Spinner
Dolphins of Hawaii |
Family
Genus
Species
Delphinidae
Stenna
Longirostris |
|
| Habitat: Hawaiian Islands, mostly an open water dolphin,
but comes to the islands to rest in the shallow water bays. with sandy bottoms making
sharks easily visible.Can be seen often in pods up to 1000, or sub pods of a few hundred.
Very animated and wildly acrobatic, repeatedly jumping and spinning high in the air on
their tails and turning somersaults several feet out of the water. |
| Description: Long slim snout, dark at tip, dorsal fin is
triangular in shape, and dark gray in color. Dorsal fins are usually bordered on
edges with darker gray or black. They are erect and triangular in shape; those belonging
to older males seem to be tilted slightly more forward with age. Generally there are
three shades of gray, sometimes some tan, darkest near the dorsal fin. They are white from
bottom of snout to anus.. Males reach lengths between 6 to 7 feet and 200 pounds; an
anal hump on its underbelly near the tail helps distinguish sex. |
| Food source: Small fish and squid are easy targets since
it is common for Spinners to dive down 200 feet |
| Survival of the species: The
Spinner Dolphin is one of the hardest hit populations of wild dolphins by the fishing
industry, senselessly killed and thrown overboard as incidental take. Unfortunately
its natural habit of traveling with yellow fin tuna causes countless dolphins to be caught
and drowned in tuna nets every day. For the last 25 years, tremendous pressure from
animal rights and other concerned groups have possibly helped the Spinners begin a slow
recovery in the Pacific, but effectively policing the open ocean for illegal nets is a
huge and dangerous endeavor.
 |
| Authors Note: After seven years of being accepted
into the family pods of Spinner dolphins, I can describe them as being very animated,
trusting and very intelligent. They are the most playful animals, even the adults
love a game. Unfortunately there are many pieces of garbage that humans carelessly
throw into the ocean, these become dangerous toys for the dolphins. The plastic bags
are their favorite. They enjoy playing wildly with them, swimming quickly with a bag
over a dorsal or pectoral fin, passing it to a buddy who is swimming toward them.
Many times we have played the plastic bag game, they drop it for me and want me to go get
it, wave it around and then drop if for them. Many times if there are no toys they will
just encircle or "buzz:" you then look you right in the eye. I always feel
like they are using their powerful sonar to check what I have eaten. They send
sonar waves out of the tops of their head (called melon). These waves bounce off of
whatever they hit and come back into the lower jaw of the dolphin. This gives them
a holographic picture of what is ahead and how far it is away. |
Spinner Dolphins don't seem to mind being very close together.
Perhaps this is a protective behavior, with the calves in the center of the group. |
 Spinner
Dolphins are excellent parents. In fact the entire pod pays close attention to the
safe up-bringing of offspring. Baby dolphins are born tail first so that even during
the most complicated births there is little possibility of drowning due to lack of air.
They weigh about 20 pounds, measure approximately 30 inches, and have long folds of extra
skin from the back of their head to tail. As they begin to eat and grow, this fold
stretches out making it easier for them to enlarge quickly. Upon completing the birthing
process, mothers and aunties are quick to help steady their bodies, gently lifting
them to the surface for their first breath. Soon after birth, mother dolphins tuck the
calf closely under their pectoral fins. This causes the water resistance to flow
over the calf instead of hitting them squarely, depleting their energy and slowing them
down. This position makes it possible for a newborn to keep up with the pod that at
full speed can travel up to 20 knots in search of food. Spinner dolphin mothers have
mammary glands which are hidden beneath slits on their under-belly. To nurse her
calf she merely rolls slightly to the side to expose the slit. The calf does not
have a tongue to facilitate sucking, so at feeding time, using it's rostrum (nose) it
nuzzles its mother at the mammary slits which causes milk rich in fat to squirt in a
stream into the baby's mouth. It is generally not long until newborns
take on the jovial dolphin life and try to propel their bodies out of the water and spin
as their family members do. Many times the babies unite to play jumping and tagging
games. This playtime is constantly overseen by mature adults who surround them in
several layers. |
| Dolphins come to the shallow bays to sleep after a night of feeding.
A few scouts are on the outside perimeters of the pod, standing guard while the
rest of the animals rest and sleep. Dolphins sleep with one eye open so that they
are able to discern shadows of predators on the white sandy floor of the bays.
During this sleeping session they are physically and vocally quiet leaving the sonar
communication for the sentries guarding against Cookie Cutter Sharks, Tiger Sharks, Orcas
or large Barracudas.
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