Population and behavioural impacts of aerial operations to control wild pigs

Context Wild pigs (Sus scrofa) are an invasive species in many locations, where they cause extensive agricultural damage. Aerial operations, where animals are shot from a helicopter, is a widely used method for reducing the size of wild pig populations. However, information is limited on the behavioural responses of pigs. Aims We used Before-After-Control-Impact (BACI) to quantify behavioural responses to two aerial operations in an agricultural matrix in northeastern Texas during spring 2020. Methods Prior to aerial operations, we trapped and fitted 26 wild pigs with GPS radio-collars. After aerial operations, we classified wild pigs as low-impact pigs (i.e. pigs located >100 m from the flight path) and high-impact pigs (i.e. pigs located ≤100 m from the flight path). Results Aerial operations did not affect resource selection; however, low-impact wild pigs were less likely to be in shelter land cover (i.e. riparian areas, forests, and shrublands) relative to high-impact pigs (selection coefficient = 0.89, 95% CI = 0.82–0.97). Helicopter tracklogs were mostly over shelter land cover (40%), which was similar to space use of high-impact pigs (50%) but higher than low-impact pigs (16%). We found no treatment effects on core and home range sizes nor interactions with conspecifics. Based on step lengths, high-impact wild pigs were 9% more nocturnal than low-impact wild pigs post operations (P < 0.01). No collared wild pigs emigrated from the area during or after aerial operations. Conclusions Overall, wild pigs locally responded to aerial operations by moving more at night but did not make large escape movements. Wild pigs present in relatively low shelter land were apparently overlooked by helicopter crews. Combining aerial operations with other, night-time-oriented removal methods (e.g. trapping, night shooting, toxic baiting) within the same area as aerial operations should increase removal of cagey wild pigs and enhance population control. Implications Aerial gunning is an effective way to rapidly reduce wild pig populations with a low risk of survivors relocating into new areas.