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CHAPTER IX

THE DESTRUCTION OF WILD LIFE BY DISEASES

Every cause that has the effect of reducing the total of wild-life population is now a matter of importance to mankind. The violent and universal disturbance of the balance of Nature that already has taken place throughout the temperate and frigid zone offers not only food for thought, but it calls for vigorous action.

There are vast sections in the populous centres of western civilization where the destruction of species, even to the point of extermination, is fairly inevitable. It is the way of Christian man to destroy all wild life that comes within the sphere of influence of his iron heel. With the exception of the big game, this destruction is largely a temperamental result, peculiar to the highest civilization. In India where the same fields have been plowed for wheat and dahl and raggi for at least 2,000 years, the Indian antelope, or "black buck," the saras crane and the adjutant stalk through the crops, and the nilgai and gazelle inhabit the eroded ravines in an agricultural land that averages 1,200 people to the square mile!

We have seen that even in farming country, where mud villages are as thick as farm houses in Nebraska, wild animals and even hoofed game can live and hold their own through hundreds of years of close association with man. The explanation is that the Hindus regard wild animals as creatures entitled to life, liberty and the pursuit of happiness, and they are not anxious to shoot every wild animal that shows its head. In the United States, nearly every game-inhabited community is animated by a feeling that every wild animal must necessarily be killed as soon as seen; and this sentiment often leads to disgraceful things. For instance, in some parts of New England a deer straying into a town is at once beset by the hue and cry, and it is chased and assaulted until it is dead, by violent and disgraceful means. New York State, however, seems to have outgrown that spirit. During the past ten years, at least a dozen deer in distress have been rescued from the Hudson River, or in inland towns, or in barnyards in the suburbs of Yonkers and New York, and carefully cared for until "the zoo people" could be communicated with. Last winter about 13 exhausted grebes and one loon were picked up, cared for and finally shipped with tender care to the Zoological Park. One distressed dovekie was picked up, but failed to survive.

The sentiment for the conservation of wild life has changed the mental attitude of very many people. The old Chinese-Malay spirit which cries "Kill! Kill!" and at once runs amuck among suddenly discovered wild animals, is slowly being replaced by a more humane and intelligent sentiment. This is one of the hopeful and encouraging signs of the times.

The destruction of wild animals by natural causes is an interesting subject, even though painful. We need to know how much destruction is wrought by influences wholly beyond the control of man, and a few cases must be cited.

Rinderpest In Africa.—Probably the greatest slaughter ever wrought upon wild animals by diseases during historic times, was by rinderpest, a cattle plague which afflicted Africa in the last decade of the previous century. Originally, the disease reached Africa by way of Egypt, and came as an importation from Europe. From Egypt it steadily traveled southward, reaching Somaliland in 1889. In 1896 it reached the Zambesi River and entered Rhodesia. From thence it went on southward almost to the Cape. Not only did it sweep away ninety percent of the native cattle but it also destroyed more than seventy-five per cent of the buffalos, antelopes and other hoofed game of Rhodesia. It was feared that many species would be completely exterminated, but happily that fear was not realized. The buffalo and antelope herds were fifteen years in breeding up again to a reasonable number, but thanks to the respite from hunters which they enjoyed for several years, finally they did recover. Throughout British East Africa the supply of big game in 1905 was very great, but since that time it has been very greatly diminished by shooting.

Caribou Disease.—From time to time reports have come from the Province of Quebec, and I think from Maine and New Brunswick also, of many caribou having died of disease. The nature of that disease has remained a mystery, because it seems that no pathologist ever has had an opportunity to investigate it. Fortunately, however, the alleged disease never has been sufficiently wide-spread or continuous to make appreciable inroads on the total number of caribou, and apparently the trouble has been local.

Scab In Mountain Sheep.—"Scab" is a contagious and persistent skin disease that affects sheep, and is destructive when not controlled. Fifteen years ago it prevailed in some portions of the west. In Colorado it has several times been reported that many bighorn mountain sheep were killed by "scab," which was contracted on wild mountain pastures that had been gone over by domestic sheep carrying that disease. From the reports current at that time, we inferred that about 200 mountain sheep had been affected. It was feared that the disease would spread through the wild flocks and become general, but this did not occur. It seems that the remnant flocks had become so isolated from one another that the isolation of the affected flocks saved the others.

