Ultrasonic Vocalizations in Golden Hamsters (Mesocricetus auratus) Reveal Modest Sex Differences and Nonlinear Signals of Sexual Motivation

Abstract

Vocal signaling is one of many behaviors that animals perform during social interactions. Vocalizations produced by both sexes before mating can communicate sex, identity and condition of the caller. Adult golden hamsters produce ultrasonic vocalizations (USV) after intersexual contact. To determine whether these vocalizations are sexually dimorphic, we analyzed the vocal repertoire for sex differences in: 1) calling rates, 2) composition (structural complexity, call types and nonlinear phenomena) and 3) acoustic structure. In addition, we examined it for individual variation in the calls. The vocal repertoire was mainly composed of 1-note simple calls and at least half of them presented some degree of deterministic chaos. The prevalence of this nonlinear phenomenon was confirmed by low values of harmonic-to-noise ratio for most calls. We found modest sexual differences between repertoires. Males were more likely than females to produce tonal and less chaotic calls, as well as call types with frequency jumps. Multivariate analysis of the acoustic features of 1-note simple calls revealed significant sex differences in the second axis represented mostly by entropy and bandwidth parameters. Male calls showed lower entropy and inter-quartile bandwidth than female calls. Because the variation of acoustic structure within individuals was higher than among individuals, USV could not be reliably assigned to the correct individual. Interestingly, however, this high variability, augmented by the prevalence of chaos and frequency jumps, could be the result of increased vocal effort. Hamsters motivated to produce high calling rates also produced longer calls of broader bandwidth. Thus, the sex differences found could be the result of different sex preferences but also of a sex difference in calling motivation or condition. We suggest that variable and complex USV may have been selected to increase responsiveness of a potential mate by communicating sexual arousal and preventing habituation to the caller.

Proximity-based vocal networks reveal social relationships in the Southern white rhinoceros

“…Consequently, adult females did not only emit Hiss and Grunt at higher rates overall, but especially when males rather than other females were potential receivers. An effect of the receiver's sex on the call rate has been found in other mammalian taxa as well (e.g., 14,33 ), suggesting that the constellation of the sex between sender and receiver is crucial for the call function. For example, in solitary living golden hamsters the highest call rates were emitted in opposite-sex dyadic encounters compared to same-sex encounters, suggesting the calls are elicited in a sexual context 33 .…”

“…An effect of the receiver's sex on the call rate has been found in other mammalian taxa as well (e.g., 14,33 ), suggesting that the constellation of the sex between sender and receiver is crucial for the call function. For example, in solitary living golden hamsters the highest call rates were emitted in opposite-sex dyadic encounters compared to same-sex encounters, suggesting the calls are elicited in a sexual context 33 . In contrast, in group-living non-human primates, females were observed to emit more affiliative calls to same-sex rather than to opposite-sex recipients, which is assumed to signal social preferences in femalebonded primate species 14 .…”

“…25 – 28 ) as well as their vocal repertoire (e.g. 29 – 33 ). Sex differences can even be found in shared call types regarding call rate (e.g.…”

Sex differences in vocal communication of freely interacting adult mice depend upon behavioral context

“…For example, the pant calls of white rhinoceroses ( Ceratotherium simum ) provide information about age, sex, and social situation [ 11 ]. In golden hamsters ( Mesocricetus auratus ), signals emitted by males are of shorter duration than signals emitted by female hamsters [ 12 ]. Moreover, individual signals emitted by males typically encompass a smaller range of frequencies than female-emitted signals [ 12 ].…”

“…In golden hamsters ( Mesocricetus auratus ), signals emitted by males are of shorter duration than signals emitted by female hamsters [ 12 ]. Moreover, individual signals emitted by males typically encompass a smaller range of frequencies than female-emitted signals [ 12 ]. Sex differences, however, are not the only factors affecting vocal activity; animals also alter patterns of vocal communication based upon behavioral context.…”