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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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Spectrograms of typical call types produced by golden hamsters after interacting with a stimulus hamster of the opposite-sex.Call subtypes are merged into 8 major categories of call types: A. Flats (Flat1–3, 2tail-flat4), B. Waves (Wave down-up1, Wave up-down2, Complex wave3), C. Humps (Center hump1, Left hump2, Right hump3), D. Chevrons (Chevron-down1, Chevron-up2), E. Sweeps (Down-sweep1, Up-sweep2), F. Broadband, G. 1-Frequency jump (1-Jump up1, 1-Jump down2), H. Multi-Frequency jumps (2-Step1, 3+Step2).
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pone.0116789.g001: Spectrograms of typical call types produced by golden hamsters after interacting with a stimulus hamster of the opposite-sex.Call subtypes are merged into 8 major categories of call types: A. Flats (Flat1–3, 2tail-flat4), B. Waves (Wave down-up1, Wave up-down2, Complex wave3), C. Humps (Center hump1, Left hump2, Right hump3), D. Chevrons (Chevron-down1, Chevron-up2), E. Sweeps (Down-sweep1, Up-sweep2), F. Broadband, G. 1-Frequency jump (1-Jump up1, 1-Jump down2), H. Multi-Frequency jumps (2-Step1, 3+Step2).

Mentions: Call type categorization. We classified hamster USV into morphologically distinct types based on the shape of the frequency trajectory or contour. We adapted the terminology used for this categorization from the descriptions of vocalizations made for other mammal species, especially those used for USV in the house mouse and in the rat [33,36,68,78–80]. Rodent USV have been described as flat or constant frequency (33,36,68,78–80), wave frequency modulation (35,36,80), hump frequency modulation (79), chevrons (or U-shaped or inverted-U modulation; 33,35,36,68,79,80), frequency-modulated sweeps (or upward and downward; 35,36,68,79,80) and frequency steps or jumps (1, 2 or multi-steps, 33,35,36,68,79,80). We identified these types in the USV produced by hamsters and classified them further into a more detailed scheme of 21 categories of call subtypes to categorize as much of the variation as possible (Table 1, Fig. 1).


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)

Spectrograms of typical call types produced by golden hamsters after interacting with a stimulus hamster of the opposite-sex.Call subtypes are merged into 8 major categories of call types: A. Flats (Flat1–3, 2tail-flat4), B. Waves (Wave down-up1, Wave up-down2, Complex wave3), C. Humps (Center hump1, Left hump2, Right hump3), D. Chevrons (Chevron-down1, Chevron-up2), E. Sweeps (Down-sweep1, Up-sweep2), F. Broadband, G. 1-Frequency jump (1-Jump up1, 1-Jump down2), H. Multi-Frequency jumps (2-Step1, 3+Step2).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4340904&req=5

pone.0116789.g001: Spectrograms of typical call types produced by golden hamsters after interacting with a stimulus hamster of the opposite-sex.Call subtypes are merged into 8 major categories of call types: A. Flats (Flat1–3, 2tail-flat4), B. Waves (Wave down-up1, Wave up-down2, Complex wave3), C. Humps (Center hump1, Left hump2, Right hump3), D. Chevrons (Chevron-down1, Chevron-up2), E. Sweeps (Down-sweep1, Up-sweep2), F. Broadband, G. 1-Frequency jump (1-Jump up1, 1-Jump down2), H. Multi-Frequency jumps (2-Step1, 3+Step2).
Mentions: Call type categorization. We classified hamster USV into morphologically distinct types based on the shape of the frequency trajectory or contour. We adapted the terminology used for this categorization from the descriptions of vocalizations made for other mammal species, especially those used for USV in the house mouse and in the rat [33,36,68,78–80]. Rodent USV have been described as flat or constant frequency (33,36,68,78–80), wave frequency modulation (35,36,80), hump frequency modulation (79), chevrons (or U-shaped or inverted-U modulation; 33,35,36,68,79,80), frequency-modulated sweeps (or upward and downward; 35,36,68,79,80) and frequency steps or jumps (1, 2 or multi-steps, 33,35,36,68,79,80). We identified these types in the USV produced by hamsters and classified them further into a more detailed scheme of 21 categories of call subtypes to categorize as much of the variation as possible (Table 1, Fig. 1).

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