Survival and causes of mortality of introduced wild pigs in the presence of cougars

Wild pigs (Sus scrofa) are an introduced species that affect ecosystems through myriad pathways. They are the target of population control efforts, but one outstanding question is the extent to which native predators affect population demography. Cougars (Puma concolor) are a known predator of wild pigs and cooccur with wild pigs in several regions of the Americas. However, investigations of wild pig survival in regions with cougars are lacking. We investigated the survival and causes of mortality for wild pigs in California, USA where cougars could act as a predator. We also explored habitat selection of wild pigs with respect to cougar predation risk. We collared 69 wild pigs, 15 adults, 15 subadults, and 39 juveniles. Captures occurred in winter and spring and survival estimates primarily reflect spring and summer survival. We estimated 6-month survival of adults and juveniles to be 0.923 (95% confidence interval: 0.789 – 1.00) and 0.563 (0.416 – 0.762), respectively, which are similar to estimates from areas without cougars. Only juvenile and one subadult wild pig were killed by cougars, suggesting that cougars are a limited predator of adults. We also investigated feeding locations of 3 GPS-collared cougars to generate a spatial layer of cougar kill occurrence. We used this layer in an integrated step selection function for wild pigs and observed wild pigs selecting areas with low probability of cougar kill occurrence during times when cougars are most active. Combined, these results suggest that cougars are a minor source of mortality for wild pigs during the spring and summer and may be unlikely to provide substantial biological resistance against the spread of wild pigs. Our monitoring occurred when native prey (e.g. ungulate neonates) are most abundant which may influence cougar predation of pigs. It is likely that a preference for native prey, the novelty of wild pigs, wild pig habitat selection, and the potential danger of adult wild pigs reduces cougar predation.

Methods
These data include capture records and telemtry tracking data for wild pigs that were monitored with GPS collars and VHF ear tags. Raw location data are provided for the GPS collars. VHF ear tag data provides the date and status of observed pigs throughout the monitoring period. Location data for cougars are not provided due to the sensitive nature of these data.