Title: House Rats and Mice
Author: David E. Lantz
Release date: March 10, 2011 [eBook #35542]
Most recently updated: January 7, 2021
Language: English
Credits: Produced by Erica Pfister-Altschul, Larry B. Harrison and
the Online Distributed Proofreading Team at
https://www.pgdp.net
Washington, D. C.October, 1917
Show this bulletin to a neighbor. Additional copies may beobtained free from the Division of Publications, United StatesDepartment of Agriculture
WASHINGTON: GOVERNMENT PRINTING OFFICE: 1917
The rat is the worst animal pest in the world.
From its home among filth it visits dwellings andstorerooms to pollute and destroy human food.
It carries bubonic plague and many other diseasesfatal to man and has been responsible for more untimelydeaths among human beings than all the warsof history.
In the United States rats and mice each year destroycrops and other property valued at over $200,000,000.
This destruction is equivalent to the gross earningsof an army of over 200,000 men.
On many a farm, if the grain eaten and wasted byrats and mice could be sold, the proceeds would morethan pay all the farmer's taxes.
The common brown rat breeds 6 to 10 times ayear and produces an average of 10 young at a litter.Young females breed when only three or four monthsold.
At this rate a pair of rats, breeding uninterruptedlyand without deaths, would at the end of three years(18 generations) be increased to 359,709,482 individuals.
For centuries the world has been fighting ratswithout organization and at the same time has beenfeeding them and building for them fortresses forconcealment. If we are to fight them on equal termswe must deny them food and hiding places. We mustorganize and unite to rid communities of these pests.The time to begin is now.
Losses from depredations of house rats amount to many millionsof dollars yearly—to more, in fact, than those from all otherinjurious mammals combined. The common house mouse[1] and thebrown rat[2] (fig. 1), too familiar to need description, are pests innearly all parts of the country; while two other kinds of house rats,known as the black rat[3] and the roof rat,[4] are found within ourborders.
Fig. 1.—Brown rat.Of these four introduced species—for none is native to America—thebrown rat is the most destructive, and, except the mouse, the mostnumerous and most widely distributed. Brought to America just[Pg 4]before the Revolution, it has supplanted and nearly exterminatedits less robust relative the black rat; and in spite of the constant warfareof man has extended its range and steadily increased in numbers.Its dominance is due to its great fecundity and its ability to adaptitself to all sorts of surroundings. It breeds (in the middle part ofthe United States) six or more times a year and produces from 6 to20 young (average 10) in a litter. Females breed when only 3 or 4months old. Thus a pair, breeding uninterruptedly and withoutdeaths, could in three years (18 generations) produce a posterity of359,709,480 individuals. Mice and the black and roof rats producesmaller litters, but the period of gestation, about 21 days, and thenumber of litters are the same for all.
Rats and mice are practically omnivorous, feeding upon all kindsof animal and vegetable matter. The brown rat makes its home inthe open field, the hedge row, and the river bank, as well as in stonewalls, piers, and all kinds of buildings. It destroys grains whennewly planted, while growing, and in the shock, stack, mow, crib,granary, mill, elevator, or ship's hold, and also in the bin and feedtrough. It invades store and warehouse and destroys furs, laces,silks, carpets, leather goods, and groceries. It attacks fruits, vegetables,and meats in the markets, and destroys by pollution ten timesas much as it actually eats. It destroys eggs and young poultry, andeats the eggs and young of song and game birds. It carries diseasegerms from house to house and bubonic plague from city to city.It causes disastrous conflagrations; floods houses by gnawing leadwater pipes; ruins artificial ponds and embankments by burrowing;and damages foundations, floors, doors, and furnishings of dwellings.
Unlike the brown rat the black rat rarely migrates to the fields.It has disappeared from most parts of the Northern States, but isoccasionally found in remote villages or farms. At our seaports itfrequently arrives on ships from abroad, but seldom becomes verynumerous. The roof rat is common in many parts of the South,where it is a persistent pest in cane and rice fields. It maintainsitself against the brown rat partly because of its habit of living intrees. The common house mouse by no means confines its activitiesto the inside of buildings, but is often found in open fields, where itsdepredations in shock and stack are well known.
Not only are mice and rats, especially the brown rat, a cause ofdestruction and damage to property, but they are also a constantmenace to the health of man. It has been proved that they are thechief means of perpetuating and transmitting bubonic plague andthat they play important rôles in conveying other diseases to humanbeings. They are parasites, without redeeming characteristics, andshould everywhere be routed and destroyed.
Past attempts to exterminate rats and mice have failed, not so muchbecause of lack of effective means as because of the neglect of necessaryprecautions and the absence of concerted endeavors. We haverendered our work abortive by continuing to provide subsistence andhiding places for the animals. If these advantages are denied, persistentand general use of the usual methods of destruction will provefar more successful.
First in importance, as a measure of rat repression, is the exclusionof the animals from places where they find food and safe retreats forrearing their young.
