responses in a variety of social contexts, and have memories adequate to the task of keeping track of other individuals and the status of their relationships. Dolphins apparently meet all of these requirements.
Participation in such a system also implies a cognizance of the effects of one's own actions on others and a high level of empathy that fosters reciprocation. This model may account for the occurrence of epimeletic--or care-giving--behavior in these animals. (For review, see Caldwell & Caldwell, 1966.) Dolphins have long been known to offer one another assistance, in the forms, for instance, of helping to raise a faltering animal up to the surface to breathe, of "standing by" when a schoolmate is captured, or of actively intervening to rescue or defend a threatened member of the group. Such behavior patterns have even been reported between members of different dolphin species (e.g., Brown & Norris, 1956; Caldwell, Brown, & Caldwell, 1963; Norris & Prescott, 1961).
The dependence, then, on cooperative feeding, the requirement of cohesive schools and consequent utility of symmetrical relations, and the occurence of assistance behavior, all support the reciprocal altruism model as an apt one for a principal force in structuring dolphin society. The challenge to us as researchers is to quantify the cost/benefit ratio involved--in terms of energy expenditures, changes in foraging efficiency or risk of predation, etc.--to determine if altruism, in the formal, theoretical sense, does indeed occur.
In summary, the key terms in a description of delphinid social organization and behavior are communality and flexibility. These qualities are evident in the animals' use of context-dependent signals, the alternation of social roles, the ability to respond differentially to a variety of individuals and, depending on the circumstances, to shift between hierarchical and symmetrical social interactions. In "The Social Function of Intellect," Humphrey ( 1976) suggests that the evolution of intelligence is adaptive in animals with complex social systems, where a proficiency at the subtleties of "social gamesmanship" is required. His proposal that "the chief role of creative intellect is to hold society together," suggests why the essentially communal and behaviorally variable dolphins may have been selected to develop certain complex cognitive abilities.
Au W., Floyd R. W., & Haun J. E. ( 1978). Propagation of Atlantic bottlenose dolphin echolocation signals. Journal Acous. Society America., 64(2), 411-422.