We explain how and why this is accomplished. As another novelty for frogs, we show that in addition to choosing which limb to signal with, males choose which of their two vocal sacs will be used for visual signaling. Previously unknown in frogs, we also describe a bimodal inter-sexual communication system where the female stimulates the male to emit a courtship call. We describe its repertoire of acoustic signals as well as one of the most complex repertoires of visual displays known in anurans, including five new visual displays. We investigate intraspecific communication in Hylodes japi, an endemic Brazilian torrent frog with territorial males and an elaborate courtship behavior. Intraspecific communication in frogs plays an important role in the recognition of conspecifics in general and of potential rivals or mates in particular and therefore with relevant consequences for pre-zygotic reproductive isolation. Recorded on 6 March 2012, using the camera’s ‘NightShot’ function (infrared sensitivity).

Finally, once male and female reach the fast-flowing stream margin, we can see the exact moment when, while maintaining physical contact with the female, the male slightly moves his body forward, consequently moving the female body as well then the male dives followed by the female, marking the beginning of the underwater part of the courtship (leading to the oviposition site). The movie is slowed down for better observation (rate 0.25). Next, we can observe two events whereby the female triggered the male’s courtship calls via bimodal stimulation (visual plus tactile) first by arm lifting display plus tactile stimulation and second by arm waving display plus tactile stimulation. Then, we can observe the male emitting peep and squeal calls with only one vocal sac inflated, the one nearer the female (his left vocal sac), demonstrating the visual component of his bright whitish vocal sacs. That couple position is kept during the acceptance courtship step. Movie starts showing female approaching the male and the exact moment when the female adopts the acceptance position, touching the male’s dorsum with her gular region.

S5 Movie: Hylodes japi couple during the elaborate courtship ritual.

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