Tursiops truncatus
The bottlenose dolphin is perhaps one of the most well known
cetaceans, because of its widespread use in marine parks and
research facilities. The bottlenose dolphin may be best known
as "Flipper" (as seen in the television series).
This is the dolphin most frequently seen along the shores
of the United States. This species is very flexible in its
behavior.
This is a relatively robust dolphin with a usually short and
stubby beak – hence the name "bottlenose".
The bottlenose dolphin (like the beluga) has more flexibility
in its neck than other oceanic dolphins, because 5 of the
7 neck vertebrae are not fused together as in the other oceanic
dolphins. There are 18-26 pairs of sharp, conical teeth in
each side of its jaw.
The color of the bottlenose dolphin varies considerably,
but generally this dolphin is light gray to slate gray on
the upper part of the body shading to lighter sides and pale,
pinkish gray on the belly. The belly and lower sides are sometimes
spotted.
The dorsal fin is high and falcate (curved) and located near
the middle of the back. The flukes are broad and curved with
a deep median notch. The flippers are of moderate length and
pointed.
Length is from 6-12 feet (1.9-3.8 m). These dolphins may
weigh as much as 1430 pounds (650 kg) off Great Britain, though
most are much smaller in other parts of the world. Males are
somewhat larger than females.
Feeding behaviors are diverse, ranging from coordinated efforts
to catch food, feeding in association with human fishing,
to chasing fish into mudbanks. An adult bottlenose dolphin
may consume 15-30 pounds (8-15 kg) of food each day. Bottlenose
dolphins eat a wide variety of food, including fishes, squid,
and crustaceans.
Males reach sexual maturity at about 11 years. Females reach
sexual maturity at about 5-7 years. The gestation period is
12 months. Calving can take place year-round with peaks in
some areas during spring and fall. Calves nurse for over a
year (12-18 months), and stay with their mothers for up to
three years learning how to catch fish and other important
tasks.
Bottlenose dolphins are found worldwide in temperate and tropical
waters, absent only from 45 degrees poleward in either hemisphere.
They are frequently seen in harbors, bays, lagoons, estuaries,
and river mouths. There appear to be two ecotypes: a coastal
form and an offshore form. Population density appears to be
higher nearshore. Biochemical studies now are providing more
information about the relationship within and between the
ecotypes. In some areas, dolphins have limited home ranges;
in others, they are migratory generally ranging further.
Based on a number of studies of nearshore populations, bottlenose
dolphins seem to live in relatively open societies. Mother
and calf bonds and some other associations may be strong,
but individuals may be seen from day-to-day with a variety
of different associates. Group size is often less than 20
nearshore; offshore groups of several hundred have been seen.
Much of what we know of the general biology of dolphins comes
from studies of bottlenose dolphins, both in captivity and
in the wild.
The bottlenose dolphin is protected in U.S. waters by the
Marine Mammal Protection Act. Bottlenose dolphins are still
generally plentiful in numbers, but are at or near depletion
in some areas. Both incidental and direct exploitation of
bottlenose dolphins are known to occur, generally at low to
moderate levels. The largest direct kills have traditionally
been in the Black Sea, where Russian and Turkish hunters apparently
have reduced local populations. Bottlenose dolphins are accidentally
caught in a variety of fishing gear, including gillnets, purse
seiners used to catch tuna, and shrimp trawls. These dolphins
also are occasional victims of harpoon and drive fisheries.
Live captures of bottlenose dolphins for captivity have had
effects on some local dolphin populations in the Gulf of Mexico
and southeastern United States. Bottlenose dolphins are vulnerable
to pollution, habitat alteration, and human disturbance (such
as boating). Several die-offs of bottlenose dolphins have
occurred. Retrospective analysis of tissues of dolphins that
died in 1987-1988 during a large die-off (approximately 800-1,000
dolphins) on the Atlantic U.S. coast indicates that mortality
may have been caused by a morbillivirus. This virus has been
linked to dies-offs of Gulf of Mexico bottlenose dolphins
as well. Dolphins with disease symptoms appeared to have elevated
levels of PCB’s, leading researchers to conclude that
pollutants are playing a role in these events.
Caldwell, D.K. and M. C. Caldwell. 1972. The World of the
Bottlenose Dolphin. Biological Systems, Inc., St. Augustine,
Florida.
Jefferson, T.A., S. Leatherwood, and M.A. Webber. 1993. Marine
Mammals of the World. FAO Species Identification Guide. FAO,
Rome.
Leatherwood, S. and R.R. Reeves. (editors) 1990. The Bottlenose
Dolphin. Academic Press, San Diego.
Shane, S. H. 1988. The Bottlenose Dolphin in the Wild. Hatcher
Trade Press, San Carlos, CA.
Shane, S.H., R.S. Wells, and B. Würsig. 1986. Ecology,
behavior and social organization of the bottlenose dolphin:
a review. Marine Mammal Science 2(1): 34-63.
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