Love Songs; Frogs in Taiwan Using Storm Drains to Amplify Mating Calls

Frogs in Taiwan are using storm drains as microphones to amplify their mating calls, researchers find.

Despite a name like Kurixalus idiootocus, the tiny mientien tree frog in Taiwan is a clever creature. The males of the species have found that the storm drains along roads carry sounds farther and louder. The frogs are now exploiting the feature to ramp up their love lives in the gutters of Taipei.

The study was conducted by researchers at National Taiwan University, according to a press statement.

Audio recordings showed that frogs crooning inside the drain had longer and louder mating calls than frogs that were shouting from land near the drains. Louder and longer mating songs increase the frogs' chances of mating.

"Structures, such as wall surfaces, may change the acoustic environment for signals transmitted by animals," wrote study authors Wen-Hao Tan and colleagues, according to Discovery, "creating novel environments that animals must either adapt to or abandon."

"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," said Mark Bee, a biologist at the University of Minnesota, Twin Cities, in St Paul, Nature reported. "These males could be taking advantage of the enhanced acoustics in drainage ditches to outdo their competition."

Will Sing for Love

Males of the species take part in an elaborate annual singing competition to seduce the females. The breeding season lasts from March to June and males form groups or leks to take part in a ritual called lekking, Nature reported.

Their mating songs resemble birds' warbling. Biologists describe the ritual to be an "aggressive one" with males approaching each other while crooning for their lady-love. The competition ends when the weaker male stops its mating call.

The team from National Taiwan University even created storm drains in a laboratory setting and let frogs shout their best mating calls. They found that males chose locations with good acoustics, Discovery reported.

Researchers found that the calls from inside the drain could up the males' chances of mating as they are louder and were longer. Acoustic analysis software showed that the songs inside the drain were 4 decibels louder than those from outside. Also, the length of all 13 notes in a frog's call was also 10 percent longer in the drain than outside, according to Nature.

The study is published in the Journal of Zoology.