Social behaviour of adult male northern muriquis (Brachyteles hypoxanthus) in heterosexual and all male group, at the Estação Biológica de Caratinga, MG

Author(s)

Marcos Tokuda

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Psicologia (IP/SBD)
• Defense date: 2007-08-06

Examining board members

Patricia Izar Mauro; Dilmar Alberto Gonçalves de Oliveira; Briseida Dôgo de Resende

• Advisor: Patricia Izar Mauro
• Field of knowledge: Humanities - Psychology
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP; Index Psi Teses - IP/USP
• Location: Universidade de São Paulo. Biblioteca do Instituto de Psicologia; QL737.P9; T646c

Abstract

Northern muriquis (Brachyteles hypoxanthus) are characterized by male philopatry, by multi-male/multi-female groups and by a polygamous mating system, with high levels of promiscuity. Nevertheless, environmental changes (ecological or demographic) can lead to changes in the social system (in the social structure, as well as in the social organization, or in the mating system) considered as typical of the species. Behavioural patterns such as the formation of an all male group (called UM), constantly associated with a multi-male/multi-female group (called Nadir group), and the transfer of males between distinct groups, are not described yet for northern muriquis of the Estação Biológica de Caratinga, MG. Therefore, the aims of this research were: 1) to analyse the social interactions between the UM males and the adult males of the Nadir group, 2) to compare the behaviour of UM males and the behaviour of adult males of the Nadir group, and 3) to analyse the social relationships among the adult males of the Nadir group. Seventeen adult males were the subjects of this research, 8 individuals belonged to the UM and 9 belonged to the Nadir group. The adult males of Nadir group were separeted into: immigrant (males that transfer from UM to Nadir group, 4 individuals), and resident (males that founded the Nadir group, 5 individuals). Afilliative interactions, spacial dynamics and neighbours at different categories of spacial distances were registered by focal animal sampling. The all occurrences sampling was used to record episodes of copulation and agonistic interactions. The results indicated that the social interactions between UM e GN males did not characterize social relationships between members of the same group, even though the UM males associated with the Nadir group, being often observed at the border or even inside the group. The interactions between males of the two groups did not obey a unique pattern. The interactions with immigrant males were different from those with resident males. The comparison between the UM and GN male behaviour revealed significant differences only in the pattern of spatial association. The analysis of GN males social relationships revealed an asymmetry, because the immigrants had stronger associations with residents than among themselves and were the responsible for approaching and for mantaining afilliative interactions with residents. GN males, particularly immigrants, were tolerant towards UM males, probably due to the familiarity among them. Regarding the social relationships among GN males, it was possible to distinguish the social status between immigrants and residents, since resident males were highly attractive to the immigrant males. The adaptive capacity to adjust to specific demographyc conditions, trough changes in the social organization and structure, highlights the behavioural flexibility of the species. (AU)