The best way to keep rats from buildings, whether in city or incountry, is to use cement in construction. As the advantages of thismaterial are coming to be generally understood, its use is rapidly extendingto all kinds of buildings. The processes of mixing and layingthis material require little skill or special knowledge, andworkmen of ordinary intelligence can successfully follow the plaindirections contained in handbooks of cement construction.[5]
Many modern public buildings are so constructed that rats canfind no lodgment in the walls or foundations, and yet in a few years,through negligence, such buildings often become infested with thepests. Sometimes drain pipes are left uncovered for hours at a time.Often outer doors, especially those opening on alleys, are left ajar.A common mistake is failure to screen basement windows which mustbe opened for ventilation. However the intruders are admitted, whenonce inside they intrench themselves behind furniture or stores, andare difficult to dislodge. The addition of inner doors to vestibules isan important precaution against rats. The lower edge of outer doorsto public buildings, especially markets, should be reinforced withlight metal plates to prevent the animals from gnawing through.Any opening left around water, steam, or gas pipes, where they gothrough walls, should be closed carefully with concrete to the fulldepth of the wall.
Dwellings.—In constructing dwelling houses the additional cost ofmaking the foundations rat-proof is slight compared with the advantages.The cellar walls should have concrete footings, and thewalls themselves should be laid in cement mortar. The cellar floorshould be of medium rather than lean concrete. Even old cellarsmay be made rat-proof at comparatively small expense. Rat holesmay be permanently closed with a mixture of cement, sand, andbroken glass, or sharp bits of crockery or stone.
[Pg 6]On a foundation like the one described above, the walls of a woodendwelling also may be made rat-proof. The space between the sheathingand lath, to the height of about a foot, should be filled with concrete.Rats can not then gain access to the walls, and can enter thedwelling only through doors or windows. Screening all basementand cellar windows with wire netting is a most necessary precaution.
Old buildings in cities.—Aside from old dwellings, the chief refugesfor rats in cities are sewers, wharves, stables, and outbuildings.Modern sewers are used by the animals merely as highways and not asabodes, but old-fashioned brick sewers often afford nesting crannies.
Fig. 2.—Rat-proofing a frame dwellingby concrete side wall (United States Public Health Service, New Orleans,La., 1914).Wharves, stables, and outbuildings in cities should be so built as toexclude rats. Cement is the chief means to this end. Old tumble-downbuildings and wharves should not be tolerated in any city.(See fig. 2.)
In both city and country, wooden floors of sidewalks, areas, andporches are commonly laid upon timbers resting on the ground.Under such floors rats have a safe retreat from nearly all enemies.The conditions can be remedied in towns by municipal action requiringthat these floors be replaced by others made of cement. Areas orwalks made of brick are often undermined by rats and may becomeas objectionable as those of wood. Wooden floors of porches shouldalways be well above the ground.
[Pg 7]Farm buildings.—Granaries, corncribs, and poultry houses may bemade rat-proof by a liberal use of cement in the foundations andfloors; or the floors may be of wood resting upon concrete. Objectionhas been urged against concrete floors for horses, cattle, and poultry,because the material is too good a conductor of heat, and the healthof the animals suffers from contact with these floors. In poultryhouses, dry soil or sand may be used as a covering for the cementfloor, and in stables a wooden floor resting on concrete is just as satisfactoryso far as the exclusion of rats is concerned.
The common practice of setting corncribs on posts with invertedpans at the top often fails to exclude rats, because the posts are nothigh enough to place the lower cracks of the structure beyond reachof the animals. As rats are excellent jumpers, the posts should betall enough to prevent the animals from obtaining a foothold at anyplace within 3 feet of the ground. A crib built in this way, however,is not very satisfactory.
For a rat-proof crib a well-drained site should be chosen. Theouter walls, laid in cement, should be sunk about 20 inches into theground. The space within the walls should be grouted thoroughlywith cement and broken stone and finished with rich concrete for afloor. Upon this the structure may be built. Even the walls of thecrib may be of concrete. Corn will not mold in contact with them,provided there is good ventilation and the roof is water-tight.
However, there are cheaper ways of excluding rats from eithernew or old corncribs. Rats, mice, and sparrows may be kept outeffectually by the use of either an inner or an outer covering of galvanized-wirenetting of half-inch mesh and heavy enough to resistthe teeth of the rats. The netting in common use in screening cellarwindows is suitable for covering or lining cribs. As rats can climbthe netting, the entire structure must be screened, or, if sparrows arenot to be excluded, the wire netting may be carried up about 3feet from the ground, and above this a belt of sheet metal about afoot in width may be tacked to the outside of the building.
Complete working drawings for the practical rat-proof corncribshown in figures 3 and 4 may be obtained from the Office of PublicRoads and Rural Engineering of the department.
Buildings for storing foodstuffs.—Whenever possible, stores of foodfor man or beast should be placed only in buildings of rat-proofconstruction, guarded against rodents by having all windows nearthe ground and all other possible means of entrance screened withnetting made of No. 18 or No. 20 wire and of ¼-inch mesh. Entrancedoors should fit closely, should have the lower edges protected bywide strips of metal, and should have springs attached, to insure thatthey shall not be left open. Before being used for housing stores,the building should be inspected as to the manner in which water,[Pg 8]steam, or gas pipes go through the walls, and any openings foundaround such pipes should be closed with concrete.
Fig. 3.—Perspective of rat-proofcorncrib, showing concrete foundation by dotted lines; alsobelt of metal.If rat-proof buildings are not available, it is possible, by the useof concrete in basements and the other precautions just mentioned, tomake an ordinary building practically safe for food storage.
