Chapter II: Foreword: BY

CHARLES B. PENROSE

The work on which this book is based was begun in November, 1901. From that date, systematic autopsies were made on animals dying in the Philadelphia Zoological Garden. Previously autopsies had been made very rarely and only on animals of especial importance and interest. Pathological conditions were occasionally noted in animals subjected to anatomical study. The work was strictly volunteer, for there was no one on whom the Society had the right to call. Dr. Henry C. Chapman, a former Director, whose interest was in physiology and comparative anatomy, made nearly all the autopsies that were made before the beginning of the present work. In the annual reports from the foundation of the Garden in 1872, very few such examinations are recorded. In some reports there are lists of important deaths, but no record of the cause of death.

This state of things was not peculiar to the Philadelphia Garden. It existed in every zoological garden in the world. It exists in most of them to-day. When an animal died it had no interest or value except for its hide and bones. Rare specimens were sent to the Academy of Natural Sciences from the Philadelphia Garden. The great majority, however, were immediately destroyed, and thus during the twenty-nine years from the foundation of the Garden, preceding this work, there have been lost many opportunities—some of which will never recur—of increasing our knowledge of pathology.

This book gives results of the study of animals that have not been subjected to experimental procedures and conditions, and though their mode of life has not been that strictly natural to them, yet they have not been influenced by any of the artificial procedures of the laboratory which are usually followed in investigations on animals. Though the object of the work was the pursuit of knowledge for its own sake, yet results of practical value have followed: hygiene has been improved; disinfection has been made scientific; epidemics have been arrested; some diseases, notably tuberculosis in monkeys, and spiropteriasis in parrots, have been practically eliminated.

The value of the work is recognized by the keepers. Their interest has increased and their morale has improved. The frequent deaths in a large collection of animals are discouraging, and a good animal man must have courage and optimism—traits that are stimulated by the knowledge that every animal that dies is studied to determine the cause of death, and to prevent its recurrence.

Some results of this study are to be considered as “raw material,” while others permit cautious or tentative conclusions. The first include— visceral weights, incidence of certain lesions like anemia and hepatic cirrhoses, occurrence of calculi and observations on weak hind quarters, convulsions and constitutional diseases. The second include—eradication of tuberculosis and spiropteriasis, the response of the mammalian and avian heart to strain and disease viruses, the origin of pneumonia in birds, the genesis of bronchiectasis, the nature of osseous degeneration with relation to diet and alimentary tract, the comparative anatomy, physiology and pathology of the female genitalia, the occurrence of lesions in the thyroid comparable to those in man, the character of kangaroo disease.

Great praise is due Dr. Herbert Fox and his assistants Drs. F. D. Weidman and E. P. Corson-White, for the splendid scientific spirit and thoroughness with which they have done this work, with no adequate remuneration, except the intangible reward appreciated only by the real research worker.

It is a mistake to think that all animals in the wild state are healthy. The healthy wild animals that we see are the survivors, the sick and the weaklings having died. Undoubtedly diseases are fewer than in captive animals; but on the other hand wild animals are exposed to dangers to which captive animals are not exposed—such as lack of care in sickness and old age, starvation, and attacks of enemies that feed on them. The maximum longevities in some species are probably in captive animals. It is doubtful if a wild animal ever reaches the greatest age possible to it.

Many kinds of parasites have been found in wild animals captured only a short time before arriving at the Garden, so that they must have existed in the wild. Thirteen wild cats received from South Carolina within a few days after capture were infested with intestinal, muscular, and pulmonary parasites. Several years ago there were received from the Island of Chincoteague, off the coast of Virginia, a number of native birds recently captured, all of which had mould disease of the air sacs. This happened on several occasions, so that it became necessary to reject all birds from this locality. Among the birds were meadow larks and cardinals.

