Aerial culling feral fallow deer with shotguns improves efficiency and welfare outcomes

Abstract

Feral deer are some of Australia’s worst emerging pest species. Recently, the Government of South Australia launched a four-year program to reduce the populations of feral fallow deer (Dama dama). The program will focus on coordinating landscape-scale aerial culls and seeks to deliver the most efficient and humane approach to aerial culling. We sourced data from a recent program trialling a new approach to aerial culling that incorporated advanced thermal technology and a second shooter with a shotgun to target fallow deer. We reviewed available video and audio records of 104 deer culled in the program to assess efficiency and welfare outcomes. We collected information on the number of shotgun and rifle rounds fired per animal, time between first shot with a shotgun and confirmed death, and pursuit time. We completed field dissections of 20 individuals targeted in the program to assess the lethality of wounds inflicted with shotgun pellets. We also compared program costs and efficiency against published and unpublished data from ten other aerial-culling programs for feral deer in South Australia since 2009. A total of 383 shotgun rounds and 10 rifle rounds were used on 104 fallow deer in the focal program. We documented strong improvements to animal welfare for feral deer targeted with shotguns. The mean (± standard error) time between first shot and confirmed kill with a shotgun was 11.1 ± 0.7 seconds; mean pursuit time between detection and a confirmed kill was 49.5 ± 3.4 seconds. Pursuit time increased with subsequent deer controlled within a group; the maximum pursuit time for any individual was 159.0 seconds. All autopsied animals had received lethal wounds from shotgun pellets, with 100% receiving lung-penetrating damage and 70% also receiving heart-penetrating damage. While a program that uses a shotgun and rifle combined with a second shooter and thermographer can cost more to mobilise, the outcomes measured in cost deer-1 made it the most cost-effective approach of any program we assessed. Control options that deliver improved animal welfare outcomes and increase efficiency are desirable for managing expanding populations of feral deer in South Australia and elsewhere.

Stochastic population models to identify optimal and cost-effective harvest strategies for feral pig eradication

“…On Kangaroo Island, private landholders have historically used shooting, trapping, and dogs to control pigs, while government agencies have trialled alternative methods such as poisoning with sodium fluoroacetate (1080/PIGOUT®), as well as investigating the use of radio-collared ‘judas’ pigs to improve pig detection of remaining herds (Masters et al 2011). Methods currently used on Kangaroo Island include ground-based shooting, poisoning with sodium nitrite (HOGGONE®), trapping, and thermal-assisted aerial culling — a novel approach to aerial culling that uses thermal imagery to improve detection (Cox et al 2022, Bradshaw et al 2023).…”