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Ecoenergetics of the Western Swamp Tortoise: Modelling the Translocation Viability of Australia’s Rarest Reptile
It is now widely accepted that many parts of Australia will undergo relatively rapid changes in climate. In the past, species could move into neighbouring habitats as environmental conditions changed. But now, habitat destruction and fragmentation will prevent many species from dispersing into areas capable of supporting them in the long term. Australia is likely to become a hotspot for species extinctions unless new solutions can be discovered to mitigate the effects of environmental change. One promising, but controversial, solution to protect vulnerable species is to physically translocate them into climatically suitable areas - a process termed ‘assisted colonisation’. This process has been identified as being a potential management option for Australia’s rarest reptile – the Western Swamp Tortoise (Pseudemydura umbrina). Current conservation practices have demonstrated that P. umbrina bred in captivity can be successfully introduced into the wild, but translocation sites that can offer good habitat under future climates are urgently required to ensure the long-term survival of the species in the wild.
My research aims to address how we can pinpoint the sites where threatened species are most likely to survive under future climates, by modelling the fundamental niche of the Western Swamp Tortoise under multiple climate scenarios. I am collaborating with the University of Melbourne, Perth Zoo, and the Department of Environment and Conservation in project SWAMPI – the South West Assisted Migration for endangered Populations Initiative. I will measure the metabolic rates, growth rates, digestive physiology and thermal physiology of P. umbrina. The data I collect will be integrated with an independent model of their wetland habitat, and the resulting model will be used to predict tortoise survival, growth and reproduction under different climate scenarios. These models will allow me to predict which wetlands will allow tortoises to survive and reproduce under hotter, drier climates.
Any model that can predict the future distribution of a species under climate change will be a valuable tool in the selection process for translocation sites in the future. Unfortunately, current modelling approaches have little value for threatened species because they require broad species distribution records, which are often unavailable for conservationally significant species. Mechanistic models can be used to circumvent this issue, and my research will be the first to apply a mechanistic modelling approach to translocation outcomes for any species. While the resulting model will be specific to the western swamp tortoise, it will be broadly applicable to species with an aquatic phase to their lifecycle, and the approach will also serve as a template for other threatened species. Importantly, my research will address existing knowledge gaps on western swamp tortoise ecophysiology, and will be a vital tool for securing the ongoing survival of the species in the wild.