Marine mammals can be difficult to identify at sea. Even under ideal conditions, an observer often gets little more than a brief view of a splash, blow, dorsal fin, head, flipper, or back, and this is often at a great distance. Rough weather, glare, fog, or other bad sighting conditions compound the problem. Even experts often must log a sighting as “unidentified” or on an easily confused pair or group of species. In all cases, this designation, accompanied by a detailed description is preferable to recording an incorrect identification.

Contact Dipani Sutaria or Pooja Gupta to get a copy of this guide
Character Matrix 1: Beaked Dolphins WITH prominent markings. All these species are about 2m long.
Species | Distinctive marks and colouration | Teeth (pairs in each jaw) |
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Long-beaked common dolphin , Delphinus delphis |
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Small, pointed (47– 67) |
Indian Ocean common dolphin Delphinus delphis tropicalis |
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54-67 teeth in upper jaw side |
Spinner dolphin , Stenella longirostris |
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Sharply pointed (45– 65) Please check the groove between the two lower jaws; |
Striped dolphin, Stenella coeruloealba |
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Small and sharp (45 –50) |
Pan-tropical spotted dolphin, Stenella attenuata |
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Small (40) |
Character Matrix 2: Beaked Dolphins WITHOUT prominent markings.
Species | Length (m) | Prominent Features | Colour |
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Rough-toothed dolphin , Steno bredanensis |
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Indo-Pacific humpback dolphin , Sousa chinensis |
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Indian Ocean humpback dolphin , Sousa plumbea |
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Bottlenose dolphin , Tursiops truncatus |
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Indo-Pacific bottlenose dolphin , Tursiops aduncus |
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Fraser’s dolphin , Lagenodelphis hosei |
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Character Matrix 3: Irrawaddy Dolphin, Risso’s Dolphin & Finless Porpoise
Species | Length (m) | Colour | Dorsal fin | Flippers | Teeth (pairs) | Neck crease |
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Irrawaddy dolphin , Orcaella brevirostris |
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Large, with curved leading edge |
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Present |
Risso’s dolphin , Grampus griseus |
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Long & falcate, with pointed tips |
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Absent |
Finless porpoise , Neophocaena phocaenoides |
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Long, tapering to a blunt tip |
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Slight depression behind the blowhole |
Character Matrix 4: The Blackfish
Species | Length (m) | Colour | Dorsal fin | Flippers | Teeth (pairs) |
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Pygmy killer whale , Feresa attenuata |
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Curved along leading edge, rounded at tip |
High pointed |
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False killer whale Pseudorca crassidens |
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Broad hump on leading edge |
Upright, slightly rounded at tip, located at mid-back |
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Melon-Headed whale , Peponocephala electra |
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Long,generally pointed | Tall, distinctly back-curved |
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Short-finned pilot whale Globicephala macrorhynchos |
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Falcate, up to one-sixth of body length |
Low rounded |
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Character Matrix 5: The Small Sperm Whales
Species | Length (m) | Head | Dorsal fin | Group Size | Teeth (pairs) |
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Pygmy sperm whale , Kogia breviceps |
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Small, located behind mid-point of back |
Small groups of fewer than five individuals |
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Dwarf sperm whale Kogia sima |
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Tall, broad-based, with a concave trailing edge, located farther forward than in the Pygmy Sperm Whale |
Up to 10 individuals |
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Character Matrix 6:The Beaked Whales ( note position & shape of blowhole, flipper shape, head shape, fin position and teeth)
Species | Length (m) | Colour | Teeth | Position of Teeth in Lower Jaw(from tip) |
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Ginkgo-toothed beaked whale Mesoplodon ginkgodens |
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One-fourth |
Blainville’s beaked whale Mesoplodon densirostris |
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One-third |
Cuvier’s beaked whale Ziphius cavirostris |
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At tip |
Longman’s beaked whale Indopacetus pacificus |
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At tip |
Deraniyagala’s beaked whale Mesoplodon hotaula |
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Middle |
Character Matrix 7:The Rorquals
Species | Length (m) | Baleen | Throat grooves | Flipper to total length ratio | Distance of fin from tail relative to total length | Ridges on top of head | Flippers | Colour |
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Minke whale Balaenoptera acutorostrata |
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Yellowish white, including frayed edge | About 50 | 1:8 | One-third | 1 | Blue-grey with white patch above, white below |
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Bryde’s whale Balaenoptera edeni |
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Front plates whitish, back plates blackish, long stiff bristles | 40-50 | 1:10-1:12 | Greater than one-third | 3 | Dark bluish grey above, grey below |
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Blue whale Balaenoptera musculus |
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Jet black including frayed edge | 55-100 | 1:7 | One-fourth | 1 | Slate-blue above |
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Humpback whale Megaptera novaengliae |
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Dark gray baleen plates with coarse gray bristles hanging | 14-35 | 1:3 | Greater than one-third | 1 | Black above, white below |
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