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Mating decisions of female frogs influenced by 'decoy effect'

Scientists say the female is likely overwhelmed by the stimuli and simply takes the most convenient option.

By Brooks Hays

AUSTIN, Texas, Aug. 28 (UPI) -- The mating decision of a female frog is rather simple to predict when she is presented with only a binary choice. She will make the rational decision and select the more "attractive" of the two males.

Add a third male suitor to the equation and the decision becomes less easily explained. New research suggests the presence of a third option acts as a "decoy effect," inspiring the female to consistently select the less attractive of the two original options.

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The researchers who arrived at the unique discovery have dubbed the phenomenon "irrational mate choice."

"Attractive" doesn't always mean looking just right. Properly executing a mating call is also important. When a team of researchers from Panama and Texas presented female tungara frogs (a native species of Panama) with two mating calls, the most attractive call always won out. But when a third call was introduced, whether localized or emanating from an unspecified location, the female opted for the lesser of the first two calls.

Researchers watched the same thing they had witnessed in the lab happening out in the field. Unattractive of "decoy" frogs, with a less-than-stellar voice and slow call rate, would consistently infiltrate a pair or group of presenting males. When this happened, the female was more likely to choose the closest male.

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Scientists say the female is likely overwhelmed by the stimuli and simply takes the most convenient option.

The intent of the decoy, on the other hand, isn't clear. Are his action deliberate? Is he helping out a less-attractive fellow like himself? Or is the drive to mate so strong that even the most unattractive frogs refuse to give in to a life of sexless solitude?

"Further research is required to better understand the role of the 'decoy' effect in maximizing fitness," researchers wrote in a recent press release.

The new study, published in the journal Science, isn't just about frogs. It offers insights to the animal condition, more broadly. Psychology studies have highlighted a variety of cognitive biases and irrational tendencies common in humans.

These lapses in logic may have ancient evolutionary roots. This much is clear: complex social situations lead to irrational behavior, in humans and animals.

"These results suggest that the choice of mates by animals may be context dependent," the researchers concluded. "It appears that rational choice may not always drive sexual selection."

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