|Young female platypus survives flood|
Date of release: December 6, 2011
Wimmera Catchment Management Authority says a young female platypus netted during a trapping survey in the MacKenzie River is a ray of hope a viable population of the animals survives in the region.
But the three-day trapping program by Melbourne-based environmental research group cesar failed to find any other platypus, leaving the CMA and researchers concerned last summer's floods have hit the monotremes hard.
The young platypus measured 40 centimetres from the tip of her bill to the tip of her tail and the ecologists believe she might be 10 to 12 months old. Platypus breed between August and October, young hatch within two weeks and remain in the burrow with their mother for about four months before emerging as juveniles from February to April.
Wimmera CMA catchment monitoring officer Mark Toomey says researchers will return to the river next autumn to continue its trapping program for the CMA.
“We are quietly optimistic, but finding only one platypus doesn’t give us firm evidence about the impact that the January floods had on the river’s platypus population,” Mr Toomey says. “We'll keep our fingers crossed that when ecologists return in six months they will find more than one platypus in their nets and give us more proof the river's population is hanging on and hopefully increasing.”
Wildlife ecologist Josh Griffiths and fellow cesar ecologist Tom Kelly set 38 nets between Lake Wartook in Grampians National Park and Laharum.
“We caught the female on the very first night, just downstream from Zumsteins picnic area,” Mr Griffiths says. “It's exciting that we actually found something still there after the floods. And it's really good it's a new animal, not one caught in a previous trapping, that it's a female and probably born in the area.”
Mr Griffiths says they don't catch all animals in the area when doing a survey. “Given there's a female there, there's a good chance there'll be a male too but we don't know for certain,” he says. “We just don't know how many animals survived the floods and it's disappointing we didn't catch an animal we'd previously tagged.”
Strong currents, debris and stress from being washed into a different environment during floods can all have a deadly effect on platypus. Juveniles, which are about three-quarters grown when they emerge from burrows, have little experience in foraging for food. The January floods hit when the youngsters were most vulnerable.
The cesar team has found platypus in the area every year since starting its trapping program in 2008. In autumn last year they trapped four platypus in the same section of MacKenzie River. They microchip each animal before releasing them.
Mr Toomey says the CMA has positive hopes for the future of the platypus due to the health of waterways right across the Wimmera being much improved thanks to the rain of the past 12 months and continuing environmental water releases.
“The MacKenzie River is one of the most flow-stressed rivers in Victoria and is a high priority for the CMA’s environmental water release program. We do ongoing releases in the river which are planned to mimic the river’s natural flow cycle, from higher to lower to no flows. This diversity of flow encourages diversity of aquatic life, such as the macroinvertebrates, or bugs, that are the staple diet of platypus.”
Mr Toomey says during future surveys the CMA was hopeful of finding platypus in different sections of the MacKenzie River as well as in the Wimmera River. “Now there is more water around, we hope to catch platypus outside the range we have seen in the past decade or so,” he says.
Mr Griffiths says similar netting surveys across flood-impacted parts of Victoria have revealed a drop in platypus numbers. Researchers had recorded a steady decline in population during harsh years of drought before the species began to recover when the rains finally returned more than 18 months ago.
“But after floods earlier this year they were depleted again,” Mr Griffiths says of the broader picture. “We've had low catch rates after the floods - even fish numbers were down - and only now we're starting to see some recovery. We just don't have a good handle on how platypus cope with floods, especially with one so severe and widespread (as the one in the Wimmera early this year). And because this is such a small population and effectively an isolated one, they could be quite severely impacted by localised events and last summer's flood was one such event.”