Cetacean vocalizations have been studied for many years, specifically those of the bottlenose dolphin, humpback whale, killer whale, and sperm whale. Since the early 1970s, scientists have studied these four species in depth, finding potential cultural attributes within group dialects, foraging, and migratory traditions. Hal Whitehead, a leading cetologist, and his colleagues conducted a study in 1992 of sperm whale groups in the South Pacific, finding that groups tended to be clustered based on their vocal dialects. The differences in the whales' songs among and between the various groups could not be explained genetically or ecologically, and thus was attributed to social learning. In mammals such as these sperm whales or bottlenose dolphins, the decision on whether an animal has the capacity for culture comes from more than simple behavioral observations. As described by ecologist Brooke Sergeant, "on the basis of life-history characteristics, social patterns, and ecological environments, bottlenose dolphins have been considered likely candidates for socially learned and cultural behaviors," due to being large-brained and capable of vocal and motor imitation.
