Dear Marmam readers, The following paper has recently been published in the Proceedings of the Royal Society B: Randic, S., Connor, R. C., Sherwin, W. B., and Krutzen, M. (2012) A novel mammalian social structure in Indo-Pacific bottlenose dolphins (*Tursiops*sp.): complex male alliances in an open social network. Proceedings of the Royal Society B. doi: 10.1098/rspb.2012.0264 ABSTRACT: Terrestrial mammals with differentiated social relationships live in ‘semi-closed groups’ that occasionally accept new members emigrating from other groups. Bottlenose dolphins (*Tursiops* sp.) in Shark Bay, Western Australia, exhibit a fission–fusion grouping pattern with strongly differentiated relationships, including nested male alliances. Previous studies failed to detect a group membership ‘boundary’, suggesting that the dolphins live in an open social network. However, two alternative hypotheses have not been excluded. The *community defence model* posits that the dolphins live in a large semi-closed ‘chimpanzee-like’ community defended by males and predicts that a dominant alliance(s) will range over the entire community range. The *mating season defence* model predicts that alliances will defend mating-season territories or sets of females. Here, both models are tested and rejected: no alliances ranged over the entire community range and alliances showed extensive overlap in mating season ranges and consorted females. The Shark Bay dolphins, therefore, present a combination of traits that is unique among mammals: complex male alliances in an open social network. The open social network of dolphins is linked to their relatively low costs of locomotion. This reveals a surprising and previously unrecognized convergence between adaptations reducing travel costs and complex intergroup–alliance relationships in dolphins, elephants and humans. The paper can be accessed via the website: http://rspb.royalsocietypublishing.org/content/early/2012/03/20/rspb.2012.02... or via email requests to: Richard Connor (rconnor@umassd.edu) or Srđan Randić (srdan.randic@u-psud.fr) Best wishes, Srđan ------------------------- Srdan Randic Laboratoire Ecologie, Systématique et Evolution Université Paris-Sud XI Batiment 362 F-91405 Orsay Cedex France