the dolphins organize themselves into a gang to access the females

Two bottlenose dolphins (“Tursiops truncatus”), in Shark Bay (Australia), in March 2013.

La series Pinball the dolphin fed generations of children. Created in 1964, constantly broadcast around the world (in France until 2009), it celebrated, with clicks and whistles, the generosity, gentleness and loyalty of the cetacean. A friend of the Ricks family, Flipper saved swimmers and castaways there week after week, before returning to the open sea.

For four decades, science has drawn a somewhat different picture of the animal. In the “shark bay”, Shark Bay, in the far west of Australia, the teams of researchers have certainly confirmed the degree of intelligence suggested by the soap opera. For example, to avoid injury when fishing in rough terrain, the Shark Bay dolphin protects its rostrum with a sponge. A behavior akin to mastering a tool, socially transmitted and specific to this region: what ethologists call a “culture”. But biologists have also shown how, without its congeners, the marine mammal was not much, as the species appears highly social. On the female side, the search for food and the care of the young are carried out collectively, the most experienced teaching their “sisters” good manners. On the side of the males, knowledge remained more incomplete.

In an article published Aug. 30 in the Proceedings of the American Academy of Sciences (PNAS), Richard Connor of the University of Massachusetts at Dartmouth, along with Stephanie King of the University of Bristol and their colleagues, describe the extent of male networks. From adolescence, young males look at each other, look for each other, and find each other. Duos are formed, sometimes trios, united for life. In these “first-order alliances”, food is shared, but above all females.

Between these groups, the battle can be violent. Also “second-order alliances” are established, which include individuals who have remained solitary. During previous work, the American biologist had shown the central role of these “groups of groups”, composed of four to fourteen individuals. One call, and the acolytes turn up. No mistake possible because, in dolphins, the whistle is a signature, with a main sound envelope determining the lineage, and individual variations – surname, first name, in a way.

Third-rate alliances

It is, moreover, thanks to the monitoring of these whistles and to aerial photos that Richard Connor and Stephanie King have revealed alliances of the third order. First observed in 2001, these clans have been the subject of long observation. Result: bands of 22 to 50 individuals, determining to have time alongside the females and thus to ensure the male a good reproductive success, demonstrates the article. What makes a good gang? “This time, size matterssmiles Richard Connor. But not only: the intensity of the links, the number of interactions is also important. »

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