There’s been good and bad news for Victorians worrying about the native platypus population.
A DNA study of the upper Wimmera river in western Victoria has revealed the local population of platypus has gone “functionally extinct”, but it appears young animals in the Yarra have escaped the worst of the recent rainstorms.
The study was conducted over the past three months by researchers at EnviroDNA and not-for-profit Project Platypus, as part of a $35,000 grant from the Wimmera Catchment Management Authority.
Samples at 35 sites along the Wimmera near Stawell and Ararat were analysed for the DNA that platypuses leave in the water via their skin and hair cells, along with faecal matter and urine.
EnviroDNA senior ecologist Josh Griffiths said the millennium drought of the early 2000s had ravaged the local population, with most of the Wimmera drying out.
“There was a couple of isolated puddles that was all that was left of the river,” he said.
“So whenever these systems that were traditionally healthy flowing rivers become intermittent and have stop flow events, that has major impacts on everything.”
Help needed to rebuild population
Mr Griffiths said while samples were not taken from waterways outside of the Wimmera system, any platypus population would not be big enough to re-establish itself.
DNA sampling of the ‘weird’ platypus has students leading conservation efforts
Primary school students took part in a cutting-edge program that used DNA samples from waterways along the Wimmera catchment to trace platypuses.
“If there are one or two individuals around, particularly in refuge areas like farm dams … they’re not going to recover and breed up to have a population in five years’ time or 10 years’ time,” he said.
“There’s really no way that platypus are going to get back into that system without any help, but before you’d even think about moving animals back into that system, you’d need to make sure that habitat is healthy enough to sustain them long term.”
Mr Griffiths said conservation efforts by groups like Landcare, which restores vegetation around river banks, needs to increase, along with the assistance of landholders whose properties are adjacent to the upper Wimmera River.
Isolated platypus colony all that remains
Project Platypus manager John Pye said the long-term survival of the iconic species in western Victoria now largely depended on a solitary colony of platypus at McKenzie Creek, west of the upper Wimmera near Horsham.
“There is a weir there on McKenzie Creek and that’s a barrier to platypus getting further downstream,” Mr Pye said.
“There’s a fish ladder there but it doesn’t seem like it’s being used, and if platypus have to walk across the ground then they are extremely vulnerable to predators.”
Mr Pye said the survival of iconic species like the platypus gave conservation efforts a goal and specific target areas
“We need some icon species so we can measure the success of any our actions,” he said.
“If we’re planning revegetation, if we’re planning fencing off waterways, we still need to look at the best places to get the best results.”
The study also found no traces of the native blackfish in the upper Wimmera, while results on the population of rakali, or native water-rat, are expected to be finalised next year.
Yarra population escaped worst of rainstorm
In Melbourne, the Yarra riverkeeper Andrew Kelly said that river’s baby platypuses appeared to be safe and sound after the recent storms.
While the storms were large enough to flush the river with pollution it appears many burrows were not affected.
In Victoria, platypuses mate between August and October, after which the pregnant females build deep and complex burrows or renovate another female’s burrow from a previous year. Before the storms Mr Kelly was concerned the burrows along Melbourne’s main river would be flooded, drowning the babies.
“The burrows are in the bank, positioned above the waterline,” he said.
“Platypus can only be under water for a few minutes at best.
“The risk was that the burrows would be flooded, but I’m confident that didn’t happen because there was no extreme rise in water level.”
Previous Melbourne floods had taken their toll on the Yarra’s platypus population.