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A retractable larynx and adaptations of the vocal folds in the males of several polygynous ruminants serve for the production of rutting calls that acoustically announce larger than actual body size to both rival males and potential female mates. Here, such features of the vocal tract and of the sound source are documented in another species. We investigated the vocal anatomy and laryngeal mobility including its acoustical effects during the rutting vocal display of free-ranging male impala (Aepyceros melampus melampus) in Namibia. Male impala produced bouts of rutting calls (consisting of oral roars and interspersed explosive nasal snorts) in a low-stretch posture while guarding a rutting territory or harem. For the duration of the roars, male impala retracted the larynx from its high resting position to a low mid-neck position involving an extensible pharynx and a resilient connection between the hyoid apparatus and the larynx. Maximal larynx retraction was 108 mm based on estimates in video single frames. This was in good concordance with 91-mm vocal tract elongation calculated on the basis of differences in formant dispersion between roar portions produced with the larynx still ascended and those produced with maximally retracted larynx. Judged by their morphological traits, the larynx-retracting muscles of male impala are homologous to those of other larynx-retracting ruminants. In contrast, the large and massive vocal keels are evolutionary novelties arising by fusion and linear arrangement of the arytenoid cartilage and the canonical vocal fold. These bulky and histologically complex vocal keels produced a low fundamental frequency of 50 Hz. Impala is another ruminant species in which the males are capable of larynx retraction. In addition, male impala vocal folds are spectacularly specialized compared with domestic bovids, allowing the production of impressive, low-frequency roaring vocalizations as a significant part of their rutting behaviour. Our study expands knowledge on the evolutionary variation of vocal fold morphology in mammals, suggesting that the structure of the mammalian sound source is not always human-like and should be considered in acoustic analysis and modelling., (© 2019 Anatomical Society.)

The pronouncedly enlarged and descended larynx in male goitred gazelles (Gazella subgutturosa), Mongolian gazelles (Procapra gutturosa) and fallow deer (Dama dama) represents an interesting parallel to the 'Adam's apple' of human males. Goitred gazelles, as humans, are not born with a descended larynx. Therefore the sexual dimorphism of larynx size and position develops during ontogeny. In this study, the vocal ontogeny of male and female goitred gazelles was investigated across five age classes from neonates to adults. The acoustic variables of nasal contact calls were measured in 53 (24 male, 29 female) individuals, body mass and neck dimensions in 63 (31 male, 32 female) live individuals and nasal vocal tract and vocal fold lengths in 26 (16 male, 10 female) anatomical specimens. Call fundamental frequency (f0), the acoustic correlate of the ontogenetically enlarging larynx, decreased significantly in either sex. Call formants (second, third and forth), the acoustic correlates of the ontogenetically elongating vocal tract, did not differ significantly between sexes up to early adulthood, but clearly diverged in adults. Significant differences between sexes in neck circumference at the level of the larynx emerged already at 2-3 months of age, whereas body mass, neck circumference at the neck-body transition and the degree of larynx descent significantly differed in adults only. We discuss that, in contrast to humans, the accelerated enlargement of the larynx in male goitred gazelles starts early in ontogeny. A moderate descent of the larynx develops equally in both sexes before early adulthood, whereas the additional prominent descent of the larynx in males is shifted to late ontogeny. This might avoid selective disadvantages of this sexually dimorphic trait on males during their period of growth. As has been previously proved for humans, the emergence of the strong male-specific descent of the larynx in goitred gazelles may go along with the increasing social status and the males' increasing chances of siring offspring. Similar to the Adam's apple of human males, this may indicate the important role of the enlarged and descended larynx for signaling male status via masculine voice., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

In goitred gazelles (Gazella subgutturosa), sexual dimorphism of larynx size and position is reminiscent of the case in humans, suggesting shared features of vocal ontogenesis in both species. This study investigates the ontogeny of nasal and oral calls in 23 (10 male and 13 female) individually identified goitred gazelles from shortly after birth up to adolescence. The fundamental frequency (f0) and formants were measured as the acoustic correlates of the developing sexual dimorphism. Settings for LPC analysis of formants were based on anatomical dissections of 5 specimens. Along ontogenesis, compared to females, male f0 was consistently lower both in oral and nasal calls and male formants were lower in oral calls, whereas the first two formants of nasal calls did not differ between sexes. In goitred gazelles, significant sex differences in f0 and formants appeared as early as the second week of life, while in humans they emerge only before puberty. This result suggests different pathways of vocal ontogenesis in the goitred gazelles and in humans.