<P> The cane toad in Australia is regarded as an exemplary case of a "feral species"--others being rabbits, foxes, cats, dogs and giant mimosa . Australia's relative isolation prior to European colonisation and the industrial revolution--both of which dramatically increased traffic and importation of novel species--allowed development of a complex, interdepending system of ecology, but one which provided no natural predators for many of the species subsequently introduced . The recent, sudden inundation of foreign species has led to severe breakdowns in Australian ecology, after overwhelming proliferation of a number of introduced species for which the continent has no efficient natural predator or parasite, and which displace native species--in some cases these species are physically destructive to habitat as well . Cane toads have been very successful as an invasive species, having become established in more than 15 countries within the past 150 years . In the Environment Protection and Biodiversity Conservation Act 1999, the Australian Government listed the impacts of the cane toad as a "key threatening process". </P> <P> Native to South and mainland Middle America, cane toads were introduced to Australia from Hawaii in June 1935 by the Bureau of Sugar Experiment Stations, now the Sugar Research Australia, in an attempt to control the native grey - backed cane beetle (Dermolepida albohirtum) and Frenchi beetle (Lepidiota frenchi). These beetles are native to Australia and they are detrimental to sugar cane crops, which are a major source of income for Australia . Adult cane beetles eat the crop's leaves, but the main problem is the larvae, who feed on the roots . Adult cane beetles have a heavy exoskeleton and their eggs and larva are often buried underground, making them difficult to exterminate . Furthermore, conventional methods of pest control, such as pesticide use, would eradicate harmless species of insects as well, making it an unsatisfactory method . Cane toads were to replace the use of pesticides like arsenic, pitch and copper . The success of using the moth Cactoblastis cactorum in controlling prickly pears in Australia also contributed to hopes for the cane toad . </P> <P> The cane toads bred immediately in captivity, and by August 1935 more than 102 young toads were released in areas around Cairns, Gordonvale and Innisfail in northern Queensland . More toads were released around Ingham, Ayr, Mackay and Bundaberg . Releases were temporarily limited because of environmental concerns but resumed in other areas after September 1936 . Since their release, toads have rapidly multiplied in population and now number over 200 million and have been known to spread diseases affecting local biodiversity . Unfortunately, the introduction of the toads has not only caused large environmental detriment, but there is no evidence that they have affected the cane beetles they were introduced to predate . The toads have steadily expanded their range through Queensland, reaching the border with New South Wales in 1978 and the Northern Territory in 1984 . The toads on the western frontier of their advance have evolved larger legs; this is thought to be related to their ability to travel farther . As a consequence of their longer legs, larger bodies, and faster movement, about 10% of the leading edge cane toads have also developed arthritis . It was estimated that cane toads migrate at an average of 40 kilometres (25 miles) per year as of 1994, but new research in 2014 indicated that the migration rate had increased to 60 km per year on the western front . </P>

Where were cane toads first introduced in australia