The ecology and conservation of southern squirrel glider populations in agricultural landscapes

Abstract

Much of the world's terrestrial environment is transformed by human activities, particularly agriculture. Within these anthropogenic landscapes some wildlife persists but, with varying degrees of success. Increasingly, there is a realisation of the importance of natural and seminatural features within agricultural landscapes for biodiversity conservation. For species whose geographical range or habitat preference largely coincides with landscapes transformed by other land uses, understanding key habitats, how they are used, and the threats posed to these habitats is essential. This work focuses on the southern population of the squirrel glider Petaurus norfolcensis, a genetically distinct subpopulation with a geographic range that largely coincides with the sheep/wheat belt of eastern Australia. This thesis explores the use of relictual and seminatural habitats of the species in highly modified agricultural landscapes, via radio-tracking collared individuals. The research aims to examine key habitats and their use, and to close some of the knowledge gaps relating to their ecology and conservation. I describe crucial denning and feeding habitats of the species. Detailed field measurements and logistic regression models were used to identify key physical characteristics of these habitats and their biophysical context. Large, healthy Eucalyptus trees were significant in all models. Gliders used numerous den sites, often sharing with other individuals. Den tree selection was often associated with the location of nocturnal activity, indicating the role of den trees in facilitating efficient foraging. The majority of nocturnal activity took place in the canopy of Eucalyptus trees, with a strong preference for those trees in flower. In the absence of flowering, gliders focused their feeding activity in Eucalyptus trees close to drainage lines. These results highlight the importance of habitats in different parts of the landscape and of maintaining connectivity across them, but particularly, the importance of the mesic parts of the landscape in sustaining populations between flowering events. Gliders used four distinct countryside elements: linear roadside remnants, native vegetation patches (typically on travelling stock reserves), native tree plantings, and scattered trees. Gliders were found to survive entirely within these four elements, with some individuals able to persist in just one element (with the exception of native tree plantings). I demonstrate that the relative habitat value of each element varied, evident from the preferential selection of elements and the impact of their availability on home range size. Scattered trees had a disproportionately high value when compared to other countryside elements. My thesis presents new knowledge of key habitats of the squirrel glider, their use and threats (including a detailed examination of the threat of wildfire on scattered trees). This information has direct conservation implications for the species and adds to the broader discussion on conservation in agricultural landscapes. The thesis is concluded with a synthesis of the new and existing knowledge of southern squirrel gliders and an assessment of the strengths, weaknesses, opportunities and threats, apparent in the conservation efforts for the species. I recommend ten points of action to improve the conservation outcomes of the southern squirrel glider population.