CALIFORNIA FISH AND GAME 



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value of high mountain plants." Russell also points out that it is not 

 low temperature alone that causes the mule deer to migrate to lower 

 regions each fall, but ratlier it is the deep snow which, while it does 

 not destroy the food value of plants, does render these food plants 

 inaccessible to deer and hence is the chief causative factor in the fall 

 migration of mule deer. Not only does a heavy snowfall cover up many 

 food plants but it also makes effective travel for deer difficult or 

 impossible. Unlike the white-tailed deer of the eastern United States 

 our mule deer do not "yard" in winter but choose open hillsides where 

 the snow is not too deep to prevent their moving freely about. Not 

 only is free movement necessary in order that the mule deer may be 

 able to obtain a livelihood on winter range where forage is relatively 

 sparse but, most important of all, free movement is essential if the 



Pig. 76. Mule deer trails all inade in twenty-four hours, after a snow.storm on 

 typical winter range. Pilot Ridge, Mariposa County, January 9, 1922. Mas. Vert. 

 Zool. No. 3427. 



mule deer are to evade capture by their natural enemies such as the 

 coyote and the cougar. 



In 1922, I spent two weeks in midwinter, January 4-17, on snow- 

 shoes studying food habits and the relation of coyotes to deer on the 

 upper winter range. Pilot Ridge and Crane Flat, which lie between 

 Hetch Hetcliy and Yosemite valleys, were chosen for this study. The 

 deer which range over the central portion of Yosemite National Park 

 in summer, winter almost entirely within this area. At Hazel Green, 

 5665 feet altitude, the five feet of recently fallen snow had settled 

 down to forty inches. At this date, January 9, 1922, tracks of mule 

 deer made since the last snowstorm, on January 6, were abundant on 

 the warm south side of the ridge (see Fig. 76) where in numerous 



