social behaviour

defined as interactions among individuals, normally within the same species, that are usually beneficial to one or more of the individuals. It is believed that social behaviour evolved because it was beneficial to those who engaged in it, which means that these individuals were more likely to survive and reproduce. Social behaviour serves many purposes and is exhibited by an extraordinary wide variety of animals, including invertebrates, fish, birds, and mammals. Thus, social behaviour is not only displayed by animals possessing well-developed brains and nervous systems.