Camera traps show foxes are the major predator of flatback turtle nests at the most important mainland western Australian rookery

J. King; S. D. Whiting; P. J. Adams; P. W. Bateman; P. A. Fleming

doi:10.1071/WR22109

RESEARCH ARTICLE (Open Access)

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Camera traps show foxes are the major predator of flatback turtle nests at the most important mainland western Australian rookery

J. King ^A ^B , S. D. Whiting ^A , P. J. Adams

^B ^C , P. W. Bateman

^D and P. A. Fleming

^B ^*

+ Author Affiliations

- Author Affiliations

^A Marine Science Program, Department of Biodiversity, Conservation and Attractions, 17 Dick Perry Avenue, Kensington, WA 6151, Australia.

^B Terrestrial Ecosystem Science and Sustainability, Harry Butler Institute, Murdoch University, 90 South Street, Murdoch, WA 6150, Australia.

^C Present address: Department of Primary Industries and Regional Development, 3 Baron-Hay Court, South Perth, WA 6151, Australia.

^D Behavioural Ecology Lab., School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, WA, Australia.

^* Correspondence to: t.fleming@murdoch.edu.au

Handling Editor: Alexandra Carthey

Wildlife Research 51, WR22109 https://doi.org/10.1071/WR22109

Submitted: 22 June 2022 Accepted: 27 April 2023 Published: 11 July 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

Quantifying marine turtle-nest depredation by daily observer monitoring requires substantial labour.

Aims

To quantify nest depredation of the Vulnerable flatback turtle (Natator depressus) at one of its largest rookeries and to compare effectiveness of different monitoring methods.

Methods

We used daily observer monitoring and passive infrared-camera traps separately or in combination to record nest depredation, and identified impacts on remaining eggs and hatchlings in depredated nests.

Key results

More than a quarter (28%) of the 69 monitored nests were confirmed as depredated, although this figure is an underestimate of total losses because camera traps detected twice as many depredation events (39%) as did direct observation (17%) (P = 0.012). Cameras also provided important behavioural data and identified predators. Although reptile and bird predators were also recorded, the introduced red fox (Vulpes vulpes) was the primary predator identified, digging into 26% of the monitored nests. More than half of the depredation events by foxes (58% or 11/19 nests) occurred late term, between turtles hatching and emerging from the nest, which therefore means that losses calculated through counts of eggshell left in the nest are underestimates because predation of hatchlings is not included by the eggshell count method. Furthermore, almost half (42%) of all depredated nests were depredated more than once, with some nests opened up to five times, potentially exacerbating clutch losses due to environmental exposure.

Conclusions

Egg losses for confirmed depredated nests (27 ± 37%, range 0–100%) were three times the background levels (i.e. 9.3% of eggs that failed to hatch as a result of embryo death during development).

Implications

The results of this study strongly warrant the implementation of ongoing fox predator monitoring and mitigation strategies to protect nests at this nationally, and internationally, conservation-significant population of flatback turtles.

Keywords: conservation management, depredation, hatchling, invasive species, monitoring, monitoring methodology, Mundabullangana rookery, red fox.

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