Abstract

Abstract Great ape life-history data are especially relevant for tests of the predictions of life-history theory and to establish firmly the derived features of human life history and therefore the changes that took place during hominin evolution. This chapter compares what is known about life history data on Sumatran and Bornean orangutans. The results indicate that interbirth intervals are longer for Sumatran than Bornean orangutans. In addition, interbirth intervals on Borneo appear to decrease with a west–east gradient. The chapter proposes that these differences might be related to fruit availability differences between and within the islands of Sumatra and Borneo. As mortality data are at present not available from Borneo we compared mortality rates of captive Sumatran and Bornean orangutans. No differences for captive Sumatran and Bornean orangutans were found, however. Interbirth intervals between Sumatran and Bornean orangutans were also not found, but overall interbirth intervals were significantly shorter in captivity. We discuss these results in comparison with other hominoids.