Delphinid Social Organization and Social Behavior
Christine M. Johnson
Kenneth S. Norris
Center for Marine Studies, University of California, Santa Cruz
Although there are over twenty genera of dolphins and porpoises in the rivers, lakes and oceans of the world, only about half a dozen of these have been the object of detailed study. Most of the schools whose behavior has been documented frequent coastal waters where they can be watched from shore, or reliably found by boat or plane. Riverine species often live in virtually opaque waters and rarely perform the aerial behavior patterns that help researchers locate their marine counterparts. The difficulty, in turn, of locating and accompanying open- ocean species has limited our knowledge of these animals to serendipitous sightings, extrapolations from related species found, for instance, off the coasts of islands, and from captive observations. In fact, the most detailed accounts of dolphin social organization and behavior involve animals held in captivity. Many researchers believe, however, that the captive situation may distort the natural patterns, and caution must be used in interpreting such evidence.
The logistics of studying these fleet, elusive creatures in their natural habitats are complicated and demanding. Observations have been made from aircraft, boats, and clifftops, the last often involving the use of surveyors' transits to track the animals' movements (e.g., Norris & Dohl, 1980a; Saayman & Tayler, 1979; Würsig & Würsig, 1979a). Identifying individuals often requires long hours of scrutinizing photographs for subtle scars and marks (e.g., Shane, 1977; Würsig & Würsig, 1977). Reliably determining the age and sex of wild dolphins may require the actual capture of the animals involved (e.g., Irvine, Scott, Wells, & Kaufamn, 1981; Perrin, 1975; Sergeant & Brodie, 1969). Killer whales (Orcinus orca) with their distinctive, ideosyncratic coloring and marked sexual di-