Most male frogs protect their territory and advertize their willingness to mate by vocalizing. But what do you do when background noise is so loud that it can drown out your calls?
You can resort to semaphore, like this rock skipper frog:
This video was filmed by University of Vienna students Doris Preininger and Markus Boeckle, who participated in a study in this behaviour which was released in 2009.
Acoustic signals are constrained by background noise. Visual signals are an alternative or complementary communication mode in noisy habitats and play a fundamental role in anuran communication. The Bornean rock-skipper frog, Staurois latopalmatus, is a diurnal species living along fast-flowing streams and waterfalls. Males perform foot-flagging displays with either one or two legs to advertise their readiness to defend their territories. In quantitative video analyses of visual displays during 14 male-male agonistic interactions, totaling 106 minutes, foot flagging performed in the direction of the interacting male was the most common display and was performed at a higher rate than advertisement calls. According to a dyadic transition matrix, foot flagging was preceded by foot-flagging displays of interacting males. Advertisement calls were temporally coupled with foot flaggings and act as introductory components to direct the receiver’s attention to the subsequent visual display. We conclude that foot flagging acts as a spacing mechanism and may have resulted from the ritualization of agonistic male behavior to minimize physical attacks.
Communication in Noisy Environments Ii: Visual Signaling Behavior of Male Foot-flagging Frogs Staurois latopalmatus. Doris Preininger, Markus Boeckle, and Walter Hödl. Herpetologica 65(2):166-173. 2009
Hat-tip to Wildlife Extra.