The platypus is a semi-
The unusual appearance of this egg-
Until the early 20th century, it was hunted for its fur, but it is now protected throughout its range. Although captive breeding programmes have had only limited success and the platypus is vulnerable to the effects of pollution, it is not under any immediate threat.
While both male and female platypuses are born with ankle spurs, only the male's spurs produce a cocktail of venom, composed largely of defensin-
The venom appears to have a different function from those produced by nonmammalian species; its effects are not life-
The body and the broad, flat tail of the platypus are covered with dense, brown fur that traps a layer of insulating air to keep the animal warm. The fur is waterproof, and the texture is akin to that of a mole. The platypus uses its tail for storage of fat reserves (an adaptation also found in animals such as the Tasmanian devil and fat-
Unlike a bird's beak (in which the upper and lower parts separate to reveal the mouth), the snout of the platypus is a sensory organ with the mouth on the underside. The nostrils are located on the dorsal surface of the snout, while the eyes and ears are located in a groove set just back from it; this groove is closed when swimming. Platypuses have been heard to emit a low growl when disturbed and a range of other vocalisations have been reported in captive specimens.
Weight varies considerably from 0.7 to 2.4 kg (1.5 to 5.3 lb), with males being larger than females; males average 50 cm (20 in) in total length, while females average 43 cm (17 in), with substantial variation in average size from one region to another, and this pattern does not seem to follow any particular climatic rule and may be due to other environmental factors, such as predation and human encroachment.
The platypus has an average body temperature of about 32°C (90°F) rather than the 37°C (99°F) typical of placental mammals. Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes.
Modern platypus young have three-