United States

Arrangement of the account of the distribution of the fauna according to the climatic and vegetal regions has the merit that it can be compared further with the distribution of insects and of other invertebrates, some of which may be expected to fall into the same patterns as the vertebrates, while others, with different modes or different ages of dispersal, have geographic patterns of their own.

The transcontinental zone of coniferous forest at the north, the taiga, and the tundra zone into which it merges at the northern limit of tree growth are strikingly paralleled by similar vertical zones in the Rockies, and on Mount Washington in the east, where the area above the timberline and below the snow line is often inhabited with tundra animals like the ptarmigan and the white Parnassius butterflies, while the spruce and other conifers below the timberline form a belt sharply set off from the grassland or hardwood forest or desert at still lower elevations.

A whole series of important types of animals spread beyond the limits of such regions or zones, sometimes over most of the continent. Aquatic animals, in particular, may live equally in forest and plains, in the Gulf states, and at the Canadian border. Such widespread animals include the white-tailed (Virginia) deer and black bear, the puma (though only in the remotest parts of its former range) and bobcat, the river otter (though now rare in inland areas south of the Great Lakes) and mink, and the beaver and muskrat. The distinctive coyote ranges over all of western North America and eastward as far as Maine. The snapping turtle ranges from the Atlantic coast to the Rocky Mountains.

In the northern coniferous forest zone, or taiga, the relations of animals with European or Eurasian representatives are numerous, and this zone is also essentially circumpolar. The relations are less close than in the Arctic forms, but the moose, beaver, hare, red fox, otter, wolverine, and wolf are recognizably related to Eurasian animals. Even some fishes, like the whitefishes (Coregonidae), the yellow perch, and the pike, exhibit this kind of Old World–New World relation. A distinctively North American animal in this taiga assemblage is the Canadian porcupine.

The hardwood forest area of the eastern and the southeastern pinelands compose the most important of the faunal regions within the United States. A great variety of fishes, amphibians, and reptiles of this region have related forms in East Asia, and this pattern of representation is likewise found in the flora. This area is rich in catfishes, minnows, and suckers. The curious ganoid fishes, the bowfin and the gar, are ancient types. The spoonbill cat, a remarkable type of sturgeon in the lower Mississippi, is represented elsewhere in the world only in the Yangtze in China. The Appalachian region is headquarters for the salamanders of the world, with no less than seven of the eight families of this large group of amphibians represented; no other continent has more than three of the eight families together. The eel-like sirens and amphiumas (congo snakes) are confined to the southeastern states. The lungless salamanders of the family Plethodontidae exhibit a remarkable variety of genera and a number of species centring in the Appalachians. There is a great variety of frogs, and these include tree frogs whose main development is South American and Australian. The emydid freshwater turtles of the southeast parallel those of East Asia to a remarkable degree, though the genus Clemmys is the only one represented in both regions. Much the same is true of the water snakes, pit vipers, rat snakes, and green snakes, though still others are peculiarly American. The familiar alligator is a form with an Asiatic relative, the only other living true alligator being a species in central China.

In its mammals and birds the southeastern fauna is less sharply distinguished from the life to the north and west and is less directly related to that of East Asia. The forest is the home of the white-tailed deer, the black bear, the gray fox, the raccoon, and the common opossum. The wild turkey and the extinct hosts of the passenger pigeon were characteristic. There is a remarkable variety of woodpeckers. The birdlife in general tends to differ from that of Eurasia in the presence of birds, like the tanagers, American orioles, and hummingbirds, that belong to South American families. Small mammals abound with types of the worldwide rodent family Cricetidae, and with distinctive moles and shrews.

American bisonAmerican bison, or plains buffalo (Bison bison).Alan G. Nelson/Root Resources