Consequences of a male takeover on mating skew in wild Sanje mangabeys

Among primate species living in multimale-multifemale groups, the number of receptive females may determine the rank of the lowest male that copulates (priority of access model, or PoA [Altmann SA. 1962. A field study of the sociobiology of rhesus monkeys, Macaca mulatta. Annals of the New York Academy of Sciences 102:338-435]). Factors, such as temporary instability in the hierarchy and female behavior can, however, affect high-ranking males' ability to monopolize females, reducing mating skew and causing the hierarchy to depart from predictions of PoA. Here, I use behavioral data collected over a 22-month period on a wild group of Sanje mangabeys (Cercocebus sanjei) to examine the effect of a takeover by two immigrating males who became α and β in the hierarchy, and of female behavior on male mating skew. Data on male agonistic interactions were collected on nine males using ad libitum observations, while information on male mating success (i.e., daily proportion of ejaculatory copulations with the focal female) was collected through focal follows of 12 sexually receptive females. Before the takeover, the hierarchy was stable and highly skewed, with the α-male monopolizing up to 75% of copulations. At this time, however, mating skew did not follow the predictions of PoA. During the takeover, from the time one of the newly immigrant males replaced the α until the second immigrant male became the new β, the stability of the hierarchy dropped significantly and mating was no longer skewed. Accordingly, the top two ranking males at that time (i.e., the new α and former β) accounted for only 33% of copulations. After the takeover, rank stability increased, and mating skew followed the PoA. Female mating solicitations also had a significant positive effect on male mating success, and may have contributed to the deviation from the PoA. This study demonstrates that temporary rank instability decreases high-ranking males' ability to monopolize copulations, causing a departure from the predictions of the PoA. Am. J. Primatol. 79:e22532, 2017. © 2016 Wiley Periodicals, Inc.