When it is necessary to erect temporary wooden structures to holdforage, grain, or food supplies for army camps, the floors of suchbuildings should not be in contact with the ground, but elevated, thesills having a foot or more of clear space below them. Smooth postsrising 2 or 3 feet above the ground may be used for foundations,and the floor itself may be protected below by wire netting or sheetmetal at all places where rats could gain a foothold. Care should betaken to have the floors as tight as possible, for it is chiefly scatteredgrain and fragments of food about a camp that attract rats.
Rat-proofing by elevation.—The United States Public Health Servicereports that in its campaigns against bubonic plague in SanFrancisco (1907) and New Orleans (1914) many plague rats werefound under the floors of wooden houses resting on the ground.These buildings were made rat-proof by elevation, and no case ofeither human or rodent plague occurred in any house after thechange. Placing them on smooth posts 18 inches above the ground,with the space beneath the floor entirely open, left no hiding placefor rats.
This plan is adapted to small dwellings throughout the South, andto small summer homes, temporary structures, and small farm buildingseverywhere. Wherever rats might obtain a foothold on thetop of the post they may be prevented from gnawing the adjacentwood by tacking metal plates or pieces of wire netting to floor or sill.
The effect of an abundance of food on the breeding of rodentsshould be kept in mind. Well-fed rats mature quickly, breed often,and have large litters. Poorly fed rats, on the contrary, reproduceless frequently and have smaller litters. In addition, scarcity of foodmakes measures for destroying the animals far more effective.
Merchandise in stores.—In all parts of the country there is a seriouseconomic drain in the destruction by rats and mice of merchandiseheld for sale by dealers. Not only foodstuffs and forage, but textiles,clothing, and leather goods are often ruined. This loss is due mainlyto the faulty buildings in which the stores are kept. Often it wouldbe a measure of economy to tear down the old structures and replacethem by new ones. However, even the old buildings may often berepaired so as to make them practically rat-proof; and foodstuffs, asflour, seeds, and meats, may always be protected in wire cages atslight expense. The public should be protected from insanitarystores by a system of rigid inspection.
Fig. 4.—Floorplan of rat-proof corncrib shown in figure 3.Household supplies.—Similar care should be exercised in the home toprotect household supplies from mice and rats. Little progress inridding the premises of these animals can be made so long as theyhave access to supplies of food. Cellars, kitchens, and pantries oftenfurnish subsistence not only to rats that inhabit the dwelling, but tomany that come from outside. Food supplies may always be keptfrom rats and mice if placed in inexpensive rat-proof containerscovered with wire netting. Sometimes all that is needed to prevent[Pg 10]serious waste is the application of concrete to holes in the basementwall or the slight repair of a defective part of the building.
Produce in transit.—Much loss of fruits, vegetables, and other produceoccurs in transit by rail and on ships. Most of the damage isdone at wharves and in railway stations, but there is also considerablein ships' holds, especially to perishable produce brought from warmlatitudes. Much of this may be prevented by the use of rat-proofcages at the docks, by the careful fumigation of seagoing vessels atthe end of each voyage, and by the frequent fumigation of vessels incoastwise trade; but still more by replacing old and decrepit wharvesand station platforms with modern ones built of concrete.
Where cargoes are being loaded or unloaded at wharves or depots,food liable to attack by rats may be temporarily safeguarded by beingplaced in rat-proof cages, or pounds, constructed of wire netting.Wooden boxes containing reserve food held in depots for a considerabletime or intended for shipment by sea may be made rat-proof bylight coverings of metal along the angles. This plan has long been inuse to protect naval stores on ships and in warehouses. It is basedon the fact that rats do not gnaw the plane surfaces of hard materials,but attack doors, furniture, and boxes at the angles only.
Packing houses.—Packing houses and abattoirs are often sourcesfrom which rats secure subsistence, especially where meats are preparedfor market in old buildings. In old-style cooling rooms withdouble walls of wood and sawdust insulation, always a source ofannoyance because of rat infestation, the utmost vigilance is requiredto prevent serious loss of meat products. On the other hand, packinghouses with modern construction and sanitary devices have no troublefrom rats or mice.
Garbage and waste.—Since much of the food of rats consists ofgarbage and other waste materials, it is not enough to bar the animalsfrom markets, granaries, warehouses, and private food stores. Garbageand offal of all kinds must be so disposed of that rats can notobtain them.
In cities and towns an efficient system of garbage collection anddisposal should be established by ordinances. Waste from markets,hotels, cafés and households should be collected in covered metalreceptacles and frequently emptied. Garbage should never bedumped in or near towns, but should be utilized or promptly destroyedby fire.
Rats find abundant food in country slaughterhouses; reform in themanagement of these is badly needed. Such places are centers of ratpropagation. It is a common practice to leave offal of slaughteredanimals to be eaten by rats and swine, and this is the chief means ofperpetuating trichinæ in pork. The law should require that offal bepromptly cremated or otherwise disposed of. Countryslaughter[Pg 11]housesshould be as cleanly and as constantly inspected as abattoirs.
Another important source of rat food is found in remnants of lunches leftby employees in factories, stores, and public buildings. This food, whichalone is sufficient to attract and sustain a small army of rats, is commonly leftin waste baskets or other open receptacles. Strictly enforced rules requiringall remnants of food to be deposited in covered metal vessels would make trappingfar more effective.
Military training camps, unless subjected to rigiddiscipline in the matter of disposal of garbage and waste, soonbecome centers of rat infestation. Waste from camps, deposited incovered metal cans and collected daily, should be removed far fromthe camp itself and either burned or utilized in approved modernways.
The Biological Survey has made numerous laboratory and fieldexperiments with various agencies for destroying rats and mice.The results form the chief basis for the following recommendations:
Owing to their cunning, it is not always easy to clear rats frompremises by trapping; if food is abundant, it is impossible. A fewadults refuse to enter the most innocent-looking trap. And yet trapping,if persistently followed, is one of the most effective ways ofdestroying the animals.
Fig. 5.—Guillotinetrap made entirely of metal.Guillotine trap.—For general use the improved modern traps with awire fall released by a baited trigger and driven by a coiled springhave marked advantages over the old forms, and many of them maybe used at the same time. These traps, sometimes called "guillotine"traps, are of many designs, but the more simply constructed are preferable.Probably those made entirely of metal are the best, as they[Pg 12]are more durable. Traps with tin or sheet-metal bases are not recommended.
Guillotine traps of the type shown in figure 5 should be baitedwith small pieces of Vienna sausage (Wienerwurst) or fried bacon.A small section of an ear of corn is an excellent bait if other grainis not present. The trigger wire should be bent inward to bringthe bait into proper position for the fall to strike the rat in the neck,as shown in figure 6.
Other excellent baits for rats and mice are oatmeal, toasted cheese,toasted bread (buttered), fish, fish offal, fresh liver, raw meat, pinenuts, apples, carrots, and corn, and sunflower, squash, or pumpkinseeds. Broken fresh eggs are good bait at all seasons, and ripetomatoes, green cucumbers, and other fresh vegetables are verytempting to the animals in winter. When seed, grain, or meal isused with a guillotine trap, it is put on the trigger plate, or the triggerwire may be bent outward and the bait placed directly under it.
Oatmeal (rolled oats) is recommended as a bait for guillotine trapsmade with wooden base and trigger plate (fig. 7). These traps areespecially convenient to use on ledges or other narrow rat runs orat the openings of rat burrows. They are often used without bait.
Fig. 6.—Methodof baiting guillotine trap.A common mistake in trapping for rats and mice is to use onlyone or two traps when dozens are needed. For a large establishmenthundreds of traps may be used to advantage, and a dozen is none toomany for an ordinary barn or dwelling infested with rats. Housemice are less suspicious than rats and are much more easily trapped.[Pg 13]Small guillotine traps baited with oatmeal will soon ridan ordinary dwelling of the smaller pests.
Fig. 7.—Guillotinetrap with wooden base and trigger plate.Cage trap.—When rats are abundant, the large Frenchwire cage traps may be used to advantage. They should be madeof stiff wire, well reinforced. Many of those sold in stores are useless,because a full-grown rat can bend the light wires apart and so escape.
Cage traps may be baited and left open for several nights until therats are accustomed to enter them to obtain food. They should thenbe closed and freshly baited, when a larger catch may be expected,especially of young rats (fig. 8). As many as 25, and even more,partly grown rats have been taken at a time in one of these traps.It is better to cover the trap than to leave it exposed. A short boardshould be laid on the trap and an old cloth or bag or a bunch of hayor straw thrown carelessly over the top. Often the trap may beplaced with the entrance opposite a rat hole and fitting it so closelythat rats can not pass through without entering the trap. If a singlerat is caught it may be left in the trap as a decoy to others.
Notwithstanding the fact that sometimes a large number of ratsmay be taken at a time in cage traps, a few good guillotine trapsintelligently used will prove more effective in the long run.
Fig. 8.—Cagetrap with catch of rats.Figure-4 trigger trap.—The old-fashioned box trap set with a figure-4trigger is sometimes useful to secure a wise old rat that refusesto be enticed into a modern trap. Better still is a simpledeadfall[Pg 14]—aflat stone or a heavy plank—supported by a figure-4 trigger. Anold rat will go under such a contrivance to feed without fear.
Steel trap.—The ordinary steel trap (No. 0 or 1) may sometimes besatisfactorily employed to capture a rat. The animal is usuallycaught by the foot, and its squealing has a tendency to frighten otherrats. The trap may be set in a shallow pan or box and covered withbran or oats, care being taken to have the space under the trigger pan freeof grain. This may be done by placing a very little cotton under the triggerand setting as lightly as possible. In a narrow run or at the mouth of a burrowa steel trap unbaited and covered with very light cloth or tissue paper isoften effective.
The best bait usually is food of a kind that the rats and mice do notget in the vicinity. In a meat market, vegetables or grain shouldbe used; in a feed store, meat. As far as possible food other thanthe bait should be inaccessible while trapping is in progress. Thebait should be kept fresh and attractive, and the kind changed whennecessary. Baits and traps should be handled as little as possible.
