Part 21
The best pot in which to burn sulphur is 6 inches deep, has a flare of 6 inches—that is, the diameter at the top exceeds the diameter at the bottom by that much, is from 16 inches to 24 inches in diameter at the top and has four hemispherical legs about the size of half a billiard ball. These pots when in use are set in a galvanized iron tub. These tubs contain a little water, and are of a diameter 6 inches greater than the top of the pot. The hemispherical legs of these pots will not punch holes into the tub. The pots are filled with sulphur, which is hollowed out into a little crater at the top, into which crater from 4 to 6 ounces of alcohol are poured and when all are ready a lighted match is dropped into each little crater and the compartment is closed.
In actual practice it was found that an exposure of five hours to a 3 per cent gas would not destroy all the rats in absolutely every case. Some ships afford better hiding places than others, and on these an occasional rat would escape. It was the custom, however, to fumigate all vessels every thirty days and after the third fumigation, on vessels that did not carry general cargo, no more rats were obtained, though the fumigations were continued for a number of months.
On those vessels that carried miscellaneous general cargoes a few rats were found after almost every fumigation. These vessels touched no wharf from the time they left San Francisco until their return, except for a short time in Honolulu, where adequate precautions were observed, and it is difficult to understand how these rats got on board if they were not carried on in cargo.
For vessels with cargo in their holds the pot and pan method is dangerous owing to the possibility of fire. For these vessels one of the other methods of generating the sulphur gas must be used. This involves the use of an expensive plant consisting of a furnace, cooling chamber, blower, or fan, and a system of mains and delivery pipes by means of which the gas is delivered to the various holds and compartments of the vessel. To be at all effective the gas must be 4½ per cent strength, with at least twenty-four hours exposure. The one recommendation of such a system is its freedom from danger by fire. It is too slow; the pipes, even where 6 inches in diameter, are liable to clogging with sublimed sulphur, an inevitable result if the fans are driven too rapidly, and it is not possible to do more than one or at most two ships at a time. The inadequacy of such a method when compared to the work done in San Francisco where we averaged over nine vessels every day for almost fourteen months is at once apparent. Many ships now carry their own disinfecting plants, by means of which not only is sulphur dioxide generated and pumped into a compartment, but at the same time also the air of this space is sucked out. This principle is excellent, but in its application the machines used are wholly inadequate, having a very limited sulphur capacity per hour and equipped with delivery pipes in many instances only 2 or 3 inches in diameter. It would be a matter of days to disinfect some of these ships with the machines they carry. In San Francisco we again and again used pots and pans to fumigate these vessels, including the very compartments in which their own machines sat doing nothing.
The Marot system of generating the gas from compressed liquid sulphur dioxide has in this country been found too expensive to apply to vessels. Probably no system will effectually destroy all the rats on a cargo-laden vessel.
SUMMARY.
To summarize then:
1. The rat is found on all vessels, sometimes in enormous numbers, and is able to adapt himself to all sorts of conditions. He either gets on board himself or is carried on in cargo. Owing to his seagoing tendency, his distribution is world-wide.
2. On shipboard, to live he must do damage to either cargo or stores, or both.
3. Plague is primarily a rat disease; it may exist in the rat in a chronic form. Hence where ships go plague will go sooner or later.
4. To prevent the ingress of rats and the consequent spread of plague, ships should observe antirat precautions, and cargo inspection should be included in these.
5. At stated intervals, three or, better still, four times a year, all vessels should be fumigated for the destruction of rats.
6. On empty vessels this can best be done by generating sulphur by the pot and pan method.
7. On laden vessels some special apparatus must be used to generate the gas. A longer exposure is required, at least twenty-four hours, and the gas should be 4½ per cent strength instead of 3 percent. It is extremely difficult by any method to kill all the rats on a cargo-laden vessel.
THE RAT AS AN ECONOMIC FACTOR.
