Bizarre, peculiar, odd or unqiue. What’s the best way to describe the platypus – a venomous semi-aquatic mammal that lays eggs and uses electroreception to find its prey?
From top to tail, platypuses (or platypodes) can be 60cm long. Males can weigh 3kg; females 1.7 kg. In colder climates individuals are slightly larger, but they don’t come close the size of prehistoric platypuses, which were 1m long!
Their appearance is indeed unusual. The name Platypus comes from the Greek word for ‘flat-footed’. They use their webbed feet to swim, and their tail to steer through the water. They’re expert swimmers.
While underwater, foraging for food, they can tightly close their eyes, ears and nostrils. In this way they hunt for prey underwater for 30 to 140 seconds at a time. Yet they’re awkward on land, walking on their knuckles to protect their webbing.
Their dense, silky brown fur is both waterproof and insulating – along with the fat reserves in their tails, their fur allows them to stay warm underwater.
The platypuses ‘duck bill’ is flexible, rubbery and feels like suede. They use their bill to dig up food from the riverbed, but it’s also highly sensitive.
Platypuses use electroreceptors on their bills to detect electrical signals given off by prey as it moves. In other words, with its eyes, ears and nostrils closed, it can use electroreception to detect movement underwater and help it find prey. This explains its characteristic side-to-side head movement while hunting.
The spur on the male’s hind foot is connected to a venom-secreting gland. Recent research suggests that the spur is used during aggressive encounters between rival males. For humans, the venom is non-fatal, but it can cause swelling, loss of muscle control and severe pain. It’s one of very few venomous mammals in the world.
It’s little wonder that 19th Century European scientists found it difficult to believe that platypuses were real, and fancied this half-beaver, half-bird hybrid to be an elaborate hoax. Years on, the platypus is celebrated as one of Australia’s most unusual and unique animals – it's the state animal of New South Wales and proudly represented Australia in the 2000 Olympics…. as a mascot!
Taxonomically, it's the only species in the family Ornithorhynchidae.
Where do Platypus live?
Platypuses are endemic to (only found in) east and south-eastern Australia. They’re found in freshwater creeks and rivers of Queensland, New South Wales, Victoria, Tasmania and South Australia. They can live in many habitats, from tropical rainforests creeks to streams in alpine areas.
Platypuses are not endangered and are ranked as animals of ‘Least Concern’ by the International Union for Conservation of Nature. Even so, because of their elusive nature there’s a general lack of knowledge about their abundance. They’re protected by legislation in all of the states where they occur.
Platypuses are mostly nocturnal. During the day they sleep in the chambers at the end of riverbank burrows. At dusk they emerge to search the river bottom for food, sometimes hunting for 10 to 12 hours a night.
They’re completely carnivorous (meat-eating) and mostly eat invertebrates: swimming beetles and waterbugs, insect larvae, tadpoles, worms, snails and shrimp. They scoop up gravel and dirt along with their prey, store it in their cheek-pouches, and bring it all to the surface to eat.
Like echidnas, platypuses don’t have teeth. Instead, they use a grinding plate to mash the gravel, soil and food slurry, scooped from the riverbed. They can eat an impressive amount of food in a night – up to 20% of their own body weight!
Females breed at 4 years. After burrowing deep into the riverbank, pregnant females lay one or two eggs. Here, curled up in protective chambers, they incubates their eggs between their tail and rump.
Bean-sized babies emerge from the egg after 10 days and are fed milk for about four months. But platypuses don’t have nipples; instead milk is secreted through pores and licked off the mother’s skin or fur.
By the time the young are weaned off milk they can swim independently. While largely solitary, platypuses don’t mind sharing their waterbody with other individuals. They can live to 12 years old in the wild.
Given their dependence on freshwater systems, habitat destruction and waterway pollution threaten this species. Water extraction, dams and diversions to water flow have a big impact. Water quality and in-stream habitat (such as submerged logs) are critical so degradation of these elements is a threat. Run-off from pasture (sediments and nutrient load) can degrade platypus habitat.
Platypuses are eaten by snakes, water rats, birds of prey and occasionally crocodiles. It’s likely that foxes, dingoes and wild dogs kill platypuses that venture on land. They were once hunted for their fur – pelts are both warm and waterproof.
What Bush Heritage is doing
Sit quietly by the water at our Liffey Valley, ‘Nameless’ Sylvan or Scottsdale reserves and you might spot this shy species. We look after their habitat by maintaining riparian vegetation (which filters run-off into waterways) and in-stream habitat (e.g. fallen logs, deep pools) and by managing stream-bank erosion.