PARENT SESSION

FOOD HABITS OF RED FOX, MARTEN AND COYOTE IN THE MOUNTAINS OF NORTHERN CALIFORNIA. John D. Perrine and Reginald H. Barrett. Department of Environmental Science, Policy and Management, 151 Hilgard Hall, Berkeley, CA.

ABSTRACT- Red foxes in the mountains of North America are rare and their ecology has been virtually unstudied. We examined food habits of red foxes in the Lassen Peak region of northern California as part of a comprehensive ecological study of this population. Lassen Peak is within the historic range of the Sierra Nevada red fox (Vulpes vulpes necator), a State Threatened species in California. We also assessed dietary overlap with marten and coyote, two common sympatric carnivores that may be competitors with red fox. We collected scats from 1998 through 2002 while conducting radio telemetry, behavioral observations and other field activities, at elevations from 1500 to 3200 m. The diets of all three species were composed primarily of mammals year-round, although winter sample size for marten and coyote was low. For red fox, pocket gopher and other rodents were important year-round, along with mule deer carrion. Marten diets were similar, with mice being the predominant rodent. Coyote diets were dominated by mule deer, with mice, squirrels and pocket gopher taken seasonally. Insects in summer and manzanita berries in autumn were common foods for all three species, and birds were taken at low levels throughout the year. Lagomorphs were virtually absent from all three species' diet, suggesting that population numbers in the area may be low. Dietary breadth, as measured by Levins' Index, was widest in spring and narrowest in autumn for all three species. Marten had the smallest seasonal change in dietary breadth (max/min = 1.14), while coyotes had the largest (max/min = 2.95). Dietary overlap among carnivore pairs ranged from 54% to 71%, and was largely attributable to seasonally abundant foods used by all three species. The heavy winter snows and lack of lagomorphs at high elevations may have important effects upon red foxes in this region.

KEY WORDS: red fox