Author: Kimberley Michael
Michael, Kimberley, 2025 Assessing the suitability of habitat across spatial scales for the endangered pygmy bluetongue (Tiliqua adelaidensis), Flinders University, College of Science and Engineering
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Grasslands are among the most utilised and least protected ecosystems globally. While grasslands provide agricultural products to benefit humans, they also have potential to act as off-reserve conservation areas. Animals that inhabit grasslands are inherently vulnerable because of habitat loss and degradation, but some may coexist with livestock under appropriate grazing management. This provides a unique opportunity to maintain agricultural processes alongside ecological processes to support food production and biodiversity. One such relationship is exemplified by the endangered pygmy bluetongue (Tiliqua adelaidensis) and livestock grazing.
The pygmy bluetongue is endemic to South Australia and only known to occur on private grazing properties. The lizards occupy vacant spider burrows and are anticipated to face climate change-induced extinction without translocation mitigation. My thesis focused on assessing habitat suitability at multiple spatial scales – microhabitat, site, and landscape. My original contribution is the first in-depth assessment of habitat for the pygmy bluetongue at multiple spatial scales from a mensurative approach across properties throughout their range; and the first assessment of grazing regime changes that aligned with landowner preferences while maintaining livestock productivity.
This thesis aimed to assess habitat suitability for the pygmy bluetongue at multiple spatial scales and the implications of different grazing regimes on the lizards and their habitat. This research predominantly used 30 x 30 m plots to assess habitat components on a site- and landscape-scale, and smaller 20 x 20 cm quadrats to assess the microhabitat-scale. For microhabitat- and site-scale habitat assessments, no manipulation to grazing regime was undertaken and I focused on understanding habitat components that influenced lizard occupancy. For the landscape-scale investigation, changes to grazing regime were introduced halfway through the study to allow for a “before” and “after” comparative design.
My results showed pygmy bluetongues exhibit distinct habitat associations at all three spatial scales when inhabiting low-quality sites (i.e. high bare ground cover). Lizards consistently showed a preference to occupy burrows or areas that had greater vegetation cover at the northernmost and driest property. Whereas pygmy bluetongues did not exhibit distinct associations at any spatial scale when inhabiting higher-quality sites (i.e. high vegetation cover). Further, grazing regime changes increased vegetation cover on a landscape-scale. Pygmy bluetongues responded positively, with significantly more lizards and increased body condition in areas of increased vegetation cover.
This thesis has broad implications for management of the endangered pygmy bluetongue. Firstly, an understanding of lizard-habitat associations across multiple spatial scales enables informed conservation decisions to maintain current populations of pygmy bluetongues and increase future translocation success. Secondly, ensuring productivity and biodiversity are maintained equally safeguards against economic loss while fostering goodwill between landowners and researchers, ultimately supporting long-term conservation of the pygmy bluetongue. Through my research, I contributed new insights into the factors that influence pygmy bluetongue-habitat associations, specifically identifying vegetation cover as an indicator of habitat suitability. My findings offer valuable guidance to manage habitat at multiple spatial scales, a framework to assess potential translocation sites, and showcase a collaborative approach to research on privately owned properties to incentivise future long-term collaborative research.
Keywords: habitat suitability, reptile, pygmy bluetongue, grazing, translocation
Subject: Earth Sciences thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Mike Gardner