Identification Guide

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. Many species appear similar to another, especially in the brief glimpses typical at sea. Animals of some poorly known groups (most notably beaked whales and Southern Hemisphere fur seals) are especially difficult to identify to species, even with a good look at a live animal or an “in hand” specimen. For all these reasons, 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.

The species identification sheets in this guide are designed to be the primary tool used in identifying marine mammals observed at sea. A dichotomous key to marine mammals observed at sea would be virtually worthless, because of the lack of useful cues for most sightings and the variability of marine mammal behaviour. Marine mammal identification at sea is something that must be learned through doing. Experienced marine mammal observers, like birders, often will be able to make an identification based on a composite of characteristic features including behaviour, and personal knowledge of the local marine mammal fauna. This ability will come with experience, guided by working with seasoned observers and the use of a proper field 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)
Long-beaked common dolphin
Delphinus delphis
  • Dark brown to black above, including appendages
  • White below
  • Yellow front flank patches
  • Rear flanks and tail stock light grey
Small, pointed (47– 67)
Indian Ocean common dolphin
Delphinus delphis tropicalis
  • slightly longer than the common dolphin 

54-67 teeth in upper jaw side
52-64 teeth in lower jaw side

Spinner dolphin
Stenella longirostris
  • Some grey throughout, others grey with a white belly
  • Yet others with a three-part colour pattern — grey cape,
    light grey sides, white belly

Sharply pointed (45– 65)

Please check the groove between the two lower jaws;
do the jower jaws merge at the tip or do they not?

Striped dolphin
Stenella coeruloealba
  • Dark stripe from behind eye to anus
  • Belly white
  • Sides grey
  • Dark stripe from eye to flipper
Small and sharp (45 –50)
Pan-tropical spotted dolphin
Stenella attenuata
  • Stenella attenuata Dark grey cape from top of head to
    halfway down the animal
  • Lighter grey below; white spots, becoming bigger & more
    numerous with age

Small (40)

