Order: Cetacea
Suborder: Odontoceti
Superfamily: Delphinoidea
Family: Delphinidae
Subfamily: Delphininae
Genus & Species: Tursiops truncatus
APPEARANCE
Bottlenose dolphins are one of the most familiar of all the dolphin species.
Their back is black with a white belly. The head is bulbous and the beak is
well-defined. The forehead protrudes out farther in males than in females.
The flippers are of moderate size and taper to a point, and the dorsal fin
stands erect with a hooked top. They have no sweat glands - heat is lost
through the flippers.
The bottlenose dolphin is well suited for life in the water. 25-40 valves are
found in the bronchial tubes of the lungs. These valves control the pressure
in the lungs when the animal dives. As the dolphin dives deeper and deeper,
the pulse slows down. This allows more oxygen to go to the brain and heart
instead of the non-vital organs.
Bottlenose dolphins have partially stereoscopic vision and a poor sense of
smell. They communicate with high-pitched whistles and clicks and can
"see" underwater by means of echolocation.
Bottlenose dolphins grow to lengths of 11-13 ft and weigh between 330-440
lbs. Males are larger than females. 18-26 pairs of teeth are found on each
jaw. They have a life span of 50 years.
HABITAT
Bottlenose dolphins are found in the coastal Atlantic from Maine to
Florida. They are also located in the North Pacific, the Red Sea, the
Indo-Pacific region, and the Mediterranean Sea. They like coastal waters
but will swim away from shore.
FOOD
Bottlenose dolphins feed mainly on fish, including mullet, anchovies,
herring, cod, menhaden, capelin and salmon. They also feed on shrimp,
squid, and cuttlefish, spitting out the cuttlebone and feeding only on the
soft parts. They cooperate with fish hunting by driving the fish into a dense
mass and forcing them to the surface. They emit loud sounds to confuse
their prey. They hunt during the day, but will become nocturnal hunters if
food is scarce. In captivity they eat 22 lbs of fish each day.
BREEDING
Sexual maturity is reached at about 8 years of age, with no particular
mating season. Most births occur during the summer after a gestation
period of 11-12 months. One calf is born tailfirst and is pushed to the
surface by the mother to take its first breathe. Other cows protect the
mother and calf from sharks attracted by the blood released during birth.
Nursing takes place for 16 months. The females give birth every 2-3 years.
ENEMIES
Sharks and killer whales are the main enemies. Many are taken from the
wild by humans and placed in sea aquariums. Thousands of dolphins die
each year in fishing nets.
From 1986-1987 and 1992-1993, a study was done on the bottlenose
dolphins of the Sado estuary. Of those studied, 85% of the long-term
residents had skin disorders, and 40% of these had the skin disorders for
over 6 years. The cause is unknown, but is thought to have been caused by
overworked immune systems that usually fight the disease. Stress, habitat
degradation or pollution are thought to have caused the failure of the
immune systems.
SWIMMING
Bottlenose dolphins are very acrobatic, jumping over 30 ft in the air, doing
back flips, jumping through hoops. In the wild they are found in large pods
of both males and females of varying ages. They have no leader but rely on
a pecking order based on size. They assist injured members by placing one
dolphin on each side and pushing it to the surface every few minutes to
breathe. They associate with a wide variety of animals including humpback
whales, sea turtles and humans. Most are quite tame in the wild and will
chase ships.
Bottlenose dolphins can dive to depths of 70 ft, can eat at depths of 6 ft,
and can stay submerged for 15 minutes. Females lie on the surface to sleep,
with the blowhole exposed to the air. Males sleep just beneath the surface
and rise by reflex to breathe every few minutes.
Bottlenose dolphins are extremely intelligent and have been used by the
military in test maneuvers and have been reported to search for mines in the
Persian Gulf.
RELATIVES
There are at least three subspecies of the bottlenose dolphin, Tursiops
truncatus truncatus, T. t. aduncus, and T. t. gilli. They are in the same
subfamily as the common dolphin.
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