Evaluation of helicopter net-gunning to capture wild fallow deer (

Abstract

Context Safe and effective capture methods are crucial for improving our understanding and management of many wildlife species. The adaptation of established capture methods to novel situations requires critical evaluation because differences in environmental conditions and species’ susceptibility to trauma and capture myopathy can produce unexpected outcomes. Helicopter net-gunning has been a valuable tool for capturing wild deer in New Zealand and the Americas, but there are no practical records of its use in Australia and only one report of it being used to capture three fallow deer (Dama dama) elsewhere. Aims The present study aimed to evaluate the feasibility of a helicopter-based net-gun capture technique for wild fallow deer by quantifying the efficacy of the technique and the frequency of injuries and deaths. Methods We captured fallow deer over two 3-day operations at a 135 km2 site in eastern Australia. We collected data on operational efficiency and variables expected to affect animal health and welfare, such as injuries and the duration of stressful procedures. We used GPS tracking collars with an accelerometer and a mortality-sensing function to monitor post-release survival and activity of fallow deer. Key results In total, 127 deer were targeted for capture, with nets fired at 64 deer (50%) and 27 deer captured (21%). Mortality within 30 days of capture was zero. Mean chase time was 2 min 46 s and mean total time from start of chase until release was 11 min 19 s. No animals were severely injured or euthanased, but hyperthermia was observed in 33% of captured animals. Conclusions Helicopter net-gunning was an effective and safe method for capturing wild fallow deer when compared with alternative methods. Implications We recommend that researchers consider using helicopter net-gunning to capture fallow deer in Australia and elsewhere, and other deer species in Australia.