Abstract
Reptiles are declining globally as habitat fragmentation and loss intersect with a warming climate and constrict viable refugia. Ectotherms, such as lizards, depend on fine-scale thermal mosaics to sustain activity, reproduction, and survival. When conditions become extreme, individuals retreat to refugia, reducing time spent foraging and mating, and if prolonged, jeopardising fitness. For species confined to fragmented habitats, persistence hinges on behavioural responses to changing thermal environments, yet seasonal habitat selectivity and refuge use remain poorly quantified, risking mismanagement and avoidable declines. Translocations, the intentional movement of individuals from one location to another, are becoming widely implemented to mitigate declines, but the outcomes for lizards are varied and appear sensitive to the conditions of release and the thermal suitability of recipient sites. In particular, timing of release remains poorly studied and is important because seasonal thermal regimes constrain activity and survival and are likely contributors to translocation outcomes. Conservation decision-making is further limited by monitoring approaches with low detectability, observer bias, and resource-intensive sampling, obscuring demographic change and fine-scale refuge use. These gaps motivate development of high-resolution, low-disturbance, and affordable tools capable of detecting species’ fine-scale behavioural responses to environmental change.In this thesis, I focus on the critically endangered Canberra grassland earless dragon (Tympanocryptis lineata), confined to fragmented natural temperate grasslands within the Australian Capital Territory and nearby New South Wales. This dragon experienced severe population decline and local extirpation since its rediscovery in 1991, but captive breeding colonies now provide the opportunity for translocations into semi-wild or wild locations. Dragons rely on arthropod burrows and tussock grasses as refugia from extreme heat and predators, and annual monitoring via artificial burrows has low detection probabilities (0.01) limiting inference of thermal responses and space use. These gaps inhibit the management of this species.
I addressed the knowledge gaps in thermal response and space use by conducting the first captive-to-wild translocation of T. lineata. I use radiotelemetry on translocated dragons to show that seasonal release timing is a strong predictor of survival, with timing significantly contributing to post-release outcomes. In addition, I used data collected from the translocation, to quantify habitat selection across seasons and between sexes, demonstrating that T. lineata shifts microhabitat use seasonally and prefers natural temperate grasslands over alternative habitats available at the recipient site. Finally, I develop a scalable, automated monitoring system (‘smart burrows’) to detect and record burrow use of PIT-tagged individuals. I test its efficacy in semi-natural conditions by comparing detections with known burrow use and fidelity and reveal that burrow use is primarily temperature-driven and moderated by vegetation density.
Together, this thesis disentangles the interplay between behaviour and thermal environments in T. lineata and facilitates development of a framework for translocation and conservation management to enable species persistence in a changing climate. Ultimately, I show that there is no “one-size-fits-all” approach to translocation, and that integrating fine-scale behavioural and thermal insights will be critical for reptile conservation more broadly under a rapidly changing climate.
| Date of Award | 2026 |
|---|---|
| Original language | English |
| Supervisor | Bernd GRUBER (Supervisor), Stephen SARRE (Supervisor) & Richard DUNCAN (Supervisor) |
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