Add deviousness to traits dolphins share with man

February 18, 1992|By Natalie Angier | Natalie Angier,New York Times News Service

Dolphins -- long beloved for their playfulness and respected for their intelligence -- are turning out to be exceedingly clever, but not in the politically correct manner that sentimental Flipperophiles might have hoped.

Researchers who have spent thousands of hours observing the behavior of bottlenose dolphins off the coast of Australia have discovered that the males form sophisticated alliances with one another that are far more devious than any seen in animals apart from human beings.

They have found that one team of male dolphins will recruit the help of another male team to steal fertile females from a third group of males.

And after they have succeeded in spiriting a female away, the males remain in their tightknit group to assure that the female stays in line, performing a series of feats that are at once spectacular and threatening.

Two or three males will surround the female, leaping and belly-flopping, swiveling and somersaulting, all in perfect synchrony with one another. Should the female be so unimpressed by the choreography as to attempt to flee, the males will chase after her, bite her, slap her with their fins or slam into her with their bodies.

The scientists call this effort to control females "herding," but they acknowledge that the word does not convey the aggressiveness of the act.

"Sometimes the female is obviously trying to escape, and the noises start to sound like they're hurting each other," said Dr. Rachel A. Smolker of the University of Michigan in Ann Arbor. "The hitting sounds really hard, and the female may end up with tooth-rake marks."

The biologists also have evidence that females form sophisticated alliances in an effort to thwart male encroachment and that bands of females will chase after an alliance of males that has stolen one of their friends from the fold.

What is more, females seem to exert choice over the males that seek to herd them. Sometimes a female swims alongside the males in apparent contentment, but at other times she works furiously to escape -- and often succeeds.

Having mapped out the basics of male alliances, the researchers are now trying to better understand female social behavior.

"Our research has been male-centered because it's easy," Dr. Smolker said. "Males make big movements, and it's clear what's going on. But females must be playing a critical role."

Dr. Smolker, Dr. Andrew F. Richards and Dr. Richard C. Connor, who is now at the Woods Hole Oceanographic Institution in Massachusetts, report their findings about dolphin alliances and herding in the current issue of the Proceedings of the National Academy of Sciences.

The researchers said that while marine biologists have long been impressed with the intelligence and social complexity of bottlenose dolphins -- the type of porpoise often used in marine mammal shows because they are so responsive to trainers -- they were nonetheless surprised by the intricacy of their machinations.

Many male primates, including chimpanzees and baboons, are known to form gangs to attack rival camps, but scientists have never before seen one group of animals soliciting a second to go after a third.

More impressive, the two-part alliances among dolphins seem to be extremely flexible, shifting from day to day depending on the dolphins' needs, whether one group owes a favor to another and their perceptions of what they can get away with.

The creatures seem to be highly opportunistic, which means that each animal must always be computing who is friend and who is foe.

"If you think of an interaction between groups that is predictably hostile, it doesn't seem to require much gray matter to know where you stand," Dr. Connor said. "But when you have situations always changing between alliances, you get the soap opera effect. 'What did he do with her today?' 'Should we go after them tomorrow?' "

Most of the 30 species of dolphins and small whales are extremely social. They form into schools of anywhere from several to hundreds of mammals, which periodically break off into smaller clans and then come back together again in what is called a fission-fusion society.

Among other things, their sociality seems to help them evade sharks and to forage for fish more effectively.

Species like the bottlenose and the spinner dolphins make most of their decisions by consensus, spending hours dawdling in a protected bay, nuzzling each other, and generating an eerie nautical symphony of squeaks, whistles, barks, twangs and clicks.

The noises crescendo ever louder until they reach a pitch that apparently indicates the vote is unanimous and that it is time to take action -- say, to go out and fish.

"When they're coordinating their decisions, it's like an orchestra tuning up, and it gets more impassioned and more rhythmic," said Dr. Kenneth Norris, professor emeritus of the University of California at Santa Cruz and one of the world's authorities on dolphin behavior. "Democracy takes time, and they spend hours every day making decisions."

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