Hunters not infrequently kill animals with disease, and if more hunters knew enough to recognize the disease there would be more recorded cases. Sick animals are not as likely to be killed by the hunter as healthy ones, as sick animals seek seclusion and do not move about. In many localities of the United States white-tailed deer are infested with the liver-fluke. Trout and other fish in remote mountain streams are found with tapeworms. Round worms and other parasites infest the white rhinoceros in the African forest.

In many instances the parasites and the host, when in health, get on very well together; but when the host weakens the parasites may give him the finishing stroke.

Though some morbid conditions described in this book are peculiar to captivity, yet it seems reasonable to assume that many of the diseases found in captive animals occur also in the wild. Some of the extinct races of animals may have been wiped out by disease.

Captivity causes numerous physical and mental disarrangements. Unaccustomed, unnatural and unvaried food, change of climate and environment, physical and mental degeneration from disuse of muscle and brain, fear, ennui, nostalgia, lack of the exhilaration of chasing and being chased, unsatisfied sexual feeling—all react harmfully on the captive.

No captive animals get their natural food; and though some, like the carnivora, may get approximately their natural food, yet they do not get it in the natural way. They have but little variety and may miss elements important to their well-being. They get only certain cuts— muscle and bone; they do not get blood, guts and glands. The lion’s meat is handed to him. He does not tear down his prey; and one result is that the jaws of the captive-bred lion differ decidedly in shape from the jaws of the wild-bred lion. He gets his food regularly, with awful monotony—twelve pounds of meat at 3.30 p.m. day after day; there is no alternation of feasts and fasts, with consequent change in the balance of the body reserves.

Some animals, such as caribou, the moose, the black cock, the hoatzin, the koala, do not long survive captivity, because it is impracticable to obtain their natural food. Gastrointestinal disease is the commonest disease of wild animals. Twenty-five per cent. of sick humans in civilized communities also suffer from it. On the other hand, many animals become accustomed to the new diet and thrive on it.

Animals also often thrive in a climate very different from that of their natural habitat. Some animals from warm countries, though kept outside without any artificial heat, get on very well during the severe weather of Philadelphia winters, when the temperature often drops to zero Fahrenheit. For the past two years it has been the custom to put outdoors all monkeys—of value—that are suspected of having tuberculosis. The cheap monkeys are killed. The outdoor monkeys are kept in fair sized cages—five feet square and six feet high—usually singly, though sometimes two are together. The vervet, the grivet, the leonine macaque, the yellow baboon, the Hainan gibbon and many others, have not only survived the climatic conditions but have not succumbed to tuberculosis. South American monkeys do not stand cold as well as Old World monkeys, and cannot be kept out in severe winter weather.

The monkeys that are kept indoors during winter have free access to the outside through swinging doors and they often go out voluntarily in the coldest weather. The same is true of other animals. A note made several years ago (February 12, 1914) states: “Temperature last night was 1° F. At 2 P.M. outside temperature 13° F., in carnivora house 25° F., elephant house 38° F., giraffe house 39° F., monkey house 42° F. Two Bengal tigers were voluntarily outside. Monkeys that have been out all winter are: two Barbary apes, Hainan gibbon, lion-tailed macaque, yellow baboon, grivet monkey, pigtailed macaque, and eleven rhesus macaques. All the animals appeared comfortable.”

The physical condition of the animal and the kind of cold—damp or dry— have much to do with its ability to stand low temperatures. Monkeys have passed through very severe winters without damage, and subsequently in a less severe winter have had frozen fingers, toes or tail.

The size of the cage or pen has not as much effect upon the well-being of the animal as might be expected. Reptiles, birds and mammals do as well in cages and pens of medium size as in very large ones. A deer or antelope in a large enclosure does not use all its domain. It usually has a favorite corner near the food, water and shelter, and stays there. Nor has a large enclosure been found perceptibly to diminish mortality from cage-mates. The stronger will follow the weaker until he gets him, no matter what the enclosure. Even in the large flying cage for birds it is necessary to keep out those of a scrappy disposition. From the point of view of the public small enclosures are more satisfactory.

