November 29, 2018
Researchers from the University of NSW say there is mounting evidence that platypus numbers are declining to the point there are concerns about the survival of the species.
The scientists are nearing the end of a three-year national survey.
A database of the distribution and abundance of platypus over the last two centuries has been combined with data from systematic capture surveys to conduct a national risk assessment for the species.
“We have great concerns about the future survival of this unique species,” project leader Prof Richard Kingsford said.
“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.
“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 said the national survey showed great variability in platypus numbers throughout their range in eastern Australia.
“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 macroinvertebrate food sources,” he 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.
“This shift in our perception is particularly important for such a cryptic animal. Given sightings are rare, people perceive captures or sightings of just a few platypuses to be indicative of a healthy population, while historical records suggest numbers far exceeded our current observations,” PhD student Tahneal Hawke said.