Fecal DNA Analysis and Risk Assessment of Mountain Lion Predation of Bighorn Sheep

Abstract

We analyzed fecal DNA to identify individual mountain lions (Puma concolor) associated with kills of fed-erally listed endangered bighorn sheep (Ovis canadensis) in the Peninsular Ranges of California from 1993-1999. We identified 18 different mountain lions at 26 bighorn sheep kill sites, as well as 5 mountain lions not associated with bighorn sheep mortalities. Thirteen genotypes were each identified at only 1 kill site, while 2 genotypes were unambiguously detected at multiple kill sites. We developed a Monte Carlo simulation model incorporating the DNA data to evaluate the benefits (bighorn sheep saved and reduction in extinction risk) and costs (mountain lions removed) of mountain lion removal under 2 management strategies for a 5-year period. One strategy removed individual mountain lions only after they killed 1 bighorn sheep (kill-site removal), while the other strategy removed mountain lions found anywhere in bighorn sheep habitat (habitat removal). The habitat removal strategy was equal or superior to the kill-site removal in terms of reducing extinction risk for all sizes of ewe populations. However, the kill-site strategy more efficiently targeted bighorn sheep predators and resulted in the removal of fewer non-bighorn sheep-killing mountain lions than the less selective habitat removal strategy. Removal of 1-2 mountain lions per year by either strategy effectively decreased extinction risk for populations consisting of 15-30 ewes, while more intensive removal (3-4 mountain lions per year) was necessary to reduce the risk for smaller populations containing <15 ewes. Removal of mountain lions for a short period of time may be the best option available for bighorn sheep populations in immediate danger of extinction due to mountain lion predation. Given that site-specific information and several assumptions were incorporated in our model, we strongly recommend that individualized and updated assessments be performed on the potential costs and benefits of predator control actions so that the rescue of 1 species or population does not jeopardize another.