Popular Science Monthly/Volume 20/February 1882/Wild Animals as Man's Associates

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By Professor EDWARD S. MORSE.

IT would be a curious study to ascertain at what time certain wild animals came to be associated with man. We do not mean those which have become domesticated, though many of these run back far beyond the historical epoch. By wild animals we mean those which, still continuing in a wild state, build their nests or construct their burrows near, or within, the habitations of man.

The first advances in this direction must have been made by certain members that differed slightly, in their impulses, from others. It might have been the more courageous and intelligent ones, which, not fearing the presence of man, and recognizing the advantage to be gained in the greater abundance of food, selected human habitations as their abiding-places; or it might have been individuals so stupid as not to be aware of the possible danger of man's proximity, and thus unwittingly selected places in or about his dwellings.

The birds that nest in our trees we generally protect through humane or selfish motives, while with the rats, mice, and certain insects, we keep up a perpetual warfare. Yet, that these latter animals survive, indicates that, in spite of this opposition, the favorable conditions must outweigh the adverse ones, otherwise they would soon be exterminated.

A special investigation in regard to birds would be of great interest. The change that has taken place in the habits of birds in forsaking the forests and fields, and building their nests in the trees of towns and villages, must have occurred since the first settlement of this country by Europeans. After the incoming of each species from the wilderness their increase must have been rapid, as the favorable conditions far outbalanced the unfavorable ones. Not only does the bird secure a certain immunity from danger, in the shape of predatory birds like the hawk, but it finds itself in the midst of a plentiful supply of insect-life, which has in turn been lured from the wilderness, and which has developed with frightful rapidity, owing to the dense crops which man raises, and which were not always to be destroyed by every forest fire or persistent drought. Many species have been forced in by the destruction of large tracts of forest, which compelled them to seek other food, or become extinct. The destruction of forest-trees still goes on in this country with criminal celerity, and new insects injurious to vegetation will be added from year to year.

Audubon somewhere remarks that in passing through a dense forest it was the rarest thing to hear the notes of those song-birds most familiar to him, and he could always recognize his approach to a village by the notes of those birds which most commonly frequent our trees and fields. It is known historically when the cave-swallow first commenced to change its abode from cliffs to the more convenient and protective eaves of barns. Professor A. E. Verrill, in a paper on this subject in the "Proceedings of the Boston Society of Natural History" (vol. ix, page 276), records numerous examples of their first appearance about man's habitations in the East and West, and is inclined to the opinion that, "when this continent was first settled by Europeans, the cliff-swallow inhabited the whole of its breadth wherever there were extensive limestone cliffs suitable for the building of its nests; and that as civilization advanced toward its native haunts, and suitable buildings became accessible to it, it gradually abandoned the cliffs, and, increasing in numbers to a greater extent than before, on account of the protection invariably furnished by man, it gradually spread over New England and the other Northern States, where hitherto there had been no cliffs suited to its wants. In thus extending its range it probably advanced both from the western and from the northeastern parts of the country, both these regions abounding in high limestone cliffs, which are entirely wanting in New England."

A little more humanity on the part of boys, a suppression of the bird-devouring instincts in the cat, and new birds will seek the companionship of man. In Japan, owing to the gentle behavior of the people, the crow has full liberty to go where he likes. As a consequence, the densely populated cities swarm with the noisy fellows. They repay the kindness shown them by acting as scavengers. Every bit of organic matter, which in its decay might pollute the air, is seized upon by the crows and devoured; and thus it is that, by this and other means, the death-rate in these large cities, under the hot sun of latitude 35º, is lower than that of Salem, Massachusetts—for example, in latitude 42º, with its reeking bodies of filthy water. With us the crow has been driven away by constant hard usage, and now it is one of the most wary of birds. In Japan, a crow that has no timidity will, on the whole, get the most food for itself and offspring, and thus stand a better chance of surviving and raising its progeny. Here the same attribute would almost surely lead to its destruction.

It is curious to observe how soon this fear in animals may be excited by the pressure of destructive agencies. More curious still is it to note the fact that insects may be affected by it. I have repeatedly observed that, in places where the common house-flies are undisturbed, individual flies may be caught with ease. At Penikese Island I recall this peculiarity as particularly marked. The movement of the hand in the effort to catch them was invariably too quick. A friend of mine has observed the same peculiarity concerning the house-flies in a country church. They could easily be touched with the finger. It is plainly obvious that the alert flies would be the ones to escape, and, thus surviving, would perpetuate their peculiarities, while the stupid ones would be the first to perish in any attempt to get rid of them. The house rat under the same selective action has, by continual survival from the quick-witted ones, become synonymous with all that is crafty and cunning.

