Gregariousness and Communal Life 665 



IV. GREGARIOUSNESS AND COMMUNAL LIFE 



In gregariousness (gre -ga' ri us nes) (L. grex, flock) certain animals 

 may associate with each other for protection, for securing foods, or pos- 

 sibly for reproduction purposes (which may be incidental in certain 

 cases). The herding of herbaceous mammals, the flocking of birds, the 

 schooling of fish are common examples. Dogs and wolves often hunt in 

 packs, thereby attacking larger animals than they probably would if in- 

 dividuals did the hunting. The reasons for gregarious habits are not al- 

 ways known, and they are not always based on sex, because in certain 

 schools of fish only one sex is present. In the latter case foods are pos- 

 sibly a controlling factor which brings about the association of the fish, 

 and mass movements are the result of imitation of a so-called "leader." 

 Herds of large mammals also display group or mass movements because 

 of the leadership of one individual, usually a large or old male. The 

 various social groups might be classified as ( 1 ) those in which there is 

 division of labor among the various distinct castes, as in the bees, ants, 

 termites, etc., (2) those groups of animals which react more or less as a 

 unit, such as a family group of mammals, and (3) those which show a 

 social toleration of similar individuals in a certain area, such as schools 

 of fish, flocks of birds, etc. 



Gregariousness may involve diff'erent species and may be due to the 

 presence of certain desirable conditions for their existence such as shelter, 

 food, moisture, nesting materials, etc. If organisms of the same species 

 associate together, a communal society may result. In higher types of 

 animals the gregarious habit may be the result of a desire for companion- 

 ship or a feeling of safety in numbers. In the latter case alarms may be 

 given by individuals, thereby giving warning to others of impending 

 dans:ers. 



Among lower animals the best examples of communal life are shown 

 by the insects. Castes and well-developed divisions of labor are present 

 in honeybees, social wasps, ants, and termites. Possibly associations might 

 be considered as temporary groupings dependent upon environmental 

 factors, while communal societies are held together and the conducts of 

 the members influenced by the so-called social instincts. Possibly asso- 

 ciations and societies have much in common, but they are also different 

 because in the latter there is greater complexity and a variety of behaviors 

 of the diff'erent members. Frequently in a group there is one leader, who 

 is usually the strongest or most experienced. This one is followed by other 

 members, and the leader may have acquired the position of leader through 



