Pest animals

Animals which are not native to an area can cause many problems and frequently become pests.

For example, various species have been introduced into Australia which have had a severe impact on the ecology and diversity of native species. Often, these species have no native predators or other natural controls.

Feral animals are domestic animals which have become wild, such as rabbits, cats, pigs, goats, horses and camels. These were mostly introduced into Australia by European settlers. Aboriginal people, however, have a tradition of cats moving into the central desert from the west - perhaps suggesting that they arrived on the ships of explorers before settlement occurred.

Exotic wild animals are wild animals introduced into Australia for a variety of reasons. These include:

• The cane toad, introduced to Queensland from South America in 1935 to control insects in sugar plantations. The cane toad now ranges over 500,000 square kilometres of Australia. Female cane toads lay up to 30,000 eggs per year (while Australian native frogs lay only about 1,000 eggs per year). The cane toad not only eats many native species, but is also poisonous to native predators - a lizard or snake which grabs a cane toad in its jaws will die from the toxin the toad gives off.
• The red fox, introduced into Australia from Europe in 1845 for hunting. The fox spread across the Nullarbor within 50 years of its arrival. Foxes prey on small, ground-dwelling animals and have been responsible for the disappearance of whole populations in some areas. Baits of meat containing the poison 10-80 are now placed in many nature reserves to control foxes.
• The mosquitofish, introduced to Sydney from the Gulf of Mexico in 1925 to control mosquito larvae in dams. Mosquitofish attack native fish (damaging their fins) and compete aggressively for food, leading to the decline of native fish in some areas.
• The honeybee, introduced from Europe. The honeybee is more efficient at finding pollen than native pollinators, competing for the available nectar. The honeybee also stings native animals which nest in hollows where bees have a hive.

Even species native to Australia can have a devastating impact if they move into new areas where they didn't live previously. For example, the kookaburra did not occur in Western Australia, but it now preys heavily on reptiles and amphibians which were not at risk in this way before.

For many years government departments have monitored areas for pest animals. They publish Lists of Declared Animals to let people know what animals to look out for. If a pest animal is spotted and reported quickly enough, then sometimes the pest can be prevented from spreading by removing the individual or group before the numbers get out of hand.