RATS[15] (_Mus_ or _Epimys_)
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.
[15] The modern systematist now calls the black rat _Epimys rattus_,
and distinguishes two varieties—_E. rattus alexandrinus_ and _E. rattus
rattus_; the brown rat is now _E. norvegicus_.
[16] _A History of British Quadrupeds_, 2nd ed. London, 1874.
[17] London, 1833.
[Illustration: FIG. 44.—_Mus rattus._ (From Pennant.)]
_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.’
[Illustration: FIG. 45.—Head of _Mus rattus_. (From Flower and
Lyddeker.)]
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.
Day by day we passed them—
Met them unaware,
Shambling through the lobbies,
Squatting on the stair.
Not a rat among them
Moved to give us place,
Staring with its cruel eye
And its aged face.
(F. LANGRIDGE.)
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.
[18] _British Zoology._ London, 1812.
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.
[19] Ovalle’s ‘History of Chili,’ in _Churchill’s Voyages_, vol. iii,
p. 45.
_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.
[Illustration: FIG. 46.—_Mus decumanus._ (From Pennant.)]
_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_.’
[Illustration: FIG. 47.—Head of _Mus decumanus_. (From Flower and
Lyddeker.)]
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.
[20] ‘An Economic Study of Field-mice (Genus _Microtus_).’ By Dr.
Lantz, in _U.S. Dept. of Agric., Biol. Survey_, Bull. 31.
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 7_s._
6_d._ 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_:—
Of the smaller trench annoyances few are more worrying than the plague
of rats. Shelters and trenches, no matter where they are made, whether
in woods or open fields or on the mountainside, become immediately
infested with the objectionable creatures. In one case within my own
personal knowledge they drove a French officer out of a comfortable
and commodious dug-out into a damp and melancholy shelter, which was
to some extent protected from them by sheets of corrugated iron. The
plague had attained considerable dimensions before a really organised
attempt was made to deal with it, and there were many cases of rats
actually biting men who were chasing them down the trenches.
Terriers have proved of considerable assistance. Trains full of
dogs have been dispatched to the Front, and poison has been fairly
effective. Lately, a reward has been offered for every dead rat
brought in by men in the trenches, and regular battues have been
organised. In a single fortnight one army corps alone has disposed of
no fewer than 8000 rats. At a halfpenny a rat this has involved an
expense of £16, and it was certainly money well spent. The sport of
rat-catching on such very advantageous terms has proved very popular
among the men, who now suggest that the standing reward offered for
the more dangerous and more exciting form of sport involved in the
capture of a German machine-gun should be raised to a higher figure.
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!