Journal cover Journal topic
Primate Biology An international open-access journal on primate research
Primate Biol., 4, 1-7, 2017
https://doi.org/10.5194/pb-4-1-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
26 Jan 2017
Age-dependent change of coalitionary strategy in male Barbary macaques
Eva-Maria Rathke1,2, Andreas Berghänel1,3, Annie Bissonnette1,4, Julia Ostner1,5, and Oliver Schülke1,5 1Department of Behavioral Ecology, Georg-August University Göttingen, Kellnerweg 6, 37077 Göttingen, Germany
2Cognitive Ethology Laboratory, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany
3Department of Anthropology, University of New Mexico, MSC01-1040, Anthropology, 1, Albuquerque, NM 87131, USA
4Anthropological Institute and Museum, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
5Primate Social Evolution Group, German Primate Center, Leibniz Institute for Primate Research, Kellnerweg 4, 37077 Göttingen, Germany
Abstract. Inter- and intra-specific variation in the propensity to form coalitions has been explained by variation in the availability of suitable partners, distribution of fighting ability, coalition profitability, and costs of coordination. Male coalition formation can be an alternative reproductive strategy to one-on-one competition to maximize male reproductive success. Here we focus on age as a state variable to explain within-group variation in individual propensity to form coalitions against other group members. We specifically test the prediction that males conditionally switch from a solo strategy for achievement of high mating success to a cooperative strategy after reaching post-prime age in male Barbary macaques (Macaca sylvanus). We combined new observations with data collected in 2006 and 2008 on the same individuals from one captive group living in semi-natural conditions at Affenberg Salem, Germany, and found that in all years males between 5 and 13 years formed significantly fewer coalitions than males 14 years and older (post-prime). More importantly, we found those males that aged into the post-prime phase to have switched their reproductive strategy and to form significantly more coalitions in 2014 compared to 2008. These first longitudinal data together with earlier cross-sectional analyses in this and other primate species suggest that group-level measures of coalition propensity may be strongly affected by the age composition of groups and that male coalition formation can be a conditional reproductive strategy.

Citation: Rathke, E.-M., Berghänel, A., Bissonnette, A., Ostner, J., and Schülke, O.: Age-dependent change of coalitionary strategy in male Barbary macaques, Primate Biol., 4, 1-7, https://doi.org/10.5194/pb-4-1-2017, 2017.
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Short summary
Coalitions are a specific case of cooperative competition and have been explained by various factors like partner availability, distribution of fighting ability, or cost of coordination. We investigated if age is an important factor influencing coalition formation and, specifically, if males switch from a solo strategy to a cooperative one after reaching post-prime age. We found that older males formed more coalitions than younger ones, stressing the importance of age in cooperative competition.
Coalitions are a specific case of cooperative competition and have been explained by various...
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