Page last updated at 17:33 GMT, Wednesday, 6 January 2010

Female toads inflate to avoid sex

Cane toads (Ben Phillips)
Male toads grasp any female that comes within reach

When it comes to choosing a mate, female toads may have more control than previously thought, say scientists.

A report in the Royal Society's Biology Letters journal describes how a female cane toad inflates its body to prevent an amorous male from mating with it.

This makes it difficult for the male toad to "hold on".

Male toads often wrestle with each other in an effort to grasp a mate. By inflating, a female can influence the outcome of such a competition.

It is assumed that frogs and toads evolved the ability to inflate their bodies with air as a defence against predators.

The team of scientists, from Australia and the Netherlands, described in their report how this deters predators "by increasing the apparent size of the [frog or toad] and by rendering it too large to ingest".

Male cane toads competing for a mate (Michael Crossland)
Females can actually manipulate the outcome of male-male competition by inflating at the right moment
Dr Benjamin Phillips
University of Sydney

But, according to Dr Benjamin Phillips from the University of Sydney, one of the scientists involved in the study, bodily inflation could also be "a widespread mechanism of mate choice" in frogs and toads.

Dr Phillips and his team explained in their research paper that male toads will "grasp any female that comes within reach and retain their hold unless displaced by a rival male".

In their experiments, the scientists found that male toads were less able to maintain this grip if the female inflated its body.

He said that scientists had noticed previously that females inflated their bodies "during male-male wrestling matches".

"[But they] assumed that this inflation was just a response to the physical stress of being pushed, prodded and occasionally knocked over by males," he told BBC News.

"Our work now shows that females can actually manipulate the outcome of male-male competition by inflating at the right moment."

This could help ensure that the female gets to mate the the biggest, strongest male, which is likely to produce the healthiest offspring.

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