Selfish Herd Theory: Sheep in Herds Really Are Selfish Say Scientists

Posted on July 24, 2012

Animals spend time together in large groups not because they enjoy each other's company, but because it lowers their own chances of being eaten by a predator. Researchers strapped GPS-enabled backpacks to flocking sheep and a herding dog to provide some of the first hard evidence that the "selfish herd theory" is true.

Andrew King of The Royal Veterinary College, University of London, says, "We were able to track the movements of the sheep and the dog that pursued them on a second-by-second basis simultaneously. In each case, we found that the sheep exhibit a strong attraction towards the center of the flock as the dog approaches."

The researchers say the selfish herd has long been a favorite explanation for grouping behavior. But tracking the concerted movements of many individual animals at once and predicting a predator's attack is not easy to do. As a result, there had been little semblance of proof. The data now suggest that individual sheep under threat move continuously toward the center of the flock while the flock as a whole moves away from the threat. Sheep were found to exhibit a strong attraction towards the center of the flock under threat, a pattern the researchers could re-create using a simple model.

King says, "It's kind of continuously folding in on itself."

King says that some members of the flock do seem to come out better than others. The researchers can't yet say whether this is a matter of luck or ability, though they are giving the sheep physical fitness and personality tests to look for predictable patterns. The researchers also say they want to figure out the "rules" the sheep follow in order to move in such a remarkable and orchestrated way.

The findings appear here in the July 24th issue of Current Biology.

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