Dolphins
Dolphins are mammals closely related to whales
and porpoises. Dolphins have a powerful and streamlined
body. They are found in all seas and oceans. Dolphins can be
told apart from porpoises by their nose, which is beaklike, and
also their conical teeth. Porpoises have a flatter nose, sharper
teeth, and a more solid body.
There are 32 known species of dolphins. The bottle-
nosed dolphin is often the species used in aquatic shows. The
common dolphin inspired many Mediterranean folk lores. Both
of the dolphins above appear in open waters, usually around
cruise ships. They like to show off around the boat.
There are also freshwater dolphins that live in rivers
of Asia and South America. The Buffeo dolphin has been
spotted up to 1250 miles up he Amazon River. The buffeo is the
smallest of all dolphins averaging about 4 feet. The bottlenose
is closer to 10 feet. The killer whale, which is also considered a
dolphin, can grow to be 30 feet long. The pilot whale is also
considered a dolphin.
Dolphins were once hunted by commercial boats
for the small amount of oil that can be extracted from their
body. This oil is used to lubricate small parts in watches.
Cheaper oils have been found, so dolphins are not hunted for
this reason anymore. Dolphins can be caught in tuna nets by
accident. Since dolphins have to breath at the surface they
drown in tuna nets. It is estimated that 4.8 million dolphins were
killed in tuna nets from 1959 to 1972. Under pressure from
animal rights activists tuna consumers will not accept tuna from
canners that do not protect dolphins. Animal rights activists
also believe that dolphins shouldn't be in captivity for use in
aquatic shows.
Dolphins eat a lot of food in a day, usually about
one third of their body weight. A dolphin's diet consists of
mostly fish and squid. Dolphins can swim very fast, so they are
able to easily catch their food. The dolphin has 200 to 250
sharp teeth. Dolphins follow schools of fish in groups. The
Pacific white-sided species is estimated to travel in groups with
tens of thousands of members, while on the other hand
bottlenose dolphins travel in groups that contain only a few
members.
Dolphin, like whales, breathe through a blowhole in
the top of their head. While traveling dolphins break the surface
once every two minutes. When dolphins exhale water is
sometimes thrown from the blowhole. After exhaling the
dolphins inhale and disappear into the ocean. A dolphins lungs
are adapted to resist the physical problems that are caused by
quick changes in pressure. With this adaptation dolphins can
dive up to 1000 feet with no problem.
A dolphins tail is, like all other aquatic mammals,
moves in an up and down motion. Dolphins double fluke their
tale to move forward. Their flippers are used to stabilize the
dolphin as they swim.
A dolphin is very streamlined and can average a
speed of up to 19 miles per hour with bursts of over 25 miles
per hour. At these speeds, dolphins can cover great distances
in a day.
The best studied species of dolphins are the bottle-
nosed. Bottle-nosed dolphins reach sexual maturity at the ages
of 5 to 12 years in females and 9 to 13 years in males. Dolphins
mate in the spring. The dolphins carry the baby, which is called
a calf, for 11 to 12 months. At this time a single calf is born,
coming out tail first. Calves can swim and breathe minutes after
birth. A calf will nurse for up to 18 months. Calves can keep up
with their mother by remaining close and taking advantage of
it's mothers aerodynamic swimming.
Dolphins almost always emit either clicking sounds
or whistles. The clicks are short pulses of about 300 sounds
per second, which come from a mechanism located just below
a dolphin's blowhole. These clicks are used to locate objects
around a dolphin. When the sound of a click bounces off of an
object and back to the dolphin, the dolphin uses that
information to move without hitting anything. This clicking
system is similar to a bats radar system. The whistles are
single-toned squeals that come from deep in the larynx. These
whistles are used to communicate alarm, sexual excitement,
and perhaps other emotions.
Because of dolphins ability to learn and perform
complex tricks in captivity, their continuous communication
with one another, and their ability, with training, to understand a
few human words, some scientists think that dolphins could
learn a language to communicate with humans.
Most experts agree that even though a dolphins
problem-solving ability is close to that of a primate, no evidence
has been shown that dolphins communication skills even come
close to the complexity of a true language.
All dolphins belong to the order of Cetacea. The
bottle-nosed dolphin is scientifically classified as Tursiops
truncatus. The common dolphin is classified as Delphinus
delphis, and the buffeo dolphin is classified as Sotalia fluviatilis.
The killer whale is classified as Orcinus orca and the white-
sided dolphin is classified as Lagenorhynchus obliquidens.
The Dolphins are also a football team located in
Miami. They usually play good in the regular season, but when
playoff time rolls around the team falls apart. I do not like the
Dolphins and I wish that they would withdraw from the National
Football League.
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