Vocal sacs do not function in multimodal mate attraction under nocturnal illumination in Cope's grey treefrog

Hongyu Li, Katrina M. Schrode, Mark A. Bee

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Multimodal communication signals consist of two or more distinct components produced in different sensory modalities and transduced by receivers using multiple sensory systems. One evolutionary trajectory by which incipient multimodal signals may arise is when receivers are selected to attend both to a well-established signal and a cue in a different sensory modality associated with that signal's production. Previous studies of frogs suggest movement of the male's vocal sac, which is inextricably tied to vocal production in most species, functions as the dynamic visual component of a multimodal mate attraction signal that modulates female responses to sexually advertising males. Most of this work, however, has presented multimodal stimuli using video playbacks or artificially illuminated robots in laboratory settings, which leaves open the question of whether the vocal sac functions in multimodal signalling under more natural nocturnal illumination. In this study of Cope's grey treefrog, Hyla chrysoscelis, a nocturnally breeding species, we tested the hypothesis that vocal sacs are a dynamic visual component of a multimodal mate attraction signal that influences female responses to sexually advertising males. Using robotic frogs as stimuli, we performed multimodal playback experiments outdoors under nocturnal illumination. We found no evidence that vocal sacs were attractive to females or that they influenced the responses of females when acoustic information was rendered less certain due to a degraded signal structure or background noise. While these negative results may reflect genuine species differences, they also corroborate a negative result from one of the only previous studies conducted under natural nocturnal illumination to investigate frog vocal sacs as the visual component of a putative multimodal mate attraction signal (Taylor et al., 2007, Animal Behaviour, 74, 1753–1763). We consider possible proximate and ultimate explanations for our results and critically review previous research on multimodal mate attraction in nocturnal frogs.

Original languageEnglish (US)
Pages (from-to)127-146
Number of pages20
JournalAnimal Behaviour
Volume189
DOIs
StatePublished - Jul 2022

Bibliographical note

Funding Information:
We thank Miranda Dahl, Kelley Hoiseth, Chang Liu, Becky Marshall, Jordyn Massop, Annika Ruppert and Yi Fang Tan for help in collecting and testing frogs, David Tinetti for fabricating the robotic system, Katie LaBarbera for the cartoon frog included in some figures, Eric Warrant for very helpful conversations about measuring and reporting light levels and Paloma Gonzalez-Bellido, Carl Gerhardt, Saumya Gupta, Lata Kalra, Katie LaBarbera, Peter Marchetto, Peggy Nelson, Michael Reichert, Emilie Snell-Rood, Trevor Wardill and Marlene Zuk for helpful insights on this research, feedback on previous versions of the manuscript, or both. Collecting, handling and testing procedures were approved by the University of Minnesota's Institutional Animal Care and Use Committee (1701-34456A, approved 3 March 2017). This research was supported by grants from the U.S. National Science Foundation (NSF) to M.A.B. (IOS 1452831, 2022253).

Funding Information:
We thank Miranda Dahl, Kelley Hoiseth, Chang Liu, Becky Marshall, Jordyn Massop, Annika Ruppert and Yi Fang Tan for help in collecting and testing frogs, David Tinetti for fabricating the robotic system, Katie LaBarbera for the cartoon frog included in some figures, Eric Warrant for very helpful conversations about measuring and reporting light levels and Paloma Gonzalez-Bellido, Carl Gerhardt, Saumya Gupta, Lata Kalra, Katie LaBarbera, Peter Marchetto, Peggy Nelson, Michael Reichert, Emilie Snell-Rood, Trevor Wardill and Marlene Zuk for helpful insights on this research, feedback on previous versions of the manuscript, or both. Collecting, handling and testing procedures were approved by the University of Minnesota's Institutional Animal Care and Use Committee (1701-34456A, approved 3 March 2017). This research was supported by grants from the U.S. National Science Foundation (NSF) to M.A.B. (IOS 1452831 , 2022253 ).

Publisher Copyright:
© 2022 The Association for the Study of Animal Behaviour

Keywords

  • complex signal
  • gray treefrog
  • multicomponent signal
  • multimodal communication
  • multisensory perception
  • robotics

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