Collective animal behaviour describes and analyzes the behaviour of groups of animals. In these groups, the animals are often all of the same species. As an example, a school of fish will be made of mostly the same type of fish and a flock of birds will have the same type of bird. A herd is a large group of hoofed, herbivorous mammals.
Animals tend to behave in such a way because this behaviour offers them a benefit. The group of animals also behaves differently from a single animal. Collective animal behaviour is about finding the rules each animal follows; how it communicates with other members of the group and how a decision to do something is reached in the group.