Behaviour 2019
Female dominance in a male dominant, sexually dimorphic primate
Patrícia Izar1, Marcelo Fernández-Bolaños1, Lauren Seex2, Gerrit Gort3, Priscila Suscke1, Marcos Tokuda1, Olivia Mendonça-Furtado1, Michele Verderane1, Charlotte Hemelrijk2. 1University of São Paulo, São Paulo, SP, Brazil; 2University of Groningen, Groningen, , Netherlands; 3Wageningen University & Research, Wageningen, , Netherlands

Two main hypotheses explain how dominance hierarchies are established and maintained. In the orthodox view dominance ranks reflect prior fighting ability; in the alternative view dominance is acquired through winning and losing fights. By the orthodox view, in sexually dimorphic primates, males are dominant over females due to their larger body size; by the alternative view, females might become over males when circumstances allow females to defeat some males.  It was hypothesized that when the proportion of males increases, males fight more among each other and some of the losers might end up defeated by females, leading to an increase in female dominance over males.  This has been tested in computational models and with empirical data from cercopithecoids. Here we show in 9,300 hours of data on 6 wild groups of capuchin monkeys that the higher the proportion of males in a group there is an increase in female dominance over males, and in the relative frequency of male-male aggression and aggression of females to males and that the female dominance is positively associated with male male aggression. Our results contribute to the discussion on plasticity of dominance structures.