The platypus is widespread in eastern Australia, including Tasmania, ranging from tropical lowlands to sub-alpine areas. It is one of only five species of Class Monotremata (the other four are species of echidnas). The members of this class, the monotremes, are the only mammals that lay eggs. They also have lower body temperatures than other mammals, and legs which extend out, then vertically below them. These features are more reptilian, rather than mammalian.
Platypuses feature a streamlined body, webbed feet, broad tail and a characteristic muzzle, or bill, which is soft and pliable. They have a lifespan of 10 to 15 years. Their front feet have large webs of skin that help them to swim. On land the webs fold back revealing sharp claws, which are used for walking and digging burrows. The red blood cells of the platypus carry larger amounts of hemoglobin than any other mammal, allowing it to go without air for longer periods. Platypuses swim with their eyes, ears and nostrils closed, using their electro-sensitive bill to locate food. Their electro-receptor system detects the electric currents created by the muscle activity of small prey such as worms, insects, crustaceans, molluscs and tadpoles.
Male platypuses are among the very few venomous mammals, having a spur on the inner side of each hind limb, which is connected to a poison gland. The poison is capable of inflicting a very painful injury to humans.
Platypuses are shy and wary, usually venturing out only in the early morning and evening. Males and females reach sexual maturity at the age of two years. Only the left ovary of the female platypus functions, whereas the other ovary is poorly developed and not functional -- a characteristic that also occurs in birds. After mating, the female leaves the male and constructs a nesting burrow, which can be up to 20 m long, laying two to three eggs in it. The eggs have large yolks and rubbery shells like reptile eggs. When the babies hatch they nurse from the milk glands of their mother, who, like the echidna, lacks nipples; milk from the mammary glands oozes out through ducts into the pouch where the newborn platypus is.
The picture was taken at the Scienceworks museum in Melbourne, in January 2005.
Life on Earth