# National Geographic Magazine/Volume 32/Number 1/The Rat Pest
## The Labor of 200,000 Men in the United States Required to Support Rats, Man's Most Destructive and Dangerous Enemy

By Edward W. Nelson, Chief of the U. S. Biological Survey
Readers of the Geographic will recall with pleasure Mr. Nelson's informative article on the Larger North American Mammals, published in this magazine in November, 1916, and illustrated by a remarkable series of four-color reproductions of paintings by Louis Agassiz Fuertes. The following article embraces information obtained by Mr. Nelson during years of research and study of mammals, especially rats and squirrels. A third article by this author will be published in an early issue of the Geographic, his subject being the Smaller North American Mammals, illustrated by a second series of 32 pages of color illustrations reproduced from Mr. Fuertes' paintings.
House rats are extremely numerous and are world-wide in distribution. At the present time they destroy annually hundreds of millions of dollars' worth of foodstuffs and other property, and through the distribution of bubonic plague and other diseases cause the deaths of untold numbers of human beings. These facts being known, why should we delay in vigorously using known methods for the elimination from our homes and communities of these wasteful and loathsome pests?
The common house-frequenting rats are of three species, the brown, the black, and the roof rat. All are believed to be natives of Asia, whence they have spread to most parts of the world. In their relations to man their habits are so similar that they may be included in one account. The larger size, abundance, more general distribution, and aggressive predominance of the brown rat, also known as the Norway and wharf rat, has led to its being generally known as “the house rat.”
So far as known, these rodents are always and everywhere thoroughgoing pests, with no usefulness to man.
The history of the brown rat is an extraordinary one, unequaled by that of any other mammal. It was unknown in Europe until 1727, when vast hordes of them swam the Volga River. A year or two later it arrived in England on ships from the Orient. Since that time it has steadily extended its distribution by means of ships and other transportation agencies, and by migrations overland, until it shares with mankind nearly all parts of the earth from Greenland to Patagonia and around the globe.
It is a sturdy, fierce, and cunning animal with extraordinary fecundity. These characteristics have enabled it quickly to overrun and occupy new territory despite the never-ceasing warfare waged against it by man and the competition of other mammals.
The smaller black rat and roof rat formerly existed in most parts of the Old World. They preceded the brown rat also in America, but when the latter arrived were promptly reduced by it to a secondary position or exterminated. Black rats still exist in some parts of the United States, and roof rats are common with the brown rat in the milder climate of the Southern States.

### It may have twelve litters a year

The greater size of the brown rat readily distinguishes it from either of the other species. It averages from one to one and a half pounds in weight and about 18 inches in length. Occasional giants of its kind occur, however, as shown by the capture, near Canterbury, England, of one huge individual weighing over four pounds and measuring 22½ inches in length.
With an abundant food supply brown rats increase with almost incredible rapidity. They have from three to twelve litters a year, each containing from six to more than twenty young, the average being about ten. The young begin to breed when less than three months of age.
Rats are nocturnal and as a rule keep hidden during the day in holes and other places of concealment about buildings or in burrows which they dig in the ground. Within their retreats they make warm nests of shredded fibrous material, often cut from costly fabrics, in which their naked and helpless young are safely brought forth.
After careful investigation the United States Public Health Service estimates that the number of rats living under normal conditions in our cities equals the human population, but that in country districts they are relatively three or four times as numerous.
This estimate is practically the same as that obtained some years ago in Great Britain and Ireland, Denmark, France, and Germany. At intervals, as the result of especially favorable conditions of food supply and weather, extraordinary increases of rats occur over considerable areas and the damage by them is enormously increased.
A vivid realization of the multitude of rats which thrive as parasites on man's industry may be gained from the results of local campaigns against them. In 1904 a plague of rats occurred in Rock Island and Mercer counties, Illinois, and during the month ending April 20 one man killed 3,445 on his farm.
During the campaign of the Public Health Service against the bubonic plague in San Francisco from 1904 to 1907, inclusive, more than 800,000 were killed; and in New Orleans, during 1914 and 1915, 551,370 were destroyed.
During the winter and spring of a single year more than 17,000 rats were killed on a rice plantation containing 400 acres in Georgia, and by actual count 30,000 were killed on another plantation containing about 1,200 acres. On a farm of about 150 acres on Thompson Island, in Boston harbor, 1,300 occupied rat holes were counted and other rats were living about the farm buildings. At a large meat-packing establishment in Chicago from 4,000 to 9,000 have been killed yearly.

