The Mientien frog of Taiwan has learned to use drains and storm pipes to amplify their calls when they are looking for mates.
Males of the species call out, looking for females ready to mate. This sound is interpreted by the females as an indication of the health of the candidate male. The individuals, who make this call loudest, and for the greatest period of time, are the ones most likely to copulate. Many of these creatures have discovered that using drainpipes and other man-made objects allow them to amplify the volume of their calls.
Kurixalus idiootocus has one of the highest-pitch calls of any frog in Taiwan. Researchers believe that storm pipes may help lower the frequency of the cry. This would cause the sound to carry further, in a manner similar to the low bellow given off by a lighthouse.
A team of biologists from National Taiwan University, lead by Y. Kirk Lin, conducted an extensive survey of the tiny tree frogs in southeastern areas of Taiwan.
Large, open concrete drains are common throughout the area. They are found along paved roads in rural area, and also parallel many walking paths. Varying structures of the drains and pipes give calls different qualities. While some of these acoustic properties are appealing to females, some are not. The most successful frogs were those who chose concrete structures as their sounding horn. This effect was the same both in the field, and under laboratory conditions.
"A field survey indicated that male Mientien tree frogs preferred calling inside rather than outside drains. A playback showed that calls emitted from inside drains were enhanced in both amplitude and note duration. In an indoor experiment using a replica of a concrete drain, males preferred one particular type of call perch," researchers wrote in an article announcing their study.
Researchers believe that, over time, frog populations may become accustomed to the modified sounds. Females also look for other characteristics in a male when it comes time for mating, in addition to a healthy-sounding call.
The adaption of using objects like storm drains in this way is now common among males of the species. However, the researchers were unable to determine if females mate more often with those using the artificial amplifiers.
Animals, faced with human encroachment, such as pigeons, are learning to adapt in many ways to live with humans.
Study of the Meintein frog and their use of man-made structures in mating calls was profiled in the Journal of Zoology.