Australia has many species of wildlife that are not found anywhere else in the world. Among the most unusual of these species are the many Australian mammals, such as kangaroos, that carry their young in external pouches. Australia is interesting not only because of the uniqueness of its wildlife, but also because of the lack of many types of animals, such as hoofed animals, that are common elsewhere in the world. Australia's wildlife is unusual because it has evolved in isolation from the rest of the world, over a span of many millions of years.
Most species of Australia's land mammals are marsupials (so called from the mother's marsupium, an external pouch in which the young are carried and nourished). The best-known marsupials are the kangaroos. The red and the gray kangaroos are found in open grass country. Smaller kangaroos, called wallabies, are found in hilly, shrub-covered country. Another marsupial is the koala, of the eucalyptus-covered areas of the eastern part of Australia. The Tasmanian devil, found only in Tasmania, is also a marsupial. Other marsupials include pouched mice, opossums, wombats, bandicoots, and the banded anteater.
Among other land mammals are many species of rodents and bats and the dingo, a wild dog. During the latter half of the 18th century, the European, or common, rabbit was introduced to Australia. It thrived and multiplied and at times has been a serious pest. In Australia and New Guinea are found the only egg-laying mammals known—the duckbill platypus and the spiny ant-eaters, or echidnas. More than 20 species of whales, including the large sperm whale, and several species of seals are found in the ocean south of Australia. The dugong, or sea cow, is found in the warm waters of northern Australia.
Australia has a wide variety of birds. In the tropical forests of the north are large numbers of parrots, cockatoos, and other tropical birds. The emu and black swan are rare birds found only in Australia. Bowerbirds, Cape Barron and magpie geese, kookaburras, and cassowaries are some of the birds found only in Australia and New-Guinea. Among the most interesting of all Australian birds are the two species of lyrebirds, found in open woodlands. Hawks and falcons are quite numerous in the interior, while sea eagles inhabit the coastal lands. Little blue penguins, smallest of the penguins, are common along the eastern and southern coasts.
Reptiles are plentiful throughout Australia. One of the largest species is the saltwater crocodile, which inhabits the ocean and saltwater estuaries of the north. A smaller crocodile, the Johnston's, or Australian, is a freshwater species. Lizards are especially numerous. The largest, a monitor, can attain a length of more than eight feet (2.4 m). Snakes are quite abundant, and several species, including the tiger snake, the copperhead, and the taipan, are poisonous. A species of python found on the northeast coast grows up to 20 feet (6 m) in length; it is the largest nonpoisonous snake of Australia. Several species of turtles and tortoises live in the waters near the Gulf of Carpentaria. A few tortoises are found near inland waters. The only amphibians are frogs and toads.
Fish are well represented in Australian coastal and inland waters. Probably the most interesting Australian fish are found among the nearly 180 freshwater species. For example, there are the freshwater black-fish, which has no known living relative; the lungfish, which has a lung as well as gills; and the barramundi, which is believed to have existed in Australia for more than 100,000,000 years.