Page 107 - Our Vanishing Wild Life

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DESTRUCTION BY DISEASES 85
became apparent. Now, in our antelopes, the collapse and death of the victim usually occured in about 10 days from the time that the first swelling was observed: which means a very virulent disease, and rapid progress at the climax. The jaw of one of our antelopes, which was figured in Dr. Blair's paper in the Eleventh Annual Report of the New York Zoological Society (1906) shows only a very slight lesion, in comparison with those of the mountain sheep.
The conclusion is that among the sheep, this disease does not carry off its victims in any short period like 10 days. The animal must survive for some months after it becomes apparent. At least two parties of American sportsmen have shot rams afflicted with this disease, but I have no reports of any sheep having been found dead from this cause.
This disease is well known among domestic cattle, but so far as we areawareitneverbeforehasbeenfoundamongwildanimals. Theblack sheep herds wherein it was found in British Columbia are absolutely isolated from domestic cattle and all their influences, and therefore it seems quite certain that the disease developed among the sheep spon- taneously,—a remarkable episode, to say the least. Whether it will ex- terminate the black mountain sheep species, and in time spread to the white sheep of the northwest, is of course a matter of conjecture; but thereisnothingintheworldtopreventacalamityofthatkind. The white sheep of Yukon Territory range southward until in the Sheslay
Mountains they touch the sphere of influence of the black sheep, where the disease could easily be transmitted. It would be a good thing if there existed between the two species a sheepless zone about 200 miles wide.
I greatly fear that actinomycosis is destined to play an important part in the final extinction that seems to be the impending fate of the beautiful and valuable prong-horned antelope. In view of our hard experiences, extending through ten years (1902-1912), I think this fear is justified. All persons who live in country still inhabited by antelope are urged to watch for this disease. If any antelopes are found dead, see if the lower jaw is badly swollen and discharging pus. If it is, bury the body quickly, burn the ground over, and advise the writer regarding the case.
The Rabbit Plague.—One of the strangest freaks of Nature of which we know as effecting the wholesale destruction of wild animals by disease is the rabbit plague. In the northern wilderness, and par- ticularly central Canada, where rabbits exist in great numbers and supply the wants of a large carnivorous population, this plague is well known, and among trappers and woodsmen is a common topic of con- versation. The best treatment of the subject is to be found in Ernest T. Seton's "Life Histories of Northern Animals", Vol. 1, p. 640 et seq. From this I quote
"Invariably the year of greatest numbers [of rabbits is followed by a year of plague, which sweeps them away, leaving few or no rabbits in the land. The denser the rabbit population, the more drastically is it