Dolphin
Feature - The Dusky Dolphin
Author:
Carma Haley Shoemaker
Published on: April 14, 2000
First
described in 1828 by J.E. Gray, the Dusky dolphin was
given the name of “Delphinus obscurus.” Latin
in origin, Delphinus obscurus roughly translated to “dark
or dusky.” Yet another species named for its appearance,
the Dusky dolphin was born.
Often
mistaken for an Hourglass dolphin, the Dusky shares common
characteristics of the Hourglass in relation to body size,
shape, and areas of habitat. However, the unique markings
of the hourglass are not present in the Dusky.
Dusky
dolphins can reach lengths up to 7 feet, and can weigh
100 to 200 pounds. Newborn Dusky dolphins are approximately
22 to 30 inches in length and weigh from 7 to 11 pounds,
the same weight as some human babies, at birth.
Dusky dolphins have very complex color patterns. The throat
chest and belly of the Dusky are all a vivid white, while
the back is a dark black color. The edges of the dorsal
fin, the snout, the tail and the flanks are also dark
black while the rest of these areas are various colors
of gray.
Dusky
dolphins travel in pods that usually contain between 5
to 15 animals. However, it is not uncommon to see the
Dusky in pods with as many members as 1,000. Being a highly
social animal, these dolphins may also integrate other
species pods, such as the Common Dolphin, the Hourglass
Dolphin, as well as Southern Right Whale. Inshore Coastal
water of New Zealand, South Africa and South America are
the most common habitat for the Dusky dolphin, but depending
upon the pod, Dusky can travel as far east as the United
States.
Dusky
dolphins are known for their water acrobatics. They are
often seen leaping out of the water, at times with speeds
so quick they will turn themselves head over tail. From
vast research, three specific types of “leaping
behavior” have been noted. Bernd and Melany Wursig,
who have studied the Dusky dolphin for years, were the
first to identify these specific behaviors and theorize
that each was used for a specific purpose.
The
three leaping behaviors include the “head first
reentry,” the “noisy leaps,” and the
“performance leaps.” It is believed that the
“head first reentry,” in which the Dusky dolphin
leaps out of the water and dives back in with out much
noise or splash, is used to aid the Dusky in searching
for feeding seabirds which would indicate a food source.
The “noisy leaps” have been seen mainly when
a school of anchovies, or other small fish, have been
found and the leaps are a way of alerting the other members
of the pod. The final behavior, the performance leaps,
are believed to be more of a show or a time of play. These
performance leaps include various twists, turns, somersaulting
and is usually done after feeding.
The
influence of man has played a part in the Dusky’s
life just as it has thousands of other species. The fishermen
of Peru will catch and kill approximately 700 to 1,000
Dusky dolphins a year to sell the meat at local food markets.
Accidental deaths of Dusky dolphins are too common in
New Zealand, as the Dusky dolphin frequently is hunting
the same types of fish the fishermen hope to catch in
their nets.
Dusky
dolphins have been taken into captivity after found with
various injuries or after accidental beaching. However,
the Dusky dolphin has yet to thrive or reproduce in captivity.
The
Dusky dolphin is a playful, colorful, species that is
full of the life of the ocean. Just another example of
nature at it’s best….
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Reprinted from http://www.suite101.com/article.cfm/4895/37302
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