Award Holder: Adriano Reis e Lameira
University: Utrecht University
Title of Research: Variations in the Call Repertoire of Wild Orangutans
The evolutionary puzzle of human language has fascinated scientists for centuries. Where variation between languages, dialects, accents, is an important part of human culture, there is little information on the variation between populations in the acoustic repertoire of our closest relatives, namely orangutans. Hence, such research could potentially clarify whether these variations in human language are unique to our evolutionary lineage (thus that they likely date from the split with the lineage that evolved into the extant apes), or whether they differ solely in a matter of degree from our closest relatives (thus that they very probably derive from similar traits in ape acoustic repertoires). To answer these centennial questions, I aimed to determine the variation in the orangutan acoustic repertoire across several populations in Sumatra and Borneo – the last two islands where the red ape survives – by making extensive field audio recordings. By this means, it is possible to analyse comprehensively the calls produced by different individuals in the same population and by different individuals in different populations. Although the theoretical frame work of such research may seem relatively straightforward, it revealed particularly challenging physically and logistically. The remaining populations of wild orangutans in the island of Sumatra are found mainly in the region of Aceh, an area very unstable socio-politically. Fearing rebel demonstrations due to the Indonesian presidential elections of 2009, the central government refused my research requests for the region for more than a year. This proved to be a longer test of stamina than daily hikes through the rainforests. Eventually I had to reschedule my research and request a permit for other regions within Indonesia comprising orangutan territory to be able to implement my project and use my time and available funding properly. Nevertheless, the challenges did not end there. Orangutans are the only semi-solitary ape. To collect a representative amount of audio recordings from the several individuals that comprise a particular population, it was required to carry out full follow days (ca. 12 hours) with each animal, under all meteorological conditions, in a paradise of leeches and mosquitoes. At the same time, although we begin now to understand that the orangutan dispersed social system has not limited the spectrum of distinct calls they produce (as traditionally assumed; see Hardus et al. 2009), they are nonetheless calm animals, meaning that at the end of some “successful” working days I had 10 seconds of recordings (!). Initial results indicate that accents are wide spread across terrestrial mammals and that dialects, although rare, are not uniquely human; these can be present for instance in orangutans (Lameira et al. in press). Moreover, patterns of acoustic variation between populations suggest that genetic differentiation and/or ecological differences between habitats do not explain sufficiently the emergence of accents and dialects. This could indicate that, as it occurs in humans, ape acoustic repertoire derives in some measure from social factors, that is, individuals acquire a specific acoustic repertoire according to their local traditions. Altogether, this study greatly inspired me to return to the field and continue my recordings, as it partly disclosed a predicament in the evolutionary study of human language(s) by showing that, some language traits are rooted in ape acoustic repertoires.
