Platypus find raises hope
An opportunistic summer survey confirming gradual growth of a fragile Wimmera platypus population in the Mackenzie River has generated fresh confidence in the survival potential of the species in the region.
Researchers captured four of the unique animals in one night of trapping between Laharum and Cranages, the most in one night since surveys started in the 1990s.
An Ecology Australia team led by Chris Bloink and working with Wimmera Catchment Management Authority, set survey traps on Friday night.
The group, usually involved in fish surveying for Wimmera CMA, had made the most of an opportunity for a training and professional-development trapping event for team members after a sudden change in scheduling.
But its results were profound, finding three juveniles that hatched last spring, in a Zumsteins section of the river, and a sub-adult male less than two years old above Mackenzie Falls.
Two of the juveniles, now named Georgia and Frankie, were female and the other, Russell, was male. The sub-adult male won the name Perry.
Wimmera CMA waterways project officer Greg Fletcher said the find was exciting and researchers had already nicknamed Zumsteins the ‘platypus highway’.
“The fact that three of the four were young from the latest season and the other being less than two years old shows the animals have been very productive and happily breeding in the river. This bodes well for further dispersal of the species downstream,” he said.
“It also shows the environmental value regularly flowing water has on river ecology and in this case considering the Mackenzie supplies Horsham with its water supply from Lake Wartook.”
Platypus, similar to other Australian animals, have a high level of physical resilience to environmental conditions and are therefore sometimes poor bioindicators.
But their food, often involving macroinvertebrate and other aquatic life and essential for them to survive, is usually sensitive to environmental conditions. Platypus also have considerable dietary needs, especially feeding mothers that need to produce milk that, in the absence of teats, must express milk through their skin.
Mr Fletcher said researchers had fitted all platypus captured during Friday night’s survey with microchips for future reference and released them back into the river.
“This survey was a bonus. We hope to try to tee up Josh Griffiths from research company Cesar Australia, who has been regularly monitoring this population, for another survey next spring,” he said.
Waterway managers raised fears more than 10 years ago, during a long period of drought, the Mackenzie River might have been the site of localised extinction of platypus.
The fears prompted the launch of a survey program and a focus on environmental protection of the river, including environmental flows.
Platypus require specialised riverside bank burrows that exploit natural wilderness cover to lay their eggs.
They sit at the top of the aquatic food chain in many systems, often sharing habitat with native rakali, also known as water rats.
The survey team also captured a juvenile rakali on Friday night.
Parts of the Mackenzie River are home to some of the last remaining pristine stretches of natural waterway habitat in the Wimmera.