Small European treefrogs 'cheat' competitors while mating

The team from the University of Lyon studied the response of differently sized European treefrogs to a chorus of mating calls.

They found that smaller males lurked near the sound of an attractive call, rather than calling more frequently than their larger rivals.

Research suggested that "cheat" tactics are mainly caused by the intrinsic disadvantage of being small, the BBC Nature reported.

The scientists wanted to learn more about what causes animals to use "parasitic tactics" rather than "bourgeois tactics" during the mating season.

"Bourgeois" or "classic" tactics involve a high-energy investment and competition for reproduction, whereas "parasitic" or "sneaking" tactics involve exploiting the energy invested by another male.

In treefrogs these tactics manifest themselves in either calling for a mate - a bourgeois tactic - or loitering near an attractive calling male - the sneaky approach.

The scientists wanted to discover whether it was food deprivation or body size that caused the frogs to resort to this behaviour.

"The most important finding of this work is that the energetic constraint imposed by a relevant starvation period does not impact significantly the probability to switch from one tactic to another when compared to the inherent disadvantage of being small," said researcher Loic Brepson.

The study took 100 differently sized male European tree frogs from ponds outside Lyon, France.

After having their stomachs flushed, half of the frogs were fed bluebottles and house crickets, while the other half were starved for a week.

They were then placed in a makeshift pond and the sound of both "attractive" and "unattractive" calls from their own population was played to them through loudspeakers.

"Attractive" calls have a different amplitude and were more frequently made during each round of calling.

The frogs responded to the chorus by calling back, remaining near the sound, or doing nothing.

As well as finding that smaller males being more likely to "cheat" the scientists also found that "males were more likely to act as a satellite if confronted with an attractive competitor than if confronted with an unattractive one".

The food-deprived males were not more likely to use "sneaking" tactics than the frogs that were well fed, according to the study.

The study was published in the journal Animal Behaviour.