How lady frogs get tricked into mating with ugly males

 

Celebrities aren’t the only ones who sometimes appear to exhibit irrational behavior when choosing a potential mate, according to a new Science paper indicating that one type of female frog can be tricked into selecting the less attractive of two male suitors.

The study was led by researchers from the University of Texas in Austin and the Smithsonian Tropical Research Institute in Panama City, Panama, and looked at the female túngara frog, who usually prefers to be serenaded with a low-pitched song but can be fooled into picking the lesser of two potential mates through the introduction of a third candidate.

The study demonstrates that the túngara frog, small Central American frogs best known for their ballooning vocal sacks and their unusual calls, can be influenced by the “decoy effect” – a phenomenon known to decrease rational decision making in people, and which apparently causes some amphibians to make irrational choices regarding sexual selection as well.

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According to National Geographic, Amanda Lea, a Ph.D. student in integrative biology at UT-Austin, and co-author Michael J. Ryan played previously-recorded male túngara frog calls to 78 females that had been captured in Panama. The females were placed in the center of a room, and their song preferences were based on which speaker they started hopping towards.

The study authors found that the frog preferred fast-paced, low-pitched mating calls, and in a second set of experiments, 120 additional females were forced to choose between two potential mates – one a tenor with a fast call, and the other a baritone with a slow call. The frog with the faster delivery but higher-pitched, less attractive point usually won out, they explained.

Afterwards, they introduced a third frog into the mix – one with an attractive call but a call rate slower than either of the other two. When exposed to this call, the female frog changed how she evaluated the song, considering the lower pitch more important than the faster pace. As a result, the frog that lost the first, head-to-head competition now wound up being the winner.

“These results show that the relative valuation of mates is not independent of inferior alternatives in the choice set,” the study authors wrote in their paper, “and therefore cannot be explained with the rational choice models currently used in sexual selection theory.”

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Feature image: Amanda M. Lea