Common Name: Long-Snouted Spinner Dolphin
Size comparison against an average human
Spinner Dolphin range.
General Description: The Spinner Dolphin (or the Long-beaked Porpoise) is a particularly slender dolphin with a long, thin beak, and flippers which are large and pointed. Its head slopes gently towards the snout. There is however, a well-defined crease at the junction of the melon and the beak. The dorsal fin is sickle-shaped and becomes more erect with age.
The back is dark, and the belly white, with a band of intermediate pale grey separating the two. There is individual variation, and like the Maharashtra specimens some may be uniformly dark grey in colour. Still others may be grey with a white belly. Most have a dark stripe from the eye to the flipper, and dark lips and beak tip.
Size: Adults, around 2 m long. They weigh about 75 kg, but two specimens caught off Maharashtra weighed 128 and 148 kg. Calves at birth, 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.
Spinner Dolphins will often bow-ride. They are found in small to very large groups.
The usual social unit is a large school of thirty to several hundred dolphins of all ages and sexes.Sometimes they mix with schools of other dolphins.
Like Spotted Dolphins Stenella attenuata, Spinner Dolphins are frequently found in association with tuna. Fishermen in the Pacific herd the dolphins, along with the tuna, and catch them together. The dolphins are not always successfully released and many die.
Spinner Dolphins produce a range of click sounds, pulse bursts and squeals.
Found In: The Spinner Dolphin’s distribution is primarily in pelagic zones, though it will wander into shelf waters. It feeds on small fish and squid.
Records from India:This is a species caught frequently by fisheries. Spinner Dolphins are reported to form more than 44 percent of the dolphin catches on the west coast of India.
|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,
|1993 [?]||Two animals entangled in gillnets at the Calicut coast.||Lal Mohan, 1995|
There are records including sightings and catches of the species from Sri Lanka, the Maldives, Djibouti, Somalia, the Gulf of Oman, Gulf of Aden and the Red Sea.
World 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.
|Spinner Dolphin||Upright or forward-leaning fin||
|Common Dolphin||Backward-leaning fin||
There is also a possibility of confusion with the Spotted Dolphin and the Bridled Dolphin which often school with Spinner Dolphins, but the Spinner Dolphin’s dark-tipped beak helps in distinguishing it from these species which have light-tipped beaks.
Diagnostic Features: At sea, Upright or forward-leaning fin, grey back and dark-tipped beak.
Stranded Specimens:Spinner Dolphins have 45 to 65 or more sharply pointed teeth in each row. This is the largest number of teeth found in any cetacean.