Lumpy-Jaw In Antelope And Sheep.—It is a lamentable fact that some, at least, of the United States herds of prong-horned antelope are afflicted with a very deadly chronic infective disease known as actinomycosis, or lumpy-jaw. It has been brought into the Zoological Park five times, by specimens shipped from Colorado, Texas, Wyoming and Montana. I think our first cases came to us in 1902.

In its early stage this disease is so subtle and slow that it is months in developing; and this feature renders it all the more deadly, through the spread of infection long before the ailment can be discovered.

One of our antelope arrivals, apparently in perfect health when received, was on general principles kept isolated in rigid quarantine for two months. At the expiration of that period, no disease of any kind having become manifest, the animal was placed on exhibition, with two others that had been in the Park for more than a year, in perfect health.

In one more week the late arrival developed a swelling on its jaw, drooled at the corner of the mouth, and became feverish—sure symptoms of the dread disease. At once it was removed and isolated, but in about 10 days it died. The other two antelopes were promptly attacked, and eventually died.

The course of the disease is very intense, and thus far it has proven incurable in our wild animals. We have lost about 10 antelopes from it, and one deer, usually, in each case, within ten days or two weeks from the discovery of the first outward sign—the well known swelling on the jaw. One case that was detected immediately upon arrival was very persistently treated by Dr. Blair, and the animal actually survived for four months, but finally it succumbed. From first to last not a single case was cured.

In 1912, the future of the prong-horned antelope in real captivity seems hopeless. We have decided not to bring any more specimens to our institution, partly because all available candidates seem reasonably certain to be affected with lumpy-jaw, and partly because we are unwilling to run further risks of having other hoofed animals inoculated by them. Today we are anxiously wondering whether the jaw disease of the prong-horn is destined to exterminate the species. Such a catastrophe is much to be feared. This is probably one of the reasons why the antelope is steadily disappearing, despite protection.

In 1906 we discovered the existence of actinomycosis among the black mountain sheep of northern British Columbia. Two specimens out of six were badly affected, the bones of the jaws being greatly enlarged, and perforated by deep pits. The black sheep of the Stickine and Iskoot regions are so seldom seen by white men, save when a sportsman kills his allotment of three specimens, we really do not know anything about the extent to which actinomycosis prevails in those herds, or how deadly are its effects. One thing seems quite certain, from the appearance of the diseased skulls found by the writer in the taxidermic laboratory of Frederick Sauter, in New York. The enormous swelling of the diseased jaw bones clearly indicates a disease that in some cases affects its victim throughout many months. Such a condition as we found in those sheep could not have been reached in a few days after the disease became apparent. Now, in our antelopes, the collapse and death of the victim usually occurred 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 are aware it never before has been found among wild animals. The black 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 spontaneously—a remarkable episode, to say the least. Whether it will exterminate the black mountain sheep species, and in time spread to the white sheep of the northwest, is of course a matter of conjecture; but there is nothing in the world to prevent a calamity of that kind. 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 particularly 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 conversation. The best treatment of the subject is to be found in Ernest T. Seton's "Life Histories of Northern Animals", Vol. I, 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 ravaged by the plague. They are wiped out in a single spring by epidemic diseases usually characterized by swellings of the throat, sores under the armpits and groins, and by diarrhea."

"The year 1885 was for the country around Carberry 'a rabbit year,' the greatest ever known in that country. The number of rabbits was incredible. W.R. Hine killed 75 in two hours, and estimated that he could have killed 500 in a day. The farmers were stricken with fear that the rabbit pest of Australia was to be repeated in Manitoba. But the years 1886–7 changed all that. The rabbits died until their bodies dotted the country in thousands. The plague seemed to kill all the members of the vast host of 1885."

The strangest item of Mr. Seton's story is yet to be told. In 1890 Mr. Seton stocked his park at Cos Cob, Conn., with hares and rabbits from several widely separated localities. In 1903, the plague came and swept them all away. Mr. Seton sent specimens to the Zoological Park for examination by the Park veterinary surgeon, Dr. W. Reid Blair. They were found to be infested by great numbers of a dangerous bloodsucking parasite known as Strongylus strigosus, which produces death by anemia and emaciation. There were hundreds of those parasites in each animal. I assisted in the examination, and was shown by Dr. Blair, under the microscope, that Strongylus puts forth eggs literally by hundreds of thousands!

The life history of that parasite is not well known, but it may easily develop that the cycle of its maximum destructiveness is seven years, and therefore it may be accountable for the seven-year plague among the hares and rabbits of the northern United States and Canada.

