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A REWARDING TALE


Photograph: Chris Draper

May I help? No, I'm fine. Really, I insist.
Thanks, but no. It's my pleasure...

ARABIAN BABBLERS ARE the ultimate Mr Nice Guys. These unremarkable little brown birds, which are found on the Arabian and Sinai peninsulas, are so very nice to each other that they compete for who can be the nicest. Of course, the competitions are carried out in the nicest possible way, with rivals making friendly gestures in defence of their right to be nice. In a world where only the fittest survive, this kind of behaviour seems dysfunctional. But Amotz Zahavi and his team at Tel Aviv University, who have been watching the babblers (Turdoides squamiceps) for almost three decades, have an explanation. This is the story of the babblers' generosity.

They live in groups of up to 20 adults, each group having its own territory that it defends against marauders from other groups. All the members of a group work together to raise the young of a few dominant birds. But their cooperative behaviour extends well beyond feeding the young. Adult babblers also feed each other, preen each other, watch over each other and even keep each other warm at night.

What lies at the root of all this altruism? The most obvious explanation is that birds help each other because they are related. An individual can gain some sort of genetic legacy by promoting the survival of other birds with whom it has genes in common. As these relatives are likely to share genes for helping behaviour, the trait will flourish. But Zahavi and his team have tracked the breeding history of individuals in more than 20 groups of babblers, and they know that not all the members of a group are related.

Besides helping relatives, there is another potential indirect benefit to be gained from cooperating. It is possible that there are advantages for the whole group which outweigh the disadvantages to the individual of spending time helping others. Groups of babblers that help each other may do better than groups that do not, because they are less susceptible to attack, or because they make a better job of feeding the young. But there is a serious objection to the idea that babblers are nice because they gain indirect benefit through their kin or their group. In both cases, a babbler would get the same benefit at less cost to itself by letting others do the helping. Yet, far from exploiting the altruistic tendencies of fellow babblers, the birds actually waste energy stopping others from helping them.

Nice work

Babblers have an elaborate social hierarchy. The ranking system is primarily based on age and sex, with males taking precedence over females, and older birds dominating younger ones. But within this rigid framework there is another system operating. Between birds of the same age and sex, social status is variable, changing over time depending on how nice each bird can manage to be. And since being the recipient of good deeds may actually lower status, the business of being nice is fraught with contradictions.

For example, a subordinate bird may refuse to be fed by another, even when it is hungry, because by doing so it effectively lowers its standing. Subordinates spend as much time as possible feeding the young, because this raises their social status. But when a dominant bird is at the nest, the lesser individual moves away. If it does not, the dominant helper will ward it off by preening it--a non-aggressive display of social status. The birds compete in the same way for sentinel duty. It is the alpha male who is most often to be found sitting high up on a branch watching for predators. Occasionally he will be replaced by a less dominant bird, but when he wishes to return, he will approach the sentinel and relieve him of his duties by feeding him.

Another common explanation for generous acts is reciprocity. Do the babblers all help each other because they expect their favours to be returned in the future, either in kind, or in another form? Zahavi is not convinced. Within the babbler social system, the favours all go one way. So, for example, a dominant babbler that has relieved a subordinate sentinel may respond aggressively if a subordinate later tries to relieve him.

Recently, a new type of reciprocity has been suggested which can evolve even when the same two individuals never meet again. Indirect reciprocity, proposed by Martin Nowak and Karl Sigmund, uses computer modelling. All the animals in the model are assigned an "image score", apparent to all the other players, and an individual's image score changes according to how it is seen to behave. This model bears striking resemblance to what seems to be happening in Arabian babblers. But it does not satisfy Zahavi. "In the model, animals are giving more so that they can be reciprocated more, even if it is by a different individual," he says. "But babblers are hostile to birds who reciprocate. They seem to gain from the giving itself."

Zahavi rejects the idea in favour of a much simpler one. He argues that a babbler's niceness is a signal of its quality or biological fitness. Such a signalling system can only work if it cannot be faked. The peacock's tail, for example, is such a huge disadvantage to the male that it is an honest signal of health, because a sick bird could not carry it. Being nice is just such a signal. "Babblers are proud of being able to waste time, or take a risk, and they show off about it," says Zahavi. This type of signal has the added advantage of demonstrating to a potential breeding partner, or collaborator, what a great partner you would be. What's more, you avoid injury to yourself and others.

If babbler altruism has evolved as a social signalling system, it is no longer difficult to explain in terms of natural selection because the behaviour brings direct advantages for the individual. The further you climb up the ladder, the more likely you are to get a chance to breed. There is no threat of cheating in this system, because a bird that did not cooperate would stay right at the bottom of the social pile and always be outdone by rivals when it came to breeding opportunities.

"Signalling is probably the motivation in most cases of animal altruism, although researchers have been blind to it, because of the dominance of theories of kin selection and reciprocity," says Zahavi. He points out that cooperation often develops without kinship and there are many examples of altruism without reciprocity.

This conclusion may be controversial, but countless charity balls testify to the fact that, in humans at least, being nice can certainly be a display of social status. "Altruism is like any other characteristic," says Zahavi. "It is a simple selfish activity."

from New Scientist, 06 March 1999

 


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