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The Spinners of Hawaii
A Day in the Life of a Hawaiian Spinner Dolphin (pdf)
Spinner Dolphins in Hawaii; Biology, Abundance, Distribution (pdf)
Spinner Dolphin Potential Threats (pdf)
During the night, a deep sea community of marine life that spends daylight hours at depths of up to 3,000 feet, migrates upward and towards the shore. As these riches come within reach, spinner dolphins begin to hunt. Small subgroups spread out, swimming across, the sea. Using echolocation, the spinners scan the darkness. and using their whistles, they call members of the school back together to unite in defense. The collective defenses of the dolphin school protect each member from harm. By dawn, the spinners regroup. Well-fed, they move again towards the shelter of the islands.
The spinners have chosen bays with sandy bottoms — against which they can visually detect the approach of a predator. Sharks are a concern to dolphins of all kinds.
Mornings, they meet, and play together. Youngsters practice their lessons. Much affectionate touching and rubbing occurs at this time...one swimming underneath another while scissoring their pectoral fins back and forth. Others "hold hands" Some caress each other with their tail flukes...
Over the next two hours — as the dolphins enter a resting state — the school tightens up, synchronizes its breathing, and begins to prepare for sleep. The subgroups of the school move closer together. Coalitions of adult and sub-adult males move alongside groups of females and small calves. The warm, clear waters entice them to rest, the dolphins draw closer. Together they rise and fall from the surface until each spinner slips into sleep, safe inside a cocoon of friends.
This period of rest does not resemble sleep as we know it. The dolphins are not actually unconscious as only parts of their brains are asleep at any one time. The spinners have turned their sonar off, without sound, they rely heavily on sight. And this is why clear water and white-sand bays are so important to them.
During the period of rest, the dolphins group very tightly together, combining their eyes into a "super-organ" upon which all of the animals rely.
As the spinners awaken from their rest, some members begin
to spin, urging the school to move out of the bay. But other
members are reluctant to leave just yet, and slowly nudge
the school back into the bay, back into resting behavior.
For the next hour or more, the spinners perform this zigzag
pattern. Going airborne, moving out, then quieting down and
drifting back toward shore. Finally they head offshore for
another night of hunting.
So called for their high, spinning leaps, spinner dolphins
are known as playful, eager bow-riders. But in the eastern
tropical Pacific, where tuna fishermen have killed millions
of spinners since 1959, the dolphins no longer approach ships.
In Hawaii, spinners (Nai`a) not only approach ships,
but could be termed oceanic "Ambassadors of Aloha." There
is belief that Native Hawaiians deemed dolphins to be
a oceanic tribe with equal rights as human villagers. To this day, they
work cooperatively with them to fish.
Probably since the islands have formed, Hawaiian spinner
dolphins have come into nearshore daytime habitats. WDF has traced it back at least 800 years on Oahu.
Hawaiian Spinner Dolphins (Nai`a)
are shaped and colored somewhat differently from other spinner
dolphins.
Threats to Hawaiian Spinner Dolphins
Stenella longirostris
Hawaiian Name: Nai'a
Size: 1.7 to 2.2 meters, 75 kilograms; males slightly larger than females
Teeth: 45 to 65 sharp-pointed teeth
Food: Fish — small deep-ocean species like lantern
fish, shrimp and squid
Habitat: Mainly offshore, nearshore in certain island
chains
Range: Tropical, subtropical and warm temperate world ocean
Status: Population unknown, but common in most parts of its range; substantial declines have occurred in the eastern tropical Pacific
Parts above condensed from the film narration "Ocean Acrobats: The World of the Spinner Dolphin." |
