Sneak copulations in long-tailed macaques (Macaca fascicularis): no evidence for tactical deception
Sexual competition is highly prevalent within multi-male multi-female primate groups and may lead to copulations in absence of potentially interfering bystanders. Such avoidance of bystanders may result from tactical deception or from simpler mechanisms such as taking advantage of encountered situations without bystanders, operant conditioning or a peripheral positioning of non-alpha males. We investigated which individuals are avoided as bystanders, how individuals react to the presence of bystanders and whether copulation partners separate themselves from the group in a tactical way. Our observations of a group of 15 female and seven male long-tailed macaques housed in three interconnected, but visually separated compartments revealed that both males and females can interrupt sexual behaviour and that bystanders of both sexes were avoided during copulations (n = 256). The strength of the effect of bystanders tended to decrease with the dominance rank of male bystanders, but did not depend on the dominance rank of female bystanders. The audience effects of non-alpha individuals did not depend on the strong audience effect of the alpha male in combination with proximity with the alpha male. The effects that we found for separate bystanders suggest that sexual competition concerns rank dependent male–male competition and rank independent female–female competition. Additionally, both male and female copulation partners paid attention to the presence of bystanders and conducted fewer copulation solicitations in their presence. The timing of a male and female’s separation from the group suggests that exploitation of the peripheral position of non-alpha males, and not tactical deception, may cause these audience effects.
KeywordsTactical deception Audience effect Mating tactics Sexual competition Primates Monopolization Macaques
We would like to thank Nick Stolk for his contribution to the data collection, three anonymous reviewers for the thoughtful comments and the animal caretakers for their care for the monkeys. This research was funded by the Biomedical Primate Research Centre, Rijswijk, the Netherlands.
This research complied with protocols approved by the Animal Ethical Committee of the Biomedical Primate Research Centre and with the legal requirements of the Netherlands.
- Angst W (1974) Das Ausdrucksverhalten des Javaneraffen Macaca fascicularis Raffles 1821. Parey, BerlinGoogle Scholar
- Byrne RW, Whiten A (1990) Tactical deception in primates: the 1990 database. Primate Rep 27:1–101Google Scholar
- Davies NB (2000) Multi-male breeding groups in birds: ecological causes and social conflicts. In: Kappeler PM (ed) Primate males: causes and consequences of variation in group composition. Cambridge University Press, Cambridge, pp 11–20Google Scholar
- de Ruiter JR, Scheffrahn W, Trommelen GJM, Uiterlinden AG, Martin RD, van Hooff JARAM (1992) Male social rank and reproductive success in wild long-tailed macaques. In: Martin RD, Dixson AF, Wickings EJ (eds) Paternity in primates: genetic tests and theories. Karger, Basel, pp 175–191Google Scholar
- Development Core Team R (2009) R: A language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Dixson AF (1998) Primate sexuality: comparative studies of the prosimians, monkeys, apes, and human beings. Oxford University Press, OxfordGoogle Scholar
- Kummer H (1968) Social organization of Hamadryas baboons: a field study. University of Chicago Press, ChicagoGoogle Scholar
- Stephenson GR (1975) Social structure of mating activity in Japanese macaques. In: Kondo S, Kawai M, Ehara A, Kawamura S (eds) Proceedings of the Fifth Congress of the International Primatological Society. Japan Science Press, Tokyo, pp 63–115Google Scholar
- Vernes MK, Louwerse AL (2010) BPRC's enrichment manual for macaques and marmosets. Biomedical Primate Research Centre, RijswijkGoogle Scholar