Selfish herd theory

[1] The basic principle governing selfish herd theory is that in aggregations, predation risk is greatest on the periphery and decreases toward the center.

[2] The hypothesis has been used to explain why populations at higher predation risk often form larger, more compact groups.

To illustrate his theory, Hamilton asked readers to imagine a circular lily pond which sheltered a population of frogs and a water snake.

Movements that Hamilton proposed would lower an individual's domain of danger were largely based on the theory of marginal predation.

These factors include initial spatial position,[3] population density,[3] attack strategy of the predator,[3] and vigilance.

[2] Members at the back of the herd have the greatest domain of danger and suffer the highest predation risk.

[2] If the leader chooses an escape strategy that promotes the dispersal of the slowest member of the herd, he may endanger himself—causing dissipation of his protective buffer.

In order for the selfish herd to have evolved, movement rules that decreased domains of danger within a population must have been selected.

[9] This proposed succession would only occur if individuals who moved toward their nearest neighbor in the face of predation showed a higher survival than those who did not.

[10] A study conducted by Reluga and Viscido found that natural selection of localized movement rules of members within a population could, in fact, promote the evolution of the selfish herd.

[9] Further, it has been shown that how the predator attacks plays a crucial role in whether or not selfish herd behavior can evolve.

When exposed to a predator, fiddler crabs move in ways that are consistent with the selfish herd theory.

[3] This means that the grouping behavior of flying birds and some aquatic animals is unlikely to be explained by the selfish herd theory.