Urban frogs use drains as mating megaphones

This month saw a press release about some very peculiar frog behavior, that even made it into the mainstream media. Scientists discovered that frogs living in the urban parts of Taiwan make clever use of manmade storm drains during the mating season to amplify their love serenade.

A Mientien tree frog (Metaphrynella sundana) in its natural habitat. Credit: Brandon Po-Han Chou

A Mientien tree frog (Metaphrynella sundana) in its natural habitat. Credit: Brandon Po-Han Chou

The males of the tiny Mientien tree frog (Metaphrynella sundana), native to Taiwan,  congregate during the mating season in leks (groups) to compete for fertile females. A research team found, in a suburb of Taipei, that males preferentially come together in open concrete drains along roads, different from their natural habitat of ponds. When they recorded the songs of the males they found that songs were on average 4 dB louder than calls from frogs outside these drains and that all 13 notes they use, would tend to last 10% longer. The research team analyzed the densities of male frogs inside these manmade drains and in plots outside the drains and found more than three times as many frogs inside compared to outside the drains. This suggests these male tree frogs are deliberately selecting  the storm drains as stage for their songs. As Mark Bee, a biologist at the University of Minnesota, told Nature.com, “this is perhaps the first study to show that an animal preferentially uses human-made structures to potentially enhance the sounds of its vocal communication signals”.  He added, “these males could be taking advantage of the enhanced acoustics in drainage ditches to outdo their competition”.

However, it hasn’t been shown yet that the amplification of their song also provides the males frogs with more mating success. So it would be too soon to suggest they really use the storm drains, because their longer and louder songs make them more attractive to females. Predator-avoidance might be another reason why these males preferentially hide out in these structures. First these alternative hypotheses have to be ruled out.

For more information, read the article from Nature.com



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