Dolphins and whales: taking the cognitive research out of the tanks and into the wild

The whales and dolphins (order Cetacea) are a highly diverse group of animals. They have some commonalities (e.g. mammalian body plan and reproductive strategy, complete adaptation to an aquatic lifestyle), but there are several key differences in feeding ecology, social structure and sensory perception that have considerable repercussions on their cognitive abilities. While the taxonomic position of the cetaceans was disputed for a long time, it now seems reasonably clear that they are located within the superorder Cetartiodactyla, along with the even-toed ungulates (e.g. Price et al., 2005; Agnarsson and May-Collado, 2008). Molecular studies (e.g. Price et al., 2005; Agnarsson and May-Collado, 2008) have confirmed that within the Cetacea, the major taxonomic distinction lies between the toothed whales (suborder Odontoceti) and the baleen whales (suborder Mysticeti), and this distinction is delineated by major behavioural and ecological differences. The taxonomic position of the 3 species of sperm whales (families Physeteridae and Kogiidae) has been subject to some discussion, but they are now generally included within the suborder Odontoceti (e.g. Heyning, 1997; Nikaido et al., 2001; May-Collado and Agnarsson, 2005; Agnarsson and MayCollado, 2008).