Abstract
Testosterone affects physical and motivational states, both of which may strongly influence vocalization structure and acoustics. The loud complex calls (i.e., songs) of male rock hyraxes (Procavia capensis) are used as honest signals for advertising physical and social states. The snort, a low frequency, noisy element of the song, encodes information on the singer's age and social rank via harshness, as measured by jitter (i.e., acoustic frequency stability) and duration; suggesting that the snort concomitantly advertises both vocal stability and aggression. Our past findings revealed that testosterone levels are related to both vocal elements and social status of male hyraxes, suggesting that hormonal mechanisms mediate the motivation for aggressive and courtship behaviors. Here we examined whether long-term androgen levels are related to snort acoustics and song structure by comparing levels of testosterone in hair with acoustic and structural parameters. We found that songs performed by individuals with higher testosterone levels include more singing bouts and longer, smoother snorts, but only in those songs induced by external triggers. It is possible that hyraxes with higher levels of testosterone possess the ability to perform higher-quality singing, but only invest in situations of high social arousal and potential benefit. Surprisingly, in spontaneous songs, hyraxes with high testosterone were found to snort more harshly than low-testosterone males. The context dependent effects of high testosterone on snort acoustics suggest that the aggressive emotional arousal associated with testosterone is naturally reflected in the jittery hyrax snort, but that it can be masked by high-quality performance.
Original language | English |
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Article number | 104535 |
Journal | Hormones and Behavior |
Volume | 114 |
DOIs | |
State | Published - Aug 2019 |
Bibliographical note
Publisher Copyright:© 2019 Elsevier Inc.
Funding
We are grateful for the professional advice received from Nori Jacobi, Noam Amir, and Ofer Amir, and to Naomi Paz for her editorial services. We wish to thank the Ein Gedi Nature Reserve and the Ein Gedi Field School staff for their hospitality and logistic support. Our long-term research was supported by five consecutive grants from the Israel Science Foundation (577/99, 488/05, 461/09, 550/14, 767/16), and YW was supported by a Bar-Ilan University Presidential PhD scholarship. The first author (YW) dedicates this manuscript in loving memory of his father, Haim G. Weissman (1961–2018) who supported and encouraged him along the way. The MATLAB script used in this study was written with his insightful help. We are grateful for the professional advice received from Nori Jacobi, Noam Amir, and Ofer Amir, and to Naomi Paz for her editorial services. We wish to thank the Ein Gedi Nature Reserve and the Ein Gedi Field School staff for their hospitality and logistic support. Our long-term research was supported by five consecutive grants from the Israel Science Foundation (577/99, 488/05, 461/09, 550/14, 767/16), and YW was supported by a Bar-Ilan University Presidential PhD scholarship. The first author (YW) dedicates this manuscript in loving memory of his father, Haim G. Weissman (1961?2018) who supported and encouraged him along the way. The MATLAB script used in this study was written with his insightful help. The authors declare no competing interests.
Funders | Funder number |
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Ein Gedi Nature Reserve | |
Israel Science Foundation | 550/14, 767/16, 461/09, 488/05, 577/99 |
Keywords
- Androgens
- Hair steroids
- Inner arousal theory
- Jitter
- Nonlinear vocalizations
- Source-filter theory
- Vocal communication