THE ECONOMIC VALUE OF PREDACEOUS BIRDS AND MAMMALS.

By A. K. FISHER,
In Charge of Economic Investigations, Biological Survey.

GENERAL REMARKS.

As a class the predaceous animals have a most important function to perform in the economy of nature. Before man interfered with the intricate relations of wild creatures and disturbed the balance of nature, the carnivorous animals served admirably to prevent undue increase of the hordes that fed on herbage, seeds, fruits, and other vegetable life. So perfectly was the balance regulated that a temporary increase or decrease in one direction was followed sooner or later by a corresponding change in another.

But valuable as many predaceous animals are in aiding to maintain the balance of Nature, man looks askance at every mammal or bird that molests his poultry or the game of the State, and without regard to consequences sets out to kill everything that resembles the particular offender. Ho declines to give a mere pittance in return for value received, and visits indiscriminate persecution on the humble and faithful workers that have helped to save his harvest or orchard.

Most flesh-eating animals change their ordinary diet only under pressure of hunger. In the main they prey upon some abundant species, which, when available, furnishes almost their entire subsistence. For example, if meadow mice were always present, the red-tailed hawk would rarely touch other food. It is when normal food is scarce that predatory birds and mammals are from necessity forced to take what they can find and thus become trespassers. It is true that there are perverted individuals among animals, just as there are objectionable characters among men, and these by their overt acts tend to discredit their class as a whole. Yet the man-eating tiger and the poultry-eating skunk, weasel, and hawk are rare, though their deeds have been heralded far and wide and their names have become notorious.

In many cases—it might be safe to say in almost all—depredations by normally useful species are the work of exceptional individuals which for some reason depart from the habits of their kind. Thus among the beneficial hawks and owls it has been found that the transgressors usually are immature birds, which, it is fair to assume, lack skill and experience in hunting their normal prey and consequently are forced to feed upon anything that offers.

A given species in a certain locality, and under what may be termed normal conditions of food supply, may be a most valuable factor in controlling a pest, while in another part of its range it may be undesirable on account of its inroads on poultry or stock. The great horned owl and coyote are examples in point. In rabbit-infested regions and in vineyards, orchards, meadows, or gardens overrun by field mice they are among the best friends of man; but in thickly settled regions comparatively free from rabbits and mice, both the owl and coyote have to be summarily dealt with, as also does the coyote in sections where sheep raising is an important industry.

Nature carefully safeguards the permanency and welfare of a species by making the healthy and virile individuals wary, agile, and elusive, so that their natural enemies are forced in the main to content themselves with the less favored individuals. The wolf that pulls down the sick or enfeebled deer, or the hawk that devours the crippled quail, is really benefiting the species it preys upon, though at the expense of the individual, since by the removal of the weak and unfit, more vigorous breeding stock is secured, and the danger of outbreaks of disease materially lessened.

It would be easy to define the economic value of all predaceous animals, were it not for the complications resulting from civilization, which introduces problems that materially affect the status of animated things.

It may be of interest to consider briefly the relations of some of the better known predaceous species.

WOLVES AND COUGARS.

In the present period of diminishing game supply and increasing live-stock interests, little can be said in favor of either the wolf or the cougar, animals that derive the greater part of their subsistence from big game, sheep, cattle, or horses. While they kill considerable numbers of rabbits and smaller pests, the good thus accomplished is rarely sufficient to offset the harm they do.

COYOTES AND BOBCATS.

In parts of the West where fruit growing and farming are dominant industries, it may be wise to encourage coyotes and bobcats within certain limits, provided poultry and sheep are properly protected at night. Numerous ranchmen and fruit growers have learned by experience that these animals if unmolested will free their premises from rabbits and other crop or tree destroyers. Where coyotes and bobcats have been allowed to do their work thoroughly they are fully appreciated, and many ranchers would almost as soon shoot their own dogs and cats as their wild benefactors. At times the coyote feeds entirely on large insects, as May beetles, crickets, and grasshoppers, and accomplishes much good.

THE HOUSE CAT.