By DAVID E. LANTZ,
_Assistant Biologist, United States Department of Agriculture_.
INTRODUCTION.
The world has rightly learned to dread rats as disseminators of disease, and recent efforts to rid cities of the pests have resulted chiefly from sanitary considerations. Yet the material losses due to depredations of rats are now, and always have been, a sufficient argument for their destruction. The requirements of sanitation and public health are slowly bringing to pass what economic interests failed to accomplish, namely, a general recognition of the fact that the rat is a standing menace to prosperity. To point out some of the many ways in which rats inflict injury and the extent to which they drain the resources of the people is the object of the present chapter.
UTILITY OF THE RAT.
Do rats serve any useful purpose? With very slight reservation, the question may be answered in the negative. There have been times and places in which the rat’s work as a scavenger accomplished good, but modern methods of garbage disposal are superseding the feeding it to rats.
It was Robert Southey, the poet, who, nearly a century ago, humorously suggested as the first three steps to eradicate rats—first, introducing them as a table delicacy; second, utilizing the skins; and third, inoculating them with a contagious disease.[BY] The last of these plans is now receiving considerable attention from bacteriologists, but the others, for obvious reasons, have been neglected.
Footnote BY:
Omniana, vol. 1, p. 25, 1812.
It is true that under exceptional circumstances the rat has been a source of human food. The principal instances on record were during the siege of Paris in 1870, and during the siege of the French garrison at Malta, 1798–1800, when food was so scarce that rat carcasses brought high prices. Another was on board the ship _Advance_ during an arctic winter, when Doctor Kane attributed his entire immunity from scurvy to his diet of fresh rats, of which none of the other members of the party would partake.[BZ]
Footnote BZ:
Second Grinnell Expedition, vol. 1, p. 393, 1856.
The statement is often made in newspapers, and even in encyclopedias, that in Europe, and especially in France, rat skins are extensively used in the manufacture of gloves. The late Frank T. Buckland, about a half century ago, made diligent inquiry in London, and through friends in Paris and other places on the Continent, but found no confirmation of such statement. He concluded that either rat skins were not used for making gloves or the manufacturers were unwilling to acknowledge such a use.[CA] Personally, the writer has been unable to learn of any demand or market for rat skins at the present time. They are not strong, and the fur is of inferior quality. The occasional finding of one or more rat skins in the fur lining of coats is probably to be explained by the fact that they are sometimes included in lots of small muskrat skins (“kitts”) and overlooked by the buyer.
Footnote CA:
Curiosities of Natural History, first series, p. 83, 1857 (Reprint 1900).
DESTRUCTIVENESS OF THE RAT.
Rats inflict injury in a surprising number of ways, and before an attempt is made to consider the magnitude of the losses due to these animals a statement of the nature of their depredations should be made.
DAMAGE TO GRAINS.
Cultivated grains are the favorite food of rats. The animals begin their depredations by digging up the newly-sown seed. They eat the tender sprouts when they first appear, and continue destroying the plants until the crop matures. They then attack the grain itself, and after harvest take toll from shock, stack, mow, crib, granary, elevator, mill, and warehouse. When rats are abundant their depredations amount to an appreciable percentage of the entire yield of grain, and in exceptional cases whole crops have been ruined.
INDIAN CORN.
Probably this crop suffers greater injury from rats than any other in the United States. To some extent the animals dig up newly planted corn, but their injury to the maturing grain is far greater. They are especially fond of corn in the milk stage, and often climb the upright stalks and strip the cobs bare. In this way sometimes whole fields are destroyed.
Corn in the shock is often attacked by rats, especially in parts of fields adjacent to hedges, drains, or embankments that afford shelter for the animals. A pair of rats often make a corn shock their home, and soon destroy both grain and fodder.
