In a state of nature pocket gophers are constantly bringing the subsoil to the surface and burying humus. Over an enormous area they exist in such countless thousands that their work, like that of angleworms, is often of the most beneficial character. On bare slopes, however, their work is highly injurious, as it greatly increases erosion of the fertile surface soil and thus has its direct influence in changing world contours.
When civilized man arrives in their haunts and upsets natural conditions with cultivated crops the new food supply stimulates an increase in the gopher population and their activities immediately become excessively destructive and necessitate unremitting warfare against them.
THE KANGAROO RATS (Dipodomys spectabilis and its relatives)
(For illustration, [see page 518])
The desert regions of western North America have developed several peculiar types of mammals, and among them are none handsomer or more interesting than the kangaroo rats. These rodents, despite their name, are neither kangaroos nor rats, but are near relatives of the pocket mice, which share their desert haunts.
All are characterized by a kangaroo-like form, including small fore legs and feet, long hind legs and feet for jumping, and a tail longer than the body to serve as a balance. In addition, they have large, prominent eyes and are provided with skin pouches on each side of the mouth for use in holding food to be carried to their store chambers.
The color pattern, like the form, of the kangaroo rats is practically uniform throughout the group. Both are well shown in the accompanying plate of Dipodomys spectabilis, the largest and most strongly marked species. Its total length is from 12 to 14 inches; most of the other species are much smaller.
Kangaroo rats of many species are distributed over most of the arid and semiarid regions of the United States and Mexico, from Nebraska, Oklahoma, and the Gulf Coast of Texas west to the Pacific coast, and from Montana and Washington southward to the Valley of Mexico and throughout Lower California. They are especially numerous in the southwestern deserts, where they are the oddest and most picturesque of animals.
Although they have no near relatives in the Old World, some of the African and Asiatic jerboas are externally almost perfect replicas of the kangaroo rats in every detail of form, color, and color pattern, even to the tail markings. This extraordinary likeness in appearance of two widely separated and unrelated animals is made doubly significant by the fact that both live in deserts and have similar habits.
Peculiarly desert animals, kangaroo rats live like the pocket mice, without drinking, but obtain the necessary water through their digestive processes. They are most numerous in sandy areas, and there the earth is sometimes so riddled by their burrows as to render horseback riding difficult.