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(Lesson, 1828) - Rough-toothed dolphin

Distinctive Characteristics

The rough-toothed dolphin is relatively robust, with a conical head and no demarcation between the melon and the snout. It has a somewhat reptilean appearance. This species has large flippers (seemingly oversized for the animal) that are set far back on the side, and a prominent falcate dorsal fin.

The body is dark grey, with a prominent narrow dorsal cape that dips slightly down onto the side below the dorsal fin. The belly, lips, and much of the lower jaw are white, often with a pinkish cast. White scratches and spots, apparently mostly caused by bites of cookie-cutter sharks and probably other rough-toothed dolphins, often cover much of the body.

The 20 to 27 teeth in each row have subtle, but detectable, vertical wrinkles or ridges. These ridges give rise to the species' English common name.

Can be confused with

Rough-toothed dolphins are generally easy to identify when seen at close range; however, they may be mistaken for bottlenose dolphins if seen at a distance. The narrow cape and cone-shaped head are the best clues for identifying rough-toothed dolphins.

Size

Adults are up to about 2.8 m long. They are known to reach weights of up to 150 kg. Length at birth is unknown.

Geographical Distribution

The rough-toothed dolphin is a tropical to subtropical species, which inhabits deep oceanic waters, rarely ranging north of 40°N or south of 35°S.

Biology and Behaviour

Rough-toothed dolphins have been seen most commonly in groups of 10 to 20, although herds of over 100 have been reported. They are often lethargic and individuals bowride occasionally. They often move at high speed with the chin and head above the surface, in a distinctive skimming behaviour described as “surfing.” In the eastern tropical Pacific, they tend to associate with floating objects and sometimes with other cetaceans.

Rough-toothed dolphins feed on cephalopods and fish, including large fish such as mahi mahi (also called dorado or dolphinfish).

Exploitation

Rough-toothed dolphins are sometimes taken incidentally in purse seines in the eastern tropical Pacific, and in small numbers in directed fisheries in Japan, the Lesser Antilles, and Sri Lanka. A few have been captured live for public display.

IUCN Status

Insufficiently known.

Rough-toothed dolphin (Steno bredanensis)