8 ANIMAL LIFE IX THE TOSEMITE 



particular state of affairs found in the Yosemite region. Since all animal 

 life is more or less directly dependent upon plant life for its existence, the 

 zoologist who seeks to explain the distribution of animals must concern 

 himself attentively also -with the botany of the region he is studying. A 

 very useful essay on the distribution of plant life on the upper western 

 slope of the Yosemite section is contained in Professor and Mrs. Hall's 

 Yosemite Flora-; and further valuable data on the distribution of plants 

 in the Sierras will be found in a report by Dr. Smiley.^ 



All of the six life zones in the Yosemite region are represented in full 

 measure on the western slope of the section. There the distance involved 

 in the slope is so great, over seventy miles, that there is plenty of room 

 for the development of a separate representation of species, both plant 

 and animal, in each zone. But on the eastern slope the situation is some- 

 what different ; and we find the zonation there obscure. Indeed, in our 

 field work below the Hudsonian Zone we met with much trouble in 

 diagnosing many of the localities; for instance, whether to call the upper 

 meadows on the Farrington ranch (pi. 19a.), Canadian or Transition; the 

 south face of Williams Butte (pi. 196), Transition or Upper Sonoran. 



On the basis of the facts obtained within the eastern boundary of our 

 Yosemite section alone, the situation would be exceedingly difficult, even 

 impossible, of explanation. But when we take into account the ea.st-Sierran 

 region generally, especially toward the southern end of the Sierran ridge 

 in the vicinity of Walker and Tehachapi passes, it becomes fairly easy to 

 see why conditions are as we find them between Mono Lake and Mono and 

 Tioga passes. 



Base-level in the Mono Basin is high, averaging 7000 feet in altitude. 

 Furthermore, the distance between Mono Lake and the high Sierran crest, 

 which is 10,000 to 13,000 feet in altitude, is short. In other words, this 

 slope is abrupt ; in fact, close to the divide, a declivity. The life zones, 

 in so far as characteristic representatives of them are to be found, are 

 crowded together — telescoped, as it were. There is a well established law 

 that a sequestered faunal area can be too small to support a permanent, 

 distinctive fauna of its own, even though conditions be otherwise wholly 

 propitious. The Sierra Nevada, which by area is of mainly western slope, 

 supports a large mass of 'boreal' plant and animal life; the Great Basin 

 area to the east is the metropolis of a highly developed 'austral' assemblage 

 of species. These two major areas adjoin one another at the steep eastern 

 declivity of the Sierras. On the long western slope where austral adjoins 



2H. M. Hall and C. C. Hall, A Yosemite Flora (Paul Elder, San Francisco, 1912), 

 pp. viii + 282, 170 text figs., 11 pis. 



3 F. J. Smiley, A Rejjort upon the Boreal Flora of the Sierra Nevada of California 

 (Univ. Calif. Publ. Bot., vol. 9, 1921), pp. 1-423, pis. 1-7. 