Mental disease in captive animals offers a fascinating field for study— now chiefly speculative. Many conditions are present to produce it—all the conditions that cause prison psychoses in man. And many if not all the insane and perverted acts of animals have their counterpart in the human. Masturbation is very common in mammals. Eating of their own feces, coprophagy, is not infrequent, and is especially notable in one of the highest types—the Chimpanzee. Perhaps occasionally coprophagy may be due to some defect in diet. There is no instinctive disgust at excrement in the lower animals any more than there is in the uneducated child. Nevertheless, eating feces cannot be healthful, and probably does not occur in nature; and occurs only in the human with mental disease.

Some of the insane acts of animals if prevalent in the wild would probably cause the extinction of the race. Such are killing of the young by the father and by the mother; killing of the female by the male, usually during rutting time, in some instances reminding one of Sadism in man. This kind of sexual killing does not often occur in the wild. The female has a better chance to escape, and the male probably does not feel so inclined to damage her when he chooses her himself as when she is chosen for him by his gaoler. When the mother devours her young it is usually shortly after birth. I have, however, the record of a Jungle cat (_Felis chaus_) who ate two of her kittens when they were seven weeks old. Some of the domestic animals devour their young; the sow often does it, and occasionally the bitch.

Sucking, gnawing and eating parts of itself or of a cage-mate is not uncommon in a variety of animals. Bears lick their paws until they are sore; a monkey may gradually gnaw away its tail from the tip to the body; an ocelot (_Felis chibigonazon_) bit open his scrotum and devoured his testicle; a Tasmanian devil (_Sarcophilus ursinus_) bit off one of his front feet at the wrist; a monkey may gradually gnaw away its fingers; and numerous other self-inflicted mutilations occur. Often there is a local irritating cause, as skin disease, lice, or freezing. But in many cases no local cause can be found, as no local cause can be found for thumb-sucking or nail-biting in the human.

The surgery done by monkeys on their frozen fingers and toes is interesting. After the flesh has sloughed the monkey bites off the protruding phalanges, apparently without pain, so that satisfactory well-covered stumps are made.

Animals often mutilate their cage-mates in an amicable way as distinguished from fighting. A bear may lick its mate’s ears until the hair and skin are gone. A monkey may eat its mate’s tail or patches of its skin, the victim lying placidly while the process goes on. Many animals are addicted to perverted acts on their own or their mate’s sexual organs.

It is probable that the phenomena just mentioned are due to confinement, idleness and ennui, and that they do not often happen in nature where an animal is kept busy seeking his food, fighting and avoiding his enemies, attending to his mate or mates, and meeting the various vicissitudes of his environment.

It should be remembered, however, that the members of a wild species vary in intelligence and temperament, as humans do. There are morons and perverts among animals in the wild; but not being coddled by the normal members of the species, they have a poorer chance than has the subnormal human of surviving and of transmitting their peculiarities.

Fear, ennui, loneliness and nostalgia, by affecting the minds of captive animals, react on their physical condition. Some animals have the fear of man bred in them. The young often show it from time of birth. This is especially common in animals that have survived for generations in proximity to man. It is one reason for their survival. The mother and father may have become tame and gentle in captivity and yet the young one may be a wild thing from birth. Such fear is sometimes uncontrollable, an apparently slight cause making the animal dash itself against the fence of the enclosure. It is not mere speculation to discuss the physical effects of the emotions on the animal body. It has been shown that fear, anger, and grief bring about distinct measurable physical changes. Dr. Corson-White has found that the red corpuscles are increased by over two million per cubic centimetre in the blood of a cat frightened by a dog barking at it. The amount of blood sugar is also increased.

Such observations are suggestive in a consideration of the changes that may occur in a captive animal subjected to acute and chronic fear.

