Response of white-tailed deer to removal of invasive wild pigs

Context With the range expansion of invasive wild pigs (Sus scrofa) in North America during the past decades, there has been an increasing concern with how wild pigs affect native species. An abundance of research on their impacts has been through the lens of damage to anthropogenic resources and plant communities. However, quantitative research on how wild pigs affect populations of native animal species is an understudied topic.Aims Our goal was to assess how wild pigs affect white-tailed deer (Odocoileus virginianus) at a population level by measuring changes in deer abundance as wild pigs are removed. White-tailed deer are an economically valuable game species in North America, and negative impacts of wild pigs on their populations could have trickle-down impacts on conservation funding for all wildlife.Methods On three treatment areas (34.07-55.31 km2) and one control area (25.10 km2), we used N-mixture models to compare data from camera-trap surveys of white-tailed deer before and after wild pigs were removed from treatment areas.Key results We removed 1851 pigs from the treatment sites between May 2019 and March 2021. We found that wild pigs did not significantly affect white-tailed deer abundance, but that white-tailed deer were 1.12 (1.02-1.23; 95% CL) times as likely to be detected when the number of pigs removed was equal to our baseline population estimates compared with when no pigs were removed. Although results from similar analyses on separate age and sex classes of white-tailed deer exhibited similar results, analyses of impacts on immature males differed.Conclusions Our overall results are congruent with those of other research that suggest that wild pigs affect white-tailed deer behaviour at a local scale, although eliminating pigs from an area does not appear to quickly lead to increased abundance of deer.Implications Although the interspecific interactions between white-tailed deer and wild pigs are unlikely to lead to a decline in the population of white-tailed deer, removing wild pigs may decrease the behavioural implications of these interactions. The recent range expansion of invasive wild pigs in North America has lead to increasing concerns of how they affect native species. This study aims to investigate how white-tailed deer respond to wild pig removals and found that, although relative abundance did not change, detection of white-tailed deer increased as wild pigs were removed. We suggest that wild pigs affect white-tailed deer behaviourally at a local scale and that behavioural changes may not result in population-level effects. Photograph by Matthew McDonough.