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Friday, February 01, 2008

Dolphin quick facts

Author: SeaWorldAdventurePa rk.info

Dolphins are marine mammals found in all the world's oceans, relatives to whales and porpoises. River dolphins live in freshwater rivers and lakes. They are intelligent and playful creatures and friendly to humans.

Dolphins have a sleek body shape, which helps them to be good swimmers. They have long snouts, a row of sharp teeth, and a blowhole for breathing on top of the head. They feed on fish, squid, and other small marine life.

Dolphins are social animals, and usually live and hunt in groups. They communicate with each other with sounds such as whistles, screeches, and clicks. Dolphins are often friendly to humans, riding on waves produced by boats, aiding lost swimmers, and adapting to life in captivity performing tricks and jumps.

There are at least 40 different species of dolphins. The one most commonly used in amusement parks and performances is bottlenose dolphin, which has a 'built-in' smile formed