The monotony of a captive animal’s life is broken only by feeding, the sight and sounds of others in the same building or nearby, and by visitors. Many animals show their appreciation and pleasure when visitors approach, and some of the more intelligent animals, bears and monkeys and some birds, “show off” apparently to keep the visitors there. When there is nothing doing, some stand swaying their heads, like a weaving horse, or pacing the cage, inanely tagging at each turn the side of the cage with the head or other part of the body—often so persistently that a sore is produced. Nearly all animals are social and suffer from loneliness when kept by themselves. This is true even of the lowly forms. The keeper of the reptile house reported that a giant tortoise became despondent and refused to eat when his companion, a leopard tortoise, was taken from him, and that he braced up as soon as the leopard tortoise was returned. It is not necessary that the companion be of the same species, or even of the same family. A lion or a tiger may be satisfied with a little dog for a companion, and there was an African rhinoceros at the Philadelphia Garden that was very discontented and unhappy when alone and became perfectly satisfied when she was given a domestic goat as a cage-mate; and the huge rhinoceros stood for a good deal of butting and bullying from the goat without retaliating. A sympathetic keeper may do much to relieve the loneliness of the animals in his care.

Nostalgia, or homesickness, has been felt by all men. Some have died of it. The tradition among writers is that it affects young people and those who have been living nearest to a state of nature. In this country the American Indian and the negro are affected more than the whites. Much was written of it after the Franco-Prussian War and the American Civil War. It is a real condition, capable in extreme cases of causing death and of so weakening the sufferer as to make him more susceptible to the invasion of other diseases. At the present day we hear less of it among civilized people than formerly, perhaps because the conception of home has been broadened by modern methods of intercommunication. The wild animal’s conception of home is narrow; he comes directly from it into an environment where he may see many other animals, but not one of his own kind. Predisposing causes of nostalgia are stronger with him than with the human. That home means a great deal to animals is shown by the migration of birds—the return of the carrier pigeon, and of the lost dog, and of the swallow, which returns every year to the same nesting place.

All animals long for the things of nature—open air, earth, grass and water. They are thrilled when their feet touch the sod. Even the hippopotamus gambols when he leaves his concrete house and his feet touch earth and grass.

The face and carriage of many animals cannot express feelings as in the human, though it is not unreasonable to assume that animals may indicate feelings by expression understood by their mates, though not understood or even noticed by man. When they can express it in a human way their feelings may be read. The dejection of nostalgia is especially shown by anthropoid apes. Gorillas have been noted for it from the earliest writers. The orang is prone to it, shows it by his attitude and expression, and sometimes dies of it.

It is stated in _A Handbook of the Management of Animals in Captivity in Lower Bengal_, p. 130, that elephants have been observed to shed tears abundantly if forced to leave their old home and surroundings. How much other animals who cannot express homesickness may feel it, and how often it is a cause of unhappiness, depression and predisposition to disease, it is impossible to say.

Most wild animals in captivity are sterile. The reason is not known. It shows the profound effect of captivity. It would be difficult to determine whether the sterility of a mating is the fault of the male or the female.

There is no apparent rule for sterility. Some families are always sterile in captivity, others are fertile, even with very unfavorable surroundings. The deer, horses, hippopotamuses, pigs, goats, sheep and oxen, are good breeders; while antelopes, rhinoceroses, giraffes, elephants, are poor breeders. Some members of a family may be good, others poor. The lion and puma breed fairly well; the tiger, leopard and jaguar, very poorly. Bears breed well, but the mother usually destroys her young.

We cannot mate wild animals and birds simply by putting males and females together in the same cage. Domestic mammals and birds usually mate under such conditions, but wild ones often refuse. Many mammals and probably all birds that are not polyandrous or polygamous reserve the right to select their mates, and if the sexes are put together by man they may view each other with indifference or with animosity. There are many males and females of the same species of mammals at the Zoological Garden that will not consent to live together. A male monkey in a cage with several females will very often select one female for his mate and will have nothing to do with the others.

