Brown Rat (Epimys norvegicus, Erxleben).

The Brown Rat still has two alternative names applied to it, though the inappropriateness of one was shown by Pennant more than 150 years ago. These names are Norway Rat and Hanoverian Rat. Pennant does not mention the second, but of the first he says that the Brown Rat is quite unknown in Scandinavia and is not mentioned by Linnæus. The name Hanoverian appears to have been given to it because it was believed to have made its entry into England with George I. Writing in 1776, Pennant says: "This animal never made its appearance in England till about forty years ago." Recent researches into its distribution make it appear that the species originated in Trans-Baikal, whence it has spread westwards, even to America by way of the British Isles. Both species hit upon an improved method of extending their range over the earth. The old-fashioned natural way for mammals to spread was for a few adventurous individuals to make food-finding excursions beyond the district in which they were born; but climate, mountain ranges, broad rivers or seas often checked further progress. The Rats discovered that by keeping close to man they were always in the neighbourhood of food, whether intended for himself or his domestic animals; and even these tame creatures would at times serve for the Rats' meals. So when they found man loading ships with grain and other desirable food they decided to go with him. Often they contrived to get into his bales of merchandise and so conveyed to the hold. If not, there were always mooring ropes which served as bridges from the quay to the vessel. And so they got themselves conveyed in comfort, sure that wherever the goods went there would be settlements of their biped friends to house them and serve their ends generally. Now, wherever man has established himself, you are almost certain that the Rat is close at hand.

Mr. A. W. Rees, in his interesting "Creatures of the Night," has summarised the chief characteristics of this species in a paragraph. He says: "Brown Rats are an insufferable nuisance. There is no courtesy or kindness in the nature of the Rat; no nesting bird is safe from his attacks, unless her home is beyond his reach in some cleft of a rock that he cannot scale or in some fork of a tree that he cannot climb. He is a cannibal—even the young and the sick of his own kind become the victims of his rapacious hunger—and he will eat almost anything, living or dead, from the refuse in a garbage heap to the dainty egg of a willow-wren in the tiny, domed nest amid the briars at the margin of the river."

As compared with the Black Rat he is more heavily built, and the combined length of head and body is eight or nine inches, whilst the thicker, scaly-ringed tail is only equal to, or less than, the length of the body alone. His head is proportionately shorter, with blunter muzzle, much smaller ears and more prominent though smaller eyes. The fur on the upper parts is grey-brown with a tawny tinge, and dirty white on the under parts. The ears, feet, and tail are flesh-coloured. It sometimes occurs with black or blackish fur, and is then frequently mistaken for the Black Rat; but the relative length of tail to body is a superficial character by which they can be separated at once. There is a black race of this species on the east coast of Ireland to which some authors have given the distinctive name of Epimys hibernicus. It appears to have extended its range from Ireland to the Hebrides. In one form or other the Brown Rat has extended to nearly every part of the British Islands and their islets.

Skeleton and Molars of Brown Rat.

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The Brown Rat becomes a parent at the age of six months, and produces four or five litters in a year. Ordinarily these consist of from four to ten blind, deaf, and naked young; but much larger litters are on record, the highest of which we have seen a note being twenty! Sometimes the young grow up hairless or blind. Some years ago we disturbed a nest in the garden from which issued half a dozen young Rats about four inches long (head and body), all blind. They moved about in a very uncertain manner, and were easily despatched. Similar cases have been recorded. At the meeting of the Zoological Society in December, 1902, a hairless Rat was exhibited on behalf of Mr. G. A. Doubleday, one of three captured at Leyton, Essex, in the same condition. The skin, which was slate-coloured, was wrinkled into folds all over the body. Millais mentions a hairless Rat with yellow skin.