Platypus

When the first platypus specimen reached Britain in the 1790s, naturalists assumed it was a hoax — a duck’s bill sewn onto a mole’s body. It is real, and almost every part of it breaks a rule about what a mammal is supposed to be.

Overview

Platypuses live in freshwater across eastern Australia and Tasmania — rivers, creeks, farm dams, and lakes with earthen banks they can burrow into and enough invertebrate life to eat. They are mostly active at dusk, dawn, and night, spending the rest of the time in a burrow above the waterline. Each platypus holds a stretch of waterway and forages along it in a series of dives.

An animal assembled from parts

• The bill looks like a duck’s but is soft, flexible, and leathery. It is the platypus’s main sensory organ — not for smelling or seeing, but for electroreception. It carries tens of thousands of receptors that detect the faint electric fields of muscle activity in prey.
• The body is streamlined and otter-like, covered in dense double-layered fur that traps a warming layer of air. The tail is flat and paddle-like and stores fat.
• The feet are webbed for swimming, with the webbing folding back on land to expose strong digging claws.
• The males carry a venomous spur on each hind ankle.
• Reproduction is by egg. Females lay one to three grape-sized leathery eggs in a nesting burrow, curl around them for about ten days, and then feed the hatchlings milk that oozes from patches on the belly — platypuses have no nipples.

Hunting

A foraging platypus dives for 30 to 60 seconds at a time, closing its eyes, ears, and nostrils and relying entirely on its bill. Sweeping its head back and forth, it reads the electric signature of a shrimp or a mayfly larva in the sediment, cross-references it with the pressure wave the prey creates, and works out exactly where to dig or snap. It stores the catch in cheek pouches and chews it at the surface between dives, grinding food with horny plates because adult platypuses have no teeth.

Threats and conservation

The platypus is listed as Near Threatened and declining, and it has vanished from around a fifth of its historical range. It is highly sensitive to the health of the waterways it lives in:

• Water extraction and drought. Rivers drawn down for irrigation, and prolonged droughts, dry out platypus habitat and isolate populations.
• Dams and weirs that block movement and stop young platypuses dispersing.
• Land clearing and erosion that destroy the vegetated banks platypuses burrow into and muddy the water they hunt in.
• Drowning in illegal fishing nets and enclosed yabby (crayfish) traps, a significant and preventable cause of death.
• Bushfire and heatwaves, worsening with climate change.

Because the platypus is cryptic and hard to survey, its decline went largely unnoticed for decades. Removing enclosed traps, keeping rivers flowing, and protecting stream banks are the practical priorities.