Many an innocent hawk, skunk, owl, and weasel has been shot for the deeds of that sleek highwayman, the house cat. It is safe to say that this marauder, which enjoys all the comforts and protection of a home, destroys in the aggregate more wild birds and young poultry than all the native natural enemies combined. A cat has been known to kill a whole brood of chickens in a day, a feat unequaled by any predaceous animal, with the possible exception of the mink. Others in the course of a season have practically destroyed whole coveys of quail or grouse, or nests full of young songsters. A well-known naturalist estimates that in the New England States alone 1,500,000 birds are destroyed annually by cats.

The offender is not so often the well-fed household pet as it is the abandoned and neglected outcast. In 1905 the Society for the Prevention of Cruelty to Animals in New York City killed monthly an average of 6,000 sick, injured, or homeless cats—a total for the year of over 70,000. A considerable proportion of these were pets abandoned by people who had gone to the country for the summer. Moreover, summer visitors to the mountains or seashore sometimes take with them their cats, which, on their return home, are too often left behind to swell the local overflow and make serious inroads on the birds of the region. It is safe to assume that in the rest of the State outside of New York City as many cats follow a nomadic life as in the city, and if we assume that each cat kills one bird a week, we have a grand total of over 8,500,000 birds destroyed annually. In the milder parts of our country, as in the chaparral region of California, where bird life is abundant, cats often revert to a semi-wild state and never revisit their old homes except for plunder. Sportsmen and bird lovers should be ever watchful and whenever possible remove marauding cats from the coverts.

The principal reasons given for keeping cats are their attractiveness as house pets, their usefulness as companions for children, and their alleged value as rat and mouse killers. It is impossible at present to obtain correct figures on the subject, but it is safe to say that few persons during a normal lifetime run across more than half a dozen cats that habitually attack rats. Occasionally a hunter cat is found which seems to delight in catching rats, gophers, or ground squirrels. It has been the common experience of the writer to find premises that were well supplied with cats overrun with rats and mice. At a certain ranch house in the West he trapped in his bedroom 12 mice in a week, although 8 cats had access to the place.

Lovers of the cat should be content with one, or at the most two, of these pets, and should see to it that outcasts do not run at large on their premises. Now that cats are known to carry in their fur the germs not only of ringworm, but also of such dreaded diseases as tuberculosis, diphtheria, scarlet fever, and smallpox, the presence in the household of Tabby is not without its dangers.

THE FOX.

The fox, from its occasional misdeeds, is looked upon by the majority of mankind as a deep-dyed villain that devotes its entire life to robbery and derives all its forage from the chicken yard or duck pen.  As a matter of fact, even in localities where foxes are abundant, it is comparatively rare that poultry is destroyed by them. On all well- regulated farms chickens are housed at night, and the fox necessarily turns his attention to field mice, rabbits, ground squirrels, and insects, such as grasshoppers, crickets, and May beetles, to the great benefit of the farmer. Although it is true that the fox destroys a considerable number of birds, yet a ruffed grouse has been known to rear its young within 100 feet of a fox den, and the tracks of the young birds have repeatedly been seen on the fresh earth before the entrance. Among the food brought to the young of this litter and left outside were rabbits, mice, and a half-grown woodchuck, but no birds of any kind.

THE MINK.

The mink feeds on fish, crayfish, mussels, birds, and, like the weasel, is indefatigable in its search for meadow mice and other marsh- loving rodents. It is very fond of muskrats, and one of its most important services to man is the destruction of these pests about mill- dams, canals, and dikes, where their burrows undermine the embankments and cause disastrous overflows. The mink, although semi- aquatic, sometimes travels long distances from water in search of rabbits, ducks, and chickens. When it finds an unprotected poultry house, it sometimes contents itself with a single victim; at other times it kills all the inmates within reach. A single mink has been known to kill 30 or 40 ducks or chickens in one night. Fortunately such occurrences are rare and necessarily will become less frequent, since the demand for mink fur is constantly increasing.

THE WEASEL.