Corn in cribs is often damaged by rats. Many cribs are built close to the ground, and rats take up their abode under the floor. They soon gnaw through the wooden barrier and have free access to the grain. They shell the corn and eat the soft part of the kernels, wasting much more than they eat. They carry the grain into underground burrows and bring up moist soil from below, which in contact with the grain makes it moldy and unfit for market or for feeding to stock. A number of farmers have reported the loss by rat depredations of from a fifth to a half of the contents of a large corn crib during a single winter.
An Iowa farmer, writing to an agricultural journal, relates the following experience:
We had about 2,000 bushels of corn in three cribs to which rats ran, and they ate and destroyed about one-fourth of the corn. Much of it was too dirty to put through the grinder until it had been cleaned an ear at a time. All the time we were poisoning and trapping the rats. We killed as high as 300 rats in two days and could hardly miss them. They destroyed more than enough corn to pay taxes on 400 acres of land.[CB]
Footnote CB:
Missouri Valley Farmer, April, 1907.
Throughout the United States, but especially in the West and South, corn is often stored for months in rail or other open pens, to which rats have free access. Often the loss in a single season would pay for the construction of rat-proof cribs, or at least for wire netting, that would fully protect the crop.
SMALL GRAINS.
Much has been written about the rat as a house and barn pest, but its depredations in the fields have usually been overlooked. In some localities the common rat, as well as the house mouse, swarms in the fields, especially in summer, and subsists entirely upon the farmers’ crops.
Stacked grain is peculiarly exposed to rat depredations. In the United States, although the cost of protection is small, rats are seldom fenced away from stacks, and, if threshing is delayed, serious loss results. Often, at the removal of a stack, large numbers of rats are discovered, which have been living at the expense of the farmer. As early as 1832 a farmer in Frederick County, Md., with the help of men and dogs, killed 217 large brown rats from one stack of rye.[CC] In England instances are on record of the killing of over a thousand rats from one stack of wheat.
Footnote CC:
Am. Turf. Register, vol. 3, p. 632, August, 1832.
The destruction of feed by rats is a serious loss not only on the farm but also in city and village. The feed bin or barrel is often left uncovered and rats swarm to the banquet thus exposed. Small feeders suffer greater proportional losses, for managers of larger barns recognize the enormous drain and usually provide rat-proof bins, if not rat-proof stables. When rats have access to a stable they take a good share of the feed directly from the mangers, but the loss is seldom noticed.
Rats are exceedingly fond of malt, and in malt houses and breweries constant watchfulness is needed to prevent losses. Mills, elevators, and warehouses in which grain and feed stuffs are stored are subject to constant invasion by rats and mice.
A full-grown rat consumes about 2 ounces of grain daily. A half-grown rat eats nearly as much as an adult. Fed on grain, therefore, a rat eats from 45 to 50 pounds a year. The cost depends somewhat on the kind of grain. If wheat, the value is 60 to 75 cents; if oatmeal, about $1.80 to $2. Several feeders of horses in Washington, D. C., estimated the cost of keeping each rat on their premises at $1 a year. Even though half the grain eaten is waste, the direct loss from this source to feeders is enormous.
MERCHANDISE IN STORES AND WAREHOUSES.
The loss from depredations of rats on miscellaneous merchandise in stores, markets, and warehouses, is second only to the losses on grains. Not only are food materials of every kind subject to attack, but the destruction of dry goods, clothing, books, leather goods, and so on is equally serious. Merchandise other than foodstuffs is usually destroyed for making nests, but books and pamphlets, especially the newly bound, and some other articles, furnish food in the glue, paste, oils, or paraffin used in their manufacture. Some kinds of leather have a peculiar attraction for rats, while others are never touched. Shoes are seldom gnawed unless they have cloth uppers or are made of kid. New harnesses are not often attacked, except collars, which contain straw, and cruppers, which are stuffed with flaxseed. Old harness leather is salty from the perspiration of horses, and rats and mice gnaw it for this reason. Kid gloves and other articles made of similar leather are often destroyed by rats.
