Rodent control

“ A few concrete examples will illustrate the great good that has resulted from the E.C.W. rodent-control program. A group of farmers living at Springfield, Idaho, suggested to the camp superintendent there that the jack rabbit control work done by the E.C.W. crew during the summer of 1935 might pay the cost of the camp. It is estimated that not less than 600,000 rabbits were - 5 - killed by this crew on public lands adjacent to farming areas between American Falls and Moreland, Idaho. ”

“ The most concrete proof of the necessity of rodent control is found in the amount of money expended by private individuals throughout the West for this purpose. The Federal Government, while owning as much as 60 percent of the land in many of the Western States, contributes only about 25 percent of the total cost of rodent-control operations. During the fiscal year 1936, States, counties, and private individuals expended $665,785 for the purpose, while the Biological Survey was able to expend only $226,623 from regular appropriations. ”

“ Extreme care should be exercised in handling poisons in rodent-control work. Prepared poisons should be placed in strong, properly labeled containers and should be distributed only to assistants working under the direct supervision of bureau leaders or to responsible cooperators. ”

“ As a result of the investigations conducted much has been learned concerning the economic status of most of the more important groups, and the knowledge already gained forms the basis of the extensive rodent-control work already in progress, and in which many States are cooperating with the bureau. ”

“ Certain species of the rodents that in large numbers infest lands of value for crop or forage production must be eradicated locally to meet the requirements of agriculture and forestry. Those that figure most largely in the cooperative control operations in one part or another of their ranges are the prairie dogs, ground squirrels, pocket gophers, jack rabbits, porcupines, and native and introduced rats and mice. ”

“ Though the chief control work directed by the Biological Survey is concerned with injurious rodents and predatory mammals, it sometimes becomes necessary to investigate cases of damage by other classes of animal life, including moles, crawfishes, and land crabs, and to recommend measures for their control. ”

“ It is the persistent destruction of these, the beneficial and harmful alike, that has brought about the present condition of growing scarcity of predacious mammals and birds and corresponding increase of rodent pests of the farm, especially rats and mice. ”

“ Whilst man is busy killing off the carnivora and the birds of prey, these natural checks to the multiplication of the Rodents are being missed seriously, and Rats, Hamsters, and Voles prove a serious menace to man's agricultural produce, and the Rat to his health owing to its instrumentality as a carrier of disease.
A distinctive character of the Rodents, additional to the chisel-teeth and the absence of canines, is the possession of hairy linings to the mouth, the external skin being continued into the sides of the mouth behind the upper front teeth. ”

“ Other groups that locally become unduly numerous and destructive may also on occasion come within the control program. It would be impossible to eradicate everywhere the ground squirrels, prairie dogs, and other rodents that range over vast areas of relatively worthless lands, and such action is not desirable, even on the public domain. In areas of economic importance, however, definite tracts are established where the rodents can be kept under thorough control, and operations are extended sufficiently to prevent reinfestation. ”

“ It is common to find well-beaten paths from the animal’s “front door” to the forage areas. Moving about on a grassy slope the fat, lazy rodent seems anything but alert, as he crawls from one spot to another. But the observer soon becomes aware that the chuck’s pauses to survey the landscape are frequent; his head is raised, if no danger threatens his tail flips and feeding is resumed. If frightened, swift retreat is generally preceded by the shrill whistle, and the sluggish, crawling fat one becomes a scurrying bundle of fur following a well-worn and familiar route to the sanctuary of his den. ”

“ Many men have devoted their lives to a study of methods of rat control, and as a result countless preparations, devices, and contrivances are constantly being made available. Trapping, snaring, trailing, flooding, digging, hunting, ferreting, poisoning, and fumigating are employed, and rat limes, rat lures, rat repellents, and bacterial viruses are resorted to, and even antirat laws, local. ”

