"This dark gray species is actually in the black dolphin family. It is smaller than almost all the other North American members of this family and is approximately the size of a bottlenose dolphin. This whale lives in deep tropical and subtropical waters around the world and is relatively rare; the total population in the world is believed to be perhaps 2,000. They frequently school together in large herds (200) and with other small whales and dolphins. Their diet includes fish, squid, and sometimes crustaceans, similar to that of Fraser's dolphins with whom they often associate. They are very aggressive and do not survive well in captivity."
Links:Mammal Species of the World
Original description: Gray, J.E., 1846. On the cetaceous animals. Pp. 13-53, in The zoology of the voyage of H.M.S. Erebus and Terror, under the command of Captain Sir James Clark Ross, R.N., F.R.S., during the years 1839 to 1843 by the authority of the Lords Commisioners of the Admiralty (J. Richardson and J.E. Gray, eds.) p. 35. E.W. Janson, London.