Wolf, Prairie, or Plains Coyote 424 423 Wolf, Timber or Gray 421 423 Wolverine 428 427 SMALLER MAMMALS OF NORTH AMERICA BY EDWARD W. NELSON CHIEF, U. S. BIOLOGICAL SURVEY _With illustrations in color from paintings by Louis Agassiz Fuertes_ In that part of North America lying north of Mexico more than 1,300 species and geographic races of mammals are known to exist. Of these by far the greater number, both of species and individuals, fall into the class of smaller mammals. Some of the most characteristic types which appear to have originated in North America are the mountain-beavers, pocket-gophers, kangaroo-rats, pocket-mice, wood-rats, white-footed mice, muskrats, skunks, and ring-tailed cats. In Siberia and Europe live close counterparts of our northern weasels, minks, martens, field-mice, lemmings, northern hares, conies, marmots, moles, and others; and on our southern border the armadillo and the hog-nosed skunk introduce a faint tinge of a strange fauna from South America. FURRY FRIENDS AND ENEMIES The muskrats, minks, martens, and skunks for many years have yielded an enormous annual return from their furs; the squirrels and rabbits afford sport and a large supply of excellent flesh for food; the prairie-dogs and some of the ground-squirrels existing in enormous numbers have been excessively destructive to crops; and others, like the porcupine and the armadillo, have attracted particular attention because of their strange characteristics. ANIMALS THAT LEARNED TO “DIG IN” The smaller mammals live everywhere, from the tropical end of Florida to the uttermost lands of the frozen North, and from the seashore to the limit of vegetation on the high mountains. The heaviest forests, open meadows, rugged mountain slopes, arctic barrens, and sun-scorched desert plains all have their small four-footed habitants. Many modifications of parts and organs of the various species have been necessary to adapt the small mammals to specialized modes of life. This is strikingly illustrated in the case of those true rodents, the pocket-gophers, which apparently found competition on the surface of the ground so acute that they took the unoccupied territory below the surface, where they live as miners and tunnel from place to place in search of edible roots, with an occasional stealthy excursion above ground to seize some of the food available there. Another excellent illustration is furnished by the moles, which, leaving the numerous closely related species--the shrews--to feed upon insects above ground, have descended and, like the pocket-gophers, live in tunnels which they make in the pursuit of earthworms and insects below the surface; like the gophers, they, too, make occasional excursions above ground in search of food.