### Amazing numbers infest grain vessels

Islands in the tropical or semitropical seas furnish ideal conditions for rats, and in many instances they have increased until they have become intolerable pests, threatening the total ruin of the inhabitants. On one sugar-cane plantation in Porto Rico 25,000 rats were killed in less than six months.
In Jamaica an effort was made to suppress them by introducing the mongoose, which resulted in the establishment of a second pest. In the Hawaiian Islands the introduction of the mongoose caused the rats to take refuge in the tree-tops, where many of them have nests and have arboreal habits, like squirrels. Wherever present on these islands the mongoose has rendered it exceedingly difficult to raise domestic fowls of any kind.
As has long been known, rats are very numerous on ships. After the fumigation of a grain vessel at Bombay 1,300 dead rats were found, and the fumigation of the steamship Minnehaha at London yielded a bag of 1,700. In eight years 572,000 were killed on the London docks, including those on the ships.
As reported to Parliament by the Famine Commission, in 1881, a rat plague existed in southern Deccan and the Mahratta districts of India. Bounties were paid for destruction of rats and more than 12,000,000 were killed. On many occasions, both on the mainland as well as on islands, the unlimited increase of rats has finally led to the almost total loss of crops and other food supplies and resulting famines.
One of the most amazing accounts of the abundance of these animals comes from the Island of South Georgia, on the border of the Antarctic east of Cape Horn. For some years summer whaling operations have been conducted at this island and great numbers of whale carcasses, after being stripped of the blubber, have drifted ashore. The short cool summers and long cold winters of this region preserve the bodies from rapid decay and the rats which have landed from the ships find there a never-ending surplus of meat.
As a consequence they have multiplied until they now exist literally by millions. They make their nests in the grass and peat back from the shore and swarm along well-worn roads they have made on the mountain sides.

### They march like armies

The ready adaptability of rats to their surroundings is one of the qualities which has enabled them to conquer the world. On the approach of warm weather in summer large numbers of them leave buildings and resort to fields on farms, or to the outskirts of the towns, where the growing vegetation, particularly cultivated plants, affords them an abundant food supply until the approach of winter. At the beginning of cold weather they return again to the shelter of buildings, where they find the harvested crops ready for their consumption.
When the food supply suddenly decreases, following a period of plenty during which the rats have greatly increased in numbers, a migratory impulse appears to affect the entire rat population over large areas and a general migration takes place. At such times the rats are extraordinarily bold, swimming rivers without hesitation and surmounting all other natural obstacles. The first invasion of Europe, when rats swam the Volga, was an instance of this kind. Experiments by the U. S. Public Health Service have shown that when released in the water of a harbor rats may swim ashore for a distance of 1,500 yards.
An observer in Illinois, who saw a more local migration, states that he was passing down a road in the moonlight one night in the spring when he heard a rustling in a field near by. Soon a great army of rats swarmed across the road before him, extending as far as he could see. This district afterward suffered severely from the presence of these pests.
The extent to which rats wander from centers of abundance was well illustrated in New Orleans by experiments of our Public Health Service. One hundred and seventy-nine marked rats were released at a point in the residential part of the city. In less than 60 hours one of the marked rats was captured in a trap about a mile from the point where it was liberated, and within two weeks others were taken at various points in a direct line up to a distance of four miles.
Rats are excellent climbers, as every one appreciates who has seen them about barns and other buildings. They have also demonstrated their skill in this in the Hawaiian Islands and elsewhere.
In cities they have been seen to climb iron pipes for the purpose of entering buildings, to travel from one house to another on telephone wires, and to perform other extraordinarily ingenious feats in maintaining themselves.

