NATURAL AREAS AND REGIONS 



195 



tain species of 5-toed kangaroo rats. 

 Of the birds, we must call particular 

 attention to the California thrasher, 

 . . . the California brown towhee, 

 the California bush-tit, the rufous- 

 crowned sparrow, the Bell sparrow, the 

 California jay, and the wren-tit. . . . 



Birds and mammals in the northern 

 coast belt are, relatively to adjacent 

 districts, more plentiful in individuals 

 than they are in species. Of the more 

 interesting kinds may be mentioned the 

 Columbian black-tailed deer, . . . 

 the Roosevelt elk. . . . The strange 

 rodent called Aplodontia or mountain 

 beaver, which lives in burrows in wet 

 hillsides overgrown with rank clumps of 

 sword fern; the peculiar shrewmole; 

 . . . the varied thrush, . . . 

 south even to the Humboldt redwoods 

 and in winter generally over west-central 

 and southern California; and the diminu- 

 tive western winter wren whose creaking 

 song greets one from dense tangles in 

 ravine bottoms or from mossy logs in the 

 deepest shade of the redwoods. There 

 are, in addition, a number of other mam- 

 mals and birds, of more or less wide 

 general range elsewhere, though pre- 

 senting local species or subspecies in 

 different parts of the humid coast belt. 



While reptiles are very few in species 

 and individuals in the coast belt, amphib- 

 ians are correspondingly numerous in 

 both respects, and include some species 

 of exclusively Pacific distribution. The 

 big, slug-eating salamander (Chrondro- 

 tus) is one of these. 



The author calls attention to the fact 

 that the mammals are nearly all of 

 nocturnal habits whereas the reptiles 

 are more active during daylight hours. 

 This accounts for the fact that the rep- 

 tiles are the most conspicuous of the 

 vertebrates on the desert. Few reptiles 

 can be seen abroad during the cool days 

 of the midwinter season on the western 

 deserts, but by April they appear in 

 considerable numbers. Of the poison- 

 ous reptiles found on the deserts of the 

 Southwest, only the rattlesnakes occur 

 in California. Several lizards are com- 

 mon, including the chuckwalla (Sauro- 

 malus), the fleet-footed lizards (Scelopo- 

 rus) and the whiptails (Cnemidophorus) . 

 Of these, the chuckwalla (S. ater) of 

 black and orange coloring is the largest, 

 attaining a length of 15 in. and having a 

 proportionately stout body. The desert 

 tortoise (Gopherus agassizii) is found 



excavating its burrows in sandy places 

 and wandering about over the great 

 stretches of the Mohave. That there is 

 a sufficient food supply for the numerous 

 reptiles of the deserts is accounted for 

 by the fact that nearly all parts of the 

 southwestern deserts are visited at 

 irregular intervals by heavy rains fol- 

 lowed by luxuriant growths of herbs 

 which produce an abundance of seeds. 

 These seeds, lasting over periods of 

 drouth, support great numbers of in- 

 sects and rodents, and these in turn 

 furnish the food supply of the reptiles. 



Notwithstanding that reptiles are 

 more conspicuous, due to their daylight 

 habits, Grinnell believes that indi- 

 vidually, mammals outnumber the com- 

 bined birds and reptile population on 

 many parts of the Mohave and Colorado 

 deserts. Among these the seed-gather- 

 ing rodents, Dipodomys and Perogna- 

 thuS) known as the kangaroo-rats and 

 pocket-mice are the commonest. The 

 deer-mice, the carnivorous grasshopper- 

 mice (Onychomys) and the desert wood- 

 rats are other night-roaming rodents. 

 Three species, the antelope ground- 

 squirrel (Ammospermophilus leucurus), 

 the round-tailed ground-squirrel (Citel- 

 lus tereticaudus), and the desert jack- 

 rabbit (Lepus californicus deserticola), 

 are found abroad during the early morn- 

 ing and evening hours of daylight. 

 Two carnivorous mammals are present: 

 the big-eared kit fox (Vulpes arsipus) 

 and a species of coyote (Cam's ochropus 

 estor), small and pale in color. There 

 are also quite a large number of different 

 kinds of bats which feed upon the abun- 

 dant insect life of these deserts. 



Birds of the deserts 



are few in individuals save on the bot- 

 tomlands along such streams as the Gila, 

 Colorado and Mohave. Here, where the 

 deciduous mesquite, cottonwood and 

 willow furnish directly or indirectly 

 abundance of food and shelter, birds are 

 plentiful. . . . The tit-mouse-like 

 verdin, Abert towhee and crissal 

 thrasher are resident the year through, 

 while the Lucy warbler, plumbeous 

 gnatcatcher, Cooper tanager, white- 

 winged dove, Sonora yellow warbler, 

 and a score of other species are but 



