Introduced species are a major cause of frog declines in Australia. They have been so successful in this country because they can out-breed, out-eat and out-compete Australian native animals and plants, and have few natural predators.
Animals that have been introduced to Australia include:
- Foxes
- Rabbits
- Cane Toads
- Pigs
- Goats
- Camels
- Mice
- Cats
- Dogs
- Fish (e.g. Carp & Gambusia)
Some of these animals listed above can change entire ecosystems. For example Carp alter aquatic ecosystems through their feeding and breeding habits that change environmental parameters such as turbidity, light and water temperature. Other animals, like foxes, can have a more direct effect whereby they prey on native animals.
Introduced animals that effect frogs
Many introduced animals either eat frogs or destroy their habitats. The main threats include:
Introduced fish
Introduced fish in Australia include Carp, Rainbow Trout, Goldfish and Redfin Perch. Some of these exotic species were brought to Australia in the late 1800s to stock waterways with fish that were familiar to European settlers. Others were released aquarium fish. All of these fish either prey on frog eggs and tadpoles or change aquatic ecosystems so they are no longer suitable for frogs.
The Eastern Gambusia (Plague Minnow) was originally introduced throughout Australia in an unsuccessful attempt to control mosquitoes. This fish is known to feed on tadpoles and frog eggs and poses a great threat to frog populations.
Cane Toad
The Cane Toad was introduced to eat the destructive Cane Beetles in Queensland. The plan failed and the toads have multiplied dramatically and now present a threat to many native species. They feed on almost any animal that is small enough to fit in their mouth, including frogs.
More information on Cane Toads.
Cats and Foxes
Cats came to Australia with Europeans when they first settled. The fox was introduced into Victoria in the late 1800s to be hunted. Cats and foxes have since become some of Australia's most widely-spread feral animals. Both these animals kill and eat frogs.