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The natural world. Looking pretty for 3.5b years.

Study finds irrational mating habits in frogs

The Túngara frog exhibits the decoy effect

Author: Trevor Quirk/Saturday, August 29, 2015/Categories: natural history, marine mammals

Túngara frogs have been found to choose mates in seemingly irrational ways. Insert some lame crack about romantic complexity in people that also applies to these small creatures.

Anyways, the Túngara frog is a small Leptodactylid found in the forests, savannas, grasslands, marshes, pastureland, ponds -- basically all over South and Central America.

For scientists, these specimens have been an avenue for studying natural selection because of their obvious mating habits. In particular, the Túngara mating call turns out to be important. The broad convention was that female frogs, who choose suitors, like longer, low-frequency calls that happen at a fast rate.

Yet, is the choice of a female frog really as simple as maximizing these variables? A new study published this month in Science found that the actual reality of mate choice gets complicated very quickly.

This happened to be one scientific question that lends itself to elegant, experimental simplicity. The researchers placed a female frog in a room with speakers, altering different attributes in emitted male calls. If the female frog had to choose (by choose, here, we mean "move towards") between a less attractive call that happened at a fast rate and a more attractive, slow-rate call, the female consistently chose the faster rate.

However, when the researchers introduced a third option, an attractive call that happened at a very slow rate, the entire dynamic changed. Though the female never chose this option, its mere existence altered her rubric. She picked the call she had passed on in the first experiment.

This effect is actually not particular to these frogs. It's called the 'decoy effect' (technically: asymmetric dominance effect) and it can be found in other species like hummingbirds and bees and, you guessed it, human beings.

Image credit: Brian Gratwicke
Video credit: A.M. Lea
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