Popular Science Monthly/Volume 83/August 1913/The Future of the North American Fauna

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By the late WALTER L. HAHN, Ph.D.

THAT the animal life of North America is changing is a statement requiring no proof. Every one knows that deer, elk, moose, wolves, bison and many other animals are no longer found in places where they were once numerous. Nearly every one also knows that some pests, such as rats and mice and several noxious insects, have been brought to this country from Europe, while the potato beetle and some other species, natives of North America, have multiplied and extended their range.

It is impossible, within the limits of this paper, to specify all the changes that have taken place and are now in progress. Hence it will be my aim to point out certain general tendencies, and certain general influences at work upon our fauna, the word fauna being a somewhat technical term used to designate the sum total of the animal life, great and small, in any circumscribed region.

If asked why the great game animals have disappeared from certain regions, most people would doubtless say, "Indiscriminate slaughter has exterminated them." This answer is undoubtedly correct as far as it goes. For a full explanation of all of the changes that have taken place in our fauna we must seek deeper reasons. Why has not "indiscriminate slaughter" exterminated the mice and rats and other noxious creatures against which we have waged ceaseless war for many generations? In other words, what are the biological and physical conditions that determine whether an animal species shall survive or perish in modern America?

A living organism, even the simplest, is a thing of vastly greater complexity than any mere chemical compound or any physical law. We know how to kill individual organisms, but frequently we do not know what will exterminate a species. If a lion and a lamb lie down together, we know which will be on the inside. But if a given number of lions and a given number of lambs inhabit a great area we can not predict the exact results; and this illustrates the futility of trying to make a definite analysis of the future of any particular species.

I shall now consider the future of North American animals from the general standpoints of size, habitat, relation to man, fecundity, mental traits, and finally give a few interesting facts not comprehended in the above classification.


Size is the most obvious characteristic possessed by an animal. Whether we are naturalists or sportsmen, or neither, we instinctively classify all animals as large or small. Likewise there is nothing about our fauna so obvious as the fact that the larger animals are disappearing. The bison is gone, except for a few small and protected herds. The elk, moose, caribou, mountain sheep, antelope, cougar and grizzly and black bears are gone, except in sparsely settled regions. On the other hand, rodent pests swarm throughout every city, and the field mice, ground squirrels, cabbage butterflies, house-flies and hosts of other small insects continue to make trouble for the agriculturist.

Large size increases the value of an animal whose products are useful and hence makes it more desirable game for the pioneer who hunts to supply his larder and also for the sportsman who hunts for the sake of trophies. Large size also makes an animal apparently more dangerous if it has rapacious habits. I say apparently, for the microscopic bacillus tuberculosis kills more people in North America every year than all the beasts of prey have killed on the same continent since Columbus first sighted San Salvador, while the house-fly, disseminating the germs of typhoid fever and kindred diseases, is more deadly than all the wolves, panthers and rattlesnakes.

Sometimes we find related species having the same habits and living in the same region, but differing in size. Invariably the larger species is more sought after and diminishes more rapidly than the smaller. Squirrels illustrate this statement very well. In the northeastern United States three species of tree squirrels were once abundant. All had very similar habits, and ate practically the same kind of food. The fox squirrel and the gray squirrel are now on the verge of extinction in many places, while their smaller relative, the little red squirrel, thrives. Likewise the coyote fares better in contact with civilization than does the wolf, and the cottontail rabbits thrive where the larger jack rabbits and snowshoe hares are being exterminated.

Eight species of woodpeckers were once abundant in the forests all over the eastern states. Six of these are still common while the two largest species are extinct except in a few inaccessible swamps.

Large size means great strength. In the past this has been an advantage, within certain limits, by making an animal invincible to the attack of other animals. It is of no avail in stopping bullets, and hence is a disadvantage to a species that must count civilized man as one of its enemies.

The animals of the future, not only in North America but the world over, will have a smaller average size, and most large species-will cease to exist unless they are domesticated.


Some animals live, either by preference or necessity, in the forest; some live in meadows or prairies; some prefer uplands and some swamps; others must live in the water. A few are adapted to life in a variety of situations.

By far the greater part of North America east of the Mississippi "River was at one time forest clad. The trees have been cleared away from this region until now they are limited to scattered tracts a fraction of a square mile in area with a few larger forests still more widely separated.

