Other Common Name: Long-beaked Dolphin
General Description: The Rough-toothed Dolphin (also called the Long-beaked Dolphin) is a slender dolphin. Its forehead and the sides of the head slope smoothly on to a long and slender beak, making the entire body in front of the flippers appear very long and nearly conical. There is no prominent melon and no crease between the beak and forehead, unlike many other dolphins. The flippers are moderately long. The dorsal fin is relatively tall and sickle-shaped.
Rough-toothed Dolphins are variable in coloration, but are generally dark grey to purplish black above. This colour forms a narrow cape or band of varying width along the back and tail stock. These dolphins are white or sometimes pink below. The body has many light-coloured blotches. The lips and often the lower jaw may be white or flecked with white. The eyes are large and bulging.
Size: Rough-toothed Dolphins attain a length of about 2.4 m. They weigh about 150 kg.
Appearance At Sea: Schools of several hundreds of Rough-toothed Dolphins have been reported, but little is known of the habits of this species. They sometimes school with tuna. Captive specimens have proved themselves to be very creative in inventing tricks.
Small groups of these dolphins have been noted skimming – swimming quickly for long periods with the snout near the surface, with the dorsal fin exposed continuously.
Found In: Rough-toothed Dolphins are to be found mainly at and beyond the edges of the continental shelves in deep water. Rough-toothed Dolphins feed on octopus, squid and fish.
Records from India: Jerdon mentions Delphinus maculiventer as a species described by Owen from Elliot’s collections on the East Coast. Finn states that the Spot-bellied Dolphin Steno maculiventer is found on the ‘Madras coast’. They probably refer to the Rough-toothed Dolphin. The species is reported from the Nicobar Islands by Blanford. More recently, it is reported to be caught in gill nets in India, but no specific details are available.
The species is known to have stranded in Pakistan. Small numbers are brought to Sri Lankan fish markets, harpooned or caught in gill nets. Rough-toothed Dolphins are said to occur in the Gulf of Aden, and have been tentatively identified in waters near the Seychelles.
World Distribution: The species is widely distributed, occurring in tropical and warm temperate waters of all oceans. It is believed to prefer waters with surface temperatures greater than 25°C.
Could Be Confused With: Due to the shape of the fin and marks on the body there is a possibility of confusion with Bottlenose Dolphins Tursiops truncatus and Spotted Dolphins Stenella plagiodon. The following characteristics can be used to tell them apart:
Species : Rough-toothed Dolphin
Beak : Long conical beak, continuous with forehead
Markings : Few large and irregular markings
Species : Spotted Dolphin
Beak : Long beak, sharply set of from head by transverse line
Markings : Many small regular spots
Species : Bottlenose Dolphin
Beak : Stubby beak, sharply set of from head by transverse line
Markings : No spots
Diagnostic Features: At sea, relatively tall dorsal fin, white tip and white sides on a narrow pointed beak. At close quarters the narrowness of the head is apparent, which accentuates the eye sockets giving the dolphin a goggle-eyed appearance.
Stranded Specimens: The number of teeth in each row (or side of each jaw) is 20 to 27. Unlike the smooth, conical teeth of other dolphins, the crown of these teeth have fine wrinkles, giving the animal its common name.