Are animals in herds selfish?


When groups of animals are frightened, perhaps because they detect a predator, they tend to bunch tightly together. In 1971, the biologist WD Hamilton gave a name to this: The Selfish Herd. He suggested that each individual in the group was behaving in such a way as to reduce its own risk of being the one targeted by the predator, but at the expense of others in the group (which is why the herd is selfish).

Dr Lesley Morrell and a team of researchers created a simulation model of the behaviour of individuals in a selfish herd, asking how an individual should behave in order to do to – what “movement rule” should it follow? The paper on this research was published last week.

In the past, researchers have proposed several of these rules, ranging from the simple “move towards your nearest neighbour” to complex rules where many individuals influence an animal’s choice of movement direction, but closer ones have a stronger influence.

In this new research, the team tracked how rules might evolve over many generations, if predators picked off individuals using rules that were less effective at increasing their safety.

This research found that complex rules are generally most effective at moving individuals to positions of safety within the group, and these are the rules that tend to dominate. But if most of the individuals in a group are using a simple rule, it’s difficult for a more complex rule to gain a foothold, so in nature we might expect to see groups of animals that use simple rules.

The next step in this research is to explore the rules that real animals use when forming selfish herds.

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