SPINNER DOLPHIN (T)
Stenella longirostris Gray 1828
Other Common Names
Long-snouted dolphin, long-beaked porpoise, spinner porpoise, rollover (St. Vincent).
Description
Spinner dolphins reach a maximum length of about 7 feet (2.1 m). The body is slender. The beak varies from extremely long and slender (Fig. 123) to relatively short (Fig. 125); the beak is usually dark on top and clean white below, though there may be some white above. The tip of the snout and the lips are distinctly black, while those of both species of spotted dolphins are light. The back is dark gray to black, the sides are tan to yellowish brown, and the belly is white. Some of the larger animals appear almost all black with faint, light speckling. The dorsal fin is generally moderately falcate, but may be almost triangular in adult males. It is often a lighter gray near the middle, bordered by black or dark gray.
Natural History Notes
Spinner dolphins derive their common name from their habit of leaping clear of the water and spinning on their longitudinal axis. The reasons for this behavior are unknown. Individuals may rotate 2 times, or more, in one leap but spinning behavior is not observed as frequently in the western North Atlantic as it is in the eastern tropical Pacific.
Spinner dolphins occur in herds of up to several hundred individuals and are often seen jumping clear of the water, working the sea surface into a froth. They frequently come to the bow of a boat from considerable distances to ride in the bow wave and may ride for protracted periods.
May Be Confused With
Spinner dolphins may be confused with saddleback dolphins. Both species occur in large herds and often come to moving vessels to ride the bow wave. The two can be distinguished, however, by these differences: