More Minor Horrors

Now, Muse, let’s sing of rats!

(Grainger.)

The overwhelming majority of rats fall under two species: (i) Mus rattus, the black rat, and (ii) Mus decumanus, the brown rat. The original home of both species is, according to Dr. Blandford, Mongolia; but the date of their first appearance in our islands is a matter of some uncertainty. According to Helm, M. rattus passed into Europe at the time of the Völkerwanderung, and doubtless accompanied the migrating Asiatic hordes on their journeys westward. The name rat appears in early High-Dutch glossaries, it is mentioned by Albertus Magnus, and occurs in early Anglo-Saxon writings in England. This evidence is, however, not conclusive that in those times the rat had entered Great Britain; indeed, according to Bell,[16] the black rat was not known here until before the middle of the sixteenth century: at least, he says, no author more ancient than that period has described, or even alluded to, it as being in Great Britain, Gesner being the first to do so. Jenyns, in his ‘Manual of British Vertebrate Animals,’[17] describes M. rattus as ‘truly indigenous’; but this is in comparison with the brown rat, whose comparatively recently arrival he chronicles. M. rattus is said to have been common on the continent of Europe in the thirteenth century.

M. rattus has, as a rule, greyish-black fur above, ash-coloured below, with a tail a little longer than the body and head. It is smaller and more elegantly built than the brown rat; its snout is longer and more slender, and the long, thin, scaly tail is about eight or nine inches in length. The British forms average in length seven inches from the tip of the nose to the origin of the tail. Although known as the black rat, its bluish, or greyish-black colour is, both in the East and in Northern America, frequently replaced by brown on the upper surface, and by white fur on the lower, or by a yellowish-brown rufous colour. The ears, feet, and tail are black. When kept as pets—and they frequently are—white and piebald varieties are often bred. The ears are larger in proportion than in M. decumanus, the rings of scales on the tail better marked, and spines in the fur are not uncommon.

The black rat, or Old-English rat, begins to breed under the age of one year, and goes with young six weeks; it breeds frequently during the year, but does not commence in Bombay, according to the Plague Commission, until it has attained the weight of at least 70 grammes. In India they breed all the year round. In Britain they produce six to eleven young at a time; in India the average is 5·2; the largest number found by the Plague Commission having been nine. In Bombay it is noteworthy that in both species the percentage of young rats to the total rat population is greater during the warmer months—from June to October—than at other times of the year. It is also noteworthy that the fall in fertility begins before the onset of the plague epizootic, though, later, it roughly coincides with it. In Britain they increase so fast as to overstock their abode, and thus they are forced, from deficiency of food, to devour one another, and this alone, Pennant thinks, ‘prevents even the human race from becoming a prey to them, not but there are instances of their gnawing the extremities of infants in their sleep.’

The black rat is catholic as to its diet, omnivorous, and it devours every kind of human food. It is more domesticated than its congener, more devoted to human habitations, and it does immense damage to stored grain, seeds, and cereals. It is a better climber than M. decumanus, which accounts for its being par excellence the ship-rat, since it can climb hawsers and more readily ‘comes on board.’ It makes its way up to the higher rooms of the tenement houses in Indian cities, where it nests and breeds undisturbed by the human inhabitants.

Pennant[18] draws attention to the harm the black rat causes by gnawing and devouring not only edibles, but paper, cloth, water-pipes, and even furniture. In England it makes a lodge—either for the day’s residence or a nest for its young—near a chimney, and ‘improves the warmth by forming in it a magazine of wool, bits of cloth, hay, or straw.’ In the East it nests in the indescribable rubbish and ‘unconsidered trifles’ the natives accumulate in their rooms, and is seldom, if ever, interfered with.

Its climbing-habits enable it to ascend trees, and in India it frequently nests among the branches. In some tropical islands M. rattus lives exclusively in the crowns of coco-nut palms, feeding almost entirely on their fruit.

Contrary to the opinion of Blandford, Oldfield Thomas thinks that the black rat originally came from India, and thence spread all over the world, exterminating the indigenous rats of other countries, only to be exterminated later by the arrival of the stronger M. decumanus. At the present time the last-named species is not yet established in some countries—for instance, in those of western South America. On that continent, M. alexandrinus, a tropical variety of M. rattus, is waging war on the less highly organised native rice-rats (Sigmodon). M. alexandrinus has a grey or rufous back, and a white belly.

M. rattus has a milder, more amenable, and tameable character than M. decumanus, and the white, or pied varieties, so dear to schoolboys, are of this species. It is cleanly in its habits, and the skin is kept in excellent order. Like other rats, it holds its food in its hands whilst eating, and it drinks by lapping.

Although the black rat is tending to be driven out by the brown rat, it still lingers on in some warehouses in London, at Yarmouth, in Sutherlandshire, I believe in Lundy Island, and I have been told it occurred not so very long ago on the island in the Serpentine. It doubtless occurs in many other places.

Mus decumanus, the so-called brown rat, undoubtedly comes from Central Asia; and at the present time there is a rat in China described under the name M. humiliatus, which is so little distinguishable from the brown rat that it is thought to be the parent form.

The migration westward of the brown rat certainly took place much later than that of M. rattus. Its first appearance is difficult to date. Undoubtedly large hordes of them crossed the Volga in the year 1727, and continued their journey towards Central Europe. The following year, according to Pennant, brown rats, appeared in England—Jenyns says not till 1730—and almost certainly they came in ships, for on its journey overland it only reached Paris about the year 1750. Reaching England about the year of the second George’s accession, and but thirteen years after the first of the House of Hanover succeeded to the throne, it was called—probably by the adherents of the Stuart cause—the Hanoverian rat. It was also called the Norwegian rat—possibly from the mistaken idea that it reached these islands from that country. It has now passed to the northern half of the New World, where it is gradually driving out many of its weaker brethren. Its numbers are, however, kept within certain limits by wolves, lynxes, raccoons, coyotes, opossums, and other carnivora, and especially by the skunks, which enter barns and out-houses in search of it.

Until the discovery of America, the rat and mouse were unknown in the New World, and the first rats who ever saw it are said to have been introduced in a ship from Antwerp.[19]

The brown rat is of a greyish-brown colour, tinged with yellow and white beneath. The tail is not so long as the body. It is a larger rat than M. rattus, has shorter ears, a more powerful skull, and ten to twelve mammae. Its ears, feet, and tail are flesh-coloured. Like M. rattus, colour varieties occur often: the melanistic variety, not uncommon in Ireland, being sometimes mistaken for the black rat. It is a larger animal than its congener, more heavily built, with a more powerful head, and blunter jaws. The head and body measure some eight to nine inches, but the tail, as a rule, does not surpass the length of the body alone. Its weight averages about nine ounces. It is extremely fierce and extremely cunning, and in the struggle for existence with allied species has hitherto been consistently successful in the fight.

Mus decumanus is very prolific, and produces several litters a year, each averaging eight to ten in number, but twelve or even fourteen young are not very uncommonly born at one time. It begins breeding young—a half-grown female producing a litter of three or four; but in Bombay the sexes do not breed until they have attained at least a weight of 100 grammes. The young are naked, i.e. without hairs, and of a beautiful pink colour. They are blind, and their ears are gummed down over the auditory meatus. They are very weak and helpless, and need that maternal care, which, to do the female rat justice, is never withheld.

M. decumanus is less attached to the dwellings of man than M. rattus; still, it does live in houses, though, owing to a lack of climbing power, it is never found above the third floor. It is largely a burrowing animal, and makes its nests in its burrows. M. rattus can also burrow, but not so readily, and it nests not in the burrow, but in some obscure corner. A curious instance of the nesting habits of this species was found during the rebuilding of my ‘lodgings’ in 1911. In searching under the boards of the floor of the rooms of our Foundress the Lady Margaret, Mother of Henry VII, now the drawing-room, the workmen found the mummified remains of four rats, which had taken to themselves coverings or shrouds; and upon investigation these proved to consist of a vellum deed relating to the College, some paper documents relating to Thomas Thompson, who was Master of the College from 1510 to 1517, and some fragments of printed matter which turned out to be part of an early Virgil; four leaves of a Horace; two leaves of a primer of Wynkyn de Worde; and finally a leaf of a work by Caxton. In addition, four playing-cards of the sixteenth century were found.

The brown rat frequents barns, granaries, stables, slaughter-houses, rivers, ponds, ditches, drains, gullies, and sewers—it is, in fact, sometimes called the sewer-rat. It is less particular in its food than the black rat, which is more usually found in grain-stores. Although in Bombay the relative numbers of M. rattus and M. decumanus caught was as seven is to three, in open spaces, gardens, &c., the latter was much the commoner. Yet the report of the Plague Commission states that the authors ‘do not think it an exaggeration to state that every inhabited building in Bombay City and Island, not excepting even the better-class bungalows, shelters its colony of M. rattus.’

Both species readily take to water, though M. rattus, being the better climber, more readily gets on shipboard. They will swim rivers and arms of the sea. The rats which infest the London Zoological Gardens are said to swim nightly the canal in Regent’s Park. Rats constantly make their way to coastal islands, and in a comparative short time clear the place of indigenous rabbits and birds. Puffin Island, off the coast of Anglesea, and the Copeland Islands, in Belfast Bay, are two examples of islands at one time leased for the sake of their rabbits to people who had to give up the lease after the rats had landed on them. Similar cases are known off Denmark. They greedily eat birds’ eggs, and are said to convey them over considerable distances, though how they do this is not very clear. After the destruction of the vertebrate land-fauna, they fall back upon the dwellers in the littoral, and live on prawns, shrimps, and molluscs. They are very fond of fish, and Lyddeker, in the ‘Royal Natural History,’ states that they occasionally catch and eat young eels. As their parasites show, they eat insects such as the meal-beetle, and when in the field they eat land-snails, insect larvae, and other food, which conveys into their bodies the same tape-worms, &c., which we find in the hedgehog and in the smaller carnivora.

They are, in fact, omnivorous, and nothing in the way of human food is alien to them. They do enormous harm to corn-ricks and to stored grain. They are inveterate enemies of the hen-roost, the pigeon-house, and, as we have seen, of the rabbit-warren. When pressed by hunger, they readily turn cannibal, and the brown rat easily masters the black. There are stories of some few specimens of each species being left in a cage overnight; on the following morning there were only brown rats in that cage. To some extent they help to keep down one of the field-mice (Genus Microtus), and this is especially the case in North America;[20] but the benefit is doubtful since they are held to be at least as destructive to the crops as the field-mice, and probably more so.

The ferocity with which they defend themselves when attacked is well known, and at times, when they are driven by hunger, they do not hesitate to attack man. They are said to nibble the extremities of infants, and in one—apparently authentic—instance they overcame and devoured a man who had entered a disused coal-mine tenanted by starving rats. The bite is said to be severe (they will bite through a man’s thumb-nail into the flesh), and the bite is long in healing.

Rats eat much garbage and offal, and readily feed upon dead bodies. About sixty years ago there stood, at Monfaucon, a slaughter-house for horses, and this it was proposed to remove still farther from Paris. It is stated that the carcasses of the horses slaughtered—which sometimes amounted to thirty-five a day—were cleared to the bone by rats in the course of the following night. This excited the attention of a M. Dusaussois, who made the following experiment: He placed the carcasses of two or three horses in an enclosure, which permitted the entrance of rats by certain known and closable paths. Towards midnight, he and some workmen entered the enclosure, closed the rat-holes, and in the course of that night killed 2650 rats. He repeated the experiment, and by the end of four days had killed 9101 rats, and by the end of a month 16,050 rats. During the process of these experiments other carcasses were exposed in the neighbourhood, so that in all probability M. Dusaussois attracted to his enclosure but a small proportion of the total available number of rats. All around this slaughter-house the country was riddled with extensive burrows, so that the earth was constantly falling in. In one place the rodents had formed a pathway, 500 yards long, leading to a distant burrow.

A rat census can never be taken; but, estimating that there is one rat for every human being on these islands, or less than one rat for every acre of ground, a moderate estimate would give us 40,000,000 rats at any one time. It has been calculated that a rat does at least 7s. 6d. worth of damage during the course of the year: hence in Great Britain and Ireland, we may annually charge them with a loss of at least £15,000,000!

From what has been said it is obvious that rats cause enormous damage to humanity, which is counterbalanced by the almost infinitesimal good they do as scavengers. I do not propose to consider in detail the harm they do as disease-carriers, but one cannot forget that the rat is the primary host of Trichinella spiralis, which, when conveyed from the rat to the pig, and—by eating uncooked or imperfectly cooked pork—from the pig to man, causes severe and very fatal epidemics, and enforces the expenditure of large annual sums on meat inspection. They further convey a virulent form of equine influenza from one stable to another, and also the ‘foot-and-mouth’ disease. But what is infinitely more important to man than all the other injuries put together is the harm they bring to suffering humanity by conveying the bubonic plague from one patient to another. The plague under which India and great parts of Burma are ‘groaning and travailing,’ is caused by a specific bacillus discovered in 1894 by Yersin at Hong-Kong. It flourishes in other vertebrates besides man and the rat, but, owing to the migratory habits of the latter, the rat is the most effective agent in the spread of the disease. Both species of rat seem about equally susceptible, and the presence of the microbe showed no special relation to either the age or the sex of either species. The microbe is conveyed from rat to rat and from rat to man by a flea.

The destruction of the rat is now being urged on all hands, and in the near future we shall probably see a considerable diminution in their numbers in the more civilised countries of the world. This will mean a considerable upset in the balance of power of the almost hidden fauna which surrounds us on all hands. It may even, as the Medical Officer of Health for Bristol has pointed out, lead to an increase of immigration of ship-rats—those most likely to be infected by plague—to take up the places vacated on land by the slain. By one of those commercial agencies—I do not propose to go into the merits of any one of them—which the enterprise of our merchants is now pressing on the public, a large landed proprietor a few months ago completely freed his buildings of rats and mice. A few weeks later his house and out-buildings were overrun by swarms of what to him—for in the time of the rats and mice he had never seen one—was a new and formidable insect. He sought the aid of the Royal Agricultural Society, who referred the matter to their scientific adviser, who pronounced the insects to be cockroaches!

Mr. H. Warner Allen, the representative of the British Press with the French Army, writes as follows in the Morning Post:—

Ferrets have been largely used in the British trenches, but their price is now very high, and the supply is very limited. The method which has had some success in combatting the rabbit-plague of Australia—killing all captured females and let all captured males loose—is certainly worth a trial. Rats will gnaw through concrete, but not if plenty of pieces of broken glass be mixed with the concrete. They will never cross a band of tar which has been kept liquid by mixing with grease. In the French trenches, special rat-runs are dug and these are provided with ‘live’ wires. On touching one of these the rat is electrocuted.

In the eighteenth century, among the officers of his ‘Britannic Majesty,’ was an official rat-catcher, whose special uniform was scarlet, embroidered in yellow worsted with figures of field-mice destroying wheat-sheaves. Inquiry at the Lord Chamberlain’s office has satisfied me that the officer still exists and still catches rats, but I fear the uniform has been abolished. However, a book has recently appeared dealing officially and exhaustively with all matters of this kind, and as soon as I can come by it, I will look the matter up. Should this dignified uniform have really disappeared, might not a humble petition be presented that it be revived? Surely, never more than at the present time should the honour and glory of the rat-catcher be exalted!