Animal aggregation.

Some animals spend most of their time alone because the presence of other conspecifics would interfere with the use of a particular resource or a suite of resources. These animals only come together with another solitary individual to pair for reproduction. Others form groups ranging from pairs of animals to large herds. Finally, some animals are brought together by phenomena over which they have no control (winds, currents, or tides) and are simply clumped in space. Groups formed for whatever reason can be either temporary or permanent and are generally theorized as being beneficial for a variety of reasons. Some associations are simply the result of congregating around a common food resource. Other associations arise for specific functions, such as finding mates, caring for the young, providing a learning environment for developing young, providing protection from the elements, thermoregulation or huddling, locomotory efficiency (swimming or flight), locating and subduing food items, resource defense against other groups or competing species, division of labor, population regulation, predator vigilance, and reduced predation risk via dilution, confusion, encounter, or group defense effects. While potential benefits can be many, aggregation can also result in distinct disadvantages for individuals making up the group. Such disadvantages include increased competition for resources (such as mates, food, or shelter), increased risk of disease and spread of parasites, and interference in reproductive behaviors.