Experimentally induced innovations lead to persistent culture via conformity in wild birds

How socially transmitted behaviours spread and persist is shown in a wild animal population, revealing an effect of social conformity. Although socially transmitted behaviours have been observed in several different species of birds and mammals, little is known about how such behaviours spread and persist. This paper demonstrates a remarkably strong effect of social conformity in wild birds, and elucidates its role in maintaining persistent foraging traditions. Lucy Aplin et al. taught two small groups of wild great tits a different novel foraging strategy and then tracked the spread of the strategy in wild populations when the trained birds were released back into their respective population groups. From just two trained birds, the strategy spread to 75% of the population, with sub-populations heavily biased to perform the technique trained in their group across at least two generations. Birds that had encountered both strategies adopted the local variant. In human societies, cultural norms arise when behaviours are transmitted through social networks via high-fidelity social learning1. However, a paucity of experimental studies has meant that there is no comparable understanding of the process by which socially transmitted behaviours might spread and persist in animal populations2,3. Here we show experimental evidence of the establishment of foraging traditions in a wild bird population. We introduced alternative novel foraging techniques into replicated wild sub-populations of great tits (Parus major) and used automated tracking to map the diffusion, establishment and long-term persistence of the seeded innovations. Furthermore, we used social network analysis to examine the social factors that influenced diffusion dynamics. From only two trained birds in each sub-population, the information spread rapidly through social network ties, to reach an average of 75% of individuals, with a total of 414 knowledgeable individuals performing 57,909 solutions over all replicates. The sub-populations were heavily biased towards using the technique that was originally introduced, resulting in established local traditions that were stable over two generations, despite a high population turnover. Finally, we demonstrate a strong effect of social conformity, with individuals disproportionately adopting the most frequent local variant when first acquiring an innovation, and continuing to favour social information over personal information. Cultural conformity is thought to be a key factor in the evolution of complex culture in humans4,5,6,7. In providing the first experimental demonstration of conformity in a wild non-primate, and of cultural norms in foraging techniques in any wild animal, our results suggest a much broader taxonomic occurrence of such an apparently complex cultural behaviour.