Its animal life is in the main distinguished in species only from that of the Upper Sonoran belt, including among birds, the desert sparrow, desert thrasher, mocking-bird, hooded oriole; and among mammals small nocturnal species of kangaroo rats, pocket mice, mice and bats.
The Lower Sonoran zone is noted for its cactuses, of which there is a great variety, and some of them grow to the height of trees; the mesquite is also very large, and the creosote bush, acacias, yuccas and agaves are common.
Noteworthy in the animal life of the lower Sonoran and tropic region are a variety of snakes and lizards, desert rats and mice; and, among birds, the cactus wren, desert thrasher, desert sparrow, Texas night-hawk, mocking-bird and ground cuckoo or road runner (Geococcyx Californianus).
The Indian wars, breeding a habit of dependence on force, and the heterogeneous elements of cattle thieves, Sonoran cowboys, mine labourers and adventurers led to one of the worst periods of American border history.
The varied fauna and flora of Texas may be classified in the following life-zones: the Canadian zone, on the highest parts of the Davis Mountains; the Transition zone, including high parts of the Davis, Chisos and Guadalupe mountains; the Upper Austral zone, Upper Sonoran division, in the Panhandle, E.
For the Colorado river and the Grand Canyon see those articles; for the Sonoran boundary region, Report of the Boundary Commission upon the Boundaries between the United States and Mexico (3 vols., Washington, 1898-1899, also as Senate Document No.
The Lower Austral zone occupies the greater part of the Southern states, and is divided near the 98th meridian into an eastern humid or Austroriparian area and a western arid or Lower Sonoran area.
Sauromalus, Crotaphytus, Callisaurus, Holbrookia, Uma, Uta are typical Sonoran genera, some ranging from Oregon through Mexico.
The Upper Sonoran life-zone comprises south-eastern Montana, central, eastern and north-eastern Wyoming, a portion of south-western South Dakota, western Nebraska and Kansas, the western extremity of Oklahoma, north-western Texas, eastern Colorado, south-eastern New Mexico, the Snake plains in Idaho, the Columbia plains in Washington, the Malheur and Harney plains in Oregon, the Great Salt Lake and Sevier deserts in Utah, and narrow belts in California, Nevada and Arizona.
In the Carolinian zone the tulip tree, sycamore, sweet gum, rose magnolia, short-leaf pine and sassafras find their northernmost limit Sage brush is common to both the western arid Transstion zone and the Upper Sonoran zone, but in suitable soils of the latter several greasewoods (Artiplex confertifolia, A.