1911 Encyclopædia Britannica/Pocket-gopher

From Wikisource
Jump to navigation Jump to search

POCKET-GOPHER (i.e. pouched rat), the name of a group of, chiefly North, American rat-like rodents, characterized by the possession of large cheek-pouches, the openings of which are external to the mouth; while their inner surface is lined with fur. The cheek-teeth, which comprise two pairs of premolars and three of molars in each jaw, are in the form of simple prisms of enamel, which do not develop roots. The fore and hind limbs are of approximately equal length, but the second and third front-claws are greatly enlarged, and all the claws are furnished at the base with bristles. The eyes are small, and the external ears rudimentary.

Pocket-gophers, which typify a family, the Geomyidae, spend the whole of their time underground, and are specially organized for such a mode of existence, their powerful claws being adapted for digging, while the bristles on the toes prevent the earth from passing between them. The upper incisor teeth are employed to loosen the ground, like a fork; and the little rodents are able to move both backwards and forwards in their runs. The cheek pouches are employed solely in carrying food, which consists largely of roots. In the typical genus Geomys the upper incisors are groove, but in the allied Thomomys they are smooth. The common pocket-gopher, Geomys bursarius, of the Mississippi Valley measures about 8 in. in length, with a tail of between 2 and 3 in.; its colour being rufous brown and greyish beneath. A well-known representative of the second genus is Thomomys tatpoides, which is considerably smaller than the former. To the farmer and the gardener pocket gophers are an unmitigated source of annoyance. (See Rodentia.)