Vocal correlates of mate quality and proceptivity in the vocalizations of white rhinoceros
Final Report Abstract
Vocal communication plays an important role in coordinating mating behaviour in animals. Vocal exchanges between males and females can give important insight into their social relationship and can indicate the reproductive phase of females. Acoustic parameters of vocalisations can correlate with the physical characteristics of the sender, indicating highquality mating partners. In this project, we investigated the role of vocal communication to coordinate social interactions and mating behaviour in white rhinoceros (Ceratotherium simum simum). We collected data on 10 males, 31 females and 13 offspring in 10 zoological gardens resulting in 616 hours video and audio material. Furthermore, we collected faecal samples to analysed the level of faecal testosterone metabolites in males and of oestrogen and progesterone metabolites in females to assess the receptive period of the female. Additionally, we performed playback experiments on 5 males and 10 females in three zoological institutions. Promoting our research to the public, we provided information posters for zoo visitors and participated in an information video at Planète Sauvage. Our results showed that the vocal repertoire of white rhinoceros is mainly innate, since we found similar call types in a hand-raised infant compared to mother-reared infants. Whereas Snort, Hiss and Pant calls were also present in the adult vocal repertoires, Whines were only recorded in infant and juveniles. This is in contrast to solitary living rhinoceros species, where Whines are also uttered in adulthood, suggesting that different social systems affect vocal communication. The publication of the infant vocal repertoire found high interest in public media, including articles in newspaper and a TV report. For further analyses, we focused on the four most common adult call types Snort, Hiss, Grunt and Pant. Snorts are noisy calls produced during resting and feeding. Hisses are noisy calls functioning as a first warning in aggressive interactions. Grunts are tonal low frequency calls followed by agonistic displays. Pants are bouts of repetitive noisy calls uttered in affiliative contexts. Thereby, Pants showed the highest level of individual distinctiveness followed by Grunt, Hiss and Snort highlighting the role of the Pant in coordinating social interactions. The vocal network analysis revealed that males directed higher rates of Pants towards females than vice versa, suggesting an active role of males in advertising behaviour. Females directed higher rates of agonistic Hisses and Grunts towards males than vice versa, suggesting a more dominant role of females than males. Comparing vocal behaviour during the receptive and non-receptive period of female rhinoceros, males increased call rate of affiliative and agonistic calls during the receptive period, whereas females increased presenting and marking behaviour. Females indicate the receptive phase by olfactory cues closely around the receptive phase, which might provoke mate-guarding behaviour of males. Preliminary analysis indicated that both sexes show a stronger response to playbacks of male Pant calls compared to Snort calls but do not differ between Pants from high testosterone versus low testosterone males. Thus, the general attractiveness of Pants is supported. To conclude, we found sex-specific vocal behaviour indicating a sexual power asymmetry in white rhinoceros. Females high rate of aggressive calls towards males indicate that they control mating by rejecting the male or leaving the territory. Males’ high rate of affiliative call and increased affiliative behaviour indicate their active role in attracting the female. Moreover, male vocalisations and female marking behaviour can serve as a real-time indicator for the receptive period of a female. These indicators have the potential to improve reproductive management strategies in captive white rhinoceros.
Publications
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First insights into the vocal repertoire of infant and juvenile Southern white rhinoceros. PLOS ONE, 13(3), e0192166.
Linn, Sabrina N.; Boeer, Michael & Scheumann, Marina
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Proximity-based vocal networks reveal social relationships in the Southern white rhinoceros. Scientific Reports, 10(1).
Jenikejew, Julia; Chaignon, Brenda; Linn, Sabrina & Scheumann, Marina
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Individual distinctiveness across call types of the southern white rhinoceros (Ceratotherium simum simum). Journal of Mammalogy, 102(2), 440-456.
Linn, Sabrina Nicolleta; Schmidt, Sabine & Scheumann, Marina
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Linking socio-sexual and vocal behaviour with faecal progesterone and oestrogen metabolite levels in Southern white rhinoceros females. Conservation Physiology, 9(1).
Jenikejew, Julia; Wauters, Jella; Dehnhard, Martin & Scheumann, Marina
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The female effect—how female receptivity influences faecal testosterone metabolite levels, socio-positive behaviour and vocalization in male Southern white rhinoceroses. Conservation Physiology, 9(1).
Jenikejew, Julia; Wauters, Jella; Dehnhard, Martin & Scheumann, Marina
