The ecology of female reproduction in wild orangutans
Orangutans have the longest interbirth interval of any mammal, with existing data suggesting that these intervals may be significantly longer in Sumatra than in Borneo. This finding presents a paradox because our models of reproductive ecology suggest that the higher habitat quality of Sumatra should lead to shorter interbirth intervals. This chapter explores this intriguing difference between Sumatran and Bornean orangutans by detailing the available evidence on how orangutan reproduction is influenced by ecology and life history. Data are evaluated in light of the models, mechanisms and hypotheses by which energetics influence reproduction in apes and humans. The chapter makes recommendations for future research that will lead to a more thorough understanding of orangutan reproductive ecology. New hypotheses about acute vs cumulative effects of energy on ovarian function, the magnitude of the shift in energy intake, and the role of developmental plasticity in orangutan reproductive functioning are also presented.
