Comparison of ontogenetic brain growth in marine and coastal dolphins

In young postnatal individuals, brain growth proceeds at a much faster rate in the high seas dolphin Stenella than in the coastal waters form Pontoporia, and the encephalization is much higher in the former than in the latter. In prenatal Stenella, brain growth is also very rapid. These results agree with indices of brain progression estimated for several families (Platinistidae, Delphinidae, Delphinapteridae, Phocoenidae). The possibility that the difference is related to more demanding conditions of life in marine than in coastal or inland environments is discussed.