Bornean Rock Frog Lures Females With Foot Flag Wave

Posted on May 3, 2016

Bornean Rock Frog foot flag wave

The Bornean rock frog uses a special wave of its foot called a foot flag to attract females. The rock frogs live near waterfalls where acoustic signals can not be heard. The frogs developed this unique method of communication. The male frogs are competitive with their foot flags.

The yoga-like foot flag move involves the frog extending their back leg over their head and then rotating it backwards in an arc. This exposes the frog's white-colored foot webbing almost like they are waving a little white flag. Researchers from Wake Forest University have been studying the role testosterone plays in the foot flag displays.

Fuxjager, a Wake Forest biologist, says in a statement, "We tested whether the evolution of these waving displays in males is marked by a change in how hormones, like testosterone, influence the muscles that control limb movement. We know that testosterone is an important regulator of many types of sexual behaviors, so it seems a natural hypothesis that this steroid might also influence waving by affecting the motor systems that control physical movement."

The researchers were able to show that testosterone increases foot-flagging behavior in rock frogs. They found the rock frogs' legs muscles are about 10 times more sensitive to testosterone than the leg muscles of a closely related frog. A research paper on the study was published here in PNAS. Here is a video of the foot flag in action.



Photo: Vienna Zoo/Doris Preininger