Plants and Animals

Traps Exploiting Cane Toad Cannibalism Have First Widespread Deployment

A set of handmade traps designed to control the spread of one of Australia’s worst pests, the cane toad, have been placed on a 7,000-hectare (27-square-mile) property south of Rockhampton, Queensland. If the early success of the traps continues, they will be a major vindication of a long-running basic research program into the toad, and a chance at redemption from one of Australian science’s stupidest decisions.

Rhinella marina originated in south and central America. It was introduced to Australia in 1935 in the belief the toads would control native cane beetles, as they had done to related species in Puerto Rico. Not only did the toads do little to combat the beetles, they multiplied from a few hundred to more than 200 million, devastating local wildlife in the process.

Largely restricted to Queensland, the toads have in recent years accelerated their spread dramatically, wrecking havoc on the Northern Territory in the process. They are now set to do the same to the priceless ecosystems of northern Western Australia, if not stopped. Fortunately, however, scientists have shown they can learn from the mistakes of their predecessors, and have studied the toad intensively.

Along with the discovery of fascinating new forms of evolution, a team that included University of Queensland’s Professor Rob Capon learned that cane toad tadpoles eat the eggs of other toads to reduce competition. The finding didn’t come easily because toads avoid laying their eggs near each other to prevent exactly this danger.

The researchers discovered that the tadpoles hone in on the toad’s famous toxin, which the mother leaves behind on the eggs. This inspired researchers to use the toxin as bait in traps, turning the toad’s cannibalism against them.

Since the toxin is available from any adult toad, and Australia has those in vast quantities, the idea seemed relatively simple, but several years of delays have ensued – not helped by a lack of funding from government agencies at crucial stages.

Pest control company SpringStar is working on a commercial version, but Capon didn’t want to wait. They established the Cane Toad Challenge to get the traps into sensitive areas.

Farmers Rob and Nadia Campbell are at the heart of the program. They’ve caught and euthanized adult toads to provide a supply of toxin glands to Capon and colleagues, who have turned them into traps to be installed on the Campbells’ 20 small dams and other sites in the region.

Each trap can capture several thousand tadpoles, which is just as well as a single female can lay 30,000 eggs every six months. Rob Campbell is encouraged by early results, telling the ABC: “If this keeps going the way it’s going, it looks really good.”


All these tadpoles came from just one egg-laying, making it clear why cane toads are so hard to control. University of Queensland

 

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