Behavioural factors affecting translocation success in the pygmy bluetongue lizard

Author: Tara Daniell

Daniell, Tara, 2021 Behavioural factors affecting translocation success in the pygmy bluetongue lizard, Flinders University, College of Science and Engineering

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Translocations are one method to conserve endangered species, but translocation success must be improved, especially for translocations of captive-sourced animals. Some reasons for translocation failure include selecting inappropriate age classes or individuals lacking foraging and predator avoidance skills. Selecting appropriate age classes is important, as behaviour can vary over life stages, making some life stages more likely to disperse or be preyed upon. Captive animals are more likely to lack foraging and predator avoidance skills, as the captive environment can be too simplistic and exclude predators to ensure the survival of the captive animals.

The pygmy bluetongue lizard (Tiliqua adelaidensis), is an endangered lizard that will require translocating to mitigate the risks of climate change and habitat loss when the current range of distribution becomes unsuitable in future. A captive breeding population can supply stocks for future translocations, but there are knowledge gaps in age specific behaviours and the effect of captivity on foraging ability and predator avoidance.

The primary aim of this thesis is to investigate factors that affect translocation success to improve the outcome of translocations, using the pygmy bluetongue lizard as a case study. I investigated behavioural differences firstly, between neonates and adults and secondly, among juvenile, immature and adult age classes to identify suitable age classes for translocation. I compared foraging ability and body condition between lizards maintained under a hand-feeding regime versus lizards that foraged on released crickets. The effect of captivity on predator recognition behaviour was investigated, comparing captive born, wild born and wild lizards to a range of reptile scents. I also investigated grass use in the pygmy bluetongue lizard, which had not been studied previously and may be an important factor in selecting appropriate translocation sites.

My results show that neonate behaviour differs significantly from adults, particularly basking and burrow movements, which makes the neonate age class less suitable for translocations. I found that pygmy bluetongue lizard behaviour changes ontogenetically, with activity levels highest in early life stages, progressively decreasing with age toward adulthood. Foraging ability and body condition were similar between the hand-fed and self-fed regimes, however hand-feeding was found to alter behaviour in a way which may increase predation risk in lizards released into the wild. Pygmy bluetongue lizards were found to innately recognise predator chemical cues, however they did not show avoidance behaviour, suggesting that other cues may be required to elicit a response. Grass tussocks were found to be an important temporary refuge for lizards when they are moving around out of burrows.

The research presented in this thesis contributes significantly to our knowledge of pygmy bluetongue lizard behavioural ecology, filling in gaps on age specific behaviours, habitat use and the effects of captivity on necessary life skills. My findings are important for future conservation management of this species and will improve translocation success. However, my research also has broader implications, and can inform captive management and translocation of other endangered species. It also highlights the importance of the captive environment in providing opportunities to study behaviour in species that can be hard to monitor in the wild and can reveal undiscovered behaviours.

Keywords: lizard, behaviour, conservation, predator recognition, pygmy bluetongue

Subject: Biodiversity and Conservation thesis

Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Science and Engineering
Supervisor: Michael Gardner