Hawaiian Name: Nai’a
Scientific Name: Stenella longirostris
Weight: 100 – 165 lbs (0.045 – 0.075 tons)
Length: 4.25 – 7 ft (1.3 – 2.1 m)
Diet: Mid-water fish, squid and shrimp
Range: Tropical and subtropical saltwater world ocean
Conservation Status: Lower risk
Spinner dolphins are slightly smaller and a bit more mellow than their more famous cousins, the bottlenose dolphins. They can be distinguished by their elongated snouts, or rostrums, along with triangular dorsal fins. Sometimes, a dark line connects their eye to their fins.
Spinners are also known for their beautiful tri-coloration. Three stripes line their bodies, with dark grey on top, medium-grey in the middle and light bellies.
Spinner Dolphins in Hawaii
Spinner dolphins were first described in Hawaii by John Gray in 1828. The dolphins have habitats in the Eastern Pacific and even Thailand, but they are most commonly encountered in the waters of Hawaii. Some native Hawaiians refer to spinner dolphins, or “Nai’a”, as their “Aumakua”, or spiritual guardians.
Spinner dolphins in Oahu spend their days resting and socializing in the bays on the Western coast of the island. Because they are voluntary breathers, they never fully sleep and keep one half of their brain awake and alert so that they may breathe. Oahu’s sandy shallows also provide refuge from the dolphins’ biggest predator: sharks.
At night, spinner dolphins head out to deeper waters further off Oahu shores in order to hunt lantern fish, shrimp and squid.
Spinner dolphins travel in schools, or pods – some up to hundreds of individuals strong. As they rest during the day, they stay tightly grouped together. But as some begin to get ready for the night’s hunting, they begin to leap and spin.
This behavior is the species’ namesake. Scientists aren’t sure why spinner dolphins spin. Some believe it is to communicate, while others think it may be a way to rid their skin of parasites. Others still believe it might be simply for the fun of it!