Evolution and the pathology of deep diving in the Bottlenosed Dolphin, Tursiops truncatus (Montagu, 1821) (Notes on Cetacea, Delphinoidea V)

Cadenat (1959) and Rancurel (1964) produced strong indirect evidence that off the west coast of Africa, the Bottle-nosed Dolphin, Tursiops truncatus, is in the habit of diving very deeply, possibly down to 600 m. Examination of the skulls of fully adult specimens of Tursiops taken off Dakar and St. Helena revealed marked distension and fenestration of bones associated with the accessory air sinuses of the middle ear. The condition suggests a pathological enhancement of the normal processes of evolution of these bones in order to adjust to excessive middle ear pressure sustained intermittently over a long period.