The species that live chiefly in the forest include among the larger kinds elk, moose, caribou, Virginia and western black-tailed deer, and black and grizzly bears. Smaller forest-dwelling species include several kinds of lynxes, the fisher, marten, Canada porcupine, several species of squirrels, as well as many birds, snakes and lesser animals. Species that live habitually in the open include the bison, antelope, coyote, jack rabbit, prairie dog, many kinds of mice, birds, snakes and smaller creatures. Among the species that get along equally well in the forest and open country, we may notice the red fox, certain mice and birds, woodchuck and chipmunk and there are many others.

It will require no argument to show that all of the forest-inhabiting species I have named are diminishing and if space permitted this could be shown for nearly every forest-loving species concerning which we have the data to form an opinion.

Turning to the plains species, we find the bison and antelope have diminished because of their large size, economic value and gregarious habits. The jack rabbit is also diminishing in regions thickly settled and the prairie dog has been found so destructive that measures have been systematically undertaken to exterminate it.

The animals mentioned above, although the most conspicuous ones of the prairies, comprise only a fraction of one per cent, of the fauna of that region, and when we consider the remainder we find many animals that, if not everywhere increasing, are at least extending their range. There is abundant proof that the "cotton-tail" rabbit of the prairies, which is a different species from that of the Atlantic Coast states, has in recent times extended its range eastward to Ontario and western New York. Some of the native field mice and ground-squirrels are working eastward.

The Harris sparrow, a typical bird of the western prairies, was reported from Indiana a few years ago for the first time. The Dickcissel, field sparrow, chipping sparrow and many others have certainly become more widely distributed in the central states than they were half a century ago. Some of the meadow butterflies are becoming more numerous in the same region and there is some reason to think that certain fishes are spreading eastward across Illinois and Indiana, the border states of the prairie region. Just how general this eastward migration may be among the various classes we do not know, but a reason for it is not difficult to find. Clearing the forests has brought about conditions somewhat similar to those of the prairies, and the small species that can exist in the pastures, meadows and roadsides now find congenial surroundings farther east, and in the east competition is less severe than it was formerly because the forest fauna has diminished.

In this connection it is worthy of note that there is also a slight but rather general tendency of our fauna to migrate northward. This may be the latter end of a general northward migration begun some thousands of years ago when the great ice sheet that then covered most of northeastern North America began to retreat. There were few, if any, animals in the region at that time, but, as the ice melted, and the climate became warmer, the region was again occupied by a fauna migrating into it from the south. At present this migration is not rapid enough to be of much importance.

In my brief enumeration above I mentioned several species that seem to do equally well in wooded or treeless regions. These are the species that are fitted par excellence to survive, and, barring some that are ill adapted because of special modifications, they are the ones that are holding and will continue to hold their own in point of numbers.

Animals inhabiting fresh water are beavers, muskrats, ducks, geese, snipe, frogs, fishes, mussels, crayfishes and a host of other animals, small in size but numberless in individuals.

What is the tendency among these animals? To answer this question we must consider the physical changes in the bodies of water. Swamps have been drained and their bottoms converted into gardens and cultivated fields. River courses are straightened and the waters confined within their banks. Sewage and refuse dumped into streams pollute their waters, and sometimes wipe out the fauna completely, and always injure the larger species. Forests are cleared away, with the result that streams, once dotted with placid pools, now become raging torrents at one season and dry channels at another.

Such changes can not fail to have a disastrous effect on all classes of aquatic animals. The diminution of waterfowl, food and game fishes, muskrat and beaver, which is the result, is too well known to need comment; the decrease of small animals is almost as great.

It may be argued that the work of drainage is counterbalanced by the digging of canals and the building of reservoirs for irrigation. There is no question but that building great reservoirs in arid regions will somewhat increase the aquatic fauna of the surrounding districts. But the isolation of these bodies of water and the obstructions in their outlets will preclude any general immigration to their waters; and their fauna, for the most part, will be restricted to minute animals, insects and food fishes artifically introduced.

It can be asserted with certainty that there is a general tendency for aquatic animals to disappear.

Relation to Man

At first thought we might assume that useful species will survive and injurious ones will be wiped out, since man is the all-powerful lord of creation. But the most useful animals are the ones that disappear first. This is because of the unfortunate fact that man is a selfish being and thinks more of the satisfaction of his immediate desires than of the good of his race. Fortunately for the animals concerned, we are waking up to their value and many useful species are now reared in small numbers in a state of semi-domestication and there is a possibility that deer, foxes and many other animals valuable for food or fur will some day be fully domesticated.

