The western ringtail possum is Critically Endangered. It faces numerous threats that have resulted in highly fragmented populations, including habitat loss, predation by introduced predators and climate change in the south-west of Australia. It is vital to understand genetic variation among these remnant western ringtail possum populations and to incorporate this knowledge into recovery efforts before genetic variability is lost. This project will assess genomic variation across the range of the possum to: 1) determine whether there are genetically distinct and evolutionarily significant lineages of the western ringtail possum; 2) assess the impact of recent population declines on genetic variation; 3) seek evidence of local adaptation to forest type, diet and/or climate; and 4) calculate the survival probabilities of current populations.