The cane toad is large, reaching up to 23cm in length. It has highly visible poison glands located near the back of the head. The back and legs of the cane toad are covered in wart-like lumps and its skin has a leathery appearance. The cane toad has conspicuous glands behind the eyes called parotoid glands. When a predator eats the cane toad, the glands release a distasteful and toxic substance forcing the predator to let go. If the predator has already partially swallowed the toad, the toxin is strong enough to kill animals as large as goannas, quolls and red-bellied blacksnakes. There are currently no control programs for the cane toad, though researchers are examining the possibility of introducing a pathogen that is specific to the toad and will not affect native amphibians.
The cane toad was originally from South America and was introduced to Hawaii. It was from Hawaii that it was introduced into north-eastern Australia around 1935 to control a major pest, the sugar cane beetle. The toad itself has become a huge problem as a single female is capable of laying many thousands of eggs a year. It is found all over Queensland and is spreading south into New South Wales and west into the Northern Territory. It is believed to be moving at a rate of 30 kilometres per year. This great expansion is deadly to many other forms of wildlife as it will either eat or poison its prey and predators. The cane toad is found in almost all types of habitat.
Cane toads are a major pest for several reasons. Their tadpoles may eat or actually inhibit the growth of other frog tadpoles and eventually species of frogs will die out as the cane toad takes over their habitats. Most animals that are small enough to fit in the mouth of a cane toad will be eaten. The cane toad wipes out all frogs, frog-eating reptiles and birds, and most other vertebrate wildlife, either directly or indirectly, when they move into an area.
With one female cane toad producing up to 35,000 eggs per year, the numbers of this species in Australia are increasing at an alarming rate. Eggs can be distinguished from those of native frogs as they are laid in long chains. The tadpoles are also distinctive because they are totally black. All native tadpoles have a lighter coloured belly.