Safety in numbers
The mathematical biologist W.D. Hamilton proposed his selfish herd theory in 1971. This theory tries to explain why animals seek central positions in a group:  each individual can reduce its own danger by putting itself in a position with neighbours all around. So it moves towards the centre of the group. The effect was tested in brown fur seal predation by great white sharks. Decoy seals were used, and the distance between them was varied to produce different levels of danger. The seals in greater danger had (as predicted) an increased risk of shark attack.  Antipredator adaptations include behaviour such as the flocking of birds, herding of sheep, and schooling of fish. Similarly, before jumping into the water, Adelie penguins wait until their group is large enough: this reduces the risk of seal predation for each penguin in the group.