The Werribee River is home to one of Australia’s most extraordinary and elusive creatures, the platypus. With many urban rivers seeing declines in platypus numbers, we are fortunate in the Werribee River to still have breeding populations of this mysterious monotreme.
One of the most important needs for platypus is daily access to healthy rivers and waterways. Platypus rely on macroinvertebrates such as waterbugs, yabbies and worms for their food. If water quality is poor, waterbugs don’t thrive. Platypus are also at risk from litter entanglement and predation by dogs and cats – so disposing of litter and fishing gear properly, and responsible pet ownership, can help them to survive.
How do we know where platypus are present in the river? Ecologists use both live trapping surveys, where platypus are captured in specially designed nets that ensure they are not harmed, and water sampling using environmental DNA (eDNA) testing. As these creatures swim about on their daily forage for food, platypus like all animals shed DNA in skin, hair and excretions, which can be detected in tiny amounts in water. Both techniques can be useful. Surveys of eDNA can reveal if platypus are present without the effort of setting up and monitoring nets through the night, and samples can be collected by citizen scientists and volunteers with some basic training. Netting surveys enable scientists to check the health condition of each animal captured and insert a tiny microchip under their skin. This means that if the platypus is recaptured later on we can tell if they have moved around and estimate their age. A platypus in Monbulk Creek was recaptured in 2023, 23 years since being tagged!
Bryce Halliday, a Senior Aquatic Ecologist with Ecology Australia, reports on their latest surveys conducted during September 2024:
“Ecology Australia has recently conducted platypus surveys using fyke nets set overnight in the Werribee River on behalf of and funded by Melbourne Water. The surveys have provided encouraging insights into the local platypus population. Two surveys were carried out: one downstream of the diversion weir (lower Werribee) and another through Bacchus Marsh (Upper Werribee).
In the lower Werribee, a single male platypus was recaptured, first identified in February 2022 by Ecology Australia. Meanwhile, the upper Werribee survey was more fruitful, with six new platypuses captured—four males and two females. Notably, a male and female pair were captured together in the same net on two occasions, hopefully hinting at potential breeding activity in the area.
These findings highlight the ongoing efforts to monitor and support the platypus population in the Werribee River, with speculative signs of breeding offering hope for the species’ future in the region.”
Photo credit: Bryce Halliday (2024)