Mountain lion predation of bighorn sheep in the Peninsular Ranges, California

We investigated survival and cause-specific mortality of 113 radiocollared bighorn sheep (Ovis canadensis) in the Peninsular Ranges of southern California from November 1992 through May 1998. Mountain lion (Puma concolor) predation was the most frequent cause of mortality, and was the cause of death for 69% (42/61) of all mortalities. Predation was documented during all months of the year except June, and 62% (26/ 42) of predation events occurred from December through March. Annual adult mortality rates due to predation ranged from 0.08 to 0.25 among 6 subpopulations of bighorn sheep, and the mean annual survival rate (0.79) was low relative to other bighorn sheep populations. Bighorn sheep in the Peninsular Ranges were listed as endangered by the U.S. Fish and Wildlife Service in 1998. We propose that a sustained high level of predation by mountain lions, such as was seen during this study, may impede the recovery of this population.