On the other hand, it is true that injurious habits tend to bring about the extermination of a species. The venomous snakes are eminently fitted for protection from natural enemies. Their deadly nature has caused man to war upon them and in some localities his warfare has met with so much success that the once dreaded copperhead and rattlesnake are now extinct. The fear in which the pioneers held panthers, wolves, lynxes and other beasts of prey, played a large part in their early extermination.


There is another group of noxious animals against which man rages in impotent wrath. These are the mice and rats, the potato beetles, scale insects, flies and various other injurious insects. Among all of these creatures small size plays an extremely important rôle in the protection of the species. If a mouse weighed 100 pounds instead of less than an ounce, it would be more easily found and killed. The yet smaller size of insects makes them even more difficult to cope with.

Of much greater importance than their small size is the fecundity of these pests. A female deer produces no offspring until three years old and then only one or two a year. The other large animals produce young at about the same rate. But a female rat begins to bear young when six or eight months old and may produce 50 or even more in a single year. A house-fly, under the most favorable conditions, may lay eggs within two weeks of the time the egg was laid from which she herself hatched.

A single pair of flies, warmed to activity in April, have within themselves the potentiality of producing before October (if every egg laid by them and their descendants should hatch into a maggot that would mature into a fly) at their normal rate of increase under favorable conditions, about one hundred trillions of flies, at a conservative estimate, or fifteen millions of tons, by weight.

Of course many flies fail to reach maturity and only a small percentage of the eggs laid ever hatch. This statement has been introduced here merely to show how ineffectual is our warfare against animals procreating their kind at such a rapid rate, as contrasted with the effect of slaughtering a few slow breeding animals. Yet many of the microscopic organisms, both harmless and disease-producing kinds, multiply infinitely faster than the house-fly.

Down to the present generation, a rapid rate of reproduction has been the surest means possessed by any animal species of withstanding the enmity of man. Now scientific knowledge is beginning to triumph over both fecundity and small size. Mosquitoes have been exterminated by the wholesale in the canal zone. Europe, Asia, Africa and Australia have been successfully ransacked to find natural enemies that will hold in check scale insects, and codling and gipsy moths. A partially successful attempt has been made to inoculate rats with a disease that will kill them as cholera once killed men. War is being successfully waged on the germs of tuberculosis, yellow fever and many other diseases, and men best qualified to judge look confidently forward to a day when not one of these infinitesimally small but infinitely baneful organisms shall exist among civilized peoples.

Mental Traits

Under this head we may group several more or less distinct kinds of traits. First, there is the gregarious instinct, the tendency to herd together so noticeable in many animals. "In union there is strength" seems to be a motto in the animal as well as the political world. By banding together into great herds the bison became invincible to all foes save man. But with the advent of civilized man, armed with breech-loading rifles, the herding instinct of the animal only made its slaughter the more easy. The same is true, to a greater or less extent, of many other animals. Colonel Roosevelt says that, "the elk is the most gregarious of the deer family," and it was also the first of its family to disappear before the advance of civilization in almost every section of the country.

In the early seventies, passenger pigeons occupied a vast breeding ground in Michigan. It is said that in many square miles of this thickly wooded area, there was not a tree without a brooding pigeon on its nest at the proper season. Pot hunters found the birds, killed them with hands and sticks and guns, packed them in barrels and shipped them to market by the ton. Recently, in an effort to save this fine bird from extermination, a prize of one hundred dollars has been offered for the first person reporting a pair of breeding passenger pigeons.

A couple of decades before the passenger pigeon's extermination, flocks of hundreds of Carolina paroquets used to swoop down on the apple orchards of Kentucky and southern Indiana. Naturally the farmers took their guns and wreaked vengeance on the birds, and to-day the Carolina paroquet is all but extinct. And it has long been driven from the region I have just mentioned.

The economic factor was an important one in the extermination of these birds, but the rapidity of their extermination was due to the fact that they flocked together and were killed by the wholesale.

Beasts of prey are more courageous than weaker animals and all of the larger ones are gone from thickly settled communities. The rabbit is notorious for its timidity and still abounds everywhere outside of city limits. True, fecundity and small size play an important part in the preservation of the rabbit, but suppose that possessing these characteristics, the instinct of self-defense were stronger than the instinct to flee? The inevitable result would be the destruction of the race.

