Tursiops aduncus

Common Name: Indo-pacific bottlenose dolphin

Tursiops spp: The Tursiops genus has been split into two, T. truncatus and T. aduncus. The taxonomy of this genus is still not thoroughly clear, however due to considerable geographic variations, additional species may be recognised in the future.

Bottlenose Dolphin
Bottlenose Dolphint

 

Bottlenose Dolphin breaching in the bow wave of a boat

Bottlenose dolphin size.svg

Size comparison against an average human

Conservation Status
bottlenose Status iucn3.1 blank.svg

Data Deficient (IUCN 3.1)

Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Mammalia
Subclass Eutheria
Order Cetacea
Suborder Odontoceti
Family Delphinidae
Genus Tursiops
Species T. truncatus
Binomial Name
Tursiops truncatus
(Montagu, 1828)

bottlenose Cetacea range map

Bottlenose Dolphin range.

Source: Wikipedia

General Description: Indo-Pacific bottlenose dolphins have a large, robust head and trunk, a gently curving melon with a sharp crease before the beak. The beak is moderately long and slender compared to the common bottlenose dolphin. The dorsal fin is tall and triangular (not as falcate as common bottlenose dolphins) and larger than in common bottlenose dolphins. The flippers are long and pointy at tips.
The colouration is variable, but usually shades of light grey on the flanks, grading to white or pink on the belly. Belly is marked with speckles or black spots in adults. Usually a dark ring is present around the eye.

Size: Calves: Length of animals at birth is approximately 85cm – 112cm. Adults: Adult dolphins are between 2.7 m, males tend to be slightly larger than the females. Maximum weight is around 230kg.

Appearance At Sea: While Tursiops is easy to identify at sea given the relatively short beak, robust body, convex melon, sharp beak crease and body colour pattern, it is not easy to separate between T. trunctus and T. aduncus. A suite of characteristics need to be checked, and good pictures is the best way to confirm.

Found In: Occur on the continental shelf in shallow coastal and around oceanic island groups.

Records from India: 

Date Details Sources
1846 Skull from Bay of Bengal, the type of Delphinus eurynome, in the British Museum (Natural History). De Silva, P.H.D.H. (1987) Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India, from the Arabian Sea and Gulf, Gulf of Aden and from the Red Sea.Journal of the Bombay Natural History Society, 84(3), 505-525.va, 1987.
1848 Delphinus perniger described by Elliot from the Bay of Bengal; stuffed skin in the Museum of the Asiatic Society, Calcutta. Jerdon, T.C.(1867) A Handbook of the Mammals of India. Indian edition, 1989, Mittal Publications, New Delhi.335 pages.;De Silva, P.H.D.H. (1987) Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India, from the Arabian Sea and Gulf, Gulf Gulf of Aden and from the Red Sea.Journal of the Bombay Natural History Society, 84(3), 505-525.va, 1987.
1866 Delphinus godama described by Owen from collections made by Sir Walter Elliot near Visakhapatnam; the skull gifted by Elliot to the British Museum (Natural History) Jerdon, T.C.(1867) A Handbook of the Mammals of India. Indian edition, 1989, Mittal Publications, New Delhi.335 pages.;De Silva, P.H.D.H. (1987) Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India, from the Arabian Sea and Gulf, Gulf Gulf of Aden and from the Red Sea.Journal of the Bombay Natural History Society, 84(3), 505-525.va, 1987.
1904 A single specimen of Tursiops gilli obtained from Travancore. Pillay, R.S.N. (1926) List of cetaceans taken in Travancore from 1902 to 1925.Journal of the Bombay Natural History Society, 31(3), 815-817., 1926.
01-10-1904 Specimen caught off Trivandrum may be this species. Lydekker, R. (1905) On dolphins from Travancore.Journal of the Bombay Natural History Society, 16(4), 730-736.
01-02-1908 Two specimens of Tursiops dawsoni purchased measuring 2.7 and 2.8 m (9 feet and 9 feet 4 inches) by the Trivandrum museum; one skeleton in the British Museum (Natural History) Pillay, R.S.N. (1926) List of cetaceans taken in Travancore from 1902 to 1925.Journal of the Bombay Natural History Society, 31(3), 815-817.;De Silva, P.H.D.H. (1987) Cetaceans (whales, dolphins and porpoises) recorded off Sri Lanka, India.
21-12-1978 One male caught off Calicut. James, P.S.B.R. & Lal Mohan, R.S. (1987) The Marine Mammals of India.Marine Fisheries Information Service Technical & Extension Series, 71, 1-13. & Lal Mohan, 1987.

Could Be Confused With: In areas where they overlap in distribution, common bottlenose dolphins can be confused with Indo-Pacific bottlenose dolphins (Tursiops aduncus), rough toothed dolphins (Steno bredanensis), and spotted dolphins (Stenella spp.). They can be distinguished based on the following characteristics:

Species Size Build Beak Markings
Common Bottlenose Dolphin Average size 3m, often more Bulky

Short beak, clearly marked off from melon

No spots

Indo-Pacific bottlenose dolphin

Average size,  2.7 m

Robust, slender

compared to 

Tursiops truncatus

Moderately long beak, less convex

 melon than T.truncatus

Flecks or black spots

on the belly

Spotted Dolphin Around 2.4 m Slender Longish beak, well demarcated from melon Many regular spots

Rough-toothed dolphin

Seldom more than 2.4m

 Slender

Long, thin beak not clearly demarcated

from melon

Irregular blotches on belly

Diagnostic Features at sea:Can be distinguished from common bottlenose dolphins based on overall size, shape of body, shape of head and beak, spots on the belly, shape of dorsal fin and colouration.

Stranded specimens: Stranded individuals can best be identified based on total length, shape of fin, length of beak and teeth count between 21-29 pairs in each jaw.