Essay/Term paper: Dolphins

Essay, term paper, research paper:  Science Reports

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.

The End!!!