Thermal-assisted aerial culling (TAAC) for the improved control of vertebrate pest animal populations

Cox, Tarnya; Matthews, Robert W.; Paine, David C.; O'Dwyer-Hall, Emma; Blumson, Tony; Florence, Brenton; Fielder, Kate; Tarran, Myall; Korcz, Matt; Wiebkin, Annelise; Hamnett, Peter W.; Bradshaw, Corey J.; Page, Brad

doi:10.22541/au.165633745.51007622/v2

Cited by 3 publications

(1 citation statement)

References 4 publications

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“…We therefore recommend that forest managers employ professionals to cull deer to the lowest levels possible. While such efforts have traditionally been costly, improvements in ground and aerial hunting techniques such as use of thermal imaging tools have doubled the efficiency of intensive culling operations and made them more viable for conservation organisations with limited resources (Cox et al., 2023). Rather than technical feasibility and cost, the primary constraint over reducing deer numbers is social will.…”

Section: Discussionmentioning

confidence: 99%

Hunting of sika deer over six decades does not restore forest regeneration

Husheer,

Tanentzap

2023

Journal of Applied Ecology

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High densities of native and introduced deer hamper the regeneration of temperate forests worldwide. Sport hunting is often the sole means of deer control, but whether it can restore forest regeneration remains uncertain. We assessed the potential to restore forest regeneration using unrestricted sport hunting alongside commercial harvesting and government‐funded culling of introduced sika deer (Cervus nippon) across a 594 km2 landscape in North Island, New Zealand. We used six decades of repeated measurements of forest regeneration and deer presence, alongside monitoring of tagged stems in a 20‐year paired exclosure experiment, to determine whether deer control restored regeneration. In our exclosure experiment, mountain beech (Fuscospora cliffortioides) seedling and sapling density, growth and survival were variable but consistently higher when deer were excluded by fencing. Sapling counts in unfenced plots were ≈3–10 times lower after 60 years of deer control compared with unfenced plots, before sika colonisation and other mountain beech forests without sika deer. This result suggests canopy replacement remains at risk despite government‐funded culling and encouragement of sport hunting. Individual‐based demographic models show that mountain beech is unlikely to regenerate following canopy gap formation in our study landscape unless deer impacts are reduced from current levels. These demographic models predicted present‐day forest regeneration far better than two widely used proxies of deer impact: plot‐based counts of saplings and estimates of deer densities from faecal pellet counts. Synthesis and applications. Here, we show that intensive culling beyond that achievable by sport hunting is needed to reduce deer densities enough to assure canopy regeneration. These interventions will be necessary in the many places worldwide where sport hunting is being relied upon to protect forests but appears to be failing. Given the controversy associated with deer culling, and the need for clear evidence to justify its implementation, we suggest managers could strengthen the evidence base for their interventions by collecting data to build demographic models.

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Section: Discussionmentioning

confidence: 99%

Hunting of sika deer over six decades does not restore forest regeneration

Husheer,

Tanentzap

2023

Journal of Applied Ecology

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

Hamnett

Saltré

Page

et al. 2023

Preprint

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Eradicating feral pigs from island ecosystems can assist in restoring damaged biodiversity values and protect commercial industries such as agriculture. Although many feral pig eradications have been attempted, management decisions are often led by practitioner experience rather than empirical evidence. Few interventions have been guided by population models to identify harvest rates necessary to achieve eradication within a specified time frame, nor have they applied data on control effort and cost to evaluate the relative cost-effectiveness of proposed control strategies. We used effort and cost data from a feral pig-control program on Kangaroo Island, South Australia over 17 months to derive functional-response relationships between control effort (hours pig-1) and pig abundance for four control methods: (i) ground-based shooting, (ii) trapping with remote triggers, (iii) poison baiting, and (iv) thermal-assisted aerial culling. We developed a stochastic Leslie matrix with compensatory density feedback on survival and fertility to project population trajectories from an initial population (N0) of 250 female pigs with an estimated island-wide carrying capacity (K) of 2500 over 3 and 10 years for populations subjected to an annual harvest of 35% to 95%. We built functional-response models to calculate annual effort and cost for six cull scenarios across all harvest rates. We derived total cost and effort over 3- and 10-year projections from the sum of annual cost and effort within the projection intervals. Pig populations were reduced to < 10%N0based on harvest rates > 70% and 50% for culls of 3- and 10-year duration, respectively. In all scenarios except ′trapping only′, the total cost to reduce population to ≤ 10% ofN0decreased with increasing harvest proportion, with lower total costs incurred over 3 years compared to 10 years. The simulations suggest that the most cost-effective approach for most scenarios is to maximise annual harvest and complete eradication effort over the shortest periods.

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Aerial culling invasive alien deer with shotguns improves efficiency and welfare outcomes

Bradshaw¹,

Doube²,

Scanlon³

et al. 2023

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Invasive alien deer (known in Australia as ‘feral deer’; hereafter, ‘alien 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 alien 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 apparent 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 alien 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 alien deer targeted with shotguns. The mean (± standard error) time between first shot and apparent death with a shotgun was 11.1 ± 0.7 seconds; mean pursuit time between detection and apparent death 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 alien deer in South Australia and elsewhere.

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Thermal-assisted aerial culling (TAAC) for the improved control of vertebrate pest animal populations

Cited by 3 publications

References 4 publications

Hunting of sika deer over six decades does not restore forest regeneration

Hunting of sika deer over six decades does not restore forest regeneration

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

Aerial culling invasive alien deer with shotguns improves efficiency and welfare outcomes

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Thermal-assisted aerial culling (TAAC) for the improved control of vertebrate pest animal populations

Cited by 3 publications

References 4 publications

Hunting of sika deer over six decades does not restore forest regeneration

Hunting of sika deer over six decades does not restore forest regeneration

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

﻿Aerial culling invasive alien deer with shotguns improves efficiency and welfare outcomes

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Aerial culling invasive alien deer with shotguns improves efficiency and welfare outcomes