MALE dolphins conduct intense social relationships and are found to engage in extensive bisexuality, according to US scientists.

Researchers from the University of Massachusetts Dartmouth studied more than 120 bottlenose dolphins in Shark Bay, Western Australia, and found their relationships were more complex than previously thought.

The creatures engaged in extensive bisexuality, combined with periods of exclusive homosexuality, 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," he 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."

His team found that the dolphins also pair-up, or swim in groups of three, to herd individual females during the mating season.

The results of the study, to be published in the Proceedings of the Royal Society B, found that most male dolphins are also members of "second order alliances" of between four to 14 males - with one known seven-member gang still together after 17 years.

Connor said that though the males are "capable of serious aggression," they do not squabble constantly and did not patrol and defend particular areas.