Cane toads are slowly marching across Australia. What’s the most humane way to kill them?

Cane toads are slowly marching across Australia. What’s the most humane way to kill them?

Scientists are advising people against bludgeoning cane toads to death with golf clubs as Queenslanders prepare to purge their local environments of the pest.

Key points:

  • Scientists recommend the “cool-and-freeze” method as a humane alternative
  • Hitting the animals can cause them to expel poison, which can temporarily blind humans
  • The Great Cane Toad Bust — a community campaign to exterminate the species — is held from January 13 to 21

Watergum invasive species project officer Nikki Tomsett said the charity was recommending the “cool-and-freeze” method, ahead of its Great Cane Toad Bust — a nationwide community campaign to exterminate the invasive species from January 13 to 21.

The cool-and-freeze method involves placing cane toads in a fridge for 24 hours, which puts them in a state of torpor, before transferring them to the freezer to finish them off.

She said this was more humane than other methods of killing cane toads, such as bashing them with cricket bats or crushing them under cars.

“Our learning and our knowledge have evolved since the days of cane toad golf,” Ms Tomsett said.

“It’s important to treat all animals humanely. Cane toads have to be removed, and it’s not their fault they’re here.”

Nikki Tomsett says cane toad golf is not recommended.(Supplied: Institute for Molecular Bioscience, UQ)

A paper in the online journal Biology Open from 2015 found refrigerated cane toads showed little brain activity when transferred to the freezer, with no telltale signs of pain signals.

The paper contradicted previous concerns that the toads could feel ice crystals piercing their skin, creating severe pain.

Lead author and Macquarie University professor Rick Shine said the toads were deep asleep before that point.

“There were absolutely no spikes in activity during the cooling-then-freezing process; the toads just went to sleep and never woke up,” Professor Shine said.

“This method is more humane than any of the other methods that are used to kill toads.”

Rick Shine says cooling and freezing is the more humane way to kill cane toads.(Supplied: Terri Shine)

Evolving for urban environments

Now found in Queensland, the Northern Territory, New South Wales and Western Australia’s north-west, cane toads are a threat to Australia’s biodiversity, as they are poisonous, and can eat and compete with our native species.

James Cook University’s Lin Schwarzkopf said cane toads were evolving longer legs and fewer poison glands to live in urban environments.

The zoologist said this posed a danger to domestic animals such as dogs and cats that ate cane toads, as well as native animals such as quolls that could live in urban areas.

She said white ibis, better known as bin chickens, had learnt how to eat cane toads without poisoning themselves. 

The birds flick the cane toads about to trick them into secreting poison, before washing them in a creek and eating them.

Ibis have figured out how to eat cane toads without getting poisoned.(ABC Radio Sydney: Harriet Tatham)

Professor Schwarzkopf said Queenslanders could expect to see more cane toads around due to the wet conditions.

However, she said it was generally not advisable to bludgeon them with sporting equipment.

“If you whack them with golf clubs you run the risk of hitting the poison glands,” Professor Schwarzkopf said.

“It if gets in your eyes it causes lots of grief, and you can be blinded momentarily.”

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