178 



ANIMAL LIFE IN 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. The 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.) 



Fig. 28. Cross-section of the Sierra Nevada through the Yosemite region showing 

 zonal 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, mariposae has been recorded at Columbia Point (5000 feet) while 

 f rater 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 geographical separation of 

 several miles. 



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

 of mammals, even of such diurnally active species as chipmunks. Data 

 obtained from field censuses are not so reliable for mammals as 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 species are uttered with more or less frequency. 

 Not so with chipmunks! When alarmed these 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 some unusual sound, several would call at once 

 from different directions, all voicing curiosity. In brief, then, while we 



