Highlights: This new research incorporates over ten years of data on dolphin behaviour, genetics and habitat use. We show how ‘sponging’ is a learned behaviour, transmitted socially between mother and (primarily female) calves. Meanwhile, habitat use and genetics do not appear to influence if a dolphin learns sponging or not. These findings build on and complement previous research, providing strong quantitative evidence for the existence of dolphin culture.
Title: Multi-network-based diffusion analysis reveals vertical cultural transmission of sponge tool use within dolphin matrilines.
Authors: Wild S, Allen SJ, Krützen M, King SL, Gerber L, Hoppitt WJE.
Abstract: Behavioural differences among social groups can arise from differing ecological conditions, genetic predispositions and/or social learning. In the past, social learning has typically been inferred as responsible for the spread of behaviour by the exclusion of ecological and genetic factors. This ‘method of exclusion’ was used to infer that ‘sponging’, a foraging behaviour involving tool use in the bottlenose dolphin (Tursiops aduncus) population in Shark Bay, Western Australia, was socially transmitted. However, previous studies were limited in that they never fully accounted for alternative factors, and that social learning, ecology and genetics are not mutually exclusive in causing behavioural variation. Here, we quantified the importance of social learning on the diffusion of sponging, for the first time explicitly accounting for ecological and genetic factors, using a multi-network version of ‘network-based diffusion analysis’. Our results provide compelling support for previous findings that sponging is vertically socially transmitted from mother to (primarily female) offspring. This research illustrates the utility of social network analysis in elucidating the explanatory mechanisms behind the transmission of behaviour in wild animal populations.
Full citation: Wild S, Allen SJ, Krützen M, King SL, Gerber L, Hoppitt WJE. 2019 Multi-network-based diffusion analysis reveals vertical cultural transmission of sponge tool use within dolphin matrilines. Biol. Lett. 15: 20190227. http://dx.doi.org/10.1098/rsbl.2019.0227
Ethics: Permits for the use of animals for scientific purposes were granted by the Department of Biodiversity, Conservation and Attractions (SF002958; SF010888; SF10388; SF002958; SF010774; 08-000920-1; 08-000706-3) and the Department of Agriculture and Food (U 10/2015-2018). The animal ethics committees of the University of Western Australia, Murdoch University and the University of Zurich provided approvals for the ethical treatment of animals in scientific research (R2649/14; RA/3/100/1449; RA/3/100/1464).
Funding: This research was funded by: Swiss National Science Foundation (31003A_149956), Seaworld Research & Rescue Foundation Inc. (SWRRFI), National Geographic Society, A.H. Schultz Stiftung, Claraz-Schenkung, Julius-Klaus Stiftung and W.V. Scott Foundation, all to M.K. S.L.K. was supported by The Branco Weiss Fellowship—Society in Science.
Acknowledgements: We thank Shark Bay Resources and the Useless Loop community for logistic support, and all researchers and volunteers who have contributed to data collection for the Dolphin Innovation Project.