Character Matrix 2: Beaked Dolphins WITHOUT prominent markings.
Species Length (m) Prominent Features Colour
Rough-toothed dolphin
Steno bredanensis
  • Max.2.4
  • Large eyes
  • Head conical, sloping evenly
    towards the tip of the
  • No prominent melon
  • Body dark grey with a narrow dorsal
  • Belly, lips & lower jaw white
Indo-Pacific humpback dolphin
Sousa chinensis
  • Newborn 1.0
  • Max. Male 3.2
  • Female 2.5
  • Dorsal fin sits on distinct hump or
    ridge midway along the back
  • Hump under the fin is not prominent
  • Melon is not as prominent as in S. plumbea
  • Adult animals of the region very pale,
    almost white, or overall light gray and mottled
  • Young lighter grey
  • 32-38 teeth in upperjaw side; 29-38 in lower jaw side 
Indian Ocean humpback dolphin
Sousa plumbea
  •  Max female: 2.6m
  •  Max male: 2.8m 
  • Hump under the fin is very prominent
  • Melon is very prominent 
  • Adults are usually brownish gray with very little mottling of white or pink
  • 33-39 teeth in upper jaw side; 31-37 in lower jaw side
Bottlenose dolphin
Tursiops truncatus
  • Newborn 1.0
  • Max. Male 4.0
  • Female 3.6
  • Well-formed melon separated from
    stocky snout by a marked crease
  • Dorsal fin is tall and falcate
  • teeth count is 18-27 in any one side of jaw
  • Belly off-white
  • Sides of the head & body light grey,
    gradually becoming deeper until it forms
    a dark bluish-grey cape on the back
Indo-Pacific bottlenose dolphin
Tursiops aduncus
  •  newborn is 85cm-112cm
  • Adult 2.7m
  • melon less convex than in common botlenose dolphin
  • dorsal fin is larger and less falcate than common bottlenose dolphin
  • teeth count 21-29 in one side of each jaw
  • belly has spots
  •  dark ring around the eye
  • lighter in colour than common bottlenose dolphins
Fraser’s dolphin
Lagenodelphis hosei
  • Newborn 1.0
  • Max. 2.6
  • Beak short but well-defined
  • Flippers and dorsal fin short
    & pointed
  • Dark brownish-grey on the sides
  • Pink or white on the belly
  • Bold dark grey striping on the flippers
    & on the face and along the sides,
    giving the face a masked effect
Character Matrix 3: Irrawaddy Dolphin, Risso’s Dolphin & Finless Porpoise
Species Length (m) Colour Dorsal fin Flippers Teeth (pairs) Neck crease
Irrawaddy dolphin
Orcaella brevirostris
  • Newborn 1.0
  • Max.Male 2.7
  • Female 2.3
  • Pale grey
  • Darker above,
    paler below
  • Small, lying
    at midback
Large, with
leading edge
  • Peglike
  • Upper jaw: 17-20
    Lower jaw: 15-18
Risso’s dolphin
Grampus griseus
  • Newborn 1.2
  • Max. Male 3.8
  • Female 3.3
  • Grey body covered
    extensively with
    white scarring
    & blotching
  • Some animals,
    especially older
    ones, appear
    almost white
  • An anchor-shaped
    white chest patch
  • Tall, slender &
  • Generally a
    darker shade of
    grey than the
    rest of the body
  • Located at
Long & falcate,
with pointed
  • Peglike
  • Upper jaw: No teeth
    Lower jaw: Upto 7
  • Teeth often badly
    worn in older
    individuals & some
    missing entirely
Finless porpoise
  • Newborn 0.55
  • Max. 1.9
  • Males slightly
  • Uniform grey, with
    often a bluish tinge
  • Ventral surface
  • Whitish zones on
    throat & sometimes
    on upper lip
  • Absent
  • Skin on the
    midback dark &
    covered with
Long, tapering to
a blunt tip
  • Spade shaped
  • 13-22 in each jaw
behind the
Character Matrix 4: The Blackfish
Species Length (m) Colour Dorsal fin Flippers Teeth (pairs)
Pygmy killer whale
Feresa attenuata
  • Newborn 0.8
  • Max. 2.5
  • Grey to blue-black
  • Darker cape from top of
    head to dorsal fin
  • Lips & tip of lower jaw
Curved along leading
edge, rounded at tip
High pointed
  • Upper jaw: 8-11 &
    Lower jaw: 11-13
False killer whale
Pseudorca crassidens
  • Newborn 1.6
  • Max. Male 5.9
  • Female 5.1
  • Black
  • Lighter areas on head
    & chest
Broad hump on leading
Upright, slightly
rounded at tip,
located at mid-back
  • Conical
  • 7 to 12 in each jaw
Melon-Headed whale
Peponocephala electra
  • Newborn 1.0
  • Max. 2.7
  • Black on back and sides,
    slightly lighter on belly
  • Lips, anal and genital areas
    may appear light-grey, white
    or pink
Long,generally pointed Tall, distinctly
  • Small, sharply pointed
  • Upper jaw: 20-25 &
    Lower jaw:22-24
Short-finned pilot whale
  • Newborn 1.4
  • Max.Male 7.2
  • Female 5.1
  • Grey-black overall
  • Many animals have a lighter
    chest patch & a grey streak
    behind the eyes
Falcate, up to one-sixth
of body length
Low rounded
  • 7-9 in each jaw
Character Matrix 5: The Small Sperm Whales
Species Length (m) Head Dorsal fin Group Size Teeth (pairs)
Pygmy sperm whale
Kogia breviceps
  • Newborn 1.2
  • Max. 3.4
  • Rectangular in adults
Small, located behind
mid-point of back
Small groups of fewer
than five individuals
  • Curved, needle-like
  • Lower jaw: 10-16
Dwarf sperm whale
Kogia sima
  • Newborn 1.0
  • Max. 2.7
  • Short, blunt and
    squarish snout
  • Some irregular
    on the throat
Tall, broad-based, with a
concave trailing edge,
located farther forward
than in the Pygmy
Sperm Whale
Up to 10 individuals
  • Upper jaw: 7-12 &
    Lower jaw: 1-3 may occur
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)
Ginkgo-toothed beaked whale
Mesoplodon ginkgodens
  • Max. about 5
  • Living specimens not
  • General colour of dead
    ones “midnight black”
  • Many oval white scars
    on sides & belly
  • Ginkgo tree leaf shaped
  • 10 cm or more wide at base
Blainville’s beaked whale
Mesoplodon densirostris
  • Newborn 2.0
  • Max. 5.2
  • Male dark all over
  • Female pale (usually white)
  • Prominent oval scarring &
    scratches overall
  • Two forward projecting massive
    teeth on prominent raised arches
    on each side of lower jaw in
  • Jaw bone greatly enlarged below
Cuvier’s beaked whale
Ziphius cavirostris
  • Newborn 2.8
  • Max. 7.5
  • Variable
  • General body colour maybe
    “acorn brown, tan,light
    brown or metal blue”
  • Males grow lighter with
    age, the head & nape
    eventually change from
    grey-brown to white
  • Two conical teeth only in the male
At tip
Longman's beaked whale
Indopacetus pacificus
  • New born: 2.9m
  • Max. 9m
  • Umber brown to brownish gray with a light coloured head
  • Steep buldging forehead
  • larger dorsal fin like a dolphin fin and behind midpoint of body
  •  Body covered with circular scars
  • Oval teeth
  • One pair, hidden in the gums
At tip
Deraniyagala's beaked whale
Mesoplodon hotaula
  • Max. 4.8
  • Counter shaded - dark grey with lighter beak
  • small dorsal fin placed two thirds from beak
  • Un-notched fluke
  • No linear scars like in other beaked whales
  • Males have one pair of S shaped recurved tusks
  • Females do not have tusks
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
Minke whale
Balaenoptera acutorostrata
  • Newborn 2.7
  • Max. 10.7
Yellowish white, including frayed edge About 50 1:8 One-third 1 Blue-grey with white patch above, white below
  • Dark slate grey, paler grey or white on belly
Bryde’s whale
  • Newborn 3.6
  • Max. 14.0
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
  • Dark grey
  • Some white on throat & chin
Blue whale
Balaenoptera musculus
  • Newborn 6.4
  • Max. 28.0
Jet black including frayed edge 55-100 1:7 One-fourth 1 Slate-blue above
  • Bluish-grey
  • May be mottled & blotched
Humpback whale
Megaptera novaengliae
  • Newborn 4.3m
  • Max. 11-17m
Dark gray baleen plates with coarse gray bristles hanging 14-35 1:3 Greater than one-third 1 Black above, white below
  • Dorsal surface is black with knobbly outgrowths
  • White below
  • Fluke has a prominent notch with a serrated trailing edge
  • Fins very long with tubercles