Stenella longirostris

Common Name:  Spinner Dolphin

Stenella spp.: Based on recent genetic studies the genus Stenella will mostly be restructured in the near future.

 

Spinner Dolphin
Longsnout Spinner dolphin jumpingt
Longsnout Spinner dolphin size.svg

Size comparison against an average human

Conservation Status
longsnoutsnipper Status iucn3.1 blank.svg

Data Deficient (IUCN 3.1)[2]

Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Mammalia
Subclass Eutheria
Order Cetacea
Suborder Odontoceti
Family Delphinidae
Genus Stenella
Species S. longirostris
Binomial Name
Stenella longirostris
(Gray, 1828)

longsnout Cetacea range map

Spinner Dolphin range.

Source: Wikipedia

General Description: Spinner dolphins are slender with a long thin beak and pointed flippers. Head slopes gently towards the snout. Dorsal fin is falcate but highly variable in shape, and becomes more erect with age. Most individuals have a tripartite colour pattern with a dark grey back and white underbelly and the sides a paler shade of grey. Individual variation in colouration can be seen. Most individuals have a dark stripe extending from the eye to the flipper. Beak tip and lips are dark. 

spinnerSpinner dolphin in Andaman islands  @ Mahi Mankeshwar

Size: Adults, around 2 m long (males:2.35m). Males maybe larger than females, most adults weigh around 75-80 kg. Calves at birth, 75-80cm long.

Appearance At Sea: The Spinner Dolphin gets its name from its habit of leaping out of the water and spinning longitudinally. Individuals have been counted rolling over seven times before falling back into the water. They are known to bow-ride. Group sizes can range from 30 to several hundreds. They are known to sometimes associate with other dolphin species (e.g. Stenella attenuata; spotted dolphins). Spinner dolphins are frequently found in association with tuna, this can result in entanglement in purse seines.

spinner3Spinner dolphins off the south-east coast of India @ Dipani Sutaria

Found In: The Spinner Dolphin’s distribution is primarily in pelagic zones, though it will wander into shelf waters. They feed on small fish and squid.

Records from India:This is a species caught frequently by fisheries by-catch

Date Details References
Prior to 1827 Photograph of skull (illustration) from Malabar in the US National Museum files. De Silva, 1987
1976–1980 Ninety-two specimens caught in gillnets off the Calicut coast. Lal Mohan, 1985
19 September 1981 Male specimen caught in gillnet off Calicut. James & Lal Mohan, 1987
1982­–1984 A number of observations off the coasts of southern India. Alling, 1986
15 May 1982 One specimen collected at Porto Novo (11º29’N; 79º46’E) in a bottom-set gillnet. Rajaguru & Natarajan, 1985;
Kumaran & Subramanian,1993
July 1983­–December 1986 18,210 kg of this dolphin landed at Fisheries Harbour, Cochin. Jayaprakash et al., 1995
11 February 1986 One male, 1.9 m long, caught at Bombay High near the ONGC offshore base in a gillnet. Karbhari et al., 1985
5 March 1986 One male, 2.28 m long, caught off Janjira–Murud, Maharashtra in gillnet. Karbhari et al., 1985
29 August 1989 One specimen caught in a gillnet in the Gulf of Mannar. Krishna Pillai, Bose et al., 1989
28 December 1990 Nearly 300 counted at sea, south of Mangalore at 11°46’N, 10°E. Jayaprakash et al., 1995
21 August 1991 One young female entangled in gillnet off Visakhapatnam – this was only 70.5 cm long & 2.66 kg
in weight .
Seshagiri Rao & Narayana Rao,
1992
1993 [?] Two animals entangled in gillnets at the Calicut coast. Lal Mohan, 1995

Global Distribution: The species is widely distributed. It is found in all oceans, in tropical, subtropical and warm temperate regions.

Could Be Confused With:The Spinner Dolphin could be confused with the Common Dolphin Delphinus delphis which has a very similar body shape. They can be distinguished based on the following characteristics:

Species Fin Markings
Spinner Dolphin Upright or leaning forwards
  • Tripartite colour pattern
  • Dark stripe from the eye to the flipper;
  • Dark lips and beak tip
Common Dolphin Fin leaning backwards
  • Hourglass pattern of yellow on side;
  • Dark stripe from flipper to chin

Diagnostic Features: At sea, tripartite colour pattern, spinning behaviour, and dark-tipped beak.

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Stranded Specimens:Spinner Dolphins have 45 to 65 or more sharply pointed teeth in each row. This is the highest tooth-count of any cetacean species.