California Mule Deer Casa Diablo Winter Ranges

Casa Diablo mule deer are largely traditional migrants, using a wide range primarily spread across public lands. The herd’s winter range stretches between the Benton Range and eastern Inyo National Forest. Snowfall can be extreme in the Sierra Nevada Range, exceeding 800 inches (in; 20.3 m) in heavy-snow winters, during which deer migrate below 6,000 ft (1,829 m) in elevation to escape deep snow. In spring, individuals move west using a wide range of routes; however, a concentrated migration corridor passes through Long Valley, across U.S. Highway 395, and into the high mountains of the Sierra Nevada Range (fig. XXX). Summer range habitat straddles both sides of U.S. Highway 395. Most deer do not move into Yosemite National Park during the summer, remaining east and south of the Park boundary. Deer typically summer at elevations of 8,000 – 11,000 feet. The primary causes of mortality include mountain lion predation, followed by vehicle collisions, which mostly occur on U.S. Highway 395 during fall and spring migrations. In 2019, the population size of the Casa Diablo herd was estimated at 2,460 (confidence interval: 2,037–3,107) individuals. These mapping layers show the location of the winter range for mule deer (Odocoileus hemionus) in the Casa Diablo population in California. They were developed from 162 sequences collected from a sample size of 84 animals comprising GPS locations collected every 1-24 hours.

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