Aggressive Behavior Toward Captive Females
Although Connor's research revealed that male dolphins form cooperative units, the purpose of these units is very different from those of the females of the species. For the male dolphins, the motivation is purely sexual. The roving groups of males observed by Connor would almost always mate with their female captives, either individually or several at a time, during the course of the females' captivity. In some cases, the teams of male dolphins would ram and bite the females to prevent them from escaping.
However, Connor said that his research found no evidence that male dolphins ever forced female dolphins to mate. In fact, some females did not seem to be bothered by being herded around by their male cohorts. But by outnumbering the females, Connor said, the male gangs do bully, and may injure, females with powerful blows from their beaks or sharp teeth.
Such aggression is not uncommon in mammals. But what amazed Connor and his colleagues was how organized the dolphins' aggressive behavior was. Connor said the herding of females by male gangs may be, in part, a reaction to female promiscuity. Biologists know that female dolphins are very sexually active and may want to mate with as many males as they can. Some researchers thus speculated that herding by male gangs is a strategy to prevent females from reproducing with rival dolphins. In this way, a male alliance may increase the chances that the group's members will breed the next generation of dolphins.
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