Bottlenose Dolphin - Taxonomy

Taxonomy

Scientists were long aware that Tursiops dolphins might consist of more than one species. Molecular genetics allowed much greater insight into this previously intractable problem. The consensus is there are two species, although a third distinct species was described in 2011:

• The common bottlenose dolphin (T. truncatus) is found in most tropical to temperate oceans; its color is grey, with the shade of grey varying among populations; it can be bluish-grey, brownish-grey, or even nearly black, and is often darker on the back from the rostrum to behind the dorsal fin.
• The Indo-Pacific bottlenose dolphin (T. aduncus) lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa; the back is dark-grey and the belly is lighter grey or nearly white with grey spots.
• The Burrunan dolphin (T. australis), found in the Port Phillip and Gippsland Lakes areas of Victoria, Australia, was described in September 2011 after research showed it was distinct from T. truncatus and T. aduncus.

The following are sometimes recognized as subspecies of T. truncatus:

• The Pacific bottlenose dolphin (T. gillii or T. t. gillii) lives in the Pacific, and has a black line from the eye to the forehead.
• The Black Sea bottlenose dolphin (T. truncatus ponticus) lives in the Black Sea.

The two ecotypes of the common bottlenose dolphin within the western North Atlantic are represented by the shallower water or coastal ecotype and the more offshore ecotype. Their ranges overlap, but they have been shown to be genetically distinct. They are not currently described, however, as separate species or subspecies. In general, genetic variation between populations is significant, even among nearby populations. As a result of this genetic variation, other distinct species currently considered to be populations of common bottlenose dolphin are possible.

Old scientific data do not distinguish between the two species, making it useless for determining structural differences between them. The IUCN lists both species as data deficient on their Red List of endangered species because of this issue.

Some recent genetic evidence suggests the Indo-Pacific bottlenose belongs in the genus Stenella, since it is more like the Atlantic spotted dolphin (Stenella frontalis) than the common bottlenose.

Dolphins belong to the suborder Odontocetae, which groups all toothed whale species, the largest of which is the sperm whale. The sister branch of Odontocetae includes all baleen-producing species (Mysticetae), the largest of which is the blue whale.