Lace curtains, silk handkerchiefs, linens, carpets, mattings, and other dry goods in stores are often attacked by rats. Some of the stuffs contain starch, which serves as food, but most of them furnish nesting materials only. A slight injury makes these articles unsalable; this is especially true of white goods, which are easily ruined by soiling. Nearly all large dry goods and department stores suffer heavy losses from rats. Grocers, druggists, confectioners, and other merchants also have similar experiences, and to the direct losses must be added the sums expended in fighting the pests.
MERCHANDISE IN TRANSIT.
Merchandise billed for shipment often lies for days in stations and warehouses or on wharves, where depredations of rats and mice cause heavy losses to shippers and consignees. Similar losses occur on boats carrying merchandise from port to port.
Fruits and vegetables in transit on steamboats are often destroyed or damaged by rats. Tomatoes, cucumbers, sweet potatoes, bananas, oranges, grape fruit, peanuts, and similar produce shipped by water from the South, especially in winter, reach northern markets with a large percentage of loss.
In view of the practicability of destroying rats on ships by fumigation, and the ease with which rat-proof compartments for stowing produce can be constructed, it would seem that losses of this nature should be entirely prevented.
POULTRY AND EGGS.
Aside from disease, the greatest enemy of poultry is the rat. The loss from rats varies with their abundance and the care taken to exclude them from the poultry yard. The magnitude of the damage is not generally known, because much of it is blamed on other animals, particularly minks, skunks, and weasels. Much of the injury occurs at night, and the actual culprit is seldom detected. Farmers have heard that minks, skunks, and weasels prey upon poultry. What more natural than to conclude that one of these animals is doing the mischief, especially if one has been seen about the premises?
Rats often prey upon small chicks, capturing them in the nests at night or even about the coops in the daytime. The writer has known rats to take nearly all the chicks on a large poultry ranch, and over a large section of country to destroy nearly half of a season’s hatching. Young ducks, turkeys, and pigeons are equally liable to attack, and when rats are numerous, are safe only in rat-proof yards.
A writer in a western agricultural journal states that in 1904 rats robbed him of an entire summer’s hatching of three or four hundred chicks.[CD] A correspondent of another newspaper says, “Rats destroyed enough grain and poultry on this place in one season to pay our taxes for three years.”[CE] When it is remembered that the poultry and eggs marketed each year in the United States have a farm value of over $600,000,000, it will be seen that a small percentage of loss represents an enormous sum.
Footnote CD:
Homemaker (Des Moines, Iowa), May 27, 1907.
Footnote CE:
Missouri Valley Farmer, April, 1907.
The destruction of eggs by rats is great, not only on the farms where they are produced, but also in the markets. Commission men and grocers complain of depredations upon packed eggs. The animals break and eat a few eggs at the top of a case and the broken yolks run down and soil the eggs below. Then, too, rats carry away unbroken eggs, displaying much ingenuity in getting them over obstacles, as up or down a stairway.
A commission merchant in Washington, D. C., states that he once stored 100 dozen eggs in a wooden tub in his warehouse and left them for nearly two weeks. He then found that rats had gnawed a hole through the tub, just under the cover, and had carried away 71½ dozen, leaving neither pieces of shell nor stains to show that any had been broken.
Besides their destruction of eggs and young fowls, rats eat much of the food put out for poultry. They are destructive also to tame pigeons and their eggs, but particularly to young squabs. They climb the wire netting and gain entrance to the cages through the same openings by which the pigeons come and go. Fanciers are often put to great trouble to protect their pigeons from rats, and because of these pests some of them have abandoned the business.
GAME AND WILD BIRDS.
The rat is the most serious pest in European game preserves. A writer in Chambers’s Journal says:
In a closely preserved country at the end of an average year the game suffers more from the outlying rats of the lordship than from the foxes and mustelines together. The solitary rats, whether males or females, are the curse of a game country. They are most difficult to detect, for in a majority of cases their special work is supposed to be done by hedgehog, weasels, or stoat.[CF]
Footnote CF:
Chambers’s Journal, vol. 82, p. 64, January, 1905.
