1911 Encyclopædia Britannica/Shrew

SHREW[1] a term applied to the species of the family Soricidae of the mammalian order insectivora (q.v.), but in the British Isles to the common and lesser shrews (Sorex araneus and S. minimus).

The common shrew, or, properly, shrew-mouse, which in England is by far the commoner of the two, is a small animal about the size of a mouse, which it somewhat resembles in the shape of its body, tail and feet. But here the resemblance ends, for, unlike the mouse, it possesses a long and slender muzzle, with prominent nostrils, which project far beyond the lower lip; the small eyes are almost concealed by the fur; the ears are wide, short and provided internally with a pair of deep folds, capable when laid forwards of closing the entrance; the tail, which is slightly shorter than the body, is quadrangular in section and clothed more or less densely with moderately long hairs, terminating in a short tuft, but in old individuals almost naked; the feet are five-toed, the toes terminating in slender, pointed claws. The dentition is very peculiar and characteristic: there are in all thirty-two teeth, tipped with deep crimson; of which twelve belong to the lower jaw; of the remaining twenty ten occupy each side of the upper jaw, and of these the first three are incisors. The first incisor is large, with a long anterior canine-like cusp and a small posterior one; then follow two small single-cusped teeth; which are succeeded by three similar progressively smaller teeth, the first being a canine and the other two premolars; the next, a premolar, is large and multicuspid, and this is followed by three molars, of which the third is small with a triangular crown. In the lower jaw there are anteriorly three teeth corresponding to the seven anterior teeth above, of which the first is almost horizontal in direction, with its upper surface marked by three notches, which receive the points of the three upper front teeth; then follow two small teeth and three molars. The body is clothed with closely set fur, soft and dense, varying in colour from light reddish to dark brown above; the under surface of both body and tail being greyish; the basal four-fifths of all the hairs above and beneath are dark bluish grey. On each side of the body, about one-third of the distance between the elbow and the knee, is a gland covered by two rows of coarse inbent hairs, which secretes a fluid with an unpleasant cheesy odour, and which is protective, rendering the creature secure against the attacks of predaceous animals.

The Common Shrew (Sorex araneus).

The lesser or pigmy shrew (S. minutus) is not so abundant in England and Scotland, but common in Ireland, where the other species is unknown. It appears at first sight to be a diminutive variant of that species, which it closely resembles in external form, but the third upper incisor is shorter, or not longer than the next following tooth, whereas in S. araneus it is longer, and the length of the forearm and foot is less in the former species than in the latter.

Both these shrews live in the neighbourhood of woods, making their nests under the roots of trees or in any slight depression, occasionally even in the midst of open fields, inhabiting the disused burrows of field-mice. Owing to their small size, dark colour, rapid movements and nocturnal habits, they easily escape observation. They seek their food, which consists of insects, grubs, worms and slugs, under dead leaves, fallen trees and in grassy places. They are pugnacious, and if two or more are confined together in a limited space they invariably fight fiercely, the fallen becoming the food of the victorious. They are also exceedingly voracious, and soon die if deprived of food; and it is probably to insufficiency of food in the early dry autumnal season that the mortality among them at that time is due. The breeding-season extends from the end of April to the beginning of August, and five to seven, more rarely ten, young may be found in the nests; they are naked, blind and toothless at birth, but soon run about snapping at everything within reach.

The alpine shrew (S. alpinus), restricted to the alpine region of Central Europe, is slightly longer than the common shrew and differs in its longer tail, which exceeds the length of the head and body, in the colour of the fur, which is dark on both surfaces, and in the large size of the upper ante penultimate premolar. The water-shrew (Neomys fodiens), the third species inhabiting England, differs from the common shrew in being larger with a shorter and broader muzzle, smaller eyes and larger feet adapted for swimming-the sides of the feet and toes being provided with comb-like fringes of stiff hairs. The tail is longer than the body, and has a fringe of moderately long regularly ranged hairs, which extend along the middle of the under surface from the end of the basal third to the extremity. The fur is long and dense, varying in colour in different individuals; the prevailing shades are dark, almost black, brown above, beneath more or less bright ashy tinged with yellowish; but occasionally we find individuals with the under surface dark-coloured. In the number and shape of the teeth the water-shrew differs from the common shrew: there is a premolar less on each side above; the bases of the teeth are more prolonged posteriorly; and their cusps are less stained brown, so that in old individuals they often appear white. This species is aquatic in habits, swimming and diving with agility. It frequents rivers and lakes, making burrows in the banks, from which when disturbed it escapes into the water. Its food consists of water insects and their larvae, small crustaceans and probably the fry of small fishes. It is generally distributed throughout England, is less common in Scotland and not recorded in Ireland.

The geographical range of the common shrew is wide, extending eastwards through Europe and Asia to Amurland. The lesser shrew extends through Europe and Asia to Sakhalin Island; and specimens of the water-shrew have been brought from different parts of Europe and Asia as far east as the Altai. In Siberia the common shrew is abundant in the snow-clad wastes about the Olenek river within the arctic circle. Other species of red-toothed shrews are restricted chiefly to North America, where they are found in greater variety than in the Old World, though Neomys is not represented. Its place is taken by Sorex palustris east of the Rocky Mountains, and S. hydrodromus in Unalaska Island, which, like the water-shrew, have fringes of hair on the feet, but the infringed tail and dentition of the common shrew. Of the American forms S. bendiri is the largest. Other red-toothed shrews belonging to the genus Blaring, distinguished from Sorex by the dentition and the shortness of the tail, are common in North America. All red-toothed shrews (except the aquatic forms) closely resemble one another in habits, but the short-tailed North American shrew supplements its insectivorous fare by feeding on beech nuts. In destroying numbers of slugs, insects and larvae, shrews aid the farmer and merit protection. Although their odour renders them safe from rapacious animals, they are destroyed in numbers by owls.  (G. E. D.) 

  1. This word, whence comes the participial adjective “shrewd,” astute, originally meant malicious, and, as applied to a woman, still means a vexatious scold. From their supposed venomous character it was applied to the Soricidae.