Thesis
Trends and determinants of nest failure in flatback turtles (Natator depressus) across the North West Shelf genetic stock
Masters by Research, Murdoch University
2025
Abstract
To effectively manage long-lived species such as flatback turtles (Natator depressus), it is imperative to understand the baseline status of the population, identify threats, and discern how they may act upon the longevity and survival of individuals. Assessing population-wide nest success, or the proportion of hatchlings that successfully emerge from nests each season, enables conservation managers to understand population trends, and identify both at-risk and resilient areas, to ultimately direct management efforts. The aim of this study was to produce a current baseline assessment of the nest success for the North West Shelf (NWS) flatback turtle genetic stock, investigate the influence of air temperature and rainfall on nest success and failure, and explore the implications for the stock in the face of global climate change. To do this, we interrogated a long-term dataset, comprising the fate of 2,411 nests (113,804 eggs), across up to sixteen seasons at seven rookeries extending over 600 km in the Pilbara region of Western Australia’s coastline. We found that although overall mean hatching (76.0 ± 26.3 SD) and emergence (72.9 ± 27.9) success (%) for the NWS stock was within a normal range for the species, the emergence success (%) at the individual NWS rookeries of Cemetery Beach (29.0 ± 33.3) and Ashburton Delta (47.1 ± 35.9) were the lowest recorded. Although fluctuations in success were exhibited between seasons, Delambre Island was the only rookery with a significant decline over time, while consistently high values were recorded at the Mundabullangana and Barrow Island rookeries. Egg mortality was strongly associated with higher mean ambient air temperatures, with the predicted temperature thresholds for 50% hatching success varying between rookeries (31.11 - 36.04 ℃). These outcomes provide insight into the current status of the North West Shelf genetic stock, indicating that some rookeries may already be exceeding their upper thermal tolerance thresholds, with others potentially at high risk of further declines with progressing climate change. Further, these findings provide a baseline for ongoing monitoring of trends in nest success and can inform management strategies for maximising the conservation outcomes for the species.
Details
- Title
- Trends and determinants of nest failure in flatback turtles (Natator depressus) across the North West Shelf genetic stock
- Authors/Creators
- Eva L Robinson
- Contributors
- Adrian Gleiss (Supervisor) - Murdoch University, Centre for Molecular Medicine and Innovative TherapeuticsSabrina Fossette (Supervisor) - Department of Biodiversity, Conservation and Attractions
- Awarding Institution
- Murdoch University; Masters by Research
- Identifiers
- 991005831941607891
- Murdoch Affiliation
- School of Environmental and Conservation Sciences
- Resource Type
- Thesis
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