No mental trait has been of greater value to an animal species warred upon by man than timidity. The trait next in order of value is cunning.

The fox has always been justly considered as a type of the cunning animal, but the trait has not been equally developed in all kinds of foxes. In eastern North America there are two very distinct races, the gray fox and the red, cross and silver foxes being mere varieties of the latter. It is highly probable that the American red fox is descended from animals brought from England by gentlemen emigrating from that country during the eighteenth century, although this fact has not been clearly established. It is certain, at least, that it was either rare or absent in Ohio, Indiana and Illinois during the days when these states were frontier regions, and at that time the native gray species was abundant. Now the gray fox is extinct except in the rougher and more wooded districts, while his red relative is a pest in even the most densely settled valleys. The two species are nearly equal in size, fecundity, value of fur and destructiveness to poultry. They eat the same food, they live in the same kind of places, with the exception that the gray species seldom makes its den in the open fields, while the red often does. The vital point of difference seems to be in their cunning. The red fox, if not the sly renard of Europe, is certainly a close counterpart in cunning, while its gray cousin is lacking in this respect. In these two species, at least, the difference between survival and extermination depends upon cunning.

Miscellaneous Peculiarities

There remain to be considered certain characteristics which can not be very accurately designated by any well-understood and precise term. I refer to what is sometimes called by biologists a high degree of specialization, and more particularly specialization in the direction of bizarre and conspicuous features.

The porcupine is a good example. This animal is of absolutely no economic importance to civilized man. It lives in the forests and eats little save twigs and bark. Its flesh was eaten to some extent by Indians and its quills were prized by them as ornaments, but neither flesh nor armature are valued by whites. It might be supposed that a few porcupines could find sufficient food and shelter in any small wood lot and that they would remain there unmolested because of their inoffensive habits. Yet few species have disappeared more rapidly before the advance of civilization.

The animal had few natural enemies because of the efficient protection of its spiny armature, consequently it had no fear and was a slow breeder. Its spines, however, afford no protection from man, and there can be no doubt that more porcupines have been killed from curiosity excited by the peculiar appearance of the animals and mere wantonness than from any other reason.

One species of armadillo is found in the Unites States chiefly in Texas. It is an animal with a head and body about a foot in length and a tapering tail of equal length. Its body is covered with an armor of bony plates, quite solidly Joined together in most places, but with overlapping Joints in the middle. When attacked it curls up, covering the poorly protected belly, throat and nose with its tail, and hence becoming invulnerable to teeth and claws. It is harmless in habit, living chiefly on insects. Its peculiar appearance frequently leads people to kill it from no motive except curiosity and wanton love of slaughter. Recently a tourist trade has grown up in the armor, which is made into a basket, the tip of the tail being brought forward to the neck and fastened there to form the basket handle. Thus an economic relation is growing out of the bizarre appearance of the animal and its extermination seems to be only a matter of a few years, unless it receives better protection.

Horned toads, lizards and, to some extent, tortoises and snakes are being slowly exterminated because their appearance arouses the desire to kill and not because of any economic motive. A few comparatively harmless species of insects, namely, the walking stick or devil's darning needle, the praying mantis or rear-horse, and the rhinoceros beetle have been nearly exterminated in some parts of the country merely because their unusual appearance arouses an interest in them and their life is forfeited therefor.

We might also include in this category the snowy heron, the roseate spoonbill and other birds that have been slaughtered for their plumage. Although the economic value is here the direct motive for the slaughter, this value grows out of unusual (and beautiful) modification of the plumage.

The preceding paragraphs are necessarily sketchy, because the subject is too large to treat in detail and it is now desirable to gather up the threads.

Briefly, the general tendency of the North American fauna is toward mediocrity. Large species are giving way to small; bizarre species to commonplace. Marsh-loving and forest-loving animals disappear with the advance of civilization, and grass-loving species that are able to exist in fence rows and pastures survive. Animals that yield products of value vanish before the hand of man; likewise his enemies are destroyed unless protected by small size and great fecundity. Courage and the social instinct are at a discount and cunning and timidity at a premium.

Finally man is beginning (and only beginning) to shape the destiny of his God-given dominion "over the beasts of the field and the fowls of the air." To make this dominion an intelligent reality is the aim of present-day biological science.