224 CALIFORNIA FISTT AND GAME 



GENERAL HABITS 



EXTENT AND CAUSES OF SEASONAL MIGRATIONS 



From the time white men tirst began to settle along the Pacific 

 slope of the Sierra Nevada in California it has been known that throngh- 

 ont this region mnle deer occupy separate and distinct summer and 

 winter ranges. 



The normal summer range lies well back in the mountain meadows 

 and along the higher ridges at elevations varying from 4000 to 12.000 

 feet. This summer range lies in the Transition, Canadian, and Ilud- 

 sonian life zones. Contrasting with this relatively liigli sunnner habitat, 

 the winter range of the same deer lies in the lower foothills from 3500 

 feet elevation near the lower limit of the yellow pine forest, down to 

 1500 feet in the rolling oak-covered foothills of the Upper Sonoran 

 life zone along the eastern margins of the great interior valley of Cali- 

 fornia. 



While the altitudinal variation between the summer and winter 

 range is considerable, the lineal distance betAveen the two ranges is often 

 fifty miles. Since two migrations are made each year, an upward 

 one in the spring and a compensating downward migration in late 

 fall, we find that many of these mule deer each year complete a total 

 migration of one hundred miles. It is reasonable to suppose that some 

 outstanding advantage must be gained to justify this annual expendi- 

 ture of energy. Various explanations have been given for these exten- 

 sive seasonal movements of mule deer. Dr. Carl P. Russell in his 

 illuminating paper on "Seasonal Migration of Mule Deer," published 

 in Ecological Monographs (vol. 2, 1932, pp. 1-46). has pointed out 

 details of mule deer migrations in the Yosemite and Yellowstone regions, 

 and has sought to correlate these movements with temperature, food 

 supply, breeding cycle, and other phases of the life history of the 

 mule deer. 



For a general review of this matter, the reader is directed to Dr. 

 Russell's excellent paper on the subject. It is not the present writer's 

 intention to enter into a detailed discussion of the migration of mule 

 deer in the Yosemite, since his findings and general conclusions, altliough 

 made independently, coincide closely witli those set forth in Dr. Rus- 

 sell's worthy paper. However, considerable added data on this sub- 

 ject have resulted from my study of mule deer in the Se(|U(»ia and Lassen 

 sections, as well as some additional data concerning the winter range 

 of mule deer in the Yosemite region. Presentation of such unpublished 

 data is believed to be desirable at this time. 



Russell has pointed out (p. 39) that: "if suitable food is available 

 in a given area throughout the year, some or all of the deer in that 

 area may not migrate." He also points out (p. 37) that : "low tempera- 

 tures, while bringing about great physical changes in forage plants, do 

 not render them unfit for food" and that "deer could safely reside 

 in winter at high levels in the mountains so far as concerns the food 