### Their depredations cover wide range

It is impossible to ascertain with precision the total losses resulting from the depredations of house rats. It is, however, practicable to secure information on which to base reasonable estimates of losses from this source. Rats are practically omnivorous and their depredations cover a wide range. They feed indifferently upon all kinds of vegetable and animal matter.
They dig up newly planted grain, destroy it while growing, and also when in the shock, stack, crib, granary, mill, elevator, warehouse, wharf, and ship's hold, as well as in the bin and feed trough. They eat fruits, vegetables, and meats in the market, destroying at the same time by pollution far more than is consumed.
They destroy enormous numbers of eggs and poultry, as well as the eggs and young of song and game birds. In addition, they invade stores and warehouses and destroy groceries of every description, as well as furs, laces, silks, carpets, and leather goods.
They cause many disastrous fires by gnawing matches, by gnawing through lead pipe near gas meters, or by cutting the insulation from electric wires in order to secure material for nests and by gathering oil-soaked rags and other inflammable material in their nests; flood houses by gnawing through lead water pipes; ruin artificial ponds and embankments by burrowing, and damage foundations, floors, doors, and furnishings of dwellings.
As disease carriers they also cause enormous commercial losses, especially through the introduction of bubonic plague and the resulting suspension of commerce. With the introduction of plague they become directly responsible for business disaster as well as for an appalling mortality.
The extent and variety of their activities may be indicated by citing instances of depredations by them. Much the greater part of losses from these pests is in foodstuffs, which, as already indicated, are destroyed at every stage from the time the seed is planted until they are ready for human consumption.

### A persistent plague

Letters received from different States by the Biological Survey report that in places the freshly planted grain has been dug up so persistently by these pests that it has necessitated a second and even a third replanting. When the corn crop is ripening, they again attack it and sometimes destroy the entire crop in small fields, as was the case in a field on the outskirts of Washington, shown on page 2. When corn or other grain is in the shock, rats take shelter under it and do great damage.
The State Commissioner of Health, writing in 1914 concerning conditions in southwestern Virginia, states that rats consume something like 10 per cent of the grain raised in many of the counties and have destroyed 75 per cent of the young chickens and turkeys. The year this statement was made this section of Virginia marketed $70,000 worth of domestic fowls. Similar complaints from all parts of the country as to the destruction of chickens, turkeys, ducks, and geese on farms, and of eggs, both on farms and in storage, indicate an impressive aggregate loss in these items.
A farmer writes from Iowa that his immediate section is terribly infested with rats, which are very destructive to grain in store. He adds that they are undermining the premises with their holes and practically ruining buildings by gnawing holes everywhere at will. Another farmer in Iowa writes that he lost about 25 per cent of 2,000 bushels of corn held in cribs.
Grain stacks are favorite resorts for these animals and hundreds of them frequently gather there, wasting the farmer's substance. In barns and stables they boldly rob cattle, horses, and chickens of their feed, frequently exacting heavy toll.
Poultry ranches often suffer extremely heavy losses, rats sometimes killing hundreds of young chickens, turkeys, ducks, and geese, and even the full-grown fowls.
A commission merchant in Washington stored 100 dozen eggs in a covered wooden tub in his warehouse and at the end of two weeks discovered that the rats had made a hole in the side of the tub near the cover and had carried away more than 70 dozen eggs without leaving any shells or other sign that a single egg had been broken. The ingenuity rats show in stealing eggs is notorious. It is a mystery how they manage to carry away unbroken such smooth, round objects, even taking them up stairways and over other obstacles.
The number of useful insect-eating birds nesting on the ground or in low bushes which fall victims to rats is extremely large and is one of the many kinds of injury done by these pernicious animals which cannot be computed. Probably few frequenters of the countryside have returned to look into a bird's nest to observe its condition without many times finding it destroyed and fragments of egg shells lying about. Unquestionably a large percentage of such nests located in the neighborhood of buildings have been raided by rats.
On one of the small Danish islands it has been authentically recorded that the progeny of a single pair of rats, which escaped from captivity, in two years time exterminated a great colony of birds for which the island had been noted.
Fresh fruits and vegetables are destroyed in the greenhouse, garden, and field; also during transportation on boats and cars and in markets. Cultivated flowers also are destroyed in greenhouses and gardens, as well as after they are cut for the florist.

