Abstract
The design of acoustic signals and hearing sensitivity in socially communicating species would normally be expected to closely match in order to minimize signal degradation and attenuation during signal propagation. Nevertheless, other factors such as sensory biases as well as morphological and physiological constraints may affect strict correspondence between signal features and hearing sensitivity. Thus study of the relationships between sender and receiver characteristics in species utilizing acoustic communication can provide information about how acoustic communication systems evolve. The genus Gekko includes species emitting high-amplitude vocalizations for long-range communication (loud callers) as well as species producing only low-amplitude vocalizations when in close contact with conspecifics (quiet callers) which have rarely been investigated. In order to investigate relationships between auditory physiology and the frequency characteristics of acoustic signals in a quiet caller, Gekko subpalmatus we measured the subjects’ vocal signal characteristics as well as auditory brainstem responses (ABRs) to assess auditory sensitivity. The results show that G. subpalmatus males emit low amplitude calls when encountering females, ranging in dominant frequency from 2.47 to 4.17 kHz with an average at 3.35 kHz. The auditory range with highest sensitivity closely matches the dominant frequency of the vocalizations. This correspondence is consistent with the notion that quiet and loud calling species are under similar selection pressures for matching auditory sensitivity with spectral characteristics of vocalizations.
Highlights
Vocal communication involves the transmission of information encoded in the acoustic features of calls by senders to receivers, and the subsequent use of that information by the receivers in social interactions [1]
Each call of G. subpalmatus consisted of 3–29 chirps with a regular temporal pattern
We found that male G. subpalmatus emit low amplitude calls, consistent with the idea that quiet calling involves many species in the genus Gekko
Summary
Vocal communication involves the transmission of information encoded in the acoustic features of calls by senders to receivers, and the subsequent use of that information by the receivers in social interactions [1]. In the case of sexual vocal communication, correspondence between the spectral energy distribution of male acoustic signals and auditory tuning (called the “matched-filter hypothesis”) is generally expected since this can minimize. Several instances of mismatches between acoustic signals and auditory sensitivity and/or behavioral preferences have been reported [11,12,13,14]; the lack of strict correspondence in these cases has been explained in term of interactions between natural and sexual selection, environmental and sensory system constraints [15,16,17,18]. The degree of concordance between acoustic sender and receiver characteristics may be determined by factors specific to each species
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