Female tree frogs suffer from choice overload during mating season, study finds

Choice stress is not reserved for humans. New research from the Smithsonian Institution shows that female tree frogs face the same problem.

When mating season arrives for the tree frog species Dryophytes chrysoscelis, the males all burst into song at the same time. Females must pick, from this wall of sound, which singer will become the father of their offspring. Researchers from the Smithsonian Tropical Research Institute and the University of Tennessee found they struggle with this: when females hear too many males singing at once, they experience choice stress.

"We wanted to find out why female tree frogs find it hard to pick a partner. Is it because they can't hear the males above the background noise, or are they simply overwhelmed by the large supply?" said biologist Claire Hemingway. "Translated to humans: is it like walking into a loud bar where no one can hear anyone talk, or like using a dating app and being unable to choose because of all the options?"

In lab experiments, researchers played recorded mating calls through speakers and measured female responses with increasing numbers of potential partners, different background noise levels, or both. The more calls, the worse the female's ability to choose. With just two calls, females went for the mating call 97 percent of the time; with eight calls, that dropped to 82 percent. Background noise made little difference. Females also took longer to decide: an average of 114 seconds with two calls versus 183 seconds with eight.

The findings show tree frogs, like humans, are susceptible to choice stress, suggesting cognitive limits in information processing play a bigger role in sexual selection in some animals than previously thought.