### Markets, restaurants, and ships their favorite abode

All ships are known to be infested by rats, and the number killed by fumigation on a single vessel has been known to reach 1,700. Taking into consideration the vast number of vessels engaged in commerce throughout the world, in all of which rats are continually destroying food and other property, it is evident that the sum lost in this way is enormous.
One steamer on a 29-day voyage from India to Antwerp had 44,000 out of 46,000 sacks of grain cut open, entailing an estimated loss of $2,200.
A large milling company in Louisville, Ky., recently asked advice as to controlling the rats and mice on their premises, stating that it has cost them $3,000 a year to repair grain sacks damaged by rodents.
The kitchens and store-rooms of hotels and restaurants are favorite resorts for these pests, which waste and defile far more than they eat. One of the last plague-stricken rats found by the Health Service officers in San Francisco was hidden in a sack of peanuts on the third floor of a warehouse.
In 1898 a large packing-house in Chicago had 3,360 hams destroyed by rats. They are also known to attack living animals, and fat pigs have died as a result of having holes eaten in them. They occasionally gnaw the hoofs of horses until they bleed, and Carl Hagenback was obliged to kill three young elephants owing to incurable wounds made on their feet by rats. When confined in cages the larger rats commonly kill and devour the smaller and weaker ones.
A large department store in Washington at one time lost as high as $30 a night in damaged goods, and a hotel in the same city averaged a loss of $75 a month in damaged linen. One merchant in this city had 50 dozen brooms, worth $2.50 a dozen, destroyed, and another had $500 worth of fine china broken in a single night. A harness dealer lost $400 worth of horse collars in a season. Mail sacks and other bags of all description have holes cut in them, and ivory on shipboard or on the docks is gnawed and its value seriously reduced.
In addition to the losses of foodstuffs and merchandise, rats seriously injure buildings, sometimes by burrowing and persistent gnawing almost destroying the foundations. They cut holes in the floors, walls, doors, as well as in chests, wardrobes, bookcases, and closets.
Through rat infestation buildings are sometimes rendered uninhabitable, forcing the tenants to abandon them and causing heavy losses to the owners. An entire block of small houses in Washington was deserted for this cause, resulting in the loss of $2,000 in rents. Occasionally a building is so undermined and weakened by these pests that it must be torn down.

### Incredible numbers in Australia

House mice share a world-wide distribution with rats, and, while much smaller, are to be included with the rats as wasters of food and destroyers of other commodities. Occasionally they increase in numbers until they rival the rats in their destructiveness. Any campaign for the suppression of the rat pest should, as a matter of course, include house mice.
The potentiality existing in these small animals to cause great losses of foodstuffs is now being demonstrated in Victoria and New South Wales, Australia, where during the last few months a plague of mice has developed. Enormous numbers of mice have swarmed about huge stacks containing millions of sacks of wheat, riddling the sacks and causing the stacks to collapse.
The Melbourne Leader of May 26, 1917, states that “in some centers the ravages of mice are so great that huge stacks erected some months ago now resemble heaps of debris.” The President of the Chamber of Agriculture estimated that the loss might exceed £100,000.
In New South Wales the Wheat Board began a campaign against the mice by double fence traps. The catch for two nights in one place is reported to have totaled seven tons weight of mice. At another point 56,000 mice were caught in four nights. A later report states that the mice had turned their attention to the seed in some districts where sowing had begun and as a result of their depredations further sowing operations had to be discontinued.
Dr. Danysz, of the Pasteur Institute of Paris, estimated the damage from field mice in France during 1903 to approximate £1,000,000.

