Known for its peculiar blend of mammal fur, an electric duck bill beak, a poisonous leg spur, and reptile egg laying traits, the platypus has long fascinated scientists. The discovery of a 24-year-old male platypus in a peri-urban (outer suburban) creek in the outer eastern Melbourne suburbs near the Dandenongs has astonished researchers and set a new record for the confirmed age of a platypus in the wild.
Surviving from the age of the dinosaurs, the platypus belongs to a group of mammals called monotremes, the most ancient lineage of mammals living today. Around 315 million years ago, mammals diverged from reptiles and birds, and monotremes branched off from other mammals. The platypus represents one of the earliest offshoots of the mammalian family tree. When European naturalists first encountered the platypus in 1798, its unusual appearance puzzled them. The almost reptile, egg-laying, duck-billed, beaver-tailed, and otter-footed mammal seemed like a fantastical creation. In fact, the first scientists to examine a preserved platypus body suspected it was a hoax, believing it was made by sewing together parts of different animals.
The male platypus possesses a venomous spur on its hind foot, making it one of the few venomous mammals. Platypus sense prey underwater using a remarkable ability called electrolocation. Their bill detects electrical signals produced by movements of aquatic organisms, helping them locate prey even in cloudy water.
The platypus is considered a near-threatened species on a national level and vulnerable in Victoria. This 24-year-old male platypus was documented in a recent study called “Platypus longevity: a new record in the wild and information on captive life span”, co-authored by director of the Australian Platypus Conservancy, Geoff Williams.
The platypus was first captured and tagged in Monbulk Creek in the year 2000 as a one-year-old juvenile (a baby platypus is called a puggle) and recaptured last year – giving it a longevity of 24 years—an rare feat in urban river platypus. However, beyond the longevity of this individual platypus lies a deeper narrative about urban stormwater.
Urban streams are threatened when development creates impervious areas. Impervious surfaces, such as roads, driveways, car parks, rooftops, and concrete pavements, prevent water from infiltrating into the ground. When rain falls on impervious surfaces, it rapidly becomes stormwater runoff, which is often piped directly to the closest waterway.
Poorly designed development and paving of catchments impact directly on platypus habitat. Excessive stormwater runoff can harm platypus and their environment by increased flooding frequency and stormwater flow volumes. Direct runoff leads to higher streamflow during rain events, potentially eroding stream banks, washing away food, destroying fine riverbed structure for insects and disrupting habitats. Unfiltered runoff carries pollutants (such as oil, nitrogen, phosphorus, chemicals, and sediment) from impervious surfaces into the creek, affecting water quality and causing algal blooms. Rapid runoff can alter water temperature, impacting aquatic life, in particular the dragonfly nymphs and yabbies that platypus love to eat.
So what are some ways that water authorities like Melbourne Water, Knox Council and Yarra Ranges Council are using in the fight to protect the streams that platypus love? By applying the planning scheme requirements for Integrated Water Management (IWM) and recent drainage engineering guidelines like the Australian Rainfall and Runoff Guide (AR&R 2019), Councils encourage urban development to be more platypus friendly. Volume Control Strategies are key, by reducing directly connected impervious areas, in particular using Water Sensitive Urban Design (WSUD) to slow down the and filter the flow of stormwater.
The stormwater and drainage design objectives to help save platypus are:
Flow restriction: Detention basins, vegetated swales, and permeable surfaces allow stormwater to infiltrate into soils or be temporarily stored. This slows down stormwater runoff flow rates, preventing erosion and stream damage. Slower runoff also reduces temperature fluctuations, benefiting platypus and other aquatic organisms.
Quality: Green infrastructure (like rain gardens) filters pollutants before they reach the creek.
Volume reduction: Large water tanks (hooked up to toilets, washing machines and irrigation) and promoting groundwater infiltration further reduces impervious areas. Water tanks capture rainwater, reducing direct runoff. Groundwater infiltration using unlined raingardens, swales, and permeable paving allows stormwater to recharge aquifers, maintaining healthy baseflow in the creek.
Healthy creeks and rivers, provided by healthy and diverse habitats, are the lifeblood of species like the platypus. The rivers and waterways need to be protected by good WSUD. Urban platypus depend on building designers and builders to protect the physical habitat that supports their diet, behavioural patterns like burrowing, and reproductive success.
As we deepen our understanding we realise the inter-connectedness of our gutters and drains with the species within urban habitats. Studying our vulnerable friends helps us get better at designing buildings that support rather than destroy urban creeks.
The discovery of the oldest platypus downstream from Melbourne’s Belgrave South in the wild serves as a reminder of the wonders hidden within our suburbs.
Additional factors critical to platypus survival are:
Riparian Vegetation: Buffering streams from adjacent development, protecting ‘green wedge’ low urban density, and planting native vegetation along stream banks provides shade, habitat, and food sources for platypus.
Pollution Prevention: Properly managing stormwater quality prevents contaminants from harming platypus and other aquatic life. Pollution prevention requires constant vigilance from business and households in the area.
Controlling animals: Foxes, cats, rats and unleashed domestic dogs can easily destroy our monotreme friends. Animal control in known platypus areas is essential.
Through continued research, conservation efforts, and a renewed commitment to preserving habitats, we can ensure that future generations will have the privilege of marvelling at the enduring legacy of these extraordinary creatures.
Further Reading:
Platypus longevity: a new record in the wild and information on captive life span, CSIRO publishing https://www.publish.csiro.au/AM/AM23048
Oldest platypus found in the wild is ‘beyond all our expectations’, say researchers, The Guardian: https://www.theguardian.com/australia-news/2024/feb/15/worlds-oldest-platypus-found-in-the-wild-age-melbourne-water
Australian Rainfall and Runoff (ARR), Book 9 https://www.ga.gov.au/
InSite Water IWM drainage design tools https://insitewater.com.au/