Innovation in wild Bornean orangutans (Pongo pygmaeus wurmbii)

In most studies to date, innovations were studied if their origination was witnessed or if they arose in response to a pronounced environmental change, making it difficult to generalize. In this study, we use an operational definition developed by Ramsey et al. (MS) to design a procedure for recognizing the standing repertoire of innovations (in the sense of behaviors) in a natural population. The data were derived from an intensive field study of orangutans at Tuanan, Borneo. The main recognition criteria are (1) the incomplete geographic prevalence of the behavior, (2) identified causes of its absence in a population or an individual, and (3) comparison with the incidence of the behavior among captive orangutans. Using this procedure, we recognized 19 innovations at Tuanan and 43 for orangutans in general. Cumulative curves of number of innovations indicated that the total number of innovations observed at Tuanan remained stable after some 3,000 hours of observation, and is thus adequate for comparison with other studies. Additionally, an individual's repertoire size remained stable after ca 1,000 hours. The results showed that innovations are found in multiple domains (subsistence, comfort. and social communication), and that innovations that are performed more often are more likely to reach cultural status in a population. Across populations, innovations that increase comfort are less likely to become cultural than those that serve subsistence or are used in communication. Orangutan and chimpanzee innovation repertoires do not show significant differences across the three domains. Systematic comparisons across sites and with captivity will make it possible to validate the approach.