Sword-slashing sailfish hint at origins of cooperative hunting

2 November 2016

By Brian Owens

 Cooperation makes it happen. Sailfish that work together in groups to hunt sardines can catch more fish than if they hunt alone, even without a real coordinated strategy.

 

To catch their sardine dinner, a group of sailfish circle a school of sardines – known as a baitball – and break off a small section, driving it to the surface.

They then take turns attacking these sardines, slashing at them with their long sword-like bills, which account for a quarter of their total length of up to 3.5 metres. Knocking their prey off-balance makes them easier to grab.

These attacks only result in a catch about 25 per cent of the time, but they almost always injure several sardines. As the number of injured fish increases, it becomes ever easier for everyone to snag a meal.

 “There’s no coordination, no strict turn-taking or specific hunting roles, it’s opportunistic,” says James Herbert-Read, from Uppsala University in Sweden.

But Herbert-Reads computer models now show that even this rudimentary form of cooperation is better than going it alone. Sailfish that work in groups capture more sardines than a lone fish would get in the same amount of time.

That rule holds for groups of up to 70 sailfish, he says.

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