basin sagcbrusli biociations, as iiulicatcd by the spe- 

 cies marked with an asterisk in tlie above Hsts, but 

 there is a sufficient difference to warrant calling the 

 two areas faunistically distinct. At the subspecies 

 level, the contrast between the two animal commu- 

 nities is more striking. In addition to a strong intru- 

 sion of grassland species, the basin sagebrush has the 

 following noteworthy species (Linsdale 1938, Hall 

 U)46, Fautin 144<i) : 



Lizards arc ninnerous and conspicuous. Counts 

 of only those seen above ground gave an average for 

 the summer season of 6.5 per hectare (2.6/acre). A 

 few ani])hibians, particularly the western spadefoot 

 toad and western toad, occur near bodies of water 

 (Linsdale 1038, Fautin 194fj). 



Inicrtchratfs 



Mammals 



Xuttall's cottontail 

 Pigmy rabbit 

 Townsend's ground 



S(iuirrel 

 White-tailed antelope 



squirrel 

 Least chipmunk 

 Little pocket mouse 

 Great Basin pocket 



Long-tailed pocket 



mouse 

 Chisel-toothed kangaroo 



rat 

 Orel's kangaroo rat 

 Dark kangaroo mouse 

 Northern grasshopper 



mouse 

 Sagebrush vole 



Rodents, exclusive of ground squirrels and pocket 

 gophers, average about 40 per hectare (16 per acre) 

 in western Utah with deer mice and kangaroo rats 

 most numerous. Ground squirrels are widespread 

 and numerous although sometimes locally restricted. 

 Black-tailed jack rabbits are important constituents 

 of the community and average numbers seen in dif- 

 ferent plant communities range from less than 0.1 to 

 0.3 per hectare. The pronghorn was once numerous 

 in the Great Basin sagebrush, but not the bison 

 (Fautin 1946). 



Birds 



There is greater contrast in the avifauna be- 

 tween the desert scrub and basin sagebrush biocia- 

 tions than in the mammalian fauna. However, more 

 species enter this community from the grassland and 

 forest-edge biociations, such as the Swainson's hawk, 

 prairie falcon, burrowing owl, and horned lark, than 

 venture into the desert scrub. Bird populations are 

 low during the breeding season, averaging only about 

 25 pairs per 40 hectares (100 acres). The principal 

 avian species in the basin sagebrush in addition to 

 those listed above are (Fautin 1946, Miller 1951) : 



Sage grouse 

 Poor-will 

 Sage thrasher 



Sage sparrow 

 Brewer's sparrow 



Reptiles 

 Collared lizard Long-nosed snake 



Sagebrush lizard Prairie rattlesnake 



Striped whi]) snake 



Actually, only two strata occur in this com- 

 munity, the shrub and ground, since herbs are few 

 and scattered most of the year. In the shrub stratum, 

 arachnids, cicadellids, fulgorids. coccids, chrysome- 

 lids, and mirids are most numerous. Grasshoppers 

 feed on the foliage and lay their eggs in open areas 

 of the ground. Arachnids, tenebrionid beetles, and 

 ants are the most conspicuous ground invertebrates. 

 The harvester ant and honey ant build conspicuous 

 mounds, the number of mounds of the former aver- 

 aging over 15 per hectare (6.2/acre) in the sage- 

 brush community. Invertebrates are most numerous 

 in sagebrush and greasewood and least abundant in 

 shadscale. Maximum populations occur in May on 

 most of the vegetation, after which they decline as 

 temperature increases, but on the greasewoods, which 

 retain their leaves and remain green, populations 

 remain more constant throughout the summer (Fau- 

 tin 1946). 



OTHER BIOCIATIONS 



The vegetation and animal life of extreme 

 deserts around the world are impoverished, but in 

 semi-deserts, similar to those in southwestern North 

 America, ecologically equivalent species occur, al- 

 though they show little taxonomic relationships with 

 each other. These organisms are derived from ad- 

 jacent, more humid floras and faunas and have many 

 similarities in adjustments and adaptations. Rodents, 

 for example, are generally numerous everywhere. In 

 North American deserts the genera Dipodomys and 

 Perognathus of the family Heteromyidae are espe- 

 cially important ; in the Eurasian deserts, Gerbillus, 

 Meriones, and Dipodillus belonging to the family 

 Muridae are found ; in South Africa Pcdetcs, family 

 Pedetidae, occurs : and in the Australian desert the 

 family Muridae is represented by Xotoiiiys. All are 

 bipedal in locomotion and have elongated hind legs 

 (Schmidt-Nielsen in Cloudsley-Thompson 1954). It 

 is also of interest that tenebrionid beetles are repre- 

 sented by different subfamilies in different deserts of 

 the world, but, contrary to the prevailing desert col- 

 ors, these diurnal beetles are predominantly black 

 (Brehm 1896, Buxton 1923, Haviland 1926, Kach- 

 karov and Korovine 1942, Bodenheimer 1953). 



Desert biome 337 