Fig. 9.—Barreltrap: 1, With stiff paper cover; 2, with hinged barrel cover;a, stop;b, baits.Barrel trap.—About 60 years ago a writer in the Cornhill Magazinegave details of a trap, by means of which it was claimedthat 3,000 rats were caught in a warehouse in a single night. Theplan involved tolling the rats to the placeand feeding them for several nights on the tops of barrels coveredwith coarse brown paper. Afterwards a cross was cut in the paper,so that the rats fell into the barrel (fig. 9 (1)). Many variations ofthe plan, but few improvements upon it, have been suggested by agriculturalwriters since that time. Reports are frequently made of largecatches of rats by means of a barrel fitted with a light cover of wood,hinged on a rod so as to turn with the weight of a rat (fig. 9 (2)).
Fig. 10.—Pit trap.aa, Rat run;bb, cover;cc, position of weights;dd, rods on which coversturn.[Pg 15]Pit trap.—A modification of the barrel trap is the pit trap (fig. 10).This consists of a stout narrow box sunk in the ground so that thetop is level with the rat run. It is fixed with a cover of light woodor metal in two sections, the sections fitting nicely inside the boxand working independently. They turn on rods, to which they arefastened. They are weighted near the ends of the box and so adjustedthat they swing easily. An animal stepping upon the coverbeyond the rods is precipitated into the box, while the cover immediatelyswings back to its place. Besides rats, the trap is welladapted to capture larger animals, as minks, raccoons, opossums, andcats. It is especially useful to protect poultry yards, game preserves,and the like. The trap should be placed along the fence outside theyard, and behind a shelter of boards or brush that leans against thefence.
Fence and battue.—In the rice fields of the Far East the nativesbuild numerous piles of brush and rice straw, and leave them forseveral days until many rats have taken shelter in them. A portablebamboo inclosure several feet in height is then set up around eachpile in succession and the straw and brush are thrown out over thetop, while dogs and men kill the trapped rodents. Large numbersare destroyed in this way, and the plan with modifications may beutilized in America with satisfactory results. A wire netting of finemesh may be used for the inclosure. The scheme is applicable at theremoval of grain, straw, or haystacks, as well as brush piles.
In a large barn near Washington, a few years ago, piles of unhuskedcorn were left in the loft and were soon infested with rats.A wooden pen was set down surrounding the piles in turn and thecorn thrown out until dogs were able to get at the rats. In this wayseveral men and dogs killed 500 rats in a single day.
While the use of poison is the best and quickest way to get rid ofrats and mice, the odor from the dead animals makes the method impracticablein occupied houses. Poisons may be effectively used inbarns, stables, sheds, cribs, and other outbuildings.
Caution.—In the United States there are few laws which prohibitthe laying of poisons on lands owned or controlled by the poisoner.Hence it is all the more necessary to exercise extreme caution toprevent accidents. In several States notice of intention to lay poisonmust be given to persons living in the neighborhood. Poison forrats should never be placed in open or unsheltered places. Thisapplies particularly to strychnin or arsenic on meat.Packages containingpoisons should always bear a warning label and should notbe kept where children might reach them.
[Pg 16]Among the principal poisons that have been recommended forkilling rats and mice are barium carbonate, strychnin, arsenic, phosphorus,and squills.
Barium carbonate.—One of the cheapest and most effective poisonsfor rats and mice is barium carbonate. This mineral has the advantageof being without taste or smell. It has a corrosive action on themucous lining of the stomach and is dangerous to larger animals iftaken in sufficient quantity. In the small doses fed to rats and miceit would be harmless to domestic animals. Its action upon rats isslow, and if exit is possible the animals usually leave the premises insearch of water. For this reason the poison may frequently, thoughnot always, be used in houses without disagreeable consequences.
Barium carbonate may be fed in the form of dough composed offour parts of meal or flour and one part of the mineral. A moreconvenient bait is ordinary oatmeal with about one-eighth of its bulkof the mineral, mixed with water into a stiff dough. A third plan isto spread the barium carbonate upon fish, toasted bread (moistened),or ordinary bread and butter. The prepared bait should be placed inrat runs, about a teaspoonful at a place. If a single application ofthe poison fails to kill or drive away all rats from the premises, itshould be repeated with a change of bait.
Strychnin.—Strychnin is too rapid in action to make its use forrats desirable in houses, but elsewhere it may be employed effectively.Strychnia sulphate is the best form to use. The dry crystals may beinserted in small pieces of raw meat, Vienna sausage, or toastedcheese, and these placed in rat runs or burrows; or oatmeal may bemoistened with a strychnin sirup and small quantities laid in thesame way.
Strychnin sirup is prepared as follows: Dissolve a half ounce ofstrychnia sulphate in a pint of boiling water; add a pint of thicksugar sirup and stir thoroughly. A smaller quantity may be preparedwith a proportional quantity of water and sirup. In preparingthe bait it is necessary to moisten all the oatmeal with the sirup.Wheat and corn are excellent alternative baits. The grain shouldbe soaked overnight in the strychnin sirup.
Arsenic.—Arsenic is probably the most popular of the rat poisons,owing to its cheapness, yet our experiments prove that, measuredby the results obtained, arsenic is dearer than strychnin. Besides,arsenic is extremely variable in its effect upon rats, and if the animalssurvive a first dose it is very difficult to induce them to takeanother.
Powdered white arsenic (arsenious acid) may be fed to rats inalmost any of the baits mentioned under barium carbonate andstrychnin. It has been used successfully when rubbed into freshfish or spread on buttered toast. Another method is to mix twelve[Pg 17]parts by weight of corn meal and one part of arsenic with whites ofeggs into a stiff dough.
