Dolphins have unique social structure in the animal kingdom

Males cultivate loose, multi-layered alliances

Two dolphin males in Shark Bay © The Dolphin Alliance Project
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Dolphins have a unique social behavior in the animal kingdom - and are more human-like than imagined. On the one hand, the dolphin males form alliances with each other and, on the other hand, live in an open, opportunistically changing social structure. This complex, multi-layered social structure has now been researched by researchers on dolphins in Shark Bay, Australia. As they report in the journal "Proceedings of the Royal Society B", the study of such animal social structures gives valuable information on the evolution of our own social behavior.

Studies in the 1990s have already shown that two to three male dolphins cooperate very closely with each other to isolate female dolphins for mating from the large group. These so-called first-order alliances sometimes unite to steal females that are monopolized by other alliances. However, this link among higher-level males is sometimes highly opportunistic and may change depending on the context. The formation of alliances with dolphins is only comparable in their complexity with that of humans.

Researchers from the USA, Australia and Michael Krützen from the Anthropological Institute and Museum of the University of Zurich now prove that these male alliances are based on an open social structure. Dolphins have complex relationships with other individuals within a complex network without an obvious group structure. This puts dolphins almost on par with us humans. As a comparison, the social structure of chimpanzees arises. Even chimpanzee males form alliances, but only between social groups. As a result, they defend their territory against conspecifics from other groups. However, this is not the case with dolphins: they defend the females and not the territories.

Unique behavior in the animal kingdom

Another explanatory model would be that dolphin males only defend females or territories during the mating season, avoiding as much as possible. Nor does this hypothesis apply to dolphins in Shark Bay, as revealed by the observation of more than 120 adult dolphins in an area of ​​approximately 600 square kilometers. "Our study shows for the first time that the social structure and the associated behavior of dolphins in the animal kingdom is unique, " explains Michael Krützen.

The behavior of groups and the social structure of other species have always fascinated biologists. Are they similar to ours - and if so, can we learn something about ourselves? The comparison of humans with monkeys, elephants and dolphins, all species with large brains and advanced cognitive abilities, allows conclusions to be drawn on the evolution of group behavior in humans. (Proceedings of the Royal Society, Doi: 10.1098 / rspb.2012.0264) Display

(University of Zurich, 30.03.2012 - NPO)