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Dolphins aren't so darling; many are downright devious

Published Oct. 10, 2005

As much as puppies or pandas or even children, dolphins are universally beloved. Their behavior and enormous brains suggest an intelligence approaching that of humans _ or even, some might argue, surpassing it.

Dolphins are turning out to be exceedingly clever, but not in the loving manner 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 the males form social alliances with one another that are far more sophisticated and 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 team of males to gang up against a third group, a sort of multitiered battle plan that scientists said requires considerable mental calculus to work out.

But the purpose of these complex alliances is not exactly sportive. Males collude with their peers as a way of stealing fertile females from competing dolphin bands.

And after they have succeeded in spiriting a female away, the males remain in their tight-knit group to assure 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 bellyflopping, 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 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."

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 the males' machinations.

Many male primates, including chimpanzees and baboons, are known to form into 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 or not one group owes a favor to another, and the dolphins' 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," said Connor. "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?'


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 swimming alongside them in apparent contentment, but at other times working furiously to escape, and often succeeding.

But female dolphin behavior is usually more subtle than the male theatrics, and hence less easily deciphered, particularly under the difficult field conditions of studying animals that spend much of their time underwater.

Connor and others suggest that the demands of intricate and everchanging social allegiances and counter-allegiances could have been the force driving the evolution of intelligence among dolphins.

"The smarter some animals get, and the greater their ability to form and use alliances, the more important it is for other animals to get as smart," said Dr. Richard W. Wrangham, a professor of anthropology at Harvard University who has studied social behavior among primates. "This could be the sort of selective pressure one is looking for to explain the evolution of the dolphin's brain."

Lest it seem that dolphins are little more than thugs with fins and a blowhole, biologists emphasize that they are in general remarkably good-natured animals, and usually live up to their reputation as sportive, easygoing and communal.

"When you put them into a captive situation, they're like little puppy dogs," said Dr. Kenneth Norris, professor emeritus of the University of California at Santa Cruz and one of the world's authorities on dolphin behavior. "Sure, sometimes they'll bite, but it's not like trying to train a leopard. They're orders of magnitude more peaceful than that."

Most of the 30 species of dolphins and small whales are extremely social, forming 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 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 Norris. "Democracy takes time, and they spend hours every day making decisions."

As extraordinary as their music is, scientists have not found evidence that dolphins possess what can rightfully be called a complex language, where a dolphin can clearly say to another, "Let's go fishing.'

"We've yet to come up with much context that is specific to any of the sounds," said Norris.

But the vocalizations are not completely random. Researchers have determined that each bottlenose dolphin appears to have its own call sign _ a signature whistle unique to that creature. Whistles are generated internally and sound more like a radio signal than a human whistle.

The mother seems to teach her calf what its whistle will be by repeating the sound over and over. The calf retains that whistle, squealing it out at times as though declaring its presence. More impressive, one dolphin may occasionally imitate the whistle of a companion, in essence calling the friend's name.

But dolphin researchers warn against glorifying dolphins beyond the realms of mammaldom.

"Everybody who's done research in the field is tired of dolphin lovers who believe these creatures are floating hobbits," said Karen Pryor, a dolphin trainer and scientist who lives in North Bend, Wash. "A dolphin is a healthy social mammal, and it behaves like one, including doing things that we don't find particularly charming."

Dolphins become particularly churlish when they want to mate, or to avoid being mated. Female bottlenose dolphins bear a single calf only once every four or five years, so a fertile female is a prized commodity to the males.

Because there is almost no size difference between the sexes, a single female cannot be forced to mate by a lone male. That may be part of the reason why males team into gangs.

In the latest research on bottlenose dolphins, Connor and his colleagues spent the last 10 years studying a network of about 300 dolphins in Shark Bay, in Western Australia, and devoted 25 months to observing male behavior in detail.

They followed dolphins around in a 12-foot dinghy, identifying individuals through scar patterns on their fins and recording their whistles and clicks whenever possible.

The researchers discovered that early in adolescence, a male bottlenose will form an unshakable alliance with one or two other males. These dolphins stick together for years and perhaps a lifetime _ swimming, fishing and playing together, and flaunting their fast friendship by always traveling abreast and surfacing in exact synchrony.

Sometimes that simple pair or triplet is able to woo a fertile female on its own, although what happens once the males have herded in a female, and whether she goes for one or all of them, is not yet known: the researchers have yet to witness a dolphin copulation.

At other times potential mates are scarce, and male alliances grow obstreperous. That is when pairs or triplets may seek to steal females from other groups.

To do that, they seek out another alliance of lonely bachelors, and somehow persuade that pair or triplet of dolphins to join in the venture.

The researchers are not yet sure what signals the males use to recruit outside aid, but they believe the supplicants use their pectoral fins to stroke the males from which they need assistance, or perhaps give them a few gentle pecks.

In simpler maneuvers among primates, scientists have observed that when one male needs the help of another, he takes a rather blunt approach.

"In baboons, a male who wants help against an enemy will look first at his friend, and then let his eyes trail over to the enemy, flicking his eyes back and forth," said Wrangham.

However the pact is sealed, the two dolphin gangs will then descend on a third group that is herding along a female. The two groups will then chase and assault the defending team, and because there are more of them, they usually win, taking away the female.

Significantly, the victorious joint alliance then splits up, with only one pair or triplet getting the female and the other team apparently having helped them strictly as a favor.

That buddy-buddy spirit, however, may be fleeting. Two groups of dolphins that cooperated one week may be adversaries the next, as a pair of males switches sides to help a second group of dolphins pilfer the same female they had helped the now-defending males capture in the first place.

How many of these encounters involve relatives ganging up against non-relatives is not yet known. The researchers hope soon to begin doing DNA fingerprinting on the dolphins to determine family trees.

The instability and intricacy of the mating games may explain why males are so aggressive and demanding toward the females they do manage to capture.

Male pairs or triplets guard the female ferociously, jerking their heads at her, charging her, biting her, and leaping and swimming about her in perfect unison, as though turning their bodies into fences.

Sometimes a male will make a distinctive popping noise at the female, a vocalization that sounds like a fist rapping on hollow wood. The noise seems to indicate "Get over here!" because if the female ignores the pop, the male will threaten or attack her.

At some point, the female mates with one or more of the males, and once she gives birth the alliances loses interest in her. Female dolphins raise their calves as single mothers for four to five years.

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," said Smolker. "Males make big movements and it's clear what's going on. But females must be playing a critical role."

The scientists said females seem to have widely varying habits. Most males form into lifelong pairs or triplets, but females may or may not ally themselves with friends.

"Some females are solitary and forage alone, some have stable relationships with a few other females, and some are all over the place, like social butterflies," said Connor.

The scientists have seen several cases when females will chase off interloping males, or jointly attack an alliance that tries to take away one of their own. Sometimes the females are successful.

Biologists suggest that the pressure to alternately cooperate and compete with their fellows may have spurred on the evolution of the dolphin brain. Dolphins have one of the highest ratio of brain size to body mass in the animal kingdom, which is often a measure of intelligence.

Like dolphins, humans evolved in highly social conditions where kin, friends and foes are all mingled together, and the resources you could afford to share today may become dangerously scarce tomorrow, igniting conflict.

In such a setting, few relationships are black or white, and the capacity to distinguish subtle shades of gray demands intelligence.