Quantifying the influence of sociality on population structure in bottlenose dolphins (Abstract)
http://www.nature.com/news/2005/051024/full/051024-10.html
David Lusseau, from the University of Aberdeen, UK, has spent years researching the social world of dolphins, to find out who knows whom and how often they meet. For the 130-strong community living off the east coast of Scotland, he found, it takes an average of just 3.9 steps to link any two dolphins by the shortest possible route through mutual friends.