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Ultrasonic vocalizations in golden hamsters (Mesocricetus auratus) reveal modest sex differences and nonlinear signals of sexual motivation.

Fernández-Vargas M, Johnston RE - PLoS ONE (2015)

Bottom Line: We found modest sexual differences between repertoires.Interestingly, however, this high variability, augmented by the prevalence of chaos and frequency jumps, could be the result of increased vocal effort.Thus, the sex differences found could be the result of different sex preferences but also of a sex difference in calling motivation or condition.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Cornell University, Ithaca, NY, United States of America.

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.

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Harmonic-to-noise ratio (HNR) (dB).HNR was quantified from a random subset of 1-note simple calls (N = 16) obtained per individual and produced in the post-interaction. (A) Mean HNR ± SE in male and in estrous female golden hamsters. (B) Kernel density estimation of HNR in males and in estrous females.
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pone.0116789.g006: Harmonic-to-noise ratio (HNR) (dB).HNR was quantified from a random subset of 1-note simple calls (N = 16) obtained per individual and produced in the post-interaction. (A) Mean HNR ± SE in male and in estrous female golden hamsters. (B) Kernel density estimation of HNR in males and in estrous females.

Mentions: Periodicity (Harmonic-to-noise ratio (HNR)). The analysis of HNR of randomly selected 1-note simple USV from each individual (n = 16) from the post-interaction period showed no significant differences between sexes (male = 9.4 ± 0.92, female = 7.98 ± 0.37, Log HNR, GLMM: F1,22.7 = 1.02, P = 0.323) (Fig. 6A). The right-skewed distribution (mass distribution concentrated to the left and a long right tail) revealed the prevalence of broadband noisiness (low HNR values) in hamster USV in general (Fig. 6B). However, measures such as skewness (t-test, t22.9 = 1.07, P = 0.296), kurtosis (t-test, t21.1 = 0.54, P = 0.591) or CV (t-test, t22.1 = -0.64, P = 0.537) of male and female HNR distributions did not differ significantly. The HNR values of female USV (without averaging data per individual) ranged between 2.52 and 19.5, while in males they ranged between 2.59 and 29.37. The maximum HNR values were registered in male calls, but only in a few individuals, causing the distribution to have a weak right tail (Fig. 6B). This measure of periodicity agreed with our finding that tonal calls are produced less frequently (Fig. 3D). Both sexes produced atonal and harsh calls more often that were equally aperiodic in terms of HNR.


Ultrasonic vocalizations in golden hamsters (Mesocricetus auratus) reveal modest sex differences and nonlinear signals of sexual motivation.

Fernández-Vargas M, Johnston RE - PLoS ONE (2015)

Harmonic-to-noise ratio (HNR) (dB).HNR was quantified from a random subset of 1-note simple calls (N = 16) obtained per individual and produced in the post-interaction. (A) Mean HNR ± SE in male and in estrous female golden hamsters. (B) Kernel density estimation of HNR in males and in estrous females.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4340904&req=5

pone.0116789.g006: Harmonic-to-noise ratio (HNR) (dB).HNR was quantified from a random subset of 1-note simple calls (N = 16) obtained per individual and produced in the post-interaction. (A) Mean HNR ± SE in male and in estrous female golden hamsters. (B) Kernel density estimation of HNR in males and in estrous females.
Mentions: Periodicity (Harmonic-to-noise ratio (HNR)). The analysis of HNR of randomly selected 1-note simple USV from each individual (n = 16) from the post-interaction period showed no significant differences between sexes (male = 9.4 ± 0.92, female = 7.98 ± 0.37, Log HNR, GLMM: F1,22.7 = 1.02, P = 0.323) (Fig. 6A). The right-skewed distribution (mass distribution concentrated to the left and a long right tail) revealed the prevalence of broadband noisiness (low HNR values) in hamster USV in general (Fig. 6B). However, measures such as skewness (t-test, t22.9 = 1.07, P = 0.296), kurtosis (t-test, t21.1 = 0.54, P = 0.591) or CV (t-test, t22.1 = -0.64, P = 0.537) of male and female HNR distributions did not differ significantly. The HNR values of female USV (without averaging data per individual) ranged between 2.52 and 19.5, while in males they ranged between 2.59 and 29.37. The maximum HNR values were registered in male calls, but only in a few individuals, causing the distribution to have a weak right tail (Fig. 6B). This measure of periodicity agreed with our finding that tonal calls are produced less frequently (Fig. 3D). Both sexes produced atonal and harsh calls more often that were equally aperiodic in terms of HNR.

Bottom Line: We found modest sexual differences between repertoires.Interestingly, however, this high variability, augmented by the prevalence of chaos and frequency jumps, could be the result of increased vocal effort.Thus, the sex differences found could be the result of different sex preferences but also of a sex difference in calling motivation or condition.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Cornell University, Ithaca, NY, United States of America.

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.

Show MeSH
Related in: MedlinePlus