Variable response to aerial culling demonstrates adaptability of feral pigs

Abstract

Feral pigs represent significant threats to the environments where they are introduced, both to the native flora and fauna, as well as agriculture and production systems as vectors of disease. Despite being subject to intermittent, intensive management efforts across much of their invaded range, how feral pigs respond spatially to control programs remains poorly understood. To examine behavioural responses to short-term aerial culling (current practice), feral pigs were fitted with GPS collars in southern Queensland, Australia at two sites with aerial culling and one nil-treatment site. Using continuous time movement models and recurse analysis, changes to feral pig home range size, location, overlap between individuals, and use of cover were compared between two consecutive months, pre- and post- aerial culling, or rainfall at the nil-treatment site. Significant disturbance did not have a consistent impact on feral pig spatial behaviour in terms of home range size, location, or home range overlap between individuals. Likewise, changes in daily activity and cover use by feral pigs were not consistent in response to aerial control. This was also reflected at the site with no aerial control, where feral pig spatial behaviour varied on a month-to-month basis and was inconsistent between the examined periods. Collectively, these results indicate that aerial culling did not represent a significant enough disturbance to induce changes in feral pig spatial behaviour, and highlights the plasticity and high spatiotemporal variability of feral pig habitat use on a month-to-month basis. The findings also support the use of aerial culling to manage pig populations, particularly during exotic disease incursions where dispersal of animals to uninfected areas must be avoided.