### Hundreds of millions of dollars destroyed annually by rats

Rats have been pests so long that they have been taken for granted by the public, much as is the weather or the forces of nature. While people are often painfully aware of individual losses, they are unaware of the vast total which these individual sums aggregate and the consequent need of community action against the authors of such far-reaching economic drains.
Denmark, one-half the size of South Carolina, estimated her losses in 1907 at about $3,000,000. The same year the losses in the rural districts of Great Britain and Ireland, not counting those in towns and on ships, were estimated at $73,000,000, and a capital of about $10,000,000 was profitably employed there in the industry of supplying means for their destruction. In 1904 the losses in France were computed at $40,000,000.
The United States has nine times the combined area of the three countries mentioned, and investigations indicate that the direct annual losses sustained here undoubtedly equal, if they do not exceed, $200,000,000, with a great additional sum in indirect losses, including the effect on the public health and commerce from the diseases carried by rats, and the necessary expenditures in combating them. The foregoing figures are based on pre-war prices and are vastly greater under present valuations.
In Europe, about 1907, after careful investigation, the estimated average annual loss caused by each rat was computed to equal $1.80 in Great Britain, $1.20 in Denmark, and $1 in France. In the United States the average is undoubtedly much larger than in any of the countries named, especially at present high prices of food and other merchandise.
There is no doubt that a very large number of rats subsist wholly on garbage and waste which is of no value, but the damage caused by rats in numerous places amounts to many dollars each a year; probably $5 a year would not be an overestimate for the average loss caused by each rat living in a dwelling, hotel, restaurant, or other place having ready access to food supplies.
Assuming, roughly speaking, that as estimated the rat population in the United States is 50,000,000 for the cities and 150,000,000 for the rural districts, it will require the destruction of property by each rat of only a little more than one-fourth a cent a day to make the aggregate great sum estimated as destroyed by these pests yearly in this country.
In 1907 a careful survey was made of the damage done by rats in Washington. More than 500 business establishments, including factories, stores, livery stables, hotels, and restaurants, were visited. As a result of this inquiry the total losses for the city were estimated at $400,000 yearly. A similar inquiry in Baltimore indicated that the annual losses in that city were about $700,000.

### 200,000 men are now working solely to feed the rats

A more definite idea of the losses from rats may be gained by considering what it means in human effort.
Taking the average yearly returns on a man's labor in agriculture, as shown by the census of 1910, it requires the continuous work of about 150,000 men, with farms, agricultural implements, and other equipment, to supply the foodstuffs destroyed annually by rats in the United States. In addition, rats destroy other property, mainly of agricultural origin, the production of which requires the work of about 50,000 men.
This gives a total of 200,000 men, with their equipment, in this country, whose economic output is devoted solely to feeding and otherwise providing for rats. If a small fraction of this army and the money involved could be concentrated in a continuous national campaign against these pests a vast saving could be achieved.
By a nation-wide effort to increase rat-proofing of structures, and to cause a stricter guardianship of food products, combined with the destruction of rats, the number of these pests could be so greatly diminished that the losses from this source would soon be reduced one-half.
Rats should be exterminated not only to stop the tremendous losses of food and other property, to which attention has already been drawn, but in order to protect humanity from some of its most dreaded diseases. It has been conclusively proved that these rodents are practically the sole distributors of the bubonic plague which is communicated to human beings from infected rats by means of fleas.

