Bottlenose Dolphins Create Gangs, Research Shows

Bottlenose Dolphin Gang

For five years researchers from the University of Massachusetts Dartmouth studied 120 bottlenose dolphins in Shark Bay, Western Australia, and found they have social lives that are intense. They also found that dolphins break out into groups to help protect their females.

Co-author Richard Connor told Discovery News: “I work on the male dolphins, and their social lives are very intense, it seems there is constant drama. I have often thought, as I watched their complicated alliance relationships, that their social lives would be mentally and physically exhausting, and I’m glad I’m not a dolphin.”

Researchers found that dolphins create allies with other dolphin groups and they organize themselves into three different types of alliances. Dolphins live in a society with a pattern of overlapping male and female ranges, without any apparent boundaries. “There isn’t a community border that males or females are patrolling,” said Connor.

Groups of two to three males form a “first-order” alliance that involve close relatives, such as cousins, co-operating to guard or act as consorts to females. “These consortships can last over a month,” Dr Connor explained.

UNSW geneticist Dr Bill Sherwin said, “Sometimes one of these first-order alliances is seen to assist another to gain access to a female, but on another day the same two groups may be opposed in a contest over a female.”

In a “second-order” group of alliance, the dolphins form “teams” of between four and 14 males which attack on other groups to take their females, or to defend against attacks.

The third group is the “friendly relations.” These dolphins maintain a relationship among all dolphin groups and join forces to form larger armies to work together to defend their females against other larger groups when needed.

Richard Connor, a Research Fellow at the UNSW Ecology and Evolution Research Center said, “We have now shown that males, like females, exhibit a continual mosaic of overlapping ranges. Humans, elephants and other mammals live in semi-closed groups with sex-biased dispersal but have relationships with other groups. So humans and elephants differ from the dolphins in that key respect of living in semi-closed groups, but have in common a nested relationship structure. All three have unusually low costs of locomotion, which would have allowed larger ranges, leading to interactions with larger numbers of individuals and groups, further complicating their social lives.”

Bottlenose Dolphin Gang

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