The platypus is an iconic Australian animal that lives in rivers and creeks across the Port Phillip and Westernport region.
Its unique characteristics, broad community interest and reliance on abundant food resources make it an ideal species to reflect the value of healthy waterways.
A key element of the strategy will include how we as a community work together to address key threats in the area so that platypus populations can be maintained and improved.
The relationships between environmental conditions and platypus communities are complex. However, in general, platypuses require stable banks for burrowing, large woody debris and coarse bed material for sourcing food. Sufficient waterway flow is an important factor for their survival, with baseflows and refuge pools providing the water required to survive in low flow conditions.
Extreme flow events can have a negative impact by flooding burrows during breeding seasons. Litter and fishing equipment can also entangle platypus, causing them to drown.
Assessment of the status of playtpus is determined through a combination of survey data and habitat suitability modelling.
Platypus are known to occur in the upper parts of the catchment, namely upper Dandenong, Dobsons, Monbulk and Ferny Creeks.
However, in recent years, targeted surveys suggest that platypus may no longer be present in Upper Dandenong and Ferny Creeks. Key threats to platypus in the Dandenong catchment are urban and industrial stormwater (including litter that may entangle and injure or drown animals), clearing of streamside vegetation, loss of instream habitat (e.g. draining of wetlands, concrete-lining and piping of streams) and fragmentation of populations from barriers to movement.
Platypus have been observed in the lower reaches of Jacksons Creek near Sunbury, Deep Creek Upper and Lower, and in the Maribyrnong River near the junctions with these creeks. The modelling has also indicated the likely presence of platypus in other streams, but this needs to be confirmed by surveys and observations.
Platypus are distributed in those parts of the Werribee River system (includes Lerderderg River) that have reliable summer flow regimes. However, they are considered to be locally threatened due to low numbers and continuing long term decline. They are observed around Werribee and further upstream around Bacchus Marsh. The intermittent flows in Little River are thought to make this part of the catchment unsuitable for platypus.
Past records suggest that platypus were previously present in Kororoit Creek, but not since the Millennium Drought.
Platypus are known to occur in the north eastern parts of the catchment, including rivers and creeks in the Bunyip, Tarago and Lang Lang river systems. There is also a reintroduced population in Cardinia Creek, with platypus released between 2004 and 2007.
Platypus are thought to be absent on the Mornington Peninsula and Phillip and French Islands. There are some historical records in the Bass River until the 1980s; recent surveys have failed to detect platypus although there have been unconfirmed sightings.
The Tarago River and Labertouche Creek in particular have been identified as important habitats for platypus, supporting the highest density of animals recorded anywhere around Melbourne since 2000. This result is likely to be linked to a large area of connected waterway reaches with steady stream flows and high-quality instream and streamside habitat.
Resilient populations of platypus have been observed in the Mullum Mullum Creek, the Yarra River at Warburton and tributaries (including McKenzie King, Surrey Road and Big Pats Creek), the McMahons Creek and the Chum Creek. Vulnerable populations of platypus have been observed in the Diamond Creek in Eltham, Lower Plenty River in Greensborough, Olinda Creek between Lilydale and Mount Evelyn and the Little Yarra River in Yarra Junction. A locally threatened population of platypus has been observed in the Plenty River in South Morang. Overall the score for platypus ranges from high and very high along the Yarra main stem and in the upper catchment, broadly east of Healesville, and very low to moderate in the catchments of the lower and middle Yarra tributaries (west of Healesville).
- Small population sizes
These are vulnerable to changes in the environment, disease, and catastrophic events such as fire.
- Lack of in-stream habitat complexity
Waterways that have submerged wood, rocks and pebbles, and aquatic plants tend to provide a greater availability of food for platypus.
- Waterway condition
Poor water quality, lack of streamside vegetation, poor bank structure, lack of habitat.
- Entanglement in litter/fishing equipment
This is a common problem for platypus and often results in severe injury or death.
- Predation by foxes/dogs
Platypus travel over land and in shallow water, which can make them easy targets for predators.
- Poor streamside vegetation quality
This reduces the protection, availability of food and feeding habitat required by platypus.
- Agricultural development
These include changes to waterways such as clearing of streamside vegetation, damage due to stock access and erosion.
This results in reduced water quality, natural vegetation and waterway form which are all important to platypus survival.
- Low flows
When the amount of water in waterways is reduced, habitat and protection from predators is lost.
Potential management actions
- Improve and maintain streamside habitat quality
Through revegetation, weed control, and management of stock and human access.
- Maintain existing areas of channel habitat
Burrow location and food supply is linked to the quality of waterway channels and stability of bed and banks. Channel quality can be assisted by on-ground works and preventing stock access to waterways.
- Implement environmental flow regimes
Provide and protect appropriate flows to ensure that platypus are protected from loss of habitat and predation.
- Improve water quality
Through improved stormwater treatment and rural land management practices that reduce inputs of nutrients, sediment and chemicals into waterways.
- Control foxes/dogs
Protect platypus from predation by foxes and dogs.
- Reduce in-stream litter
Reduce litter through public education and waterway management.
- Improve connectivity between platypus populations
Remove barriers that prohibit platypus populations from moving between waterways.
- Improve floodplain habitat
Create more floodplain-based refuges.