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Angry birds show too much war is bad

Game theory A long-standing theory that excessive conflict is bad for society has been demonstrated in an animal population, researchers report.

Aggressive and peaceful Gouldian finches can live together as long as the aggressors are not too successful, suggest the findings which are based on game theory.

The research is published today in the Proceedings of the Royal Society B.

Game theory is a branch of mathematics used to model the effects of different strategies through a series of games. It's widely used in economics.

In the 1970s it was applied to biology in the form of the 'hawk-dove game' to explain why it is that animals don't fight all the time.

In this game, 'hawks' have a strategy of aggression while 'doves' have a more peaceful strategy. According to the theory, overall conflict is minimised because while hawks fight for a resource, doves backs down and let them have it.

"It means those individuals are avoiding conflict and that's good for both of them," says Associate Professor Simon Griffith, an evolutionary biologist at Macquarie University.

While this is an advantage to an individual hawk it may backfire in the long term.

This is because hawks are generally too busy wearing themselves out fighting to look after themselves or the next generation.

"There is a trade off between how much time you spend fighting and how much time you spend at your nest looking after your chicks," says Griffith.

According to the hawk-dove theory, there is an optimal ratio of hawks to doves that allows for the fact that hawks aren't good at rearing chicks.

First evidence in animals

Despite the popularity of hawk-dove game theory, this it the first time it has been demonstrated in any animal system, says Griffith. This is partly because it's difficult to identify which animals are acting as hawks and which are acting as doves.

Griffith and colleague Dr Sarah Pryke teamed up with Professor Hanna Kokko of the Australian National University to see if the data from northern Australian Gouldian finches fitted the hawk-dove theory.

They took advantage of the fact that the 'hawks' and 'doves' in Gouldian finches are clearly identifiable.

The rarer red-headed finch is aggressive and more likely to win a fight over a nest hollow, while the more numerous black-headed variety is more passive.

Griffith and team found that the hawk-dove game predicted that the optimal ratio of reds to blacks in the population would be 30:70 - which is exactly what is seen in the field.

"The model can nicely predict the number of hawks and doves we find in real populations," says Griffith.

"Reds are very good at getting the best nest sites but the problem is they are then not producing many chicks," says Griffith. "That nest hollow would have produced more chicks had a dove been nesting in it. The doves aren't fighting, they're looking after the kids."

"If there are too many reds around then the whole population suffers because it is not producing as many chicks."

Implications for conservation

Griffith says the findings have implications for conservation biology.

"It helps us to understand the decline of this endangered bird," he says.

As increasingly hotter fires destroy the big old trees they nest in, the more conflict there is over nests.

"They could get into an extinction vortex where the numbers of both decline but as soon as the reds become very very rare then the blacks will be able to get back into the nest holes," he says.

Griffith says the hawk-dove model first arose during the Vietnam War and it has been widely applied to lots of animals including humans.

"If you have too many hawks in an organisation or a political organisation it's unsustainable," he says.