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RESEARCH ARTICLE (Open Access)
Contents Vol 51(1)

Evaluating predator control using two non-invasive population metrics: a camera trap activity index and density estimation from scat genotyping

Jessica L. Keem https://orcid.org/0000-0003-4118-0389 A * , Bronwyn A. Hradsky https://orcid.org/0000-0002-0141-020X A , Joe Benshemesh B , Mark Le Pla https://orcid.org/0000-0003-4129-815X C , Abigail Watkins D , Andrew R. Weeks https://orcid.org/0000-0003-3081-135X E F , Anthony van Rooyen https://orcid.org/0000-0002-1221-7712 F , John Black F and Darren Southwell https://orcid.org/0000-0002-8767-9014 A G
+ Author Affiliations
- Author Affiliations

A Quantitative and Applied Ecology Group, School of Ecosystem and Forest Sciences, University of Melbourne, Parkville, VIC 3010, Australia.

B National Malleefowl Recovery Group, VIC, Australia.

C Conservation Ecology Centre, Cape Otway, VIC 3233, Australia.

D Parks Victoria Wimmera, Wail, VIC 3414, Australia.

E Bio21 Institute, School of Biosciences, University of Melbourne, Parkville, VIC 3010, Australia.

F Cesar Australia, Brunswick, VIC 3056, Australia.

G Conservation Science Research Group, School of Environmental and Life Science, University of Newcastle, Callaghan, NSW 2308, Australia.

* Correspondence to: jessica.keem@unimelb.edu.au

Handling Editor: Thomas Prowse

Wildlife Research 51, WR23033 https://doi.org/10.1071/WR23033
Submitted: 2 February 2022  Accepted: 27 August 2023  Published: 12 September 2023

© 2024 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Invasive mammalian predators are a threat to biodiversity and agriculture globally, yet management outcomes for lethal predator control remain difficult to monitor and evaluate. Understanding whether changes in activity indices correspond to true changes in population density will help inform effective monitoring and management programs.

Aims

The aim of this study was to evaluate the effect of poison baiting on invasive red fox (Vulpes vulpes) populations using two alternative population metrics: fox activity from camera trap surveys and density estimation from scat genetic analysis.

Methods

We conducted before–after control–impact studies in two regions of semi-arid Australia (Wimmera and Mallee) by monitoring paired non-treatment and treatment sites during unbaited and baited periods. We estimated the effects of poison baiting on: (1) a monthly fox activity index, derived from an array of 10 off-road camera traps per site; and (2) fox density. To estimate density, we collected fox scats along 14-km transects, identified individuals using polymorphic microsatellite DNA markers and fitted spatially explicit capture–recapture models.

Key results

Fox activity remained consistently low at all sites except the Mallee non-treatment. The top-ranked models of fox activity and density contained an interaction between treatment and period, with an interactive and additive effect of region, respectively. However, there was little evidence that baiting reduced fox activity or density. In the unbaited period, fox densities ranged from 0.69 (95% CI: 0.47–1.0) to 1.06 (95% CI: 0.74–1.51) foxes km−2 and were similar across regions.

Conclusions

Camera traps have the potential to provide continuous index-based measures of fox populations but may not record sufficient observations to detect change. Indices can also be confounded by variations in animal behaviour. Scat genetic analysis is a viable option for providing direct estimates of population change at specific snapshots in time; however, this approach is considerably more expensive, and large sample sizes may be required if genotyping success is low.

Implications

Our study presents a rare example of multiple concurrent – and non-invasive – monitoring techniques to evaluate the effectiveness of predator control. We highlight the value of rigorous study designs and high-quality density information for designing predator management and monitoring programs.

Keywords: 1080 baiting, activity index, BACI design, density estimation, genetic sampling, Leipoa ocellata, non-invasive sampling, semi-arid, Vulpes vulpes.

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