302 University of California Publications in Zoology t v L - 16 



The soil in the sagebrush habitat is light and sandy and being sub- 

 jected to high winds often drifts, and areas of drifting sand are com- 

 mon. The sand heaps up about the various shrubs, forming small 

 dunes. Being continually shifting it would not seem to be a good place 

 for ground-dwelling animals to make their homes. There are small 

 areas where there are no shrubs or plants but only drifting sand, 

 which in some places near the larger rivers forms good-sized dunes. 

 Over large areas covered by sagebrush the sand is packed and is being 

 eroded by the wind. In these places the sand is removed as soon as it 

 is loosened so that little loose sand is present. By the erosion small 

 sand bluffs are sometimes exposed. 



The sagebrush association is represented by a considerable number 

 of species, most of which are characteristic of semi-desert conditions. 

 A few birds, which breed along the streams, forage out a considerable 

 distance into the sagebrush. 



Trapping in sagebrush three miles east of Wallula on the nights of 

 June 10, June 12, and June 17, 1914, produced a total of 1 Onychomys 

 leucogaster fuscogriseus, 6 Perognathus parvus parvus. and 6 Pero- 

 dipus ordii columbianus. On these nights there were 61, 66, and 61 

 traps used respectively. This gives a total of 188 "trap-nights" 

 (Grinnell, 1914, p. 92). Most of the traps were " out-o-sight " mouse 

 traps, but 5 or 6 were rat traps. 



EOCKY-SLOPE HABITAT AND ASSOCIATION (SAGEBRUSH AEEA) 



Exclusive : 



Salpinetes obsoletus obsoletus summer. 



Major : 



Crotalus oregomis. 



Minor: 



Peromyscus maniculatus gambelii. Sylvilagus nuttallii nuttallii. 



Reported : 



Buteo borealis calurus summer Neotoma cinerea occidentalis. 



The rocky-slope habitat is made up of the slopes covered by broken 

 rock and of the exposures of solid basalt and their talus slopes. Some 

 vegetation is usually found in the soil among the rocks and, because 

 the basalt rapidly decomposes, there is a tendency for plants to in- 

 crease rapidly in numbers. The vegetation usually agrees in character 

 with that of the surrounding country. Sagebrush (Artemisia tri- 

 dentata) and wheat bunchgrass (Agropyron spicatum) usually both 



