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.
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This project was supported by grants from the BBSRC (BB/L006081/1) and the ERC (AdG 250164) to B.C.S., who was also supported by a visiting professorship at Uppsala University. L.M.A. was also supported by an Australian Postgraduate Award; and A.T., by a BBSRC David Phillips Fellowship (BB/H021817/1). The EGI social networks group, S. Lang and K. McMahon provided assistance in the field, and M. Whitaker produced electronic components for the puzzle boxes.
Extended data figures
First shows great tit using option A, pushing the door to the left from the blue side. The bird extracts a reward and the puzzle-box automatically resets 1sec after its departure. Second shows great tit using option B, pushing the door to the right from the red side. Again the bird gains access to the feeder, and the puzzle-box resets back to the middle 1 sec after its departure.
Footage shows great tits interacting at the puzzle-box over a 1 min period at a busy site, with multiple birds either solving the puzzle-box, scrounging from others, or visually observing the solves of others. Up to two scrounges in the 1 sec after a solve are permitted, and are registered as such at the puzzle-box before it shuts.
Foraging social network for T3 replicate as an example. Nodes represent individuals; lines are edges indicating the strength of connection between individuals. Yellow nodes are trained demonstrators, and nodes turn red in the order in which they first performed the new behavior (whether option A/B).
About this article
Nature Ecology & Evolution (2018)