The Platypus Ornithorhynchus anatinus

The strange external features of the platypus make it unique among mammals. It looks rather like a mixture of a duck’s head grafted onto the body of a soft-furred, four-legged creature, with a flat, broad tail and webbed feet. There are no external ears, and the minute eyes are almost hidden in its beaver-like coat. Platypuses are described as ‘primitive’ because they lay eggs; the only other egg-laying mammal is the echidna. Both the platypus and echidna belong to the order Monotremata.

Although it is ‘primitive’, the platypus is highly specialised, and is well adapted to swimming. There are no sensory whiskers, but the muzzle is one of the most sensitive sensory organs of all mammals. At an early stage of its development it loses its few molar teeth, which are replaced by horny plates. Mammary glands are modified to an area of abdominal skin which secretes milk for developing young.

On the hind limb of the male, a horny spur leads to a venom-secreting gland located in the thigh and connected to the spur by a duct. The venom has similarities with that of Australian elapid snakes. Generally, the spur is used only in the breeding season, but there are numerous records of people being impaled by a spur, causing considerable pain. Females have a small spur when young, but this does not develop.

Where do Platypuses occur?

The platypus occurs naturally in suitable streams throughout eastern Australia, from around Cooktown in north Queensland to southern Tasmania, from lowland tropical streams to cold mountain streams and lakes.

A Platypus

A Platypus
Photographer / Source: Gary Lewis

What do they feed on?

The food of the platypus includes a wide range of adult and larval invertebrates as well as small fishes and amphibians. The availability of these items, and therefore their proportion in the diet, varies from one season to another.

The platypus uses its bill to search under and around stones and organic material on the bottom of watercourses to locate their food. Electroreceptors in the bill detect tiny electrical fields emitted by their prey items which may be snapped up directly. In captivity, a platypus can consume half its own body weight of food in a single feeding session.

When is their breeding season?

Spring is the breeding season of the platypus.

Following mating and a gestation period of about a month (the exact period is unknown), usually two leathery eggs are laid and held on the abdomen of the mother, who incubates them in a curled position. After six to ten days of incubation the hatchlings break free of the shell and feed on milk produced by the mother. This takes place in a complex burrow by the river, and young do not venture from this burrow for three to four months.

What is their conservation status?

Although platypuses are occasionally found entangled in fishing nets, the species does not appear to be threatened at present. They are common across their range and a breeding population exists as close to Melbourne as the mouth of the Plenty River, 15 km from the city. It is protected by law, unlike earlier times when platypus skins were taken in large numbers for the fur trade.

Further Reading

Grant, T. 1989. The Platypus. New South Wales University Press, Kensington.

Menkhorst, P. W. (ed.) 1995. Mammals of Victoria. Oxford University Press, Melbourne.

Menkhorst, Peter & Knight, Frank. 2001. A Field Guide to the Mammals of Australia. Oxford University Press, Melbourne.

Strahan, R. (ed.) 1995. The Mammals of Australia. Reed Books, Sydney.

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