Hawaiian Spinner Dolphins

Hawaiian Spinner Dolphins

by | Dec 1, 2019

CLASS: Mammalia
ORDER: Cetacea
SUBORDER: Odontoceti
FAMILY: Delphinidae
GENUS:  Stenella
SPECIES: longirostris

SUBSPECIES: Gray’s Spinner Dolphin

VAREITY: Hawaiian Spinner Dolphin

Spinner Dolphins are the undisputed gymnast of the sea!  Their ability to perform tight aerial twists and high leaping flips is the envy of any Olympian.  Spinner dolphins have four sub-species: the Eastern Spinner Dolphin, the Central American Spinner Dolphin, Gray’s Spinner Dolphin, and the Dwarf Spinner Dolphin.  Gray’s Spinner Dolphins are the most common form of spinner dolphin found around the world.  In Hawai’i we get enjoy a variety of the Gray’s spinner Dolphin affectionately named the Hawaiian Spinner Dolphin year-round.

Physical Description

The Hawaiian Spinner Dolphin or Nai’a are a smaller oceanic dolphin, the adult females are 4.6 to 6.7 feet long and adult males are 5.2 to 6.8 feet long.  Adults weigh between 130 and 180 lbs.  They have a beautiful tripartite color pattern, which is dark gray on top, lighter gray on the sides and a white belly.  Females and young Spinners have slightly curved dorsal fin, whereas the males have a triangular dorsal fin.  Unique features on the dolphin’s dorsal fin such as nicks, notches and shapes are used to identify individual dolphin.

 Distribution

Parts of the Hawaiian Islands have their own population of Hawaiian Spinner Dolphin.  The Island of Hawai’i or “Big Island” has the largest and most accurate count of Hawaiian Spinner Dolphins with 600 individuals.  Kaua’i and Ni’ihau have an estimate of about 600 Hawaiian Spinner Dolphins.  Oahu, Maui, Lana’i, Moloka’I and Kaho’olawe combined have an estimate of 300 individuals.  Populations of Hawaiian Spinner Dolphins can also be found in the northwest atolls from Pearl and Hermes Reef all the wat to the Midway and Kure Atoll.

These populations live within 10 nautical miles of the shore and stay near their residential island.  It is believed that these Hawaiian Spinner Dolphins don’t cross the channels between islands.  Researchers are able to determine through genetic testing that there is no breeding between each island’s population.  Spinner Dolphins found outside of 10 nautical miles are part of the pelagic stock.

Habitat

Most Hawaiian Spinner Dolphins live along the coast shore during the day and move out to the deep ocean at night to hunt.  During the day they seek calm, shallow, and clear bays to socialize, rest, and care for their young.  Hawaiian Spinner Dolphins prefer areas with sandy bottoms which gives the best view of incoming predators.  However, there are stocks of pelagic Spinner Dolphins which are found in deep water, 10 miles from the shore of the Hawaiian Islands.

Reproduction

Hawaiian Spinner Dolphins mate year-round, a female’s gestations is 11 months and they will give birth once every three years.  Babies will nurse for 1 to 2 years.  Babies nurse from their mother’s mammary gland which is located near her fluke. The mother’s milk is very rich, containing more than 40% fat.  The calf spends up to six years with it’s mother bonding and learning.  Once the calf reaches sexual maturity at around seven years it begins to venture out on its own.

Lifespan/Longevity

These Nai’a live to be about 20 years of age.  The oldest living to be about 25 years.  Many of the Dolphin we swim with have known us their wholes lives.

Communication

Hawaiian Spinner Dolphins communicate through a variety of clicks and whistles.  We can often hear them in the water and on the boat.  Additionally, they use echolocation to hunt for their food a night.  It is also assumed that they use their echolocation to detect pregnant women’s fetuses.  This technique is similar to a doctor administering a sonogram.  The Nai’a often take special interest with pregnant swimmers, often admitting an audible buzzing sound around the women’s belly.

Food Habits

At night they travel to deeper water to hunt for food. The consume mostly squid and other pelagic fish.  Their prey can range from 650 to 1,000 feet deep.  They cooperate with other types of dolphins such as the Spotted Dolphin and Pacific Bottlenose Dolphin to hunt.  Different pods of Hawaiian Spinner Dolphins will join together during the hunt as well.  This is called the fission-fusion social pattern where smaller schools join together to form a larger collective group.

Swimming Etiquette

 Here at Dolphin Discoveries we have developed some tried and true ways to responsibly and ethically swim with the Hawaiian Spinner Dolphins over the last 25 years.  Our goal is have a swimming experience that is conscience of the Nai’a’s environment and provides our guest an encounter of a life time.  When in the Dolphin’s environment, we let them choose to swim with us.  We present ourselves to the dolphin without interrupting their daily routine, when we do this we are often rewarded with close interaction with them.

Here are some of the best practices when swimming with Hawaiian Spinner Dolphins:

NO SPLASHING: Sometimes splashing is used by dolphins to warn of danger. Excessive splashing will sometimes spook dolphins into thinking there’s danger ahead. No overarm swimming and keep fins in the water.  When entering the water make as little noise and splash as possible.

NO CHASING: Only predators chase wild animals, so the best way to get a dolphin to swim away and keep swimming away is to chase on it. This includes diving down on top of the dolphins as this will often spook them.  Swimming along side where the dolphin can see you is best.

BE CALM:  They can sense panic and fear.  R-E-L-A-X!  You don’t need to be right next to them to have an amazing experience, keep your distance, control your breathing, and heart rate.

NO TOUCHING:  The Nai’a may come close to you, but this doesn’t mean they want to be touched.  Keep your hands to yourself.

BE AWARE OF YOUR ENVIRONMENT:  The Dolphin may approach you from different angles, keeping looking around.  Often swimmers get tunnel vision and not notice a Dolphin right next to them.

Swimming with Hawaiian Spinner Dolphins is a memory of a lifetime.  Having a dolphin interact with you in the wild is one of the most rewarding experiences you’ll have ever have.  To ensure that wild dolphin swimming continues, it is up to us to be respectful of their habitats, bring awareness to proper etiquette, and most importantly remember to let the dolphins chose to swim with us.

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