Male-Female Relationships in Bornean and Sumatran Orangutans
The social organisation of a species can only be understood in the light of male-female relationships. Orangutans are a ‘semi-solitary’ species, have a fission-fusion based social system, and the degree of sociability is tightly linked to their ecology. Yet, the social organisation is still not fully understood and there is evidence of variation and consistent differences between Sumatran (Pongo abelii) and Bornean orangutans (Pongo pygmaeus) (e.g. Delgado & van Schaik, 2000). So far, most studies focused on male-male and female-female interactions and association patterns.
The aim of my PhD project is to characterize and compare male-female social interactions and association patterns of the two orangutan species. In particular, I am interested in understanding the occurrence of sexual coercion in orangutans, most commonly reported in the form of forced copulations, which alludes to colliding male and female mating strategies.
Because in semi-solitary species data on social interactions between the sexes are scarce, we plan to use the long-term data from two study sites, Tuanan, Central Kalimantan, Borneo (P. pygmaeus wurmbii), and Suaq Balimbing, Aceh Selatan, Sumatra (P. abelii). We intend to apply an interdisciplinary approach using behavioral, endocrinological and genetic data.