Sexual selection and adaptive function of gibbon vocalizations: Do testosterone-driven males sing their own praises, but pay a cost in immuno competence?

• Applicant: Dr. Michael Heistermann
• Subject Area: Sensory and Behavioural Biology
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 144140138

Among mammals, elaborate vocalizations are quite rare. However, one of the best known exceptions are the gibbons (Hylobatidae), the small and agile apes of South-East Asia. In this primate group, both sexes sing but while females utter stereotyped songs, males sing elaborate solos, the function of which still remains enigmatic. Sex differences in gibbons’ songs suggest that it may have evolved by providing males with the most elaborate song with a reproductive advantage over their rivals. Thus, the aim of this study is to investigate whether sexual selection has driven the evolution of male vocalizations in a population of wild white-handed gibbons (Hylobates lar). The population we will investigate presents the uniqueness of a very large number of habituated animals which live in both socially monogamous and polyandrous group. We will investigate whether and to what extent male vocalizations vary between males and whether they may function as sexual signal. In particular, by using non-invasive methodologies, We will (i) test males for testosterone levels and examine whether their physiological characteristics may drive variation in the acoustic structure of male song; by measuring gibbons’ parasite load, we will (ii) assess whether male singing serves to advertise physical condition; and (iii) we investigate, using genetic paternity analysis, whether variation in ‘song quality’ is related to variation in male reproductive success.

• DFG Programme: Research Grants
• Participating Person: Dr. Claudia Barelli