定义：Number of individuals in a group that spends the majority of their time in a 24 hour cycle together where there is some indication that these individuals form a social cohesive unit.
定义：Description of the relationships among individuals within a population of organisms, including reproductive relationships (mating system), relationships within each sex, adult – young interactions, helpers and cooperation (group living).
定义：A group of species that exploit the same food resources, and/or use the same feeding or foraging methods. http://en.wikipedia.org/wiki/Guild_(ecology)
