Formants provide honest acoustic cues to body size in American alligators

Reber, Stephan A.; Janisch, Judith; Torregrosa, Kevin; Darlington, Jim; Vliet, Kent A.; Fitch, W. Tecumseh

doi:10.1038/s41598-017-01948-1

Cited by 28 publications

(15 citation statements)

References 66 publications

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“…The crocodilian “bellow” occurs as the result of active motor control of the larynx and respiratory system, as well as the viscoelastic properties of the vocal folds (Riede, Li, Tokuda, & Farmer, ). Many crocodilians also generate subaudible vibrations that seem to emanate from the torso, but the source of these vibrations is unknown (Reber et al, ; Vliet, ; Wang, Wang, Wu, Wang, & Wang, ).…”

Section: Introductionmentioning

confidence: 99%

Gular pouch diversity in the Chamaeleonidae

Huskey

Tegge

Anderson

et al. 2019

The Anatomical Record

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Numerous chameleon species possess an out‐pocketing of the trachea known as the gular pouch. After surveying more than 250 specimens, representing nine genera and 44 species, we describe two different morphs of the gular pouch. Species of the genera Bradypodion and Chamaeleo, as well as Trioceros goetzei, all possess a single gular pouch (morph one) formed from ventral expansion of soft tissue where the larynx and trachea meet. Furcifer oustaleti and Furcifer verrucosus possess from one to four gular pouches (morph two) formed by the expansion of soft tissue between sequential hyaline cartilage rings of the trachea. In Trioceros melleri, examples of both morphs of the gular pouch were observed. Morphometric data are presented for 100 animals representing eight species previously known to possess a gular pouch and two additional species, Bradypodion thamnobates and Bradypodion transvaalense. In the species with the absolutely and relatively largest gular pouch, Chamaeleo calyptratus, a significant difference was found between sexes in its width and volume, but not its length. In C. calyptratus, we show that an inflated gular pouch is in contact with numerous hyoid muscles and the tongue. Coupled with the knowledge that C. calyptratus generates vibrations from the throat region, we posit that the tongue (M. accelerator linguae and M. hyoglossus) and supporting hyoid muscles (i.e., Mm. sternohyoideus profundus et superficialis and Mm. mandibulohyoideus) are involved in the production of vibrations to produce biotremors that are amplified by the inflated gular pouch and used in substrate‐borne communication.

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Section: Introductionmentioning

confidence: 99%

Gular pouch diversity in the Chamaeleonidae

Huskey

Tegge

Anderson

et al. 2019

The Anatomical Record

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“…Larger males consistently emitted chest beats with lower median peak frequencies than smaller males. This finding is an important contribution to the growing literature on honest signaling of body size in acoustic communication, which has predominantly focused on vocalizations 5,[10][11][12][13][14][15][16][17][18] . This is one of a few studies in mammals demonstrating that body size is reliably encoded in a non-vocal acoustic signal.…”

Section: Discussionmentioning

confidence: 66%

“…Due to the allometric relationship between vocal tract length and body size, a strong association between the acoustic structure of vocalizations and body size has been observed 4,7 . For example, negative correlations between body size and formant dispersion (average spacing between resonant frequencies), indicating that (within-species) these are honest signals, have been found in a growing number of species such as rhesus macaques (Macaca mulatta) 10 , black and white colobus monkeys (Colobus guereza) 11 , red deer (Cervus elaphus) 5 , fallow deer (Dama dama) 12 , koalas (Phascolarctos cinereus) 13 , giant pandas (Ailuropoda melanoleuca) 14 , North American bison (Bison bison) 15 , southern elephant seals (Mirounga leonine) 16 , American alligators (Alligator mississippiensis) 17 and corncrakes (Crex crex) 18 .In contrast to vocal communication, the relationship between body size and non-vocal acoustic signals has received far less attention [19][20][21] . Non-vocal signals are also thought to be important in intrasexual competition and intersexual mate choice and thus under similar sexual selection pressure 1 .…”

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confidence: 99%

Chest beats as an honest signal of body size in male mountain gorillas (Gorilla beringei beringei)

Wright

Grawunder

Ndayishimiye

et al. 2021

Sci Rep

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Acoustic signals that reliably indicate body size, which usually determines competitive ability, are of particular interest for understanding how animals assess rivals and choose mates. Whereas body size tends to be negatively associated with formant dispersion in animal vocalizations, non-vocal signals have received little attention. Among the most emblematic sounds in the animal kingdom is the chest beat of gorillas, a non-vocal signal that is thought to be important in intra and inter-sexual competition, yet it is unclear whether it reliably indicates body size. We examined the relationship among body size (back breadth), peak frequency, and three temporal characteristics of the chest beat: duration, number of beats and beat rate from sound recordings of wild adult male mountain gorillas. Using linear mixed models, we found that larger males had significantly lower peak frequencies than smaller ones, but we found no consistent relationship between body size and the temporal characteristics measured. Taken together with earlier findings of positive correlations among male body size, dominance rank and reproductive success, we conclude that the gorilla chest beat is an honest signal of competitive ability. These results emphasize the potential of non-vocal signals to convey important information in mammal communication.

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“…In this study, we tested the ICHH in free‐ranging American alligators Alligator mississippiensis and examined how both intrinsic (DHEA) and extrinsic (temperature) factors modulate the relationship between testosterone and immunity. Alligators are highly sexually dimorphic (Chabreck & Joanen, 1979; Reber et al., 2017; Vliet, 1989). During the breeding season males compete aggressively for access to females (Garrick & Lang, 1977; Vliet, 1989), and correspondingly, testosterone levels of adult males peak during this period (Hamlin et al., 2011).…”

Section: Introductionmentioning

confidence: 99%

Associations between testosterone and immune activity in alligators depend on bacteria species and temperature

et al. 2021

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The immunocompetence handicap hypothesis (ICHH) postulates that testosterone supports the development of secondary sexual traits while simultaneously suppressing immune function, creating a trade‐off between trait quality and pathogen vulnerability. The nature of interactions between testosterone and immunity is complex. Conflicting patterns from the literature suggest that testosterone–immunity relationships are variable across immune measures and may be modified by factors both intrinsic and extrinsic to the organism. In this study, we tested the ICHH in free‐ranging American alligators Alligator mississippiensis and examined how both intrinsic (steroid hormone levels) and extrinsic (temperature) factors modulate the relationship between testosterone and immunity. Specifically, we quantified the simultaneous effects of testosterone and dehydroepiandrosterone (DHEA) on microbial killing capacity of three bacteria species (Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae) at two challenge temperatures (15°C and 30°C). We found that accounting for circulating levels of DHEA was important for predicting testosterone‐mediated effects on microbial killing capacity. We also found that testosterone‐mediated immunosuppression was dependent on temperature and bacteria species, with negative effects of testosterone present only for S. typhimurium at 15°C. Our results highlight the context dependency of interactions between testosterone and immunity, and illustrate the importance of evaluating the ICHH in natural systems to identify key intrinsic and extrinsic factors modulating testosterone‐immunity trade‐offs. A free Plain Language Summary can be found within the Supporting Information of this article.

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Formants provide honest acoustic cues to body size in American alligators

Cited by 28 publications

References 66 publications

Gular pouch diversity in the Chamaeleonidae

Gular pouch diversity in the Chamaeleonidae

Chest beats as an honest signal of body size in male mountain gorillas (Gorilla beringei beringei)

Associations between testosterone and immune activity in alligators depend on bacteria species and temperature

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