The platypus was recently upgraded to ‘Near Threatened’ by the IUCN based on mounting evidence of population declines, local extinctions and fragmentation. Platypus populations in Victorian were identified as under the greatest stress. However, it is recognised that there is a scarcity of data on distribution or population trajectories at a local and catchment scale to fully understand their conservation status and threats.

Traditional monitoring methods based on live-trapping using mesh or fyke nets is time and labour intensive and restricted to certain habitats by water depth and flow, which has inherently limited the acquisition of data over a broad spatial scale. Over the past few years, EnviroDNA, in collaboration with the University of Melbourne and Melbourne Water, has developed and tested environmental DNA (eDNA) as a viable method to detect platypuses using a long-term monitoring dataset from the greater Melbourne region. Direct comparisons with traditional live-trapping methods has revealed eDNA to be much more sensitive and cost-effective to detect presence/absence of platypuses.

We present the results of the first large-scale assessment of platypus distribution using eDNA across five major river catchments and highlight localised declines throughout greater Melbourne. We also demonstrate how site-occupancy data can provide reasonable estimates of abundance for the species. Environmental DNA now provides the opportunity to investigate the contemporary distribution of platypuses at a large spatial scale, understand the species’ threatening processes and help predict future impacts.