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A cane toad conundrum

The humble cane toad is one of Australia’s most invasive species. Here’s how it turned from pest-eater to pest.

Brought over from the Americas to combat pests that ate sugar cane crops, the cane toad is arguably Australia’s most prolific pest, which thrives in the humid tropics. 

Sugar cane was first brought to Australia with the First Fleet. After some semi-successful small-scale attempts at growing sugar throughout the early 1800s, more growers were encouraged to establish crops further up north. Captain Louis Hope is considered to be the father of the sugar cane industry in Australia, having turned his crops in Moreton Bay, Queensland, into a successful sugar mill in 1862. From there, the industry began to boom, reaching Far North Queensland by the 1880s; however, it was not without its challenges. Australia’s harsh, drought-prone climate, coupled with an ongoing beetle problem (as the larvae would eat the roots), made it difficult to maintain successful crops. 

Cane farmer lobbying then saw the establishment of the Bureau of Sugar Experiment Stations in 1900, where entomologists gathered to work on the sugar cane beetle issue. Despite their attempts and experiments to stop the beetle infestation with various chemical methods of control, a breakthrough finally came in the early 1930s.

Arthur Bell, a plant pathologist with the Bureau, first learnt of the success of the American toad, Bufo marinus, in helping to eradicate beetles after attending a conference in Puerto Rico.

In June 1935, Bureau entomologist Reginald Mungomery then travelled to Hawaii, where the toads had been successfully introduced from their original home in the Caribbean. Mungomery then got his hands on a breeding sample, before returning to Cairns, where a special enclosure had been made to facilitate the breeding of cane toads in Australia. 

Just two months later, the cane toads had successfully reproduced in the Cairns facility. More than 2400 cane toads were subsequently released into the Gordonvale region, near Cairns. Despite this, the Bureau had conducted virtually no studies on the environmental impact of cane toads, nor had it been confirmed if the toads would actually eat the Australian beetles. As such, entomologist Walter Wilson Froggatt expressed his concerns to the Health Department, and any future releases of the toad into the wild were promptly banned.

In 1936, however, the Queensland Government and the media succeeded in pressuring Prime Minister Joseph Lyons to uplift the ban, allowing the cane toads to run rampant. Following their release into the wild, the cane toads had little impact on the crop’s beetles, which would later be controlled by chemical pesticides.

Since their release, cane toads have thrived – much to the detriment of the native fauna in the region. Cane toads were first declared to be a pest themselves in 1950, as their poison can kill a variety of natural predators. Since their introduction to the Cairns area, the toads have spread across the Sunshine State, into coastal New South Wales, across the Northern Territory and to the Kimberley in Western Australia. It’s estimated that the cane toad population is moving 40–60 kilometres further west each year.

The toads have no known predators, and their rapid growth has had serious impacts on the ecosystems across the northern half of the country. 

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