An old formula for poisoning rats and mice with arsenic is thefollowing, adapted from an English source:
Take a pound of oatmeal, a pound of coarse brown sugar, and aspoonful of arsenic. Mix well together and put the composition intoan earthen jar. Put a tablespoonful at a place in runs frequentedby rats.
Phosphorus.—For poisoning rats and mice, phosphorus is usedalmost as commonly as arsenic, and undoubtedly it is effective whengiven in an attractive bait. The phosphorus paste of the drugstores is usually dissolved yellow phosphorus, mixed with glucose orother substances. The proportion of phosphorus varies from one-fourthof 1 per cent to 4 per cent. The first amount is too smallto be always effective and the last is dangerously inflammable. Whenhomemade preparations of phosphorus are used there is much dangerof burning the person or of setting fire to crops or buildings.In the Western States many fires have resulted from putting outhomemade phosphorus poisons for ground squirrels, and entire fieldsof ripe grain have been destroyed in this way. Even with commercialpastes the action of sun and rain changes the phosphorusand leaches out the glucose until a highly inflammable residue is left.
It is often claimed that phosphorus eaten by rats or mice dries upor mummifies the body so that no odor results. The statement hasno foundation in fact. No known poison will prevent decompositionof the body of an animal that died from its effects. Equally misleadingis the statement that rats poisoned with phosphorus do notdie on the premises. Owing to its slower operation, no doubt alarger portion escape into the open before dying than when strychninis used.
The Biological Survey does not recommend the use of phosphorusas a poison for rodents.
Squills.—The squill, or sea leek,[6] is a favorite rat poison in manyparts of Europe and is well worthy of trial in America. It is rapidand very deadly in its action, and rats seem to eat it readily. Thepoison is used in several ways. Two ounces of dry squills, powdered,may be thoroughly mixed with eight ounces of toasted cheese or ofbutter and meal and put out in runs of rats or mice. Another formularecommends two parts of squills to three parts of finelychopped bacon, mixed with meal enough to make it cohere. This isbaked in small cakes.
Poison in poultry houses.—For poisoning rats in buildings and yardsoccupied by poultry the following method is recommended: Two[Pg 18]wooden boxes should be used, one considerably larger than the otherand each having one or more holes in the sides large enough toadmit rats. The poisoned bait should be placed on the bottom andnear the middle of the smaller box, and the larger box should thenbe inverted over it. Rats thus have free access to the bait, but fowlsare excluded.
Among domestic animals employed to kill rats are the dog, thecat, and the ferret.
Dogs.—The value of dogs as ratters can not be appreciated by personswho have had no experience with a trained animal. The ordinarycur and the larger breeds of dogs seldom develop the necessaryqualities for ratters. Small Irish, Scotch, and fox terriers, whenproperly trained, are superior to other breeds and under favorablecircumstances may be relied upon to keep the farm premises reasonablyfree from rats.
Cats.—However valuable cats may be as mousers, few learn to catchrats. The ordinary house cat is too well fed and consequently toolazy to undertake the capture of an animal as formidable as thebrown rat. Birds and mice are much more to its liking. Cats thatare fearless of rats, however, and have learned to hunt and destroythem are often very useful about stables and warehouses. Theyshould be lightly fed, chiefly on milk. A little sulphur in the milk atintervals is a corrective against the bad effects of a constant rat ormouse diet. Cats often die from eating these rodents.
Ferrets.—Tame ferrets, like weasels, are inveterate foes of rats, andcan follow the rodents into their retreats. Under favorable circumstancesthey are useful aids to the rat catcher, but their value isgreatly overestimated. For effective work they require experiencedhandling and the additional services of a dog or two. Dogs andferrets must be thoroughly accustomed to each other, and the formermust be quiet and steady instead of noisy and excitable. The ferretis used only to bolt the rats, which are killed by the dogs. If unmuzzledferrets are sent into rat retreats, they are apt to make a killand then lie up after sucking the blood of their victim. Sometimesthey remain for hours in the burrows or escape by other exits andare lost. There is danger that these lost ferrets may adapt themselvesto wild conditions and become a pest by preying upon poultryand birds.
Rats may be destroyed in their burrows in the fields and alongriver banks, levees, and dikes by carbon bisulphid.[7] A wad ofcot[Pg 19]tonor other absorbent material is saturated with the liquid andthen pushed into the burrow, the opening being packed with earth toprevent the escape of the gas. All animals in the burrow are asphyxiated.Fumigation in buildings is not so satisfactory, because it isdifficult to confine the gases. Moreover, when effective, the odorfrom the dead rats is highly objectionable in occupied buildings.
Chlorin, carbon monoxid, sulphur dioxid, and hydrocyanic acidare the gases most used for destroying rats and mice in sheds, warehouses,and stores. Each is effective if the gas can be confined andmade to reach the retreats of the animals. Owing to the great dangerfrom fire incident to burning charcoal or sulphur in open pans, aspecial furnace provided with means for forcing the gas into the compartmentsof vessels or buildings is generally employed.