The propagation of game birds is becoming a promising industry in the United States. The difficulties of the business are not yet fully known, but the rat is an enemy with which the raiser of game will have to contend. The animal has already proved itself a foe in American pheasantries.
Our wild native game birds are less subject to rat depredations than birds kept in confinement. The nests of ruffed grouse are in woodlands; those of the prairie hen and related species are on plains remote from the haunts of rats. The quail, however, often makes its nest within the summer range of rats, which destroy many of its eggs.
Rats are said often to destroy the nests of wild ducks, woodcock, and other marsh birds. Terns have been entirely driven from their nesting grounds in this way. In England the common tern was extirpated from the Thames marshes; and on Loggerhead Key, Tortugas Islands, off the Florida coast, rats recently nearly exterminated a colony of least terns by destroying the eggs.
The nests of many ground-nesting and other song birds are robbed by rats. Crows, jays, snakes, and skunks are blamed for most of the destruction and the actual offender seldom suspected. While the other animals named do part of the mischief, the rat is a more serious foe of song and game birds than any of these.
FRUITS AND VEGETABLES.
A well-known form of damage by rats is the destruction of fruits and vegetables in cellars and pits. Apparently no garden vegetable or common fruit is exempt from attack. But the rat does not confine its depredations to stored fruits and vegetables. It attacks ripe tomatoes, melons, cantaloupes, squashes, pumpkins, sweet corn, and many other vegetables in the field; and often the depredations are attributed to rabbits or other animals, which may or may not be concerned in the mischief.
Rats are fond of the small fruits, eating not only the fallen but climbing vines and canes to obtain the ripe grapes or berries. They eat also apples, pears, cherries, and other fruits. The brown rat, while not so expert as the black or the roof rat, readily climbs trees and obtains fruit even at the extremities of the branches.
Among tropical fruits injured by rats are oranges, bananas, figs, dates, cocoanuts, and especially the pods of cacao (_Theobroma cacao_), from which chocolate is manufactured. H. N. Riddey, writing of his experiences on the island of Fernando do Noronha, South America, mentions the destructiveness of rats in this penal colony. They climb the cocoanut palms and papaw trees to devour the fruit, and do mischief in melon patches. To lessen the evil, each convict was required to bring in a certain number of dead rats, and battues were held monthly to satisfy the requirement. Sometimes the number killed in a single hunt reached 20,000.[CG]
Footnote CG:
Zoologist, vol. 46, p. 46, 1888.
Fruits and vegetables grown under glass are subject to injury by rats. The animals usually find entrance to greenhouses by way of openings for pipes or drains.
FLOWERS AND BULBS.
Rats attack seeds, bulbs, and the leaves, stems, and flowers of growing plants, whether in the greenhouse, propagating pits, or elsewhere. Of flowering bulbs, the tulip suffers most from rats. Hyacinths also are eaten; but, probably because they are slightly poisonous, narcissus and daffodil bulbs escape injury. Rats eat pinks, carnations, and roses, cutting the stems off clean. They denude geraniums of both flowers and leaves. They attack the choicest blooms of chrysanthemums and carnations in markets, stores, and exhibition rooms, causing heavy losses.
FIRES.
Rats and mice cause many fires. Several specific instances have been reported by the fire department of the city of Washington within the past two or three years. It is likely that some of these fires are caused by rats gnawing matches. The animals are fond of paraffin, which is often used to protect match heads. They carry the matches to their nests, which are composed of paper and other combustible materials, and the conditions for a conflagration are ready. Since the heads of matches contain from 14 to 17 per cent of phosphorus, actual gnawing is not required to ignite them, but heat or friction from any cause may suffice.