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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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Calling rates.(A) Mean (± SE) number of USV emitted by male and estrous female golden hamsters before and after an interaction with a same or opposite sex stimulus hamster. (B) Mean (± SE) number of USV emitted across the recording period after an interaction with a stimulus hamster of the opposite sex. *P ≤ 0.05, **P ≤ 0.01.
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pone.0116789.g002: Calling rates.(A) Mean (± SE) number of USV emitted by male and estrous female golden hamsters before and after an interaction with a same or opposite sex stimulus hamster. (B) Mean (± SE) number of USV emitted across the recording period after an interaction with a stimulus hamster of the opposite sex. *P ≤ 0.05, **P ≤ 0.01.

Mentions: The series of social elicitation of USV experiments showed that subjects rarely produced USV in the pre-interaction period, but produced a higher number of USV in the post-interaction period after male subjects (Wilcoxon signed-rank test: W = 68, P < 0.001, N = 18) and female subjects (W = 75.5, P < 0.001, N = 17) interacted with an opposite sex stimulus animal (Fig. 2A). There was also a significant difference between the total number of USV produced between pre- and post- interaction periods in female subjects (W = 15, P = 0.04, N = 9), but not in male subjects when interacting with a same sex stimulus individual (W = 13.5, P = 0.117, N = 10) (Fig. 2A). By comparing the post-interaction calling rates, we found that encounters with the opposite sex, and not with the same sex, elicited the largest amount of USV in male (Kruskal-Wallis test: X2 = 12.6, P < 0.01) and in female subjects (Kruskal-Wallis test: X2 = 6.02, P = 0.0141) (Fig. 2A). Thus, an interaction and removal of a conspecific elicited the production of USV in hamsters, except in male-male interactions. The interaction between opposite sexes was the strongest social interaction for eliciting vocal behavior (Fig. 2A).


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)

Calling rates.(A) Mean (± SE) number of USV emitted by male and estrous female golden hamsters before and after an interaction with a same or opposite sex stimulus hamster. (B) Mean (± SE) number of USV emitted across the recording period after an interaction with a stimulus hamster of the opposite sex. *P ≤ 0.05, **P ≤ 0.01.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0116789.g002: Calling rates.(A) Mean (± SE) number of USV emitted by male and estrous female golden hamsters before and after an interaction with a same or opposite sex stimulus hamster. (B) Mean (± SE) number of USV emitted across the recording period after an interaction with a stimulus hamster of the opposite sex. *P ≤ 0.05, **P ≤ 0.01.
Mentions: The series of social elicitation of USV experiments showed that subjects rarely produced USV in the pre-interaction period, but produced a higher number of USV in the post-interaction period after male subjects (Wilcoxon signed-rank test: W = 68, P < 0.001, N = 18) and female subjects (W = 75.5, P < 0.001, N = 17) interacted with an opposite sex stimulus animal (Fig. 2A). There was also a significant difference between the total number of USV produced between pre- and post- interaction periods in female subjects (W = 15, P = 0.04, N = 9), but not in male subjects when interacting with a same sex stimulus individual (W = 13.5, P = 0.117, N = 10) (Fig. 2A). By comparing the post-interaction calling rates, we found that encounters with the opposite sex, and not with the same sex, elicited the largest amount of USV in male (Kruskal-Wallis test: X2 = 12.6, P < 0.01) and in female subjects (Kruskal-Wallis test: X2 = 6.02, P = 0.0141) (Fig. 2A). Thus, an interaction and removal of a conspecific elicited the production of USV in hamsters, except in male-male interactions. The interaction between opposite sexes was the strongest social interaction for eliciting vocal behavior (Fig. 2A).

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