Implications of the multi-male troop structure in vervet monkeys (cercopithecus aethiops pygerythrus)

Abstract

The aim of this study is to assess the advantages and disadvantages to all the troop members, of vervet males remaining in heterosexual groups outside the mating season. Extensive data on time budgeting and social interactions have been obtained for both a caged and a free-ranging undisturbed troop. Some of the potential advantages males provide to other members of the troop are: improvement in predator detection, maintenance of the troop unity and interference in agonistic interactions involving females and immatures. Special emphasis is placed on the analysis of seasonal changes in agonistic, social, sexual and proximity relationships of male-male and male-female pairs. The influence of male and female dominance rank and the vervet male genital signalling system are discussed. Also a framework to achieve a better understanding of vervet monkey sexuality is provided. A detailed analysis of male inspection of female's genitalia (visual, tactile, olfactory and muzzling), female receptivity, attractivity and proceptive behaviour has been done in order to investigate male and female mate choice. These behaviours are expected to be related to time of conception, although it was found that male and female rank, mate choice and possibly the age of the mates influence their outcome. In addition, sexual consortships and other alternative male strategies (besides agonistic rank) to control access to receptive females are described for the first time in vervet monkeys. The multi-male structure of vervet societies has been questioned by other authors, mostly because of the absence of male-male agonistic coalition against other males, and the absence of sexual consortships and other special friendly bonds between males and females. However, the results of this study do show that all the above patterns may also occur among vervet monkeys, therefore the multi-male structure of vervet monkeys is similar to the one found in baboon and macaque societies.