### They spread the plague

The history of the plague runs back several centuries before the Christian era. There were particularly deadly outbreaks of it in Europe during the Middle Ages. In the fourteenth century it killed from two-thirds to three-fourths of the population of several countries, and it has been estimated that 25,000,000 people died in Europe from this disease, which was known as the “black death.” Sir James Crichton-Browne, president of the Society for the Destruction of Vermin, has recorded the fact that in 1907 2,000,000 deaths from the rat-borne plague occurred in India.
The bubonic plague appears to have periods of quiescence, or what might be called periods of incubation; but it is possible that these periods of inactivity may be due to the great reduction in the rat population due to the disease. Suddenly it appears to become virulently active and spreads with startling rapidity. This accounts for its recurrence at varying intervals since the dawn of history.
The chronicles of the sea, before the development of steam power, contain many grisly tales of plague ships drifting helplessly on the ocean, their crews stricken with the mortal disease which we now know must have been carried on board by rats. The serious menace from this source still exists in the face of all our modern knowledge.
In the fifteen years following the outbreak of plague in Canton, China, in 1894, this disease was discovered on 156 ships, and 51 countries are known to have been infected through its distribution by commerce.
The disease was introduced into the United States at San Francisco, where, in order to control it, the United States Public Health Service made a successful campaign against rats, which resulted in rat-proofing much of the city, and thus materially bettering conditions.
Meanwhile, unfortunately, the plague-bearing rats had passed the disease on to ground squirrels living abundantly in the hills surrounding San Francisco. Owing to the wide-spread distribution of ground squirrels in the United States, their proved susceptibility to this disease greatly increases the danger of future outbreaks of the plague in this country.
When it was learned that the bubonic plague is a rat disease which is transmitted to human beings by fleas, it became possible to fight it with intelligence. Owing to the universal distribution of rats and the increase of commerce between communities, the need of incessant vigilance to guard against sudden outbreaks of the plague is evident.
Only through the elimination of these rodents, or a very great reduction of their numbers and their control, can the world feel secure from this dread disease. Although the upkeep of quarantine precautions and other defensive measures against rats in the ports of the world, as well as in interior cities, amounts yearly to a great sum, it is worth all it costs.
In addition to transmitting the bubonic plague, the house rat is known to convey infection of trichinosis, septic pneumonia, epidemic jaundice, and rat-bite fever. It is also afflicted with rat-leprosy, a disease so like human leprosy that they are scarcely distinguishable, and the relationship of the two is still undetermined. Owing to the fact that rats haunt drains, garbage deposits, and other accumulations of filth, it is unquestionably a potential distributor of diphtheria, typhoid, scarlet fever, and infantile paralysis.

### Thieves of fertile brain

Since the early days rats of one species or another have been a burden to mankind.
The burdensome abundance of rats in Europe during the Middle Ages is indicated by the numerous legends which have come down from that time. The popular folk tale of the Pied Piper of Hamelin and its variants originated in the thirteenth century. The tales of wicked men being devoured by swarms of rats sent as a punishment for their misdeeds and the account of the death of Bishop Hatto by an attack of these rodents in a tower where he had taken refuge run back to the tenth century.
They were such persistent pests at that time and so difficult to control that many efforts were made to rid communities of them. They were anathema and persistent efforts were made to ban them by bell and book, as well as through exorcisms and other mystic ways of the “Black Arts.”
A translation of an old Gaelic exorcism against these rodents might well express the farmers' feelings at the present day. One stanza reads:
   “No corn in sheaf, nor barley snugly stacked.  Could serve thy turn; but all my garnered grain,  In well-filled sacks, is next by thee attacked.  And all is spoiled, thou thief of fertile brain;  And all my sacks are nibbled, too, and holed—  A sight most aggravating to behold.”
In 1745 the first modern attempt to control the rat pest by law was made in the English colony of Barbados, in the West Indies. Another law was passed in 1880, on the West Indian island of Antigua.
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.
Emil Zuschlag, a Danish engineer who had studied and become thoroughly impressed with the great economic waste produced by rats and mice, organized a Danish society which had a membership of more than two thousand men of standing and influence for the purpose of combating these rodents. The activities of Zuschlag and the proof he gathered of the enormous destructiveness of rats led to the passage, in 1907, of the Danish rat law. Zuschlag also formed a second society, entitled “L'Association Internationale pour la Destruction Rationelle des Rats,” in which every country of Europe was represented officially or otherwise except Great Britain. In the latter country was organized for a similar purpose “The Incorporated Society for the Destruction of Vermin.” Subsequently, England and other countries in Europe and elsewhere passed laws promoting the destruction of rats.

