Invasion wave breeds faster toads
istock_canetoad.jpg
Bufo marinus, the cane toad.
Image: iStockphoto

Cane toads moving across Australia are the fastest amphibians on earth after their rapid evolution from slow-moving homebodies into road warriors over the past 70 years.

But their rapid evolution is also contributing to their demise and showing scientists new ways of controlling them.

Professor Shine's work with the University of Sydney has focussed on toads at the front of the 'invasion' across Australia. 'Toads that run at the front of the pack are becoming bigger and faster. They have different personalities, different shapes and are developing different physiologies,' he says.

The bigger and faster invasion front toads are reproducing with each other-researchers call this the 'Olympic Village Effect'-and having fast-moving babies with bigger front legs and longer back legs.

The toads that colonised areas of Queensland move an average of ten metres overnight. The ones now approaching the border of Western Australia are ten times as fast and can move a kilometre on a wet night. That's ten times as far. But while this means toads can move more often and cover huge distances, it also has a downside for toads.

'We are seeing toads in the Northern Territory with spinal arthritis-big, bony lumps on their spine-something that has never been seen before in other amphibians,' Professor Shine says.

Professor Shine is part of a group of researchers from the Northern Territory, Queensland and New South Wales who are trying to understand cane toad biology and use this information to lessen their impact.  He says we used to focus our attention on controlling cane toads without understanding how they work.

His team has discovered a chemical that is released by cane toads when they are frightened or alarmed. They found that this 'alarm pheromone' is extremely useful for controlling tadpoles-the ones that don't die from the pheromone grow to be much smaller. They have also found a toad lungworm parasite that is particularly effective for killing baby toads.

'The great news is that the pheromones and the lungworm parasite do not affect Australian frogs,' he says. 'We have one biological control that kills tadpoles and others that are useful against baby toads. Taken together, we have a powerful set of methods for controlling cane toads from an early stage.

Professor Shine's research group is looking closely at how some Australian predators have adapted to cane toad poison and survived.

'There are quite a few Australian predators who aren't affected by the poison-some birds and meat ants. We're looking at how we can get them to clean up more,' he says.

He believes an initial exposure to smaller, sterilised cane toads, as opposed to invasion front toads, might be the answer for protecting predators not yet affected by the pest.

'After an initial exposure, some predators learn very quickly that toads are bad-some marsupials, fishes, frogs, are learning to avoid them. And they aren't the Einstein's of the animal world,' he says.

Professor Shine's research group has a cane toad information website for the general public at here.


Editor's Note: Original news release through Econnect Communications.