The platypus (Ornithorhynchus anatinus) is the only living semiaquatic monotreme, and the only species of the genus Ornithorhynchus. The only other members of the order Monotremata (monotremes) are the short-beaked echidna (Tachyglossus aculeatis) from Australia and the long-beaked echidna (Zaglossus bruijni) from New Guinea. Unlike all other mammals, the monotremes, including platypuses (often incorrectly spelled platypi) lay eggs rather than giving birth to live young.
Range and habitat
Platypuses are found only in the wetter parts of south-eastern mainland Australia and Tasmania. They inhabit rivers, lagoons and streams of less than 5 m depth, preferring to live in steep-banked areas where there are roots, overhanging vegetation, reeds and logs. They have been recorded at elevations greater than 1,000 m.
The extent of the home range varies, depending on the region, but ranges from 0.4 to 7 km. Platypuses that forage in streams generally have larger home ranges than those that forage in ponds or pools.
Platypuses are a highly distinctive animal. Streamlined and elongated, they have bills that are strongly reminiscent of those of ducks, and broad, flat tails resembling those of beavers. Their soft, dense, waterproof fur (which covers everything but the bill and feet) is medium to dark brown on the dorsal (upper) side and rufous-brown to silver-grey on the ventral side.
Their nostrils are on top of their bills, and their small eyes and ears are located in grooves on either side of their heads. The short limbs terminate in naked-soled feet with five digits. The forefeet are fully webbed with broad nails, and the hind feet are partially webbed with sharp claws. Males have venom glands attached to a spur on each of their hind legs.
Platypuses lay eggs and eliminate solid and liquid waste through a cloaca. Females have mammary glands but lack nipples. The milk teeth of the young are lost in adulthood, with mature platypuses having flattened, horny grinding plates.
Seasonal breeders, platypuses generally commence reproductive activity in August and continue into September, although breeding time varies with location (earliest in Queensland, later in New South Wales, and latest in Victoria and Tasmania). Females generally do not breed until at least two years of age or later, and do not necessarily reproduce every year. Only dominant males are able to breed successfully.
The females dig burrows in which to incubate and nurse their offspring; males seem to be uninvolved in the rearing of the young. Females lay one to three eggs (usually two) and incubation is estimated to be 10 days. The offspring use a sharp egg tooth to tear open the rubbery shell of the eggs when hatching.
The newly hatched offspring (c. 15 mm long) are highly underdeveloped, but are able to use their well-developed fore limbs to pull themselves up to nurse. The female lactates for three to four months. By the time the juvenile offspring leave the burrow for the first time (at which stage they are still nursing), males are around 410 mm long and females 370 mm. Juvenile females reach adult size earlier than the males.
Although there is little evidence about their lifespan, it is believed that platypuses may live up to 12 years in the wild.
The primary diet of platypuses is aquatic invertebrates. They also eat small fish, fish eggs and shrimp.
Platypuses, especially males, are generally solitary, although several individuals may utilise a small body of water. Little is known about their behaviour because they are semiaquatic and nocturnal, and usually return to their burrows when not feeding. Juvenile platypuses, like many juveniles of many mammalian species, are playful, and have been seen playing and splashing in water. Captive juveniles have been observed wrestling and playfully biting one another in the shallows.
The platypus has a range of vocalisations, but the role of these in communication is as yet undefined. The most common sound they make, a growling noise, is often associated with being disturbed.
Platypuses are preyed upon by foxes, humans and dogs, as well as snakes, birds of prey, feral cats and large eels. The role of introduced species in predation is notable and concerning.
- Ojo, E., Omland, K. "Ornithorhynchus anatinus", Animal Diversity Web. Retrieved on 23 August 2008.
- Pasitschniak-Arts, Maria; Marinelli, Lui (1998). "Ornithorhynchus anatinus". Mammalian Species 585: 1–9.