We commenced this article mainly to call attention to some facts concerning a certain kind of ant, which must have attracted the notice of others before. It is difficult, at first, to see what special advantages can offer to the little yellow ants that persistently, year after year, construct their burrows under our brick pavements, and use these thoroughfares for their promenades and hunting-grounds. One would consider that such regions would be almost the last places these intelligent little insects would select. Many of them must be crushed daily beneath our feet, and their little hillocks and annular tumuli trod upon or swept away. Side-walks which are much traveled on are often selected by these industrious and courageous little fellows, and here they burrow beneath the bricks, and heap up their moles undaunted by the frequent demolition of their work, and the death of many of their comrades. It is obvious that the advantages must outweigh the disadvantages, otherwise the ants could not long survive, and continue their work, as they do from year to year.

We know well enough the unfavorable conditions to which they are subjected: the crushing steps of busy feet; the wheels of boys' velocipedes, and children's hoops; the sweeping-broom, a very scourge of destruction; deluges from the garden-pipe, which to them must be Noachian, and the occasional trailing of a long skirt, with the devastating effect of a typhoon and sirocco rolled into one. All these must invariably destroy many lives and demolish many an earth-work.

Among the conditions that these ants require for their perpetuation and increase are, first, soil in which they can easily burrow their nests and galleries; second, substances which may be heated by the sun, and beneath which they may bring their pupæ, or partially developed offspring, in order to hasten their more rapid development. It is said that colonies of ants have constructed their nests in or near fire-places that they might avail themselves of the artificially heated bricks of the hearth for this purpose. In pastures ants often construct their galleries beneath large stones, and bring their pupæ up from the burrows below, placing them just beneath the stone which has been heated by the sun, and which retains the heat for a considerable time after the sun sets. It is a common experience in turning over stones in the pastures to find the galleries just beneath densely crowded with pupæ, and when the ants are surprised in this way they show great solicitude in their efforts to remove the pupæ to a place of safety. It is astonishing to see how quickly many hundreds of pupæ are removed to the burrows below. In using the brick walks of cities, the ants find the most suitable conditions for their burrows, as it is customary to bed the bricks in a layer of sifted gravel, and the ants, in mining into this material, are not interrupted by the obstacles they would naturally encounter in other deposits. The bricks become heated with every day of sunshine, and thus the ants find all the conditions necessary for the rapid development of their pupae.

Of equal importance is the fact that an abundant supply of food is ready at hand in their hunting-grounds—food already slaughtered for them—so that they are saved the time and trouble of overcoming and destroying their prey. Not only are they certain to secure the caterpillars, worms, and a variety of insects which are crushed by passing feet, but also the crumbs dropped by children, or swept from the houses, as well as the banana- and orange-peel, peach- and cherry-stones, and the like, which often litter the sidewalk. Here, then, is a variety of food to supply their tastes, and, when not otherwise engaged, they may be seen tearing off the fruit-fibers from some cherry-stone or apple-core, or tugging away busily at some maimed or crushed insect or caterpillar. In selecting proper places to build their nests, they choose, if possible, those which are neither damp nor liable to inundation. If the sidewalk, they secure a level territory from which the rain runs away as fast as it falls. With all these favorable conditions they manage to survive and flourish, despite the frequent choking up of their passage-ways, and the many deaths, by crushing, of their workers.

Thus it is that what seems to us a very precarious and unfavorable region in which to live, the ants continue to occupy from year to year, and to increase in numbers. The struggle for existence is well illustrated by this example, and it would be interesting to know just how many footsteps a day they can endure and yet survive. A densely traveled thoroughfare will be found to support but very few ants' nests, and these are upon its borders, while one less traveled, if it is comparatively dry and not heavily shaded by trees, will be found infested with them.

The mud-wasp which plasters its cells under the roofs of barns, garrets, and sheds in Northern New England, parallels the eaves-swallow which constructs its mud-nests beneath the eaves of barns. Here the brighter individuals show great judgment in selecting places removed from leaks in the roofs. We have observed many remarkable selections of building-sites among these insects, and doubtless numerous interesting facts await the patient study of these curious animals.

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