THE NECESSITY OF UNDERSTANDING THE PRESENT TO CLARIFY THE PAST: DETERMINING THE EFFECTS OF DIET AND ENVIRONMENT ON THE DENTAL MICROWEAR OF KANGAROOS

As Australia is projected to experience more extreme droughts and ~0.8 to 2.8º C temperature increases by 2050, it is critical to assess the effects of climate change on extant marsupials. Furthermore, our understanding of extant marsupials can help clarify the palaeoecology of extinct taxa, elucidating the consequences of climate change over longer time periods than accessible to neontologists. Dental microwear texture analysis (DMTA), the analysis of tooth wear surfaces in three-dimensions, records the dietary textures of consumed foods over the last few days to weeks of an animal's life - an effective tool for assessing diets just prior to the death of organisms, both today and in the past. We developed a DMTA baseline of extant macropods consuming a broad range of diets, including: Dorcopsulus vanheurni, Macropus fuliginosus, Macropus giganteus, Osphranter robustus, Osphranter rufus, Notamacropus rufogriseus, Petrogale lateralis, Setonix brachyurus, and Wallabia bicolor. By examining a range of taxa from overlapping environments and across a range of habitats, we clarified that dental microwear is reflective of diet and less affected by environmental variables including evaporative conditions. Results demonstrate the ability of DMTA variables (e.g. anisotropy and complexity) to differentiate between tough and hard food consumers, i.e. extant grazers and woody browsers, respectively. Further, when comparing M. giganteus and M. fuliginosus individuals that were killed during "normal" conditions to those killed during extreme droughts, DMTA reveals dramatic dietary shifts in both taxa to include more woody material, as inferred from significantly greater complexity, during periods of extreme aridity. These data reveal that mammalian dietary niches are not static, but change in response to extreme droughts, and DMTA is useful for identifying dietary ecology of extant and extinct macropods shortly before their death.