Monotremes in Suburban Streams: Surveying Melbourne's Platypus Population

Weaving and winding through city suburbs flow the many streams and creeks that make up Melbourne’s water catchment. These waterways extend from the mountain ranges surrounding the city where they carry away excess rainfall, guiding flows seaward into Port Phillip Bay. A multitude of life forms make use of this drainage system, although one in particular seems to capture our attention: an exceptionally peculiar creature renowned for its egg-laying abilities, venomous spurs, duck-like bill and webbed feet - the iconic platypus (Ornithorhynchus anatinus).


One of the many picturesque streams found around Melbourne which are home to Platypuses.

One of the many picturesque streams found around Melbourne which are home to Platypuses.

Despite its well-known identity and presence within metropolitan streams, the majority of Melburnians are unlikely to have seen a wild platypus due to their predominantly nocturnal behaviour and shy nature. For those who have been fortunate enough to sight the elusive creature, it surely proves for a memorable and enlightening experience. This was certainly the case for me whilst recently assisting environmental consultant and wildlife ecologist Josh Griffiths with platypus population surveys in Melbourne’s north-western suburbs.

Platypus surveys are undertaken twice yearly around Melbourne in order to assess population health and determine long-term population trends. The surveys involve setting specially designed traps at fixed locations within Melbourne waterways in the hope of catching platypuses which may inhabit an area. Once a platypus has been caught, various data is collected on the sex, weight, age and health of the individual, with each platypus also being equipped with a unique microchip (the latter being used to identify previously caught individuals in subsequent surveys).

Setting one of the many specially designed Platypus traps used during the population surveys. As can be seen in the photo one trap opens upstream whilst the other opens downstream.

Setting one of the many specially designed Platypus traps used during the population surveys. As can be seen in the photo one trap opens upstream whilst the other opens downstream.

During the volunteer placement, a male individual was caught, which allowed for a close inspection of the formidable venomous spurs that adorn the rear ankles of male platypuses. These impressive spurs, of approximately 1.5 centimetres length, are used against other males during territorial disputes throughout breeding season. In some instances, humans have been envenomated by these spurs, causing prolonged, excruciating pain. However, as Josh explains, given that a platypus is handled competently and correctly (by its tail), the spurs pose little danger to the handler. Nevertheless, as the surveys were undertaken outside of the platypus breeding season, all animals caught were relatively docile and cooperative, lying quietly in white cotton bags whilst the relevant data was collected.

The spur of a male Platypus. The pinkish sheath at the base of the spur denotes that this individual is a juvenile animal.

The spur of a male Platypus. The pinkish sheath at the base of the spur denotes that this individual is a juvenile animal.

A total of three platypuses were caught during the survey - a good result, Josh informed me, indicating that platypus numbers may be finally stabilising after a long, drought-induced decline. Drought led to reduced flows and pooling of many of Melbourne’s waterways, resulting in a drop in overall platypus abundance as individuals generally chose not to breed in the poor conditions or were unsuccessful in doing so. Josh also emphasised that the clearing of riparian vegetation hinders platypus procreation, as the burrows in which the animals rear their young require stable soils held together by tree roots. Nonetheless, such results were encouraging, indicating that the local platypus population and waterways were in good health.

All Platypuses remained relatively calm throughout the handling process. Here an individual’s bill protrudes thorough an intentionally made opening in a cotton holding bag.

All Platypuses remained relatively calm throughout the handling process. Here an individual’s bill protrudes thorough an intentionally made opening in a cotton holding bag.

An unfortunate Platypus who has become entangled in human litter—in this case a rubber wristband. The band was later successfully removed. Photo credit: Josh Griffiths.

An unfortunate Platypus who has become entangled in human litter—in this case a rubber wristband. The band was later successfully removed. Photo credit: Josh Griffiths.

To work with the enigmatic platypus has undoubtedly been an incredible experience. Such research is paramount to conserving this charismatic creature for future generations and to ensure the ecological health and functioning of our waterways. To assist in conserving this unique species, be sure to collect any artificial litter that may end up being flushed into our waterways. Disturbingly, Josh has informed me that of all platypuses caught during the 2013/2014 surveys, 10% were entangled in some form of litter, ranging from wrist bands and hair ties to balloon strings and elastic bands. To aid Melbourne Water and cesar (Melbourne Water’s research partner) in understanding and protecting platypus populations within Melbourne, submit any sightings of the species to the specifically created PlatypusSPOT online database at http://platypusspot.org/.

A Platypus re-enters a creek after being processed, within a second it is fully submerged and very difficult to see as it glides swiftly through the water.

A Platypus re-enters a creek after being processed, within a second it is fully submerged and very difficult to see as it glides swiftly through the water.