Visual cues do not function in a multimodal signalling context for mate attraction in eastern gray treefrogs

Anurans use different sensory modalities to communicate and interact socially, including acoustic, chemical, tactile, and visual signals. In a multimodal context, these sensory modes can transmit different information to the receiver or even reinforce the same message. In this study, we hypothesized that body colour traits and vocal sac movements of male eastern gray treefrogs [Dryophytes versicolor (= Hyla versicolor)] serve as secondary visual cues that increase their attractiveness while calling to attract mates. We tested this hypothesis using playback trials combining synthetic advertisement calls with a variety of visual cues, including differently coloured resin frog models, simulated vocal sacs, and live frogs. None of the visual stimuli tested impacted female choice, and there was no difference in response rate, response time, choice angle, or distance covered in the arena between multimodal and unimodal stimuli. However, females showed a strong preference for longer calls even if the less attractive calls were paired with a visual stimulus. The study provides comprehensive insights into the role of visual stimuli in the mate attraction of eastern gray treefrogs and suggests that call traits play a dominant role in the male-selection process of this species, contrary to what was observed for visual stimuli.