Prey composition and kill rates of mountain lions in California’s San Francisco Bay Area


Hettena, A.

Publication Date:
May 2019

Human development and encroachment into wild areas influence animal behavior worldwide. The San Francisco North Bay Area is a matrix of urban, semi-rural, agricultural, and natural habitat areas. Fences and habitat fragmentation may hinder wildlife movement across this mixed landscape. While mountain lions (Puma concolor) inhabit densely populated and developed areas, little is known about their feeding habits in the North Bay. We fitted four mountain lions in Sonoma and Napa counties with global positioning system (GPS) collars to conduct a GPS cluster analysis and determine prey composition and kill rates. We also compared mountain lion land use between public and private land parcels and measured the distance from mountain lion feeding sites to the nearest property boundaries, which were commonly delineated by fences. Between October 2016 and October 2017, we identified 148 feeding sites of four collared mountain lions; 112 prey items (75.7%) were black-tailed deer (Odocoileus hemionus columbianus). The average kill rate for mountain lions was 1.45 deer/week which amounted to 5.52 kg/day. Within the sampled area, 83.4% of the land was privately owned. Contrary to expectations, mountain lions did not select for public land (p = 0.2815), rather they utilized public and private land in proportion to the habitat that was available to them. The distribution of distances from GPS clusters to the nearest property boundaries (DNPB) on private lands differed significantly from that of public lands (p = 0.0048), with more clusters occurring closer to property boundaries on private land. However, there was no significant difference between the distribution of DNPB for GPS clusters and the distribution of DNPB for random GPS locations (p = 0.1088), suggesting that mountain lions did not utilize fences to increase their hunting success. Although a majority of the sampled area was private property and could be seen as sub-optimal habitat for a large carnivore, mountain lions successfully foraged in this fragmented landscape, possibly benefitting from fences on private properties that alter the behavior of their main prey. Investigation of the effects of fences and other human-constructed barriers on lion and deer behavior will inform landscape-scale management of these influential wild animals.

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Hettena, A. 2019. Prey composition and kill rates of mountain lions in California's San Francisco Bay Area. M. S. thesis. Pleasantville, NY: Pace University.