The weasel is one of nature’s most efficient checks upon the hordes of meadow mice and other rodents which at times destroy forage crops, orchards, vineyards, and garden produce. It feeds also upon rabbits, squirrels, and birds, and in many sections its occasional inroads on the poultry yard have brought it into serious disrepute. It is of course desirable to kill particular individuals which have acquired the poultry habit, but farmers and horticulturists will make a mistake if they systematically destroy weasels.

THE SKUNK.

The skunk is another “chicken thief,” which renders important service by destroying immense numbers of mice, white grubs, grasshoppers, crickets, cutworms, hornets, wasps, and other noxious forms.  Although it prefers this kind of food, like the opossum it will eat almost any animal matter and also at times certain wild fruits and berries. It is said to be fond also of eggs and young chickens; but the writer has known a mother skunk to make her nest and rear her young in the inner walls of a chicken yard and neither egg nor fowl was molested.

The following well illustrates the close relations that diverse forms of animal life bear to one another and demonstrates how easily the natural balance may be upset: An extensive marsh bordering a lake in northern New York formed a suitable home for numerous ducks, rails, snapping turtles, frogs, and other aquatic life. The turtles deposited their eggs in abundance in the sand of the old beach. These delicacies attracted the attention of the skunks of the neighborhood, and their nightly feasts so reduced the total output of eggs that only a small percentage of the young survived to reach the protective shelter of the marsh.  As time went on conditions changed. Skunk fur became fashionable and commanded a good price. The country boy, ever on the alert for an opportunity to add to his pocket money, sallied forth and captured the luckless fur bearer wherever found, so that within a comparatively short time the skunks almost wholly disappeared.  When this check on their increase was removed, the snapping turtles hatched in great numbers and scrambled off in all directions into the marsh. When their numbers had been properly controlled by the destruction of a large proportion of their eggs, their food supply was adequate, but when they had increased many-fold the supply proved insufficient. Finally, through force of circumstances, the turtles added ducklings to their fare until the few ducks that refused to leave the marsh paid the penalty of their persistency by rarely bringing to maturity more than one or two young. It is not surprising that this great aggregation of turtles, containing the essential of delicious soup, should have attracted the attention of the agents of the market men and restaurant keepers. The final chapter, the readjustment of conditions, may be briefly told: The marsh became a scene of great activity, where men and boys caught the voracious chelonians, and bags, boxes, and barrels of them were shipped away. There was also a depreciation in the value of skunk skins, with a corresponding loss of interest on the part of the trapper, so the progeny of the surviving skunks congregated at the old beach and devoured the eggs of the turtles that had enjoyed a brief period of prosperity. The broods of ducks now remained unmolested and attracted other breeding birds, with the result that the old marsh reverted to its original populous condition.

THE BADGER.

Badgers are valuable in destroying ground squirrels, gophers, and other burrowing animals, as well as various kinds of insects. They are extensive diggers and seem to have little trouble in securing their victims. For their valuable services full protection should be given them, even in irrigation sections, where they sometimes dig into dikes in pursuit of the rodents which in the role of dike borers cause so much trouble.

THE RACCOON.

Raccoons are omnivorous but rarely are abundant enough in thickly settled districts to do much harm except when they eat the fish in small artificial fish ponds and catch poultry which is left to shift for itself. In parts of the South where crayfish live in the levees and embankments, the raccoon does good service in destroying these troublesome crustaceans.


HAWKS AND OWLS.

The sooner farmers, ranchmen, horticulturists, and nurserymen learn that the great majority of birds of prey are their friends and deserve protection and that four or five species only are injurious, the sooner will depredations by noxious rodents and insects diminish.  In the more thickly settled sections of the country, except at rare intervals, the goshawk, duck hawk, and great horned owl are so infrequent that years may pass without an individual being seen.  Two species that need to be kept in check are the sharp-shinned and Cooper hawks, small and medium sized species which feed almost entirely on wild birds and poultry. The illustrations (Pls. I to III) will materially assist those interested in identifying these birds.