Among monkeys fertility varies greatly. It is not practical to determine the ratio among the various kinds, as some kinds are much commoner in zoological collections than others. I think that in general the Old World monkeys (_Cercopithecidæ_) are better breeders in captivity than those of the New World (_Cebidæ_). The anthropoid apes are very poor breeders indeed; of the many gibbons, orangs, and chimpanzees, that for years have been captive in Europe and America, it is probable that only the chimpanzee has bred, and that very rarely.

Refusal to mate, sterility, infanticide by father and mother, and sexual killing keep down reproduction in zoological gardens; and the number of young ones is a good indication of the character of a garden and of the provisions made for the happiness, comfort and health of the animals.

With the birds in a zoological garden the conditions for nesting and laying are not good. Caged birds have no material for a nest, no privacy and rarely lay an egg. The outdoor water birds and the outdoor upland birds with natural surroundings, with secluded retreats, lay and hatch very well. Birds like mammals apparently are indifferent to publicity when copulating, but seek seclusion for laying and nesting—from maternal fear for the safety of the young.

The sexual instinct in indoor caged birds in a zoological garden is dormant. Very few copulate and very few lay eggs; pigeons and Mexican conures (_Conurus holochlorus_) are exceptions to this general rule.

Probably because the sexual instinct is dormant the males never fight over the females among perching birds, and very rarely kill each other. In some species of finches, however, as the chestnut-eared (_gn. Amadina_), the females fight among themselves if there are not enough males.

Ovoviviparous reptiles breed more often in captivity than one would expect; and egg-laying snakes often lay eggs, which of course are only hatched artificially.

Birds suffer less than mammals from the psychological effect of captivity. The mental development of a bird is much lower. With few exceptions, like the ruffed grouse, the bird accepts captivity easily and becomes tame, though he will not stand being touched. He views his keeper and visitors with indifference or friendliness. If a bird house is bright, cheerful and sunny, all the inmates thrive and appear to be happy. These conditions undoubtedly affect the health of the bird, as is evidenced by their plumage; bright colors that are lost in a dark and gloomy house are retained and developed when the house is cheerful and sunny. There are some birds, however, that never retain their colors in the captivity of a zoological garden. Among them are the scarlet ibis, the American flamingo, and the roseate spoonbill. It has been suggested that the loss of color is due to the lack of something in the diet, mineral or organic, that the bird gets in its natural habitat. Tame scarlet ibises living with the chickens about the dwellings of natives in Venezuela retain their brilliant color. The material of the beautiful red color on the under surface of the wings of the touracou contains copper, yet these birds retain this color very well in captivity, even after several moultings.

The source of the copper has long been uncertain. In nature the birds are fruiteaters, and their diet in captivity consists of bone meal, zweibach, corn meal, white potatoes, eggs and carrots—foods that are usually assumed to contain no copper; and no copper utensils are used in the preparation of the food. Dr. John Marshall, however, writes me that all the common cereals contain minute quantities of copper; and Dr. Leon A. Ryan, _University of Pennsylvania Medical Bulletin_, June, 1907, states that copper may be found in animal tissues. Dr. E. P. Corson- White has found traces of copper in the bone meal used at the Philadelphia Zoological Garden. The copper in the red color of the touracou’s wing therefore comes from the food.

It is probable that a bright and cheerful bird house does not influence the color of birds by the direct action of light on the color as much as indirectly by improving the health and spirits of the birds. Coloration in birds is a very complicated proposition. It depends upon age, sex, season, health, light, heat, moisture, mode of life, and food. No one bird house can combine all the conditions necessary for the retention of natural colors in every species. The desert species from a habitat of intense light and dryness require for their color a different environment from the forest species, from a habitat of shade and moisture. The suppression of sexual feeling in captive birds may influence color. In nature the finest colors are attained by mating birds.

It may be said that all animals—except those of nocturnal habit—have a feeling of joy and well-being in fine weather and bright surroundings that reacts favorably on the general health.

