Platypus facts: the egg-laying mammal

The key platypus facts: it is a mammal that lays eggs, it feeds its babies milk without nipples, and it hunts underwater with its eyes, ears and nostrils shut. It finds food with a bill that senses touch and tiny electric signals, says the Australian Museum. Males also have a venomous spur on each back ankle.

The platypus lives only in eastern Australia, in rivers, streams and lakes. When a dried specimen first reached Europe around 1799, many naturalists thought it was a fake, the Australian Museum says. With a bill like a duck, feet like an otter and a tail like a beaver, you can see why.

What kind of animal is a platypus?

A mammal, from a very old branch of the mammal family tree. The platypus and the echidnas form a group called monotremes. They differ from all other mammals because they lay eggs.

• Class: Mammalia (mammals)
• Order: Monotremata (egg-laying mammals)
• Family: Ornithorhynchidae
• Species: Ornithorhynchus anatinus, the only living member of its family

Monotremes have a long history. The Australian Museum describes a fossil relative, Steropodon galmani, from about 110 million years ago. A platypus-like fossil tooth 61–63 million years old has even been found in Patagonia, South America.

How big is a platypus?

Smaller than most people expect, about the length of a school ruler plus a bit. Males are bigger than females.

Platypus facts at a glance (Australian Museum)

Fact	Male	Female
Length, bill to tail	40–63 cm (15.7–24.8 in), sometimes more	37–55 cm (14.6–21.7 in)
Weight	0.8–3 kg (1.8–6.6 lb)	0.6–1.7 kg (1.3–3.7 lb)
Venom spur	About 12 mm (0.5 in) on each back ankle	None as adults
Eggs per clutch	Not applicable	1–3, usually 2
Egg incubation	Not applicable	About 10 days
Milk feeding	Not applicable	3–4 months
Time underwater per dive	30–140 seconds	30–140 seconds
Lifespan in the wild	Up to about 20 years	Up to about 20 years

The biggest males weigh about as much as a small house cat. The smallest females weigh less than a litre bottle of water.

How does a platypus find food with its eyes closed?

Its bill does the work. The bill is not hard like a duck’s beak. It is soft and packed with sensors. More than 40,000 tiny touch sensors, called push rods, pick up movements in the water, explains the Australian Platypus Conservancy. They can feel a shrimp moving 15–50 cm away.

The bill also holds tens of thousands of electroreceptors. When a small animal moves, its muscles give off weak electric signals. The platypus can sense them. Electric signals travel through water faster than ripples do, so the gap between the two clues may help it judge how far away a meal is, the Conservancy says.

This is not sonar or echolocation. The platypus does not send out clicks and listen for echoes. It picks up signals that its prey gives off. It searches the riverbed for 10–12 hours a day, the Australian Museum says, and mainly eats insect larvae. It also takes shrimps, water beetles, water bugs and tadpoles.

How does a platypus swim?

With its front feet. The webbed front feet push it through the water, while the back feet help it steer, says the Australian Museum. When it walks on land, the webbing on the front feet folds back so the claws can grip and dig.

A platypus swims at about 1 m (3.3 ft) a second in fast water and forages at about 0.4 m (1.3 ft) a second. Each dive lasts 30–140 seconds. On land it is less efficient: walking costs it almost 30% more energy than a land mammal of the same size.

Thick brown fur keeps it warm in cold streams, which can be close to freezing in Tasmania’s winter. The flat tail stores fat for lean times.

Is a platypus venomous?

Yes, but only the males. An adult male has a sharp spur, about 12 mm long, on the inside of each back ankle, linked to a venom gland. The venom is not known to have killed a person. But it causes severe pain, which the Australian Museum says has been described as excruciating. Swelling spreads through the limb, and extra pain sensitivity can last days or even months.

If you ever see a platypus, enjoy it from the bank. Never pick one up, even if it seems hurt. Call a local wildlife rescue group instead, and get medical help if anyone is spurred. Compare other venomous animals in are Komodo dragons venomous and the most venomous snake in the world.

How does a platypus lay eggs and feed its babies?

After mating, the female digs a long, winding nesting burrow in the riverbank in less than a week. She then spends another 4–5 days carrying in wet leaves and grass, which stop the eggs from drying out. About 21 days after mating she lays one to three eggs, usually two, and curls around them.

The eggs hatch after about 10 days. Then comes the other strange part. Platypus mothers have no nipples. Milk oozes from two patches of skin on the belly, and the babies suckle it from the fur. They feed on milk for three to four months before leaving the burrow.

So why is it a mammal if it lays eggs? Because it has fur and feeds its young on milk, the features that define mammals. Platypuses can breed from about two years old and live up to about 20 years in the wild.

Where do platypuses live?

Only in eastern Australia. The Australian Museum lists eastern Queensland and New South Wales, much of Victoria and all of Tasmania. They need permanent fresh water with earthy banks for burrows. Australia’s other unusual mammals have their own tricks; see adaptations of a kangaroo.

Do platypuses make sounds?

A little. Captive platypuses have been recorded making low growls when disturbed or handled. They are mostly quiet, and they do not use sound to find food.

Is the platypus endangered?

Not officially, but it is in trouble. The IUCN lists the platypus as Near Threatened, in a 2014 assessment. Nationally, it is not listed as threatened under Australia’s EPBC Act. It is listed as Endangered in South Australia and Vulnerable in Victoria, says the Australian Platypus Conservancy.

Scientists at the University of New South Wales assessed the species in 2020 (Hawke, Bino and Kingsford). Sighting records suggest the area where platypuses live shrank by about 22% from 1990 to 2020. The drop was about 32% in New South Wales. Some Melbourne populations fell by 18–65% between 1995 and 2019. The team recommended listing the platypus as Vulnerable.

The main threats are rivers drying up in drought, dams and water taken for farms and towns, and cleared land along riverbanks. Introduced foxes, dogs and cats kill some platypuses, and many drown in illegal fishing nets and traps.

Frequently asked questions

Sources

1. Australian Museum. Platypus.
2. Australian Platypus Conservancy. The platypus bill: push rods and electroreception.
3. Australian Platypus Conservancy. Platypus conservation status.
4. UNSW Centre for Ecosystem Science (2020). A national assessment of the conservation status of the platypus (Hawke, Bino & Kingsford).

Sources checked 15 September 2026.