Dolphins Essay Research Paper DolphinsDolphins are mammals - Реферат

Dolphins Essay, Research Paper

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!!!

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