The Platypus is one of five species of the Order Monotremata, the smallest of the Mammalian Orders which also includes the short-beaked Echidna which occurs over most of Australia, and three species of long-beaked Echidna from Papua New Guinea.
Being Monotremes, Platypus and Echidnas are the only mammals on earth to lay eggs. The platypus is a fascinating and somewhat cryptic species. Unique to Australia, this fabulous semi-aquatic mammal confounded early naturalists for decades during the post colonial period of Australia. Debates raged in scientific circles about the authenticity of the Platypus in the 1800’s, many eminent naturalists thought it was a fake because of the duck-like bill and feet, egg-laying traits combined with mammalian fur – the existence of which forced scientists to accept the concept of evolution in a time when religion dominated public opinion about the origin of species. An excellent historical fiction called “Love and the Platypus”, by Nicholas Drayson describes Scottish Naturalist, William Caldwell’s unrelenting and somewhat disturbing field investigation into this debate, the impacts of which involve the collection and killing of over 1400 echidnas and an untold number of Platypus in SE Queensland between 1883 and 1886.
Other interesting facts about the Platypus include its production of venom – a rarity amongst mammals. Males have spurs on their rear ankles that are connected to a venom gland that enlarges when testosterone levels increase during mating season. As it turns out, their venom is structurally similar to that found in snakes, and is an interesting example of convergent evolution, meaning they don’t share a common venomous ancestor.
Other interesting evolutionary traits of the Platypus include their bone structure and arrangement. They have a relatively heavy skeleton for their size that resembles modern and fossil reptiles, with splayed legs, 5-boned pectoral girdles, and rudimentary ribs on the neck vertebrae. Indeed, their most recent shared ancestor (with reptiles) was 166 million years old, which is also when Monotremes diverged from Marsupials and Eutherian mammals (the group that includes Humans) making these incredible animals even more interesting. Read more about the evolution of the Platypus HERE.
It is thought that their ancestors were larger than modern day Platypus, reaching up to 70cm. The fossil record for Platypus is scant, and based largely on the fossilised teeth of their ancient predecessors. Modern Platypus only have teeth in juvenile life stages, which fall out before the formation of the keratin grinding plates found in adults that used to masticate their favourite food source – crustaceans.
Platypus are one of two aquatic freshwater mammals in Australia, the other being the voracious Rikali. They differ from Rikali in their dorsally flattened bill, head, body and tail. They also have webbed feet and further differ from Rikali by the lack of ear protuberances, and the ability to close off their ear canals whilst swimming. Their fur is double layered with a waterproof outer layer and a soft inner layer which traps air next to the body when swimming. This assists with buoyancy and maintains body temperature and is an excellent adaptation to a semi-aquatic life. And swim they do – up to 12 hours a day, mostly foraging for the benthic crustaceans that form most of their diet. In fact, Platypus are excellent swimmers – their front feet are large and webbed and propel them through the water, whilst the rear feet are used somewhat like a rudder and assist with guiding them and changing direction. Completely lacking teeth as adults, Platypus use their flattened bill to scoop up prey which they store in their cheek pouches before surfacing, where they eat their catch. Unlike the duck bill that it superficially resembles, Platypus bills are quite simply, an incredible piece of evolutionary adaptation. Soft and pliable like leather, Platypus bills have numerous electro- and mechano- receptors that are unique in morphology. These receptors assist them in detecting prey and navigating underwater (they swim with their eyes closed).
When not swimming and foraging, Platypus spend time sheltering under crevices and logs, or in purpose-built burrows that may be deep and multi-roomed. Ideal habitat for Platypus includes shady freshwater rivers and streams, with well vegetated earthen banks. Gravel or pebble substrates provide ideal habitat for their main source of energy – macroinvertebrates. Deep pools enable them to survive extended periods of drought and are essential Platypus habitat.
The conservation status of the Platypus is unclear, due to very poor historical population data. There is some debate about the use of anecdotal evidence and historical records to form a picture of the early post-colonial abundance of the species, but it seems they were once very abundant on the east coast of Australia. As with the Rikali, platypus were revered by early colonists for their waterproof fur and were actively hunted until the early twentieth century. One horrific record reports of a furrier with around 29000 platypus skins in his store in the early 1900’s. Whilst we no longer hunt the species for its fur, modern day threats to the platypus are real, and seem to be ever increasing. Given that their natural distribution and range overlaps with the highest density of human habitation in Australia, it is not surprising that their numbers are declining, and the ICUN recently listed them as “Near Threatened”.
So what can you do to help protect and support the Platypus? If you have creeks or rivers on your property, investing in riparian restoration and protection from stock is the most impactful action you can take. Careful regeneration of native vegetation along riparian zones, and stock exclusion fencing are essential. Following this, we can all reduce our use of plastics, assist with local clean-ups in riparian zones, and never use crab / yabby nets in freshwater systems.
For more information about the Platypus, and to get involved in community programs, head over to the Australian Platypus Conservancy
One of the main threats to Platypus is death by drowning in abandoned or illegal fishing gear, particularly yabby / crab traps, such as the Opera House trap, Eel net (Fyke), Spring trap. These apparatus have funnelled entrances that platypus cannot escape through. There are legal and safe options for yabbying, but you should never leave any fishing trap or net unattended (also true in coastal lakes and lagoons, where they are death traps for many other species, including marine turtles). Horrific stories of Platypus and Rikali drownings are unfortunately too common, and yet easily avoidable.
Entanglement in litter is also a key threat to Platypus, particularly anything resembling a ring, such as a hair tie, engine gasket, elastic band, also discarded fishing tackle (which is dangerous to many aquatic species). Pick up rubbish when you see it, and make a habit of cutting any plastic rings, gaskets and elastic bands before disposing of them.
Other major threats include: Sharp glass in sediment. Altered fire regimes and water cycles. Large dams. Pollution – nutrification of waterways, sedimentation, chemical run-off, oil, Firefighting chemicals (PFOS/PFAS).
Article written by PLCM Project Officer, Isabelle Strachan 2025
