8 ANIMAL LIFE OF CARLSBAD CAVERN 



subdivisions have been mapped and described by the 

 U. S. Biological Survey for each of the two states. The 

 map (Fig. 1) shows in greater detail the topography of 

 the Carlsbad Cave region, with such additions of local 

 information as have been gathered during the explora- 

 tions of the National Geographic Society in the vicinity 

 of the caves. 



Two of the well recognized life zones of North 

 America meet and blend at the Carlsbad Cave: the 

 Lower Austral, colored orange on the map, from below, 

 and the Upper Austral, shown in yellow on the map, 

 from above, while only fifteen miles to the westward 

 the higher and cooler Transition zone, tinted blue, 

 extends along the crest of the Guadalupe Mountains, 

 and the still higher and colder Canadian zone, in green, 

 follows the crest of the Sacramento Range some 

 seventy-five miles to the northwest. These four life 

 zones, as here shown by colors, afford a much greater 

 variety and richness of life in a restricted area than 

 could possibly be found in one uniform type of environ- 

 ment. They also mean a wider range of crop, fruit, 

 and forest products than can be found in one life zone, 

 as well as more varied and stimulating living conditions 

 for man. 



The Lower Austral zone, or the Lower Sonoran arid 

 division of it, covers the Pecos and Rio Grande valleys 

 and the low country between up to an altitude of about 

 five thousand feet on south slopes and to about four 

 thousand feet on the cooler north slopes. These limits 

 vary, however, with the steepness of slopes, the steeper 

 warm slopes (southern exposure) receiving more of the 