Hydrocyanic-acid gas is effective in destroying all animal life inbuildings. It has been successfully used to free elevators and warehousesof rats, mice, and insects. However, it is so dangerous tohuman life that the novice should not attempt fumigation with it,except under careful instructions. Directions for preparing andusing the gas may be found in a publication entitled Hydrocyanic-acidGas against Household Insects, by Dr. L. O. Howard andCharles H. Popenoe.[8]
Carbon monoxid is rather dangerous, as its presence in the hold ofa vessel or other compartment is not manifest to the senses, and fatalaccidents have occurred during its employment to fumigate vessels.
Chlorin gas has a strong bleaching action upon textile fabrics, andfor this reason can not be used in many situations.
Sulphur dioxid also has a bleaching effect upon textiles, but lessmarked than that of chlorin, and ordinarily it is not noticeable withthe small percentage of the gas it is necessary to use. On the whole,this gas has many advantages as a fumigator and disinfectant. It isused also as a fire extinguisher on board vessels. Special furnaces forgenerating the gas and forcing it into the compartments of ships andbuildings are on the market, and many steamships and docks arenow fitted with the necessary apparatus.
Several microorganisms, or bacteria, found originally in diseasedrats or mice, have been exploited for destroying rats. A number ofthese so-called rat viruses are on the American market. The BiologicalSurvey, the Bureau of Animal Industry, and the United StatesPublic Health Service have made careful investigations and practicaltests of these viruses, mostly with negative results. The culturestested by the Biological Survey have not proved satisfactory.
The chief defects to be overcome before the cultures can be recommendedfor general use are:
[Pg 20]1. The virulence is not great enough to kill a sufficiently high percentageof rats that eat food containing the microorganisms.
2. The virulence decreases with the age of the cultures. They deterioratein warm weather and in bright sunlight.
3. The diseases resulting from the microorganisms are not contagiousand do not spread by contact of diseased with healthyanimals.
4. The comparative cost of the cultures is too great for general use.Since they have no advantages over the common poisons, except thatthey are usually harmless to man and other animals, they should beequally cheap; but their actual cost is much greater. Moreover, consideringthe skill and care necessary in their preparation, it is doubtfulif the cost can be greatly reduced.
The Department of Agriculture, therefore, does not prepare, use,or recommend the use of rat viruses.
Among the natural enemies of rats and mice are the larger hawksand owls, skunks, foxes, coyotes, weasels, minks, dogs, cats, andferrets.
Probably the greatest factor in the increase of rats, mice, and otherdestructive rodents in the United States has been the persistent killingoff of the birds and mammals that prey upon them. Animals thaton the whole are decidedly beneficial, since they subsist upon harmfulinsects and rodents, are habitually destroyed by some farmers andsportsmen because they occasionally kill a chicken or a game bird.
The value of carnivorous mammals and the larger birds of prey indestroying rats and mice should be more fully recognized, especiallyby the farmer and the game preserver. Rats actually destroy morepoultry and game, both eggs and young chicks, than all the birds andwild mammals combined; yet some of their enemies among our mostuseful birds of prey and carnivorous mammals are persecuted almostto the point of extinction. An enlightened public sentiment shouldcause the repeal of all bounties on these animals and afford protectionto the majority of them.
The necessity of cooperation and organization in the work of ratdestruction is of the utmost importance. To destroy all the animalson the premises of a single farmer in a community has little permanentvalue, since they are soon replaced from near-by farms. If,however, the farmers of an entire township or county unite in effortsto get rid of rats, much more lasting results may be attained. If continuedfrom year to year, such organized efforts are very effective.
Cooperative efforts to destroy rats have taken various forms indifferent localities. In cities, municipal employees have occasionallybeen set at work hunting rats from their retreats, with at least temporarybenefit to the community. Thus, in 1904, at Folkestone, England,a town of about 25,000 inhabitants, the corporation employees,helped by dogs, in three days killed 1,645 rats.
Side hunts in which rats are the only animals that count in thecontest have sometimes been organized and successfully carried out.At New Burlington, Ohio, a rat hunt took place some years ago inwhich each of the two sides killed over 8,000 rats, the beaten partyserving a banquet to the winners.
There is danger that organized rat hunts will be followed by longintervals of indifference and inaction. This may be prevented byoffering prizes covering a definite period of effort. Such prizesaccomplish more than municipal bounties, because they secure afriendly rivalry which stimulates the contestants to do their utmostto win.
In England and some of its colonies contests for prizes have beenorganized to promote the destruction of the English, or house, sparrow,but many of the so-called sparrow clubs are really sparrow andrat clubs, for the destruction of both pests is the avowed object ofthe organizations. A sparrow club in Kent, England, accomplishedthe destruction of 28,000 sparrows and 16,000 rats in three seasonsby the annual expenditure of but £6 ($29.20) in prize money. Hadordinary bounties been paid for this destruction, the tax on the communitywould have been about £250 (over $1,200).
Many organizations already formed should be interested in destroyingrats. Boards of trade, civic societies, and citizens' associationsin towns and farmers' and women's clubs in rural communitieswill find the subject of great importance. Women's municipalleagues in several large cities already have taken up the matter.The league in Baltimore recently secured appropriations of fundsfor expenditure in fighting mosquitoes, flies, and rats. The leaguein Boston during the past year, supported by voluntary contributionsfor the purpose, made a highly creditable educational campaignagainst rats. Boys' corn clubs, the troops of Boy Scouts, andsimilar organizations could do excellent work in rat campaigns.
