Cane toads caught on the hop

12 May 2016

Researchers from UQ’s Institute for Molecular Bioscience (IMB) are at the forefront of the fight against cane toads – using new and natural methods to trap the pest in their tens of thousands while they are still tadpoles.

The significant reduction in adult toad numbers at trial locations has also led to joyful locals reporting that many types of native wildlife had returned and were flourishing.

Ironically, the cane toad was introduced to Australia to control a pest: the cane beetle, which was destroying sugar cane crops across north Queensland. This experiment failed as the toads could not jump high enough to reach the beetles, which live in the upper stalks of cane plants, and the cane toad became a pest in its own right. A little over 100 cane toads were released in 1935, a number that has now ballooned to an estimated 1.5 billion.

The toads are travelling south and west across Australia at a rate of roughly 60km per year with a damaging impact. Cane toads are wreaking havoc on native wildlife­, increasing competition for food and habitat and reducing local populations of crocodiles, freshwater turtles, quolls, snakes and other predators, after they ingest the toxic toads. Household pets are equally as susceptible to cane toad toxins.

The cane toad is now so prolific across the state, having hopped its way from Cairns, Innisfail, Mackay and Bundaberg down to NSW and across to WA, that it now features on the National Trust of Queensland list of state icons, next to the backyard mango tree and the Great Barrier Reef.

But a solution to the ever-growing and ever-spreading population of cane toads is now within reach.

IMB researchers have discovered that the chemicals used by adult toads to poison their predators can be repurposed as bait. This bait can then be harnessed to attract cane toad tadpoles into traps, while repelling the tadpoles of native frogs.

Seizing toads as tadpoles, before they can breed, is key to controlling the rapidly reproducing species – adult female toads can lay up to 30,000 eggs at once.

Image: This simple trap and bait system can capture thousands of cane toad tadpoles at a time. 

IMB's Professor Rob Capon said cane toad tadpoles are attracted to a chemical released by cane toad eggs, which is also found in the adult cane toad’s toxin.

“Cane toad tadpoles from one hatching are attracted to and feed on unhatched eggs,” he said.

“This behaviour provides food for those lucky enough to hatch first, and we can hijack it to specifically target and capture cane toad tadpoles.”

The researchers collected the toxin from adult cane toads, coated it onto airstones (such as those found in household aquariums) for controlled release, and placed these inside traps in monitored water bodies such as dams.

The traps are simple contraptions, backed up by a lot of hard science: a plastic box, a funnel for the tadpoles to enter the box through, a pool noodle to help the box float and the bait with pheromones to attract the cane toad tadpoles. Once in the box, the tadpoles cannot escape and are removed from the water.

Image: Funnel boxes containing airstones coated in cane toad pheromones are used to attract cane toad tadpoles.

Professor Capon and his team began testing their tadpole bait with the assistance of Moreton Bay Regional Council and local communities in Redlands and Bribie Island.

“The results from public trials have been extremely positive, with a handful of traps removing more than 100,000 tadpoles,” Professor Capon said.

Further trials are being undertaken through Brisbane City Council at the Brisbane Botanic Gardens at Mt Coot-tha and other sites around the city, with tens of thousands of tadpoles successfully caught so far.

Trials of the baits and traps, along with the removal of adult cane toads, seem to have resulted in the significant repopulation of bird, frog and lizard species not seen for decades at the trial sites, hinting at the long-term benefits of this population control method for the cane toad.

“The next step is to further develop our system to ensure that it lasts longer, acts over a wider catchment, and captures even more tadpoles.”

The research team is seeking philanthropic seed funding and partners to support ongoing research, and to manufacture the baits and traps on a large enough scale to make them available to the wider community. To make a donation, click here.

To watch a news report about this research, click here, and to listen to an interview about this research on 612 ABC Brisbane, click here.

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