ANIMAL LIFE IN THE YOSEMITE 



DISTRIBUTION OF ANIMAL LIFE IN THE YOSEMITE SECTION 



Probably the primary stimulus which leads people to visit our national 

 parks is the change that is experienced from familiar surrounding to those 

 which are emphatically different. This change involves 'air' (that is, 

 climate), and 'scene' (topography and vegetation). An entirely new set 

 of conditions is encountered, and the new reactions set up mean recreation 

 in the physiological sense — the exercise of faculties, both mental and 

 physical, in kind or degree, that are more or less dormant during the 

 ordinary routine of the year's program. Quick transportation between 

 the lowlands of the San Joaquin Valley and the upper altitudes of the 

 Sierras carries the traveler in either direction from one set of surroundings 

 into a totally different one where he is thrilled because of the great changes 

 which he encounters. 



Let us now discuss, then, these differences in environment and their 

 correlation with the continuous or discontinuous occurrence of vertebrate 

 animals in the region. The section of the Sierra Nevada selected for faunal 

 study is of such extent transversally to the Sierran axis that it takes in 

 almost as great extremes of conditions as are to be encountered anywhere 

 in California. Analysis of the changes to be observed as a person traverses 

 the section from the west ^^^ll soon show that he has witnessed not one single 

 change, evenly and progressively from one set of conditions to just one other 

 set, but that, having reached the highest altitudes, he has witnessed several 

 steps. There has not been a uniform and continual gradient but he has 

 passed through several belts, parallel roughly to the axis of the Sierra 

 Nevada, each characterized by a considerable degree of uniformity as 

 regards the plant and animal life. 



A total of 231 kinds of birds are now (December 31, 1920) authentically 

 known from the Yosemite section ; there are 97 kinds of mammals, 22 kinds 

 of snakes and lizards, and 12 kinds of frogs, toads, and salamanders. This 

 makes a grand total, for the vertebrate fauna outside of fishes, of 362 forms. 

 This seeming richness in number of kinds, be it emphasized, is apparent 

 only when one takes into account the full extent of the Yosemite section. 

 As a matter of fact, but a small proportion of the total number of species 

 occur together at any one level. And here is the remarkable thing: They 

 are more or less assorted and delimited in occurrence so that tlioy helji to 

 constitute the belts, or 'life zones,' just referred to. 



