Orangutan cultures revisited

Recent comparative work has claimed the presence of socially transmitted behavioral innovations, ranging from tool use to sounds produced during nest building, i.e. culture, among wild orangutans. Much independent information is corroborating this interpretation. Here, after discussing the possible sources of error in this geographic approach, the chapter updates the estimate of the orangutan’s cultural repertoire by presenting the most recent table of locally varying (i.e. non-universal) orangutan behaviors found after exhaustive comparisons of records from eight sites with long-term orangutan field studies. There now is a minimum of between 26 and 35 of such cultural variants, depending on how one assesses the risk that some of them may in fact be hidden universals, missed by some observers or performed too rarely to be reliably recorded. There was little evidence for the alternative models explaining the geographic variation as an outcome of broad reaction norms toward variable ecology or demography, or of genetic differences between populations, both indicating an absence of social learning.