by a division of labor among individuals, and by not feeding until prey have been made more vulnerable by their herding efforts ( Wilson "temporary restraint," 1975). The descriptions of herding by yellowtails appear remarkably similar to what I have observed of cooperative herding in dusky and common dolphins.
Nevertheless, I do not mean to imply that the same mechanisms are operating in cooperating fish and dolphins. Both species are presumably cooperating because each individual has a greater chance of securing more food for itself. But beyond that, I would guess that dolphin cooperation can be more varied and tuned to the particular situation of the moment than fish cooperation. I would further guess that such mechanisms as kin-selected altruism ( Hamilton, 1964) and reciprocal altruism ( Trivers, 1971) may be involved in dolphin cooperation to a higher degree than in fish cooperation (see Connor & Norris, 1982). These assertions rely mainly, of course, on a perceived notion of a great phylogenetic difference in behavioral flexibility and capability between mammals and fishes. Mammals often live in long-term associations with their relatives, and they have a sophisticated long-term memory. Social mammals can also transmit knowledge about prey and predators (and a host of other things, such as social patterns and an understanding of the abiotic environment) by social tradition ( Hendricks, 1983). There is little reason to suppose that dolphins are not at least as sophisticated as other social mammals in their individual interactions, but because relationships and details of behaviors are only incompletely known for even the best- studied delphinids, a thorough evaluation of their interactions and foraging regimes awaits further work.
I thank Susan Shane, Randall Wells and Forrest G. Wood for their conscientious reviews of this paper.
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