INFLUENCE OF DOMESTIC LIVESTOCK GRAZING ON AMERICAN PIKA (OCHOTONA PRINCEPS) HAYPILING BEHAVIOR IN THE EASTERN SIERRA NEVADA AND GREAT BASIN

In a pilot study, I observed a relationship between domestic livestock grazing and location of American pika (Ochotona princeps) haypiles in the eastern Sierra Nevada and several Great Basin mountain ranges. Where vegetation communities adjacent to talus bases (forefields) were grazed, mean distance from the talus borders to the closest fresh haypiles was 30.1 in (SD = 18.9 m, n = 27), and haypiles were found only high in the talus. In ungrazed forefields, mean distance was 1.8 m (SD = 0.9 m, n = 57), and haypiles were found along the low-elevation talus vegetation border. Where grazing was active, haypiles consistently contained vegetation gathered from plants growing within the talus. Talus vegetation appeared to be of lower diversity and the plant species of lower nutritional value than forefield plants. This difference, if real, would compromise quality of forage for summer browsing and winter haypile storage. This condition, combined with potentially less favorable summer and winter thermal conditions of upper talus locations relative to lower talus borders, suggests that grazing might be a factor compromising population conditions and status of pikas. Recent studies have reported higher extirpation rates of pika populations in Great Basin ranges (primarily in Nevada) than in adjacent regions. Because domestic livestock grazing is widely permitted on public lands throughout pika habitat in the Great Basin but not permitted (or much more restricted) in pika habitat of the Sierra Nevada, California, grazing effects might be contributing to observed regional differences in viability of pikas.