178 



JMMAL LIFE I\ THE YOSEMITE 



the Tahoe Chipmunk stands midway among the seven species of the region, 

 being smaller than the Mariposa, Long-eared, and Allen chipmunks and 

 larger than the Mono, Alpine, and Sagebrush chipmunks. Tlio coloration 

 of the Tahoe Chipmunk is brighter reddish in general effect than that of 

 any of the others, and the light stripes on the sides of the head and back 

 stand out as being more definitely or clearly white. (See pi. 3.) 



fpinuj 



MUDSONIAN 

 I I CANADIAN 



TRANSITION 



p!l UPPER SOnORAN 



ISD LOWER SONORAN 



Fi 

 zonal 



g. 28. Cross-section of the Siena Nevada through the Yosemite region showing 

 and altitudinal distribution of Chipmunks (genus Eutamias). 



In the lower part of the Canadian Zone the range of the Tahoe Chip- 

 munk overlaps that of the Long-eared. (See fig. 28.) Throughout most 

 of that zone the Tahoe and Allen chipmunks occur on common ground, 

 while the Hudsonian Zone is shared by the Tahoe and Alpine chipmunks. 

 Along the eastern slope of the mountains the Tahoe Chipmunk occurs 

 in localities tenanted by the Mono Chipmunk and in a few places its 

 range touches that of the Sagebrush Chipmunk. But at no place did we 

 find the Tahoe and Mariposa chipmunks together. On the Yosemite Falls 

 trail, mariposac has been recorded at Columbia Point (5000 feet) while 

 frate?' has been seen only 1600 feet higher, at the top of the zigzags. But 

 this difference in altitude almost anywhere else than on the nearly vertical 

 walls of the Yosemite gorge would mean a geograjihical separation of 

 several miles. 



It is difficult to determine with any degree of exactness the population 

 of mammals, even of such diurnally active species a.s chipmunks. Data 

 obtained from field censuses are not so reliable for mammals jus for birds. 

 During the springtime, the regular singing of the male birds makes locating 

 and enumerating individuals simple; then, too, in other seasons the call 

 and flock notes of each s])e('ies are uttered with more or less fre(iuency. 

 Not so with chipnninks! When alarmed tliese animals will call for long 

 periods and then, if there is no new cause for excitement, they will be 

 perfectly quiet for an even longer time. Many times while we were afield 

 in favorable surroundings we did not hear or see a single chipmunk. Then, 

 upon the occurrence of sonu' unusiud sound, several would call at once 

 from (lid'erent directions, all voicing curiosity. In brief, liieii, while we 



