Photo by Kit Hartigan
Spinner Dolphin (Stenella longirostris)
Suborder: Odonticeti Family: Delphinidae
Common in Hawaiian waters.
Other known names:
Longsnout, Long-beaked dolphin, Rollover
General description and habits:
There are a number of different varieties of spinner dolphins, each with slightly different body shapes, colors and sizes. They all have long, slender beaks and tall upright dorsal fins. They have a small notch in their flukes. Most of them have three areas of color, with a dark top through to a light belly. The eastern Pacific variety is mainly dark gray with a creamy white area on the belly and a dark stripe from the eye to the flipper. The white belly form has three very distinct color patches with the underside being almost completely white. The Hawaiian form has three distinct colors, but is darker than the white belly form. They all have long, pointed flippers and gently sloping foreheads with a crease where it joins the beak. The dorsal fin shape varies between different populations. It leans forward in the eastern Pacific form, is more triangular in the white belly and is slightly curved in the Hawaiian. There is also a Costa Rican form living in the eastern Pacific and a "dwarf" form in the Gulf of Thailand. Newborn spinner dolphins are 70-85cm long. Adults can be anywhere between 1.3 - 2.1 meters long. Animals from the eastern Pacific population tend to be the largest and those from the Gulf of Thailand are the smallest. Adult spinner dolphins weigh between 45 and 75kg. Spinner dolphins are extremely acrobatic and are famous for leaping out of the water and spinning in mid-air. They are the only species of dolphin known to perform this aerial spin. They throw themselves up to 3m (9ft 9in) into the air and twist their bodies, spinning round longitudinally. I have seen video of an animal performing 9 complete revolutions in a single leap. They will also breach in the more normal manner. The spinners in the Eastern Pacific are quite shy, but in other areas they will approach boats and bow-ride for half an hour or so. They live in large groups and are sometimes seen with pantropical spotted dolphins, yellowfin tuna and seabirds.
Identity Keys to use in the field:
Streamlined body, Long, slender beak, Long flippers with a sharply pointed tip, Black stripe from eye to flipper, Dark upper-side, Lighter under-side, Tall dorsal fin, Fast active swimmer, Highly acrobatic, Curious around boats, Often bow-rides, Frequently seen in very large groups.
Fish, Krill and/or other crustaceans, Squid, Octopus
As a species, the spinner dolphin is found in the tropical and subtropical waters of the Atlantic, Pacific and Indian Oceans. The Costa Rican form is found in a 150km (95miles) wide band of water off western Central America. The eastern Pacific form ranges from the tip of Baja California, Mexico, south to the equator. In the Atlantic, spinners are usually spotted out to sea, though they come close to the shore off the southeastern coast of the USA. The Hawaiian form comes inshore during the day to rest and goes out to sea to feed during the night. Spinner dolphins can also be seen off the coast of Japan and in the Gulf of Thailand.
Hunting/Whaling, Entanglement in fishing nets
Due to their acrobatic talents, spinner dolphins were among the first dolphins caught to perform in aquariums. They do not survive for very long in captivity.