For a continent 4,000 km across 3,750 km from north to south, Australia has an amazing set of natural environments and wildlife. There are 530 native species of bird,230 types of mammal,300 specie's of lizard,140 types of snake and two types of crocodile. Not all these animals are harmless. There are several species of poisonous spider and many poisonous snakes. Sharks, poisonous fish and salt water crocodiles are dangerous companions to swimmers.