Even sharks make friends

Sharks have a reputation for being ruthless, solitary predators, but evidence is mounting that certain species enjoy complex social lives that include longstanding relationships and teamwork. A new study, published in the latest Animal Behaviour, documents how one population of blacktip reef sharks is actually organized into four communities and two subcommunities. The research shows for the first time that adults of a reef-associated shark species form stable, long-term social bonds. The image contrasts with usual reports on this species, which mistakenly sinks its sharp teeth into surfers and swimmers from time to time. Lead author Johann Mourier told Discovery News that "other species, such as grey reef sharks and scalloped hammerheads form polarized groups where individuals have a specific place, and such species may also have complex social organization." Mourier, a scientist at the Center for Island Research and Environmental Study (CNRS-EPHE), and colleagues Julie Vercelloni and Serge Planes conducted the study at Moorea Island in the Society archipelago, French Polynesia. A total of seven sites were surveyed on a regular basis along just over 6 miles of the north shore of Moorea. The surveys included nearly hour-long dives at a depth close to 50 feet, with the diver photographing nearby sharks. Analysis of the gathered data determined that the sharks were not within non-random collections, but rather had organized themselves into meaningful social groups.