   

The important fact to bear in mind is that all hawks and owls feed largely on noxious rodents and the larger insects, such as grasshoppers, crickets, and May beetles, and, from their size and voracious appetites, are important factors in reducing the numbers of such pests and keeping them under control.

OTHER BIRDS AND MAMMALS OF ECONOMIC INTEREST.

There is a number of species of birds and mammals, which, although they do not strictly belong to predaceous groups, are nevertheless at times extensively predatory in habits. Among the better known of these may be mentioned rats, squirrels, chipmunks, ravens, crows, jays, herons, and gulls.

THE RAT.

With the exception of the house cat, the rat probably kills more young chickens than any other animal. In some places where this rodent has become well intrenched, owners have found it next to impossible to profitably raise chickens. The marauders often become so bold that they catch passing chickens in broad daylight. Rats have been known to kill newly born lambs and pigs, and they frequently destroy the young and eggs of wild birds. This is especially true in suburban districts and on islands along our coast.

RED SQUIRRELS AND CHIPMUNKS

During spring and early summer, when nuts and seeds are scarce, red squirrels and chipmunks are kept busy searching for food. This is the height of the breeding season of birds, and where the red squirrel is abundant it destroys great numbers of eggs and nestlings. This often happens where hawks, owls, weasels, and other enemies of the squirrel have been systematically persecuted and as a consequence squirrels have unduly increased.

HERONS.

It is well known that members of the heron family feed to a great extent on fish and other forms of aquatic life, and consequently do not live far from water. Two species, however, the great blue heron and the bittern, at times depart from the family traits and visit hillsides, cultivated fields, and drier meadows in search of pocket gophers, ground squirrels, and field mice, which they greedily devour. Pellets collected in one of the more inland nesting colonies of the great blue heron indicate that a very large proportion of the food of the young is made up of these injurious rodents. The remains of three pocket gophers have been found in one pellet, and a captured young bird regurgitated a like number. The herons, like other flesh-eating birds, digest their food rapidly and are disposed to gorge themselves when opportunity offers. It is fair to assume as a low average that a pair of herons with 4 or 5 young will consume a dozen or fifteen gophers daily. We should not begrudge them the fish they eat when we remember that a gopher is capable of destroying trees large enough to produce marketable fruit.

GULLS AND TERNS.

The gulls and terns that live inland do effective service in checking the inroads of injurious insects and mammals. In spring, flocks of Franklin gulls fearlessly follow the plow and glean from the upturned soil many an insect that later would have attacked the growing crop.  During the summer, and up to the time of their southern migration, the same flocks gorge on grasshoppers and crickets. The larger gulls, like the ring-billed and California gulls, feed on field mice and other small rodents, and in times of “mouse plagues” do effective work.  Terns feed on grasshoppers and other insects, and in the South the black tern has been seen capturing the moths of the cotton-boll worm in flight over the fields of young plants.

RAVENS, CROWS, AND JAYS

Ravens, crows, and jays also do effective work in destroying pests.  Occasionally, however, in localities where they have increased out of proportion to the available food supply, they become troublesome by killing small chickens and by destroying eggs and nestlings of wild birds.

IMPORTANCE OF PROTECTING BENEFICIAL SPECIES.

It is demonstrable that so long as a useful species is kept within bounds and is not allowed to increase beyond its normal food supply, just so long will it fulfill its natural mission and be of true economic value. If, however, the staple food supply temporarily fails, then in the effort to maintain life the animal is likely to become obnoxious and may have to be controlled.

The annual loss of crops by insect and mammal pests in the United States amounts to many millions of dollars. Moreover, not only is this loss not diminishing, but on the contrary it is steadily increasing, partly as a result of the encroachments of new insect enemies, partly from the increase of both insect and rodent pests—for the number of these naturally grows with the extension of tillage—and partly, perhaps mainly, because of the destruction of their natural enemies.  These, instead of being permitted to keep pace with the multiplication of the pests upon which they feed, have been destroyed until their numbers are entirely inadequate to preserve the balance. It is therefore of first importance that the farmer and stockman should everywhere seek to protect and encourage the natural foes of injurious mammals and insects.

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