### The opportunities for our citizens

Rats have been for so long a time a part of man's environment that he has finally come to accept them more or less as a matter of course. As the result, notwithstanding the enormous losses from them, it is difficult to awaken the vast majority of the public to the gravity of the situation in order that a continuous and earnest campaign may be made for their suppression.
Rats are quickly responsive to the conditions of life in every locality, and where poorly kept buildings exist and food is plentiful they will continue to abound. The householders or community abolishing sheltering places of rats and guarding food supplies from them, and trapping the resident animals, will soon have a marked diminution in their numbers.
They will, however, continue to be annoyed by the inroads of rats from neighbors, thus strongly evidencing the need of a still wider campaign against them. Any person failing to abolish rat shelters on his property is maintaining a public nuisance, menacing not only his own property and the health of his family, but that of his neighbors and the community at large.
On premises where rats occur traps should be used persistently to keep down the number, as they will continually come in from elsewhere. By a small reward to the juvenile members of the family for rats captured the pests may be kept down and the primitive joys of the chase experienced by the young trappers. The popular estimate of the usefulness of cats and ferrets in catching rats and mice is very much exaggerated.
The personal relief to be had by persistently trapping rats on the premises is indicated by the results at a suburban summer home near Washington, where from fifty to sixty (and several hundred mice) are captured each year. Without this reduction in numbers rats would increase and render conditions extremely burdensome.
Civic organizations which desire to better conditions in their communities have no more fertile field before them than that of controlling rats among the markets and establishments dealing in produce and other food in their cities. A large part of the food supplies of nearly all of our communities is handled in places swarming with rats and mice.
Produce dealers are usually located on contiguous premises, usually in old buildings under which the ground is honeycombed with rat burrows and the walls are so riddled with holes that rats pass freely from store to store through entire city blocks. Here meats, poultry, fish, fruits, and vegetables are dealt with in great quantities. For a large part of each day rats in almost unlimited numbers swarm in and over this food, eating some of it, and polluting quantities of it which pass on to the consumer.
These repulsive conditions prevail largely because property owners desire to avoid the expenditure necessary to rat-proof buildings. This could be done at so small a cost that it is a discredit to civilization that communities of intelligent people should tolerate such unsavory and unhealthy conditions.

### Our U. S. Public Health Service leads the way

Ordinances should be passed and rigidly enforced forever to end this situation. The cost of the proper rat-proofing measures would quickly pay for itself in the saving of foodstuffs, and would warrant increased rent to the owners, in addition to conferring a lasting benefit on the communities involved.
Surgeon General Blue's dictum that “rats must be built out of existence” well indicates the importance of rat-proofing in the war against these rodents.
One of the most effective campaigns ever conducted against rats has been that of the United States Public Health Service for the purpose of eradicating bubonic plague from San Francisco and New Orleans and to prevent its gaining a foothold in other American ports, but the results were much less than they might have been with more extended coöperation.
Zuschlag and others who have given the rat question serious study have agreed that it will be extremely difficult to secure the far-reaching results so desirable in the control of this public menace except by international action. The fact that when rats are destroyed in one area they tend to reinfest it from surrounding regions greatly lessens the effectiveness of local campaigns. For this reason, while local campaigns are useful and extremely desirable in relieving local conditions, the final great public relief will come when the campaign is broadened to international proportions.
At this time, when all civilized nations are care-ridden with the fear that gaunt Hunger may stalk through the world, it is essential that foodstuffs be safeguarded as never before. To accomplish this the main sources of preventable waste should be located and controlled. The foregoing pages have shown that among these elements of waste the house rat stands preëminent and deserves the most serious attention.

### Rats should not be tolerated at a time when the entire world fears a world famine

The remedies against this pest are comparatively simple and may be put in effect to advantage by every householder, as well as by mercantile establishments and organizations. For modern communities to continue to harbor these loathsome parasites is merely to prolong the survival of careless methods of individual and community housekeeping incident to barbarous times. Every health officer and every well-informed person knows the extending menace these pests present to himself and neighbors. Why, then, should we not cease feeding and sheltering them?
It should be kept in mind that so long as good shelter and plenty of food are available rats will thrive and increase. Under such conditions trapping alone will be ineffective, since unless otherwise controlled the supply of rats will be inexhaustible. Use concrete, wire netting, and sheet metal to rat-proof buildings, and keep food and foodstuffs within rat-proof containers (or buildings), and the number of rats will naturally diminish. Then by means of traps or poison the survivors can be readily eliminated from the premises.
Rat-proofing in some degree, as well as extra care in safeguarding food supplies, whether in the granary or pantry, should accompany all efforts to eliminate rats. By these methods the householder may free himself from their obnoxious presence.
It may be stated here that many claims have been made as to the effectiveness of different serums and viruses for the destruction of rats by spreading contagious diseases among them; but extended experiments, particularly in this country, have, so far as the writer is informed, failed absolutely to give the desired results. The reliable and successful remedies lie in the use of concrete and other modern building materials, with effective traps and poison used thoroughly in active, individual, community, and national campaigns.

