Sexual differences in responses to cross-species call interference in the green treefrog (Hyla cinerea)

Abstract

Many species gather in choruses to advertise and search for mates, creating noisy social environments that may impair effective communication. These challenges may be further compounded in mixed-species aggregations, where signals from different species overlap and mate-searching females may perceive heterospecific signals in more attractive relative timing positions. I conducted playback experiments with green treefrogs (Hyla cinerea) to test the effects of crossspecies call interference on sexual communication and found that the sexes responded differently to conspecific and heterospecific calls. Females differentiated between call types and preferentially approached the conspecific call, indicating that they were not negatively affected by cross-species call interference. By contrast, males did not differentiate between conspecific and heterospecific calls irrespective of the presented call type and males avoided call overlap and called shortly after the offset of any interfering call. I suggest that the observed sex difference is a function of the time frames that the individual has to evaluate the call before initiating a behavioral response. Slower behavioral responses, like phonotaxis that allows for a repeated sampling of a call during approach, may facilitate finer discrimination. Fast behavioral responses, like timing one's call relative to the call of a rival, may limit processing and result in higher permissiveness. As a result, similar call timing behavior in response to conspecific and heterospecific signals may be an artifact of strong selection for fast and precise call timing in the conspecific context and may essentially trap males into wasting time and energy interacting with heterospecifics.

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

“…Previous studies have shown that whether the impairment of call structures has a negative effect on female choice varies among species: female Hyla versicolor make more recognition errors when conspecific call structures are overlapped by heterospecific calls (Marshall et al, 2006), while female Hyla chrysoscelis and Hyla cinerea can accurately respond to conspecific calls without being negatively affected by heterospecific call interference (Höbel, 2015;Marshall et al, 2006). Our results demonstrated that the discrimination of female K. odontotarsus against noise-impaired calls is related to the order of the impaired note in the advertisement call.…”

“…Temporal characteristics of calls are critical for signal recognition and mate choice (Höbel, 2015;Marshall et al, 2006;Wilczynski et al, 1999). For example, call duration is a reliable indicator of male heritable genetic quality (Welch et al, 1998).…”

“…and green tree frogs (H. cinerea) are more likely to respond to heterospecific calls than conspecific females (Bernal et al, 2007;Höbel, 2015). The differences in behavioral responses between the sexes may be due to different methods of recognizing signals or different structures of auditory organs (Shen et al, 2011;Zhu, Wang, Zhao, et al, 2017).…”

“…The differences in behavioral responses between the sexes may be due to different methods of recognizing signals or different structures of auditory organs (Shen et al, 2011;Zhu, Wang, Zhao, et al, 2017). Females generally spend a longer time evaluating and localizing mates, which allows them to sample the signal multiple times, while males usually respond quickly to a rival's signal in a shorter time (Höbel, 2015). Therefore, our results suggest that females and males may have different ways of identifying the noise-impaired calls, and sexual difference should be considered when studying the effect of noise on acoustic communication.…”

“…Therefore, it is important to investigate the effect of calls with different notes impaired by environmental noise on signal recognition and sexual selection. Both female and male frogs rely on temporal characteristics of calls to evaluate potential mates and rivals (Gerhardt et al, 2000;Höbel, 2015;Marshall et al, 2006;Simmons, 2002), whether they can assess the duration of calls, in which different notes are impaired by noise, is crucial to their mating choice and male competition. Different components in calls may have distinct functions and biological significance (Fang et al, 2019;Yue et al, 2017).…”