Certain characteristics of their blood indicate that this form may be better suited for deep living. Its larger body helps to conserve heat and defend itself against predators. Varations in water temperature, migration of food fish, and feeding habits may account for the seasonal movements of some dolphins to and from certain areas. Some coastal dolphins in higher latitudes show a clear tendency toward seasonal migrations, traveling further south in the winter. Those in warmer show less extensive, localized seasonal movements.
Some coastal animals stay within a limited home range.
Home ranges may overlap. The worldwide population of bottlenose dolphins is unknown. Specific bottlenose dolphin populations in a few areas have been stimated. In the United States Gulf of Mexico, their numbers are estimated to be at least 67,000. The populations found in the western North Atlantic and along Japanese coasts are estimated about 35,000.