What is a platypus?

The platypus is a small egg-laying mammal with a duck-like bill, webbed feet, a beaver-like tail, and a coat of dense waterproof fur. It lives in freshwater rivers, streams, and lakes along the eastern coast of Australia from far north Queensland to Tasmania, and is one of the world's only two kinds of monotreme alongside the echidna.

Adult platypuses are about 40 to 50 centimetres long and weigh 1 to 2.5 kilograms, with males slightly larger than females. Males have a venomous spur on each hind ankle, the only venomous mammal in Australia and one of very few venomous mammals worldwide. The venom is not lethal to humans but causes intense pain that can last weeks.

The bill is not bone or beak but a soft, leathery sensory organ packed with electroreceptors and mechanoreceptors. Platypuses hunt with their eyes and ears closed underwater, detecting the tiny electric fields generated by the muscles of prey such as freshwater shrimp, insect larvae, and small crustaceans. They store food in cheek pouches and grind it with horny pads in the mouth, having no teeth as adults.

Female platypuses lay one to three soft, leathery eggs in a deep burrow dug into the riverbank. Eggs hatch after about 10 days and the young feed on milk that the mother secretes through patches of skin (platypuses have no nipples). Platypuses were so unlike anything else in European zoology that early naturalists in the 1790s suspected the first specimens shipped to London were a hoax. Today the platypus appears on the Australian 20-cent coin and is listed as near-threatened nationally because of habitat loss, drought, and water quality decline.