Press release: Primates study: Success through male bonding

Nr. 241/2010 - 18.11.2010

Göttingen scientists examine the evolution of social relationships among Assamese Macaques

(pug) Scientists from Göttingen and Leipzig have discovered that among macaques, a direct connection exists between male bonds and social success. Together with researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Dr. Oliver Schülke and Prof. Julia Ostner of Göttingen University’s Courant Research Centre ‘Evolution of Social Behaviour’ have spent several years looking at the evolution of social relationships among Assamese macaques in Thailand. The researchers have now demonstrated for the first time that the strength of a male’s social bonds with other generally unrelated macaques of the same sex has an impact on its social rise and, ultimately, the number of his progeny. These findings are being published on 18 November 2010 in the online edition of the journal ‘Current Biology’ under the title ‘Social bonds enhance reproductive success in male macaques’.

The researchers have been observing a group of 50-60 Assamese macaques in the Phu Khieo Wildlife Sanctuary, Thailand, since 2005. Investigation of the social behaviour of males has revealed strategic behaviour: if a macaque male strikes up a close relationship to one of the ten or eleven other males in the group, this ‘best friend’ also helps out in fights with other males. ‘Unlike the situation among females, this is not about accessing limited resources, but about manipulating one’s own and others’ relationships – in other words, about politics. These males are fighting for their social status’, explains Dr. Schülke. Up to now, scientists have assumed that macaque males did not join forces in competitive situations since they are usually not related.

In their long-term study, the scientists were able to show that not the number of different coalition partners but its strength of the bonds to different males is decisive for the coalitions and social ascent, and that all coalition partners profit from it. ‘The closer a male’s relationships to other males the more frequently he is successful in forming coalitions against other males. The male that maintained the closest three bonds within the group in autumn 2006 steadily rose in status and today holds sway at the top of the hierarchy together with its best friend’, says Dr. Schülke. At the same time, males that did not invest in friendships have steadily lost ground in the status stakes, or never managed to move up at all.

Ascent within the hierarchy brings with it an increase in the number of progeny, constituting reproductive success of males that are well integrated socially. The researchers have now been able to show this connection for the first time by analysing genetic paternity using DNA samples taken from faeces.

From these findings, the researchers hope also to gain insights into human behaviour. ‘Together with other recent studies, our findings suggest that the universal human tendency to engage in close social contacts have their evolutionary roots outside the extended family. This could explain why the loss of friendships or lack of social integration can result in serious health problems’, point out Dr. Schülke and Prof. Ostner.

The scientists continue to monitor the primate group. At the Excellence Initiative funded Courant Research Centre in Göttingen, Dr. Oliver Schülke is investigating the pattern of cooperation and conflict between individuals. Junior Professor Dr. Julia Ostner heads the junior research group ‘Social evolution in primates’.

Original publication:
Dr. Oliver Schülke et al.: Social bonds enhance reproductive success in male macaques, Current Biology, 18 November 2010, Doi 10.1016/j.cub.2010.10.058

Contact address:
Dr. Oliver Schülke
Georg-August-Universität Göttingen
Courant Forschungszentrum „Evolution des Sozialverhaltens“ –
Kellnerweg 6, 37077 Göttingen
Telephone (0551) 39-9636, Fax (0551) 39-9637
E-mail: oliver.schuelke@biologie.uni-goettingen.de
Internet: www.uni-goettingen.de/de/126972.html