Seasonal Variation in Sexual Segregation in spider Monkeys (Ateles GeoffroyI Yucatanensis) at Runaway Creek Nature Preserve Belize

Abstract

Sexual segregation, the separation of males and females socially or by habitat, has been recognized as a dimension of the socio-ecology of many vertebrates, but has not been quantified or systematically examined in primates. We investigated temporal patterns of sexual segregation in a population of spider monkeys in Belize. Using data collected over a 23 month study, we applied the Sexual Segregation and Aggregation Statistic to test three hypotheses: i) the sexes segregate, ii) the sexes aggregate, or iii) the sexes associated at random. Our analysis revealed that spider monkeys live in primarily sex-segregated societies, but that patterns of segregation varied within and between years: males and females segregate most of the year, except when food availability is lowest. Males and females had significantly different activity budgets; males spent more time travelling, and less time resting and feeding, than females. However, same-sex groups were less synchronous in their behavioural activities than were mixed groups. Males had a higher proportion of ripe fruit in their diets than females did, who ate more leaves and unripe fruit. We propose that sexual segregation in spider monkeys is primarily a form of social segregation that results from males and females pursuing different strategies for optimizing sex-specific energy requirements and reproductive demands. We suggest that the fission-fusion social patterning typical of spider monkeys in which males and females often form same-sexed subgroups emerges from social segregation. Supported by NSERC and Athabasca University research funds