Toads kill each other 'for their own survival'



Toads kill each other `for their own survival` Melbourne: Cane toad tadpoles ensure their own survival by launching chemical warfare against other tadpoles in the pond, a new study has found.

Biologists at Sydney University have discovered cane toad tadpoles (Bufo marinus) communicate using chemicals excreted into the water and kill each other for their own survival, a finding that may help contain their population in urban areas.

Lead biologist Professor Rick Shine said: "Cane toads produce chemicals that diffuse through the water which other cane toad tadpoles pick up and make all sorts of decisions based on."

The first of these chemicals is an alarm pheromone that causes other cane toad tadpoles to flee. Exposed to the chemical too often, the tadpoles either die or grow up as small, stunted toadlets with poor survival prospects.

"If they experience this chemical frequently while developing, many of them die apparently from stress," Prof Shine said.

The second is an attractant emitted by freshly laid eggs enabling existing Cane Toad tadpoles to seek out and kill any eggs they sense. "The big benefit of (the attractant chemical) is the removal of future competitors, because a cane toad is another cane toad's worst enemy.

"If we can find the attractant chemical, we can put it in traps and attract cane toad tadpoles into them, without attracting the native tadpoles," he said.

If the tadpoles are unable to destroy the eggs, they can also emit another chemical that kills potential new tadpoles before they hatch, or stunts their growth if they do, say the biologists.

"(Because of this) merely the presence of older cane toad tadpoles in the water surrounding the eggs is enough to wreck the development of the tadpoles which emerge from new eggs.

"Most of those die and the ones that end up turning into baby toads do so in a miniature size simply because of that very brief exposure to the chemicals that the older tadpoles have produced. Our idea is to try to take advantage of that and turn the toads' weapons against themselves," he said.

PTI