary, Merritt. North American Fauna No. 33, 1911, p. 62. 17 The Mammals of Colorado, by Warren, Edward R., 1910, p. 238.
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Last Modified: Tues,
Feb 1 2000 07:08:48 pm PDT
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