Rough-toothed Dolphin, Steno bredanensis
Rough-toothed Dolphin, Steno bredanensis. Underwater photograph taken in coastal waters off Kona, Hawaii, September 2015. Photography and identification courtesy of Bob Hillis, Ivins, Utah.
The Rough-toothed Dolphin, Steno bredanensis (G. Cuvier in Lesson, 1828), is a member of the Delphinidae Family of Oceanic Dolphins that is known in Mexico as dolphin dientes rugosos. Their common name is derived from the rough striations on their teeth. They are slender in stature with a streamlined appearance. Their heads have gradually sloping foreheads from the blowhole to the slender beak and they lack the crease that separates the melon from the beak that is found in similar species. The dorsal fin is set at mid back and is tall and moderately falcate. They have large flippers. Dorsally they are dark gray with the cape narrowing anteriorly to the dorsal fin, the sides are medium gray and they become white ventrally. There are often lighter and darker spots and blotches on the sides and belly, giving the Dolphin a mottled appearance. The top and sides are often marked with scratch marks and round scars, from fights with other Rough-toothed Dolphins, Cookie-cutter Sharks and squids. The head has dark gray beak, the mouth has white lips and the eyes are slightly bulging.
Rough-toothed Dolphins are usually found in the open ocean, far from shore in groups of 10 to 20 individuals and also in association with other dolphins and whales. They are found from the surface to depths up to 400 m (1,310 feet). They reach a maximum length of 2.8 m (9 feet 2 inches) and 160 kg (352 lbs) in weight. The feed in relatively shallow waters on fish, including large fish such as 5 kg (11 lb) Dorado), and squid and are known to follow False Killer Whales, to pick up food scrapes. In captivity, these dolphins always behead and eviscerate fish before eating them.
Rough-toothed Dolphins are found worldwide in tropical and warmer temperate seas. They are found along both the Atlantic and the Pacific coastlines of Mexico, including the Sea of Cortez. They have life spans of up to 32 years.
From a conservation perspective the Rough-toothed Dolphin is currently considered to be of Least Concern with stable, widely distributed populations.
Synonyms include Delphinus bredanensis, Delphinorhychus bredanensis, Delphinus perspicillatus, Delphinus chamissonis, Delphinus compressus, Delphinus frontatus, Delphinus oxyrhynchus, Delphinus planiceps, Delphinus reinwardtii, Delphinus rostratus, Steno frontatus, and Steno perspicillatus.