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Male bottlenose dolphins engage in extensive bisexuality

Last Updated: Wednesday, March 28, 2012 - 19:24

Washington: An unprecedented open society of bottlenose dolphins that have an extremely complex, free and open lifestyle has just been identified in Western Australia.

Social mammals usually live in well-defined and defended groups.

Most mammals, including humans, live in areas with boundaries. This population of dolphins has no such limits, even though dolphin relationships can be incredibly intense.

“Other mammals with complex social relationships live in a semi-closed group based on one or more reproductive females,” co-author Richard Connor told Discovery News, explaining that the groups or territories of these other animals “are defended by one or both sexes.”

“An open society is one without such defended boundaries,” added Connor, a biology professor at UMass Dartmouth.

He and colleagues Srdan Randic, William Sherwin and Michael Krutzen examined the ranging and behaviour of over 120 adult dolphins in a large study area at Shark Bay, Western Australia. They focused on males and their very complex social lives.

Male bottlenose dolphins also were found to engage in extensive bisexuality, combined with periods of exclusive homosexuality.

Male pairs, or even trios, cooperate to sequester and herd individual females during the mating season. Most males are also members of second order alliances consisting of 4 to 14 males. Such relationships appear to be long lasting, with one known 7-member group still intact after 17 years.

At first the researchers thought the dolphins lived somewhat like chimpanzees, since male bonding is strong, but in chimps, males can also lead to patrolling and defending community territory.

But because of their open watery range, the Shark Bay dolphins may instead have ranges that overlap with those of other dolphins in the area.

While dolphins can be aggressive, their “make love not war” lifestyle seems to be more peaceful than that of some other mammals, possibly even humans.

“We have seen precious little aggression between females. It does occur and is probably less frequent and more subtle,” Connor said.

As for males, even though “they are capable of serious aggression,” he said, “they don’t squabble constantly.”

Although males of this dolphin population do not patrol and defend territories, they have extremely complex relationships.

“I work on the male dolphins and their social lives are very intense; it seems there is constant drama,” Connor said.

“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,” he added.

The findings have been described in the latest Proceedings of the Royal Society B.


First Published: Wednesday, March 28, 2012 - 19:23
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