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At the lower elevations, 3500 ft or less, in Pine Canyon, Cnemidophorus tigris and c. scalaris occupy the same general areas. Corresponding with a rise in elevation, the increase in vegetation density forces both lizards from the flat terrain into the arroyos that drain the canyon. Of the two species, only C. scalaris is found above an elevation of 4000 ft. At this elevation the coarseness of soil texture in the arroyos becomes evident and the sides of the arroyos are steeper. These changes are the result of the increase in the slope of the canyon. Air and soil temperatures appear to offer no physical barriers to the elevation that can be attained by Q. tigris. This species is a fast and nervous forager that may require flat and sparsely vegetated areas not found at higher elevations in Pine Canyon. At one time c. tigris may have inhabited higher elevations because, according to Taylor, McDougall, and Davis (unpublished), drought and overgrazing during the 1940’ s left this area sparsely vegetated. As the area recovered, c. tigris and c. scalaris may have been forced to move down the canyon, with C. tigris moving faster because the increase in vegetation limited the area needed for foraging, whereas c. scalaris moved more slowly because it can cope with more dense vegetation.