Sharks are often thought of as solitary predators, but a study published in a recent issue of the journal Animal Behaviour has shown that they maintain friendships and enjoy complex social lives.
Johann Mourier and co-authors surveyed Blacktip reef sharks (Carcharhinus melanopterus) from seven sites in Moorea, French Polynesia and found evidence that the sharks there organised themselves into four main communities (and one splitting into two subcommunities), and that this structure arose from active social affiliations between individuals.
The four main communities comprised individuals of both sexes that use a specific home range, but within individuals these communities tended to associate more often with others of the same sex and age (as measured by length).
Senior author Johann Mourier suspects the sharks form social bonds for mutual protection and to avoid aggression with each other. He and his colleagues also observed behaviour that suggests that the sharks hunt cooperatively, "when a group of about four or five Blacktip reef sharks herded a school of fishes around a coral structure."
For more information, see the paper: Mourier, J, J Vercelloni and S Planes (2012) Evidence of social communities in a spatially structured network of a free-ranging shark species. Animal Behaviour 83, pp. 389–401.
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