Sexual signals in male crested black macaques (Macaca nigra) and their significance for male reproductive success
Final Report Abstract
This study presents for the first time thorough results on the function and physiological basis of two male signals, scrotal colouration and loud calls, occurring at the same time in a primate species, the crested macaque. Being carried out in tight collaboration with the Bogor Agricultural University, Indonesia, and combining a variety of modern non-invasive techniques used in wildlife biology, the project further has significant developmental implications for the Indonesian partner institution. Our results strongly suggest that both male traits serve as sexual signals differing however in information content and proximate function. Loud calls seem to play a role in the context of male-male contest signalling male fighting ability and reducing received aggression in males with more intense calls. Males that call more often and with more intense calls also have better access to females during fertile phases of conception cycles and can be expected to have higher reproductive success. Scrotal colour, in contrast, seems to play only a weak if not no role for male-male contest but increases in importance with increasing numbers of cycling females and thus with increasing opportunity for female mate choice. Since scrotum colour strongly correlates with male testosterone levels, this trait may signal male androgen status or another male quality linked to androgen levels to females. Our results thus for the first time show that male primates may develop a combination of sexual traits serving separate functions within the context of sexual selection, either reducing male contest or attracting females, in order to optimise individual reproductive success.
Publications
- (2008): Daytime birth of a baby crested black macaque (Macaca nigra) in the wild. Behavioural Processes 79: 81–84
Duboscq, J.; Neumann, C.; Perwitasari-Farajallah, D.; Engelhardt, A.
- (2008): Individual and contextual differences in loud calls of male crested black macaques, Macaca nigra. Folia Primatologica, 79, 366
Neumann, C.; Assahad, G.; Hammerschmidt, K.; Farajallah, D.P.; Engelhardt, A.
- (2008): Rank dependant differences in loud call frequency and structure in Sulawesi crested black macaques (Macaca nigra). Folia Primatologica, 79, 311
Assahad, G.; Neumann, C.; Hammerschmidt, K.; Perwitasari-Farajallah, D.; Engelhardt, A.
- (2008): Reproductive biology of Sulawesi crested black macaques (Macaca nigra). Folia Primatologica, 79, 326
Engelhardt, A.; Perwitasari-Farajallah, D.
- (2009): Male Sexual Signals in Crested Macaques (Macaca nigra)”, Folia Primatologica, 80, 131–2
Neumann, C.; Assahad, G.; Hammerschmidt, K.; Perwitasari-Farajallah, D. ; Engelhardt, A.
- (2009): Sex skin colouration in male Sulawesi crested black macaques (Macaca nigra), Primate Eye, 96, 337
Engelhardt, A.; Heistermann, M.; Perwitasari-Farajallah, D.
- (2010): Colour signal information content and the eye of the beholder: a case study in the rhesus macaque. Behavioural Ecology 21: 739-746
Higham, J.; Brent, L.; Dubuc, C.; Accamando, A.; Engelhardt, A.; Gerald, M.; Heistermann, M.; Stevens, M.
- (2010): Loud calls in male Macaca nigra – a signal of dominance in a tolerant primate species. Animal Behaviour 79: 187-193
Neumann, C.; Assahad, G.; Hammerschmidt, K.; Perwitasari-Farajallah, D.; Engelhardt, A.
