Innovative behaviors in wild Bornean orangutans revealed by targeted population comparison

Abstract

The aim of this study was to assess whether geographic variation in wild orangutan behavior reflected the presence of innovations or merely variation induced by genetic or environmental differences. We improved upon previous attempts to answer this question in three complementary ways. First, to minimize the possible effects of differences in genetic composition or the physical, biological and social environment, we compared a population of Bornean orangutans (Pongo pygmaeus wurmbii) at a new site (Sungai Lading) with that of an established site (Tuanan). These two populations were physically separated but showed high genetic similarity and occupied very similar habitats, leaving different innovation histories as the only plausible source of significant differences in their behavioral repertoires, if these were found. Second, we used identical observation methods and overlapping observers at both sites, deliberately attempting to record the full behavioral repertoire. Third, we introduced statistical techniques to reduce the likelihood of false absences. The results showed several behavior patterns unique to the new site, as well as the absence of several patterns observed at the established site, most of them satisfying the criteria previously proposed for recognizing innovations. We, thus, confirm that orangutans produce behavioral innovations, and conclude that the geographic method for identifying innovations in wild populations is a valid, albeit conservative, approach that can complement other techniques. Finally, the results also strongly support a cultural interpretation of geographic variation in orangutan behavior