To secure permanent results any general campaign for the eliminationof rats must aim atbuilding the animals out of shelter and food.Building reforms depend on municipal ordinances and legislative[Pg 22]enactments. The recent plague eradication work of the UnitedStates Public Health Service in San Francisco, Seattle, New Orleans,and at various places in Hawaii and Porto Rico required such ordinancesand laws as well as financial aid in prosecuting the work.The campaign of Danish and Swedish organizations for the destructionof rats had the help of governmental appropriations. The legislaturesof California, Texas, Indiana, and Hawaii have in recentyears passed laws or made appropriations to aid in rat riddance. It isprobable that well-organized efforts of communities would soon winlegislative support everywhere. Communities should not postponeefforts, however, while waiting for legislative cooperation, but shouldat once organize and begin repressive operations. Wherever healthis threatened the Public Health Service of the United States can cooperate,and where crops and other products are endangered theBureau of Biological Survey of the Department of Agriculture isready to assist by advice and in demonstration of methods.
The measures needed for repressing and eliminating rats and miceinclude the following:
1. The requirement that all new buildings erected shall be maderat-proof under competent inspection.
2. That all existing rat-proof buildings shall be closed against ratsand mice by having all openings accessible to the animals, fromfoundation to roof, closed or screened by door, window, grating, ormeshed wire netting.
3. That all buildings not of rat-proof construction shall be made soby remodeling, by the use of materials that may not be pierced byrats, or by elevation.
4. The protection of our native hawks, owls, and smaller predatorymammals—the natural enemies of rats.
5. Greater cleanliness about markets, grocery stores, warehouses,courts, alleys, stables, and vacant lots in cities and villages, and likecare on farms and suburban premises. This includes the storage ofwaste and garbage in tightly covered vessels and the prompt disposalof it each day.
6. Care in the construction of drains and sewers, so as not to provideentrance and retreat for rats. Old brick sewers in cities shouldbe replaced by concrete or tile.
7. The early threshing and marketing of grains on farms, so thatstacks and mows shall not furnish harborage and food for rats.
8. Removal of outlying straw stacks and piles of trash or lumberthat harbor rats in fields and vacant lots.
[Pg 23]9. The keeping of provisions, seed grain, and foodstuffs in rat-proof containers.
10. Keeping effective rat dogs, especially on farms and in city warehouses.
11. The systematic destruction of rats, whenever and whereverpossible, by (a) trapping, (b) poisoning, and (c) organized hunts.
12. The organization of clubs and other societies for systematicwarfare against rats.
[1]Mus musculus.
[2]Rattus norvegicus.
[3]Rattus rattus rattus.
[4]Rattus rattus alexandrinus.
[5] Farmers' Bulletin 461, Use of Concrete on the Farm, will prove useful to city andvillage dwellers as well as to the farmer.
[6]Scilla maritima.
[7]Caution.—Carbon disulphid is very inflammable and can be ignited by a match, lantern,cigar, or pipe.
[8] Farmers' Bulletin 699.
How to Destroy Rats. (Farmers' Bulletin 369.)
The Common Mole of Eastern United States. (Farmers' Bulletin 583.)
Field Mice as Farm and Orchard Pests. (Farmers' Bulletin 670.)
Cottontail Rabbits in Relation to Trees and Farm Crops. (Farmers' Bulletin702.)
Trapping Moles and Utilizing Their Skins. (Farmers' Bulletin 832.)
Destroying Rodent Pests on the Farm. (Separate 708, Yearbook for 1916.)
Harmful and Beneficial Mammals of the Arid Interior, with Special Referenceto the Carson and Humboldt Valleys, Nevada. (Farmers' Bulletin 335.)Price 5 cents.
The Nevada Mouse Plague of 1907-8. (Farmers' Bulletin 352.) Price 5 cents.
Some Common Mammals of Western Montana in Relation to Agriculture andSpotted Fever. (Farmers' Bulletin 484.) Price 5 cents.
Danger of Introducing Noxious Animals and Birds. (Separate 132, Yearbook1898.) Price 5 cents.
Meadow Mice in Relation to Agriculture and Horticulture. (Separate 388, Yearbook1905.) Price 5 cents.
Mouse Plagues, Their Control and Prevention. (Separate 482, Yearbook 1908.)Price—cents.
Use of Poisons for Destroying Noxious Mammals. (Separate 491, Yearbook1908.) Price 5 cents.
Pocket Gophers as Enemies of Trees. (Separate 506, Yearbook 1909.) Price5 cents.
The Jack Rabbits of the United States. (Biological Survey Bulletin 8.) Price10 cents.
Economic Study of Field Mice, genusMicrotus. (Biological Survey Bulletin 31.)Price 15 cents.
The Brown Rat in the United States. (Biological Survey Bulletin 33.) Price15 cents.
Directions for the Destruction of Wolves and Coyotes. (Biological Survey Circular55.) Price 5 cents.
The California Ground Squirrel. (Biological Survey Circular 76.) Price 5cents.
Seed-eating Mammals in Relation to Reforestation. (Biological Survey Circular78.) Price 5 cents.
Mammals of Bitterroot Valley, Montana, in Their Relation to Spotted Fever.(Biological Survey Circular 82.) Price 5 cents.
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