Multisensory modalities increase working memory for mating signals in a treefrog

Abstract

Animal choruses, such as those found in insects and frogs, are often intermittent. Thus, females sampling males in the chorus might have to remember the location of the potential mates' calls during periods of silence. Although a number of studies have shown that frogs use and prefer multimodal mating signals, usually acoustic plus visual, it is not clear why they do so. Here we tested the hypothesis that preference for multimodal signals over unimodal signals might be due to multimodal signals instantiating longer memories than unimodal signals, particularly during the inter‐chorus intervals. We tested this hypothesis in serrate‐legged small treefrogs Kurixalus odontotarsus whose males produce advertisement calls accompanied by conspicuous vocal sac inflation. Females were tested with acoustic and acoustic + visual (video of inflating‐deflating vocal sac) mating calls. We found that females prefer multimodal calls over unimodal, audio‐only calls. Furthermore, multimodal calls are still preferred after a silent period of up to 30 s, a time that spans the average silent period of the chorus. This was not true of unimodal calls. Our results demonstrate that a multimodal signal can engage longer working memory than a unimodal signal, and thus female memory might favour the evolution of multimodal signals in males through sexual selection. Selection might also favour female preference for multimodal signals if longer memory facilitates mate searching and assessment. Our study does not allow us to elucidate the sequence of evolution of this trait and preference.

Females and males respond differently to calls impaired by noise in a tree frog

“…The natural chorus lasts for an average of 78.7 s (Zhu et al, 2021), in which there is a lot of noise from conspecific and heterospecific individuals. Male serrate-legged small tree frogs always produce two kinds of notes: a wideband A note and a narrowband B note .…”

Acoustic signal dominance in the multimodal communication of a nocturnal mammal

“…It is important to examine receiver responses to isolated versus combined components because this approach can help us further classify multimodal signals ( Partan and Marler 2005 ). The study of multimodal communication has attracted the attention of behavioral ecologists in the last 20 years because it is critical to fully understand animal communication ( Partan and Marler 1999 ; Stevens 2013 ; Wierucka et al 2018 ; Zhu et al 2021 ). The accumulating evidence has been reported in both human and non-human primate communication via gestures and vocalizations because it is helpful to clarify human language origins ( Fröhlich et al 2019 ).…”