Australia is unusual because the animal population evolved largely out of contact with the other continents. A very high percentage of Australian animals are endemic (found nowhere else) including about 70% of its birds and 95% of its mammals. Over time, marsupials filled most of the ecological niches that are occupied by placental mammals in most other parts of the world. Australia is also home to the only three monotreme species in the world - two echidnas and the Platypus. The only placental mammals naturally found on the Australian mainland are bats; a large number of rodents which arrived only about 5 million years ago, and the Dingo, which was introduced to Australia by humans perhaps 7000 years ago.
Australia is also home to large and diverse populations of various other types of animal - snakes, lizards, insects, birds and fish.