The variability of the breeding period induced by captivity in many animals may be mentioned with sterility. It was shown some years ago in the Philadelphia Garden by the European brown bear which in one year gave birth on January 16th, and in the following year on July 25th. It is another evidence of the profound effect of captivity on the captive animal. I know of no observations of the effect of captivity on the period of gestation.

There is considerable mortality among captive animals from killing of cage-mates. I do not refer to sexual killing, already mentioned, or to fights over a female. Often males, with no females near, cannot be kept together; probably sexual jealousy is at the bottom of it. Antelope and deer are especially inclined to scrap. Even a large enclosure will not save the weaker male; the stronger follows him with horrible persistency, sometimes for days, around and around the enclosure, often at a walk, but always on the offensive, at least during the day; until, careless from weariness, the weaker is caught unawares and finished by a horn-thrust in the side.

Both birds and mammals often kill their mates when the mate is sick, or “down” from injury or disease. All animals hate sickness and death, and show their dislike by attacking or shunning it. Birds may get on happily together for months until one becomes sick, and as he crouches in a corner with ruffled feathers the others pick on him and finish him. The same is true of mammals, the sick one being horned or tramped to death by the mate with whom he had formerly been on most friendly terms. The keeper often reports an animal “killed by its mate,” whereas the mate has only given the _coup de grace_.

This brutality is not universal. Rarely a parrakeet will stand guard over his sick and dying mate; and we have seen a ratel—of a ferocious family—stand guard over and resist the removal of his sick companion.

The diagnosis of disease in wild animals is unsatisfactory; usually impossible; clinical study as we know it in the human is impossible. We know that the animal is sick, but not why. A certain group of symptoms accompanies all diseases—dull, rough coat or feathers, refusal to eat, weakness in the hind quarters, and finally getting down. They rarely show symptoms of pain—or at least we cannot read the symptoms. The pain of acute pancreatitis in man is violent, yet many animals die with it and we cannot tell that they suffer. Animals do not suffer as much as the human, and they stand the ravages of disease better than the human. At autopsy we often wonder how the animal could have lived with the conditions that are found. A monkey may be apparently well until a few days before his death, though his lungs and abdominal organs may be a mass of tubercle. A small red howler monkey (_Alonata seniculus_) was in apparent good health, playful and lively until twenty-four hours before his death from acute pancreatitis, though his stomach and intestines contained fifty-one nematode worms, some of which were eight inches in length.

As diagnosis is unsatisfactory, so is treatment. Usually all we can do is to treat symptoms; and by the time disease has advanced to the point of becoming externally noticeable, it has usually gone beyond the reach of medical treatment. It must also be remembered that drugs vary very much in their action in different families of animals. Nux vomica will not kill the gallinaceous birds of North America, and Tenant says that in Ceylon the hornbill feeds on the fruit of strychnos nux vomica. The pigeon is immune to opium. The _Felidæ_ are said to be unusually susceptible to carbolic acid; veratrum viride is harmless to sheep and elk, but poisonous to the horse; dogs can take with impunity large quantities of cyanide of potassium. These statements are true when the drugs are administered by mouth—the usual way of giving them to wild animals. The action may be different if the drugs are administered intravenously or subcutaneously. Variations in effect when they are administered by mouth are often due to chemical variations in the digestive secretions. It is probable that the action of cyanide of potash on dogs depends on the amount of hydrochloric acid in the digestive tract.

When worms or their eggs are found in the stools vermifuges are used, and with some animals especially liable to infestation by intestinal worms, periodic doses of vermifuges are given as a prophylactic. Turpentine is given to the zebra at fixed intervals for the round worm; santonin, male fern and areca nut to the carnivora for the various worms that are so common in the intestinal tracts of these animals.

The work of the Laboratory of Pathology is throwing light on the subject of diagnosis, and though from the character of the clinical material diagnosis can never be as satisfactory as in the human, yet we may fairly hope for improvement. Prophylaxis is our chief reliance, and always will be.

DISEASE IN CAPTIVE WILD
MAMMALS AND BIRDS