Mounting evidence of localised declines of platypus numbers has raised ongoing concerns among scientists nearing the end of a three-year national survey.
The UNSW-led Australian Research Council-funded project has compiled a comprehensive database of the distribution and abundance of platypus during the past two centuries, combining this with data from systematic capture surveys to conduct a national risk assessment for the species.
UNSW Centre for Ecosystem Science director and project leader Professor Richard Kingsford said the group had ‘‘great concerns’’ about the future survival of the species.
“The national risk assessment has suggested declines of up to 30 per cent across its range since European settlement, with localised declines and extinctions increasingly reported,’’ he said.
“Synergistic threats to platypus populations include river regulation and flow disruption, increasing agricultural land use, pollution, and the capture of platypus in fishing and yabby nets, all of which are contributing to these declines across its range.’’
UNSW researcher Dr Gilad Bino has been working throughout eastern Australia to assess differences in population numbers and viability of the species throughout its range, which will enable appropriate conservation actions.
‘‘On degraded rivers, typically below dams and in regions of high agricultural land use, we generally see lower numbers of platypus, likely due to the impacts these threats have on bank erosion and availability of macro-invertebrate food sources,’’ Dr Bino said.
The inclusion of historical data has suggested a significant underestimation for platypus declines and has shown that perceptions of healthy numbers has changed over time.