“ The value of carnivorous mammals and the larger birds of prey in destroying rats and mice should be more fully recognized, especially by the farmer and the game preserver. Rats actually destroy more poultry and game, both eggs and young chicks, than all the birds and wild mammals combined; yet some of their enemies among our most useful birds of prey and carnivorous mammals are persecuted almost to the point of extinction. ”

“ The control of such predatory wild animals as coyotes, wolves, mountain lions, and bobcats is concentrated on areas where serious damage is being done to domestic stock, poultry, and game. Bears are not subject to control except when individually injurious to livestock or property. ”

“ In placing traps for the capture of injurious wild animals every possible precaution is to be taken to avoid the accidental capture of valuable game and fur-bearing animals and other harmless or beneficial forms of wild life. Hunters working under the supervision of the Biological Survey are instructed to visit their trap lines « 8 » as frequently as possible and to liberate game animals and foxes, badgers, skunks, martens, minks, raccoons, and other animals accidentally caught, unless they are so injured that they can not survive. ”

“ Among the natural enemies of rats and mice are the larger hawks and owls, skunks, foxes, coyotes, weasels, minks, dogs, cats, and ferrets.
Probably the greatest factor in the increase of rats, mice, and other destructive rodents in the United States has been the persistent killing off of the birds and mammals that prey upon them. Animals that on the whole are decidedly beneficial, since they subsist upon harmful insects and rodents, are habitually destroyed by some farmers and sportsmen because they occasionally kill a chicken or a game bird. ”

“ The methods of handling poisons developed and used by the Biological Survey can be employed most effectively and economically in controlling predatory animals at proper seasons in regions where conditions are favorable. Poison is especially suitable for winter use against predators on some of the great stock ranges of the West, as it can then be employed with little or no danger to useful life. The cost of the same measure of control by any other known means would be practically prohibitive. ”

“ Mice and the black and roof rats produce smaller litters, but the period of gestation, about 21 days, and the number of litters are the same for all.
Rats and mice are practically omnivorous, feeding upon all kinds of animal and vegetable matter. The brown rat makes its home in the open field, the hedge row, and the river bank, as well as in stone walls, piers, and all kinds of buildings. It destroys grains when newly planted, while growing, and in the shock, stack, mow, crib, granary, mill, elevator, or ship's hold, and also in the bin and feed trough. ”

“ While the physicians are employing this remedy, the rat-catchers are also busy, and about a thousand rodents are captured per day, it having been demonstrated that the rat not only spreads the disease, but carries a flea that imparts it by its bite. ”

“ The only circumstance that saves these birds from instant condemnation is the delightful amount of rats, mice, moles, gophers and noxious insects that they annually consume. In view of the awful destructiveness of the accursed bubonic-plague-carrying rat, we are impelled to think long before placing in our killing list even the great horned owl, who really does [Page 81] levy a heavy tax on our upland game birds. As to the butcher bird, we feel that we ought to kill him, but in view of his record on wild mice and rats, we hesitate, and finally decline. ”

“ When inoculated, all warm blooded animals contract the disease. Thus the carnivora and omnivora (dog, wolf, fox, hyena, jackal, cat, lion, badger and skunk and, to a less extent, the pig and horse) may become active propagators of the infection, which may spread widely among their herbivorous victims (cattle, sheep, goats, deer, rats, mice, chickens and pigeons) through their bites. Man suffers mainly through the attacks of dogs, cats and, in certain localities, wolves or skunks, but he is also liable to become infected from handling rabid domestic herbivora. ”

“ Not only are mice and rats, especially the brown rat, a cause of destruction and damage to property, but they are also a constant menace to the health of man. It has been proved that they are the chief means of perpetuating and transmitting bubonic plague and that they play important rôles in conveying other diseases to human beings. ”

