Brazilian Torrent Frogs Bob Their Heads and Wave Their Toes to Attract Mates

Brazilian torrent frogs living along noisy streams of running water may find it difficult to communicate with one another. But they will not be silenced. Researchers from the Sao Paulo State University, Brazil, found these frogs will sing, squeal, wave their arms, tap their toes, and do just about anything they have to in order to attract a mate and scare off rivals. 

Male Brazilian torrent frogs (Hylodes japi) have been known to be territorial and display elaborate courtship behavior, but no one knew they could bust out this many dance moves. In the latest study, researchers observed the sophisticated audio and visual signals used by 70 male and female torrent frogs over a period of 15 months in the biological reserve of Serra do Japi, according to a news release.

The most common behaviors include loud mating calls, ranging from peeps to sequels. However, males would also occasionally inflate their vocal sacs to make calls when rival males appear, in a kind of "mine is bigger than yours" macho display, researchers say.

"Our study indicates that communication in species of the genus Hylodes is more sophisticated than expected. Also we suggest that communication in frogs is more complex than thought," Dr. Fábio P. de Sá said in the release. "Likely, that is particularly true for tropical areas, where there is a higher number of species and phylogenetic groups and/or where there is higher microhabitat diversity."

When in desire of a mate, researchers found a male will perform displays using his toes, feet, hands, legs, arms, vocal sacs, head, and body. While all of this is going on, however, females remain motionless. Only when she is ready to mate will she raise her arm and touch the male's back.  

"We found that the female stimulates the male during courtship by touching him," de Sá told IBTimes. "In addition, we observed that when a female combines the touch with an specific visual signal, she triggers courtship calls almost three more times than just touching the partner. The visual-tactile combination likely improves the efficacy of the female's message. Those behaviours are rarely observed because the species is very secretive."

Another novelty of their find is that male Brazilian frogs can choose which of their two vocal sacs to use for visual displays. Although, each sac, arm and limb seems to be tied to unique meanings, suggesting these animals have one of the most diverse repertoires of visual and audio displays known to frogs.

Their study was recently published in the journal PLOS ONE. 

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