Platypuses living in urban areas are exposed to many threats. One of the most significant disturbances to urban streams is stormwater run-off. Hard surfaces (e.g. roads, roofs, carparks) in the surrounding catchment area increases the amount and intensity of run-off after rain. This results in rapid increases of flows in local waterways with extreme peaks of high flows. These periods of high flows can erode banks and increase in-stream sedimentation, reduce benthic invertebrates (platypus food), and increase the energy required for swimming against strong currents.  

 

In collaboration with Melbourne Water, cesar ecologists used acoustic telemetry to investigate the impact of high flows on platypus behavior in a typical urban stream, Mullum Mullum Creek and the adjoining Yarra River. All platypuses used both Mullum Mullum Creek and the Yarra River and typically foraged over several kilometres each night (with one male travelling a maximum of 11.3 km during breeding season). Platypuses that were active in Mullum Mullum Creek during high flow events either moved downstream into the Yarra River, where the effects of rainfall events is less due the size of the river, or temporarily stopped activity in the creek until flow subsided. Extended or repeated periods of high flows is likely to substantially limit foraging behavior of adult platypuses and lead to lower body condition. Extreme high flows can also potentially drown dependent young in the burrow (November to February) or when juvenile platypuses first emerge and become independent (February to April)(see www.publish.csiro.au/paper/ZO13079.htm for more information). This is the first study to demonstrate direct impacts of high flows on platypus behavior although further work is required to determine how responses vary in different waterways and identify refuge areas such as wetlands and lakes.

Habitat degradation from stormwater is one of the key issues facing urban waterways with widespread impacts on the flow regimes, water quality, vegetation, substrate, invertebrates, fish and platypuses. Appropriate stormwater management is predicted to substantially improve habitat quality for platypuses and other aquatic species urban waterways.