Possibly Strongylus strigosus is all that stands between Canada and a pest of rabbits like that of Australia. Just why this parasite is inoperative in Australia, or why it has not been introduced there to lessen the rabbit evil, we do not know. Mr. Seton declares that the rabbits of his park were "subject to all the ills of the flesh, except possibly writer's paralysis and housemaid's knee."

Parasitic Infection Of Wild Ducks.—The diseases of wild game, especially waterfowl, grouse and quail, have caused heavy losses in America as well as in European countries, and scientists have been carefully investigating the cause and the general nature of the maladies, as well as probable methods of prevention and cure. Mr. Geo. Atkinson, a well-known practical naturalist of Portage la Prairie, Manitoba, writes as follows to a local paper on this subject, which I find quoted in the National Sportsman:

The question which has developed these important proportions during the past year is that of the extent of the parasitic infection of our wild ducks and other game, and the possibilities of the extended transmission of these parasites to domestic stock, or even humanity, by eating.

The parasites in question are contained in small elliptical cases found underlying the surface muscles of the breast, and in advanced cases extending deeper into the flesh and the muscular tissues of the legs and wings. They are not noticeable in the ordinary process of plucking the bird for the table, and are not found internally, so that the only method of discovering their presence is by slitting the skin of the breast and paring it back a few inches when the worm-like sacs will be seen buried in the flesh.

These parasites have come to my notice periodically during the process of skinning birds for mounting during the past number of years, but it was only when they appeared in unusual numbers last fall that I made inquiries of the biological bureaus of Washington and Ottawa for information of their life history and the possibilities of their transmission to other hosts.

Replies from these sources surprised me with the information that very little was known of the life history of any of the Sarcosporidia, of which group this was a species. Nothing was known of the method of infection or the transference from host to host or species to species, and both departments asked for specimens for examination.

Authorities are a unit in opinion that the question is one of great importance to game conservation, and although opinions of the dangers from eating differ somewhat, a record is given of a hog fed upon affected flesh developing parasites in the muscles in six weeks' time, while a case of a man's death from dropsy was found to be the result of development of these parasites in the valves of the heart.

The ability of these low forms of life to withstand extremes of heat makes it necessary for more than ordinary cooking to be assured of killing them, and since their presence is unnoted in the ordinary course of dressing the birds for the table, there is little doubt that very considerable numbers of these parasites are consumed at our tables every season, with results at present unknown to us.

The species I have found most particularly infected have been mallards, shovellers, teal, gadwall and pintails, and the birds, outwardly in the best condition, have frequently been found loaded with sacs of these parasites and only the turning back of the breast skin can disclose their presence.

The greatest slaughter of wild ducks by disease occurred on Great Salt Lake, Utah. Until the "duck disease" (intestinal coccidiosis) broke out there, in the summer of 1910, the annual market slaughter of ducks at the mouth of Bear River had been enormous. When at Salt Lake City in 1888 I made an effort to arouse the sportsmen whom I met to the necessity of a reform, but my exhortations fell on deaf ears. Naturally, the sweeping away of the remaining ducks by disease would suggest a heaven-sent judgment upon the slaughterers were it not for the fact that the last state of the unfortunate ducks is if anything worse than the first.

On Oct. 17, 1911, the annual report of the chief of the Biological Survey contained the following information on this subject:

Epidemic Among Wild Ducks on Great Salt Lake.—Following a long dry season, which favored the rearing of a large number of wild ducks, but materially reduced the area of the feeding ponds, resulting in great overcrowding, a severe epidemic broke out about August 1, 1910, among the wild ducks about Great Salt Lake, Utah. Dead ducks could be counted by thousands along the shores and the disease raged unabated until late fall. Shooting clubs found it necessary to declare a closed season. Some of the dead ducks were forwarded to the Biological Survey and were turned over for examination to the Bureau of Animal Industry, by the experts of which the disease was diagnosed as intestinal coccidiosis.

Various plans of relieving the situation were tried. The irrigation ditches were closed, thus providing the sloughs and ponds with fresh water, and lime was sprinkled on the mud flats and duck trails. Great improvement followed this treatment, and experiments proved that ducks provided with abundant fresh water and clean food began to recover immediately. These methods promised success, but later it was proposed that the marshes be drained and exposed to the sun's rays—a course which cannot be recommended. That coccidia are not always killed by exposure to the sun is shown by their survival on the sites of old chicken yards. An added disadvantage of the plan is that draining and drying the marshes would have a bad effect on the natural duck food, and upon the birds themselves.