### Organized efforts are necessary

The only really satisfactory way of handling the rat problem is by organized efforts. This is particularly true, owing to the fact that even with all property owners doing their duty many public and semi-public places will remain to be treated. Here is where civic organizations, including boards of trade, may take leading parts. Rat-proofing and the formation of rat clubs for killing these rodents may be promoted in addition to encouraging individual efforts. The following suggestions are for action along these lines:
* The public may be educated in methods of rat-proofing, protecting food supplies, and trapping and poisoning rats and mice.
* Funds may be raised for the payment of premiums or prizes for killing rats in contests arranged under local organizations or committees.
* The campaign can be enlarged by civic organizations, not only securing neighborhood action, but by their assistance in bringing about more general action.
* Voluntary coöperation for the public welfare in this matter should bring about municipal ordinances as well as State and National legislation. A beginning of such legislative action has been made in the United States, notably in New Orleans and San Francisco.
The State of Indiana has a drastic law providing for the destruction of rats on all premises, and giving the Governor authority to set aside one “rat day” in spring, when the public should join in a general effort to destroy these pests throughout the State. Unfortunately this law makes no provision for rat-proofing as well as killing rats, and until amended will be seriously defective. Meanwhile, through lack of proper public sentiment behind it, the law is not being enforced.
Measures for the control of rats should provide for certain fundamental requirements as follows:
New buildings should be made rat-proof under rigid inspection.
Existing rat-proof buildings should be closed to rats by wire mesh or fine grating over all windows and doors accessible to them. Old buildings not rat-proof should be remodeled and concrete, wire mesh, and other material used to render them practically rat-proof.
Harboring places, such as old sheds, piles of trash, old lumber, wooden sidewalks, open stone walls, and garbage dumps, should be abolished.
All garbage and food waste on which rats may feed should be protected from them and promptly removed.
All markets and other public buildings should be promptly rat-proofed and frequently inspected.
All ships engaged in sea-going, coastal, and inland waterway traffic should be fumigated at stated intervals for the purpose of destroying the rats which harbor in them and are thus transferred from place to place.
So-called civilized man has had with him from barbarous times a variety of vermin, including insects and mammals, nearly or quite all of which are carriers of deadly diseases. Only within a comparatively few years have advancing knowledge and public sentiment combined to bring about any considerable efforts to subdue and eliminate these pests. The public is rapidly awakening, however, to the dangers involved in them and is becoming more and more determined in its efforts to control these causes of enormous losses, both in property and human life.
Through the efforts of Dr. L. O. Howard and others, the house fly—the “typhoid fly,” as it has been well termed—is now under the ban of general public disapproval.
The Spanish War developed the fact that the mosquito was the carrier of yellow fever. Another type of mosquito is known to be the carrier of malaria. The European War has brought to almost universal public knowledge the fact that body lice are carriers of the deadly typhus, and many diseases are known to be carried by other insects.
Among these deadly carriers of death and destruction none equals the house rat in its tremendous drain on the prosperity of nations by its destruction of food and other property, while at the same time it is the deadliest of all to mankind as a disease carrier. Within historic times it has caused the death of untold millions of human beings and its devastations are still in progress.
There is little doubt that the time will arrive in the not distant future when persons maintaining rat-breeding resorts on their premises will be looked upon with the same disfavor that now visits those who harbor vermin of a lowlier degree.
Source: Edward W. Nelson (July 1917), “The Rat Pest”, The National Geographic Magazine 32(1): 1–23.
Notes:
* ↑ A bulletin giving brief practical advice for rat-proofing structures and for destroying rats has been published for distribution by the Biological Survey, U. S. Department of Agriculture, Washington, D. C. Written inquiries for expert information on these subjects may be directed to the same address.