A variety of chipmunk species inhabit western North America. A. Ecological variation of the Sierra Nevada resulted in the differentiation of chipmunk species. B. Only one species of chipmunk inhabits eastern North America. C. Although chipmunk species of the Sierra Nevada have the ability to live at various elevations, each species inhabits a specifically restricted one. D. Chipmunks aggressively defend their habitats from invasion by other species of chipmunks. E. Experimental studies indicate that sagebrush chipmunks live in the desert because of their physiological requirements. F. The most aggressive of the chipmunk species is the lodgepole chipmunk.