“ Man, dog, cat, horse, cattle, sheep, goat, hog, deer, etc., are subject to the disease either naturally or experimentally. The disease is confined commonly to dogs, because the dog naturally attacks animals of his own species and thus keeps the disease limited mainly to his own kind. Naturally the dog follows this rule, but on the other hand, in the latter stages of the disease he usually goes to the other extreme and even attacks his own master, etc. The dogs that are the most dangerous and do the greatest damage are of the vicious breeds. ”

“ Since that date increasing appreciation of the enormous economic losses caused by these animals, as well as the discovery that rats are primarily responsible for the distribution of bubonic plague and other diseases, has led to much and increasing agitation against them, and to the passing of many laws and regulations for their control. ”

“ Wherever rats might obtain a foothold on the top of the post they may be prevented from gnawing the adjacent wood by tacking metal plates or pieces of wire netting to floor or sill.
[Pg 9] KEEPING FOOD FROM RATS AND MICE.
The effect of an abundance of food on the breeding of rodents should be kept in mind. Well-fed rats mature quickly, breed often, and have large litters. Poorly fed rats, on the contrary, reproduce less frequently and have smaller litters. In addition, scarcity of food makes measures for destroying the animals far more effective. ”

“ The great order Rodentia—rats, mice, rabbits, porcupines, squirrels, beavers, etc., derives its name from the Latin verb rodere, to gnaw, or eat away (something) , and is characterized by the great development of the front (incisor) teeth, by means of which rodents get their living by biting off, or gnawing through, the plants and woody stems on which they feed, or which they use in constructing their dwellings. All are primarily vegetable eaters, yet none will refuse a meal of flesh when opportunity offers to get it, and some are decidedly carnivorous, especially as to fish. ”

“ And similarly, though less obviously, is this the case with the instinct of storing food for winter consumption, which is more prevalent among the rodents than in any other order of mammals—rats, mice, squirrels, harvesters, beavers, &c., all manifesting it with remarkable vigour and persistency. Here we probably have a case of similar organisation and environment determining the same instinct; for the latter [354] is not of sufficiently general occurrence among all species of rodents to allow us to suppose that the species in which it does occur have derived it from a common ancestry. ”

“ But the numbers of any wild creature depend less on its natural rate of increase than on checks, the chief being the want of food at the worst times, especially in the case of domestic parasites like rats, mice, and sparrows. These have no natural enemies in the way of wild birds or beasts of prey to thin their numbers to any extent; consequently they must be kept down by man, or they will only be limited by starvation, and will always increase up to the point which the lowest period of food supply will allow. ”

“ It has also been found that while this species of fleas have their normal residence on the body of rats, they will also desert a rat for man, if the infected rat is dying and no healthy rat is in the vicinity to receive them. It is, then, obvious that to eliminate the disease, the most direct and positive course is to destroy the rats which are the home of the disease. ”

“ To keep down Rats and Mice effectually there must be invented a succession of new modes of action, for these creatures—Rats especially—are so clever that they soon see through our devices, which then fail of effect. Generally speaking, two rules may be prescribed. In the first place it is imprudent to fill up their holes or stop their runs; let them have their way. If you stop them, they will make new thoroughfares, to the further injury of the foundation; and, besides, when you are acquainted with their runs, you know where to put traps and poison for the vermin. ”

“ Rats and Mice are, perhaps, its staple food. Of these it makes great havoc, and is therefore a useful hanger-on to the farm-yard, notwithstanding its occasional depredations in the hen-roost. When it catches a Mouse or Rat, it gives it one bite on the back of the head, piercing the most vulnerable part of the brain, and killing instantly. ”

“ We feel at first naturally inclined to attribute the result to loss of health, or at least to loss of vigour; but this view can hardly be admitted when we reflect how healthy, long-lived, and vigorous many animals are under captivity, such as parrots, and hawks when used for hawking, cheetahs when used for hunting, and elephants. The reproductive organs themselves are not diseased; and the diseases, from which animals in menageries usually perish, are not those which in any way affect their fertility. No domestic animal is more subject to disease than the sheep, yet it is remarkably prolific. ”