IMPACT OF MOUNTAIN LION PREDATION ON PRONGHORN POPULATIONS IN NORTHEASTERN CALIFORNIA: ARE LIONS USING A CHANGING LANDSCAPE AGAINST NOVEL PREY?
David K. Garcelon; Institute for Wildlife Studies; 140 H Street, Blue Lake, CA, 95525; (707) 844-3516; garcelon@iws.org; Brian R. Hudgens, Jonathan D. Ewanyk, Matthew P. Brinkman
Pronghorn in northeastern California underwent a large population decline in the early 1990's. The population did not recover to its former numbers and continued to show a 5% annual decline. From 2014-2016, we initiated an investigation into what factors might be limiting growth in the population. Over that period we captured and placed GPS telemetry collars on 48 adult female and 42 juvenile pronghorn. Vital rates were investigated and we found that the pregnancy rate (88%) was within the range found in other stable populations, and juvenile survival (44%) was equal to or higher than most other published studies. However, adult female annual survival was low (69%). We were able to assign 59% (n = 17) of known mortality to predation, of which 80% were attributed to mountain lions. Mountain lions are ambush predators and pronghorn generally occupy open stage-steppe habitats, making ambush less probable. With the expansion of juniper woodland into sage habitat, lions may be benefiting from increased opportunity to close the distance on an otherwise unapproachable prey species. Current data suggests that if mountain lion predation impacts were removed, pronghorn population growth rates would be positive.
Ecology and Conservation of Mammals I