192 ANIMAL LIFE IN THE YO SEMITE 



frightened a cliipmiink will utter a startled vjJiip-pcr'r'r as it runs to 

 shelter. On occasion a low chuckling note is given, similar to the hollow- 

 sounding 'barks' of the larger species. 



The Alpine Chipmunks, despite their boreal home, are active through 

 a rather long season. Our earliest contact with them seasonally was on 

 June 28, 1915, when a number were noted on Mount Hoffmann. As the 

 breeding season was then well advanced or nearly over it seems likely that 

 they had begun to be active much earlier in the year. On October 11, 1915, 

 several of the animals were seen still abroad in the vicinity of Ten Lakes. 

 At Tuolumne Meadows we were told that during a storm in mid-September 

 the Alpine Chipmunks had taken to cover, but that they had reappeared 

 as soon as snow ceased to fall. The individuals seen on Mount Hoffmann 

 were, in several instances, running across the snow banks. Judging from 

 observations made elsewhere upon other species of chipmunks, it seems 

 probable that weather rather than temperature alone is the determining 

 factor in limiting the season of activity for the Alpine Chipmunk. 



The time of mating is unknown. Two females collected June 30, 1915, 

 contained 4 and 5 large embryos, resjjectively, and others captured between 

 July 5 and 17 had been recently suckling young. Males collected in July 

 gave evidence that the period of sexual activity was well past. On July 30, 

 young individuals were abroad around Tuolumne Meadows. A young 

 female weighing 19.5 grams, which is only about half of the weight of an 

 average adult, was collected at 10,500 feet altitude on Mount Florence, 

 August 20, and two individuals obtained on Mount Clark on August 22 

 were scarcely two-thirds grown. By early October young-of-the-year had 

 reached nearly or quite the size of adults. 



The Alpine Chipmunks obtained at the end of June and in early July 

 are passing from the much worn and dulled winter pelage into the more 

 brightly colored new coat. By October this new pelage is completely 

 assumed and is then not only longer and denser but more grayish in tone 

 than when it first starts to appear. 



The habit of pursuing one another, noted of other chipmunks, is con- 

 spicuous in the present species. A pair will go at great speed, one indi- 

 vidual after the other, up over logs and rocks and down through crevices, 

 the two keeping always only a few inches apart. This habit is marked 

 long after the close of the mating season. One explanatory theory states 

 that this practice serves to keep the animals 'in training,' so that when a 

 real menace threatens, as, for example, when a marauding Least Weasel 

 makes its appearance, a chipmunk will find itself in optimum condition 

 for escape to some safe refuge. Another suggestion offered is to the effect 

 that this habit is acquired in order that when male pursues female for the 

 purpose of accomplishing the mating act, only the swiftest males will 



