Toads kill each other `for their own survival`

Cane toad tadpoles ensure their own survival by launching chemical warfare against other tadpoles in the pond.

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

"(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.


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