The Cane Toad Saga: Australia's Self-Inflicted Disaster

How Australia brought disaster to its shores.

Photo Credit: New York Times

Our story begins in 1861, when the first white squatters began to develop sugar and gold ports in North Queensland on the northern coast. Vast sugar plantations were set-up with the support of the Queensland Government, reckless from the desperation for income.

The plantations were plagued by white grub infestation. By 1880s, the losses were as significant as to force the Queensland government to establish the Queensland Bureau of Sugar Experiment Stations (BSES) in 1900, under pressure from cane growers.

In 1932, a paper was presented discussing the use of Bufo marinus (cane toad, our potential hero) as a way to control beetle infestations in sugar crops in Puerto Rico. From Puerto Rico, the toad was transported to Hawaiian sugar cane fields for pest control. Influenced by such reported successes in Hawaii, the Philippines and Puerto Rico, in June of 1935, a government entomologist working for BSES, Reginald Mungomery captured and bred the toads, making the first release on the 19th of August that year followed by many more.

Another Australian entomologist, Walter Froggatt, foreshadowed the troubles lying ahead - “this great toad, immune from enemies, omnivorous in its habits, and breeding all year round, may become as great a pest as the rabbit or cactus”.

A twist in the story - “There is no evidence of any pre-release testing by the BSES entomologists to determine if the toads even ate the cane beetles” (Griggs, 2005). Turns out, the toads, although, happily munching on the pest species in Hawaii and Puerto Rico, didn’t control the native Australian species. On top of this, assessment of potential risks arising from the introduction of the species was not done.

The revelation – far from being the hero, the cane toad turns out to be the antagonist of this tale. First recognised as a pest in Western Australia, the cane toad was listed as a vermin under the state’s Vermin Act in 1950. However, the Commonwealth first took serious steps towards finding a solution only in 1986, by establishing a cane toad Research Management Committee by federal funding.

Since introduction of the cane toads, their range has expanded throughout Australia’s northern landscape and they are now moving westward at an estimated 40 to 60 kilometres per year. In February 2009, they were found in areas over 2000 kilometres from the site of their initial release. To the south, cane toads had spread to Yamba and Port Macquarie in New South Wales in 2003.

There are multiple reasons behind their incontrollable spread. They can breed at any time of the year, with females laying 8,000–30,000 eggs at a time. In contrast, most native Australian frogs typically lay 1000–2000 eggs per year. They are easily transported accidentally to new locations, e.g., in potted plants or loads of timber and lack any predators or diseases that could control their numbers.

The presence of this non-native species is wreaking havoc on the native wildlife. Many predators suffer rapid deaths after ingesting the toads due to the presence of poison glands in the adults. Their arrival in Kakadu National Park has been linked to significant decline in numbers of some native predators, especially northern quolls and large goannas. The increased pressure of competition on the native species due to the addition of adult cane toads is also part of this problem.

Although, current evidence shows that some native predator species can make rapid behavioural and physiological adaptations, allowing recovery in the long term, so far there is no broad scale way to control the cane toad population, in the first place.

The moral of this story is simple. Ecosystems are highly complex with many variables, known and unknown to man. Their manipulation should never be undertaken lightly.

Editorial Support: Phoenix Content India