Order: Cetacea
Suborder: Odontoceti
Superfamily: Delphinoidea
Family: Delphinidae
Subfamily: Delphininae
Genus & Species: Lagenorhynchus obscurus
APPEARANCE
The dusky dolphin is a small dolphin with a compact body. The beak is
short and rounded and is not well-defined. The dorsal fin is slightly hooked
and more vertical than in other species. The flukes are small. The body is
dark grey on the back and white on the belly. A large grey patch runs from
the base of the beak or the eye to the anal region. A grey "flame" is located
on each flank pointing tailward. The tail flukes, pectoral fins and beak are
dark grey. A small dark patch encircles each eye. Dusky dolphins grow to
lengths of 4 ft 6 in - 5 ft 9 in. The longest one ever recorded was 6 ft 6 in.
They weigh 250-285 lbs, although the heaviest one recorded weighed 305
lbs. 48-72 teeth are found on each jaw.
Dusky dolphins are extremely intelligent and are considered to be one of the
most acrobatic of the dolphins, sometimes doing backflips in the air after
meals.
HABITAT
Dusky dolphins are found in the Southern Hemisphere, especially around
New Zealand, South America (especially Argentina and Peru) and Africa.
They prefer inshore coastal waters and make great tourist attractions in
many places.
FOOD
Dusky dolphins feed on fish, primarily anchovies and lantern fish, and
squid. While feeding they slam their bodies against the water to make a
loud noise that somehow herds the fish and notifies other dolphins of food.
BREEDING
Sexual maturity is reached in the females when they reach lengths of 5 ft 4
in. The gestation period is 9-11 months with one calf being born from June
to August. The calves weigh 11 lbs at birth with an average length of 2 ft.
Females give birth every 2-3 years.
ENEMIES
Sharks and killer whales are the main predators of the dusky dolphin. Peru
fishermen capture 700 dusky dolphins each year to be sold as food. In New
Zealand some are accidentally ensnared in fishing nets.
SWIMMING
Dusky dolphins are fast swimmers, easily following ships going 16 knots.
They surface every 4- 5 minutes to breathe and dive to depths of 500 ft.
They swim in pods of 6-15, although groups of anywhere from 20-1000 have
been seen. They sometimes swim with common dolphins and southern right
whales and will associate with petrels, jaegers, and terns.
RELATIVES
The dusky dolphin is in the same genus as the white-beaked dolphin,
Atlantic white-sided dolphin, Pacific white-sided dolphin, hourglass dolphin
and Peale's dolphin.
RESOURCES CITED
1. www.neteng.bc.ca/~tursi/dolphins/cetacea.htm
2. www.geocities.com/Rainforest/Canopy/1599/dusky.htm
3. members.xoom.com/catrust/dusky.htm
4. pc65.frontier.osrhe.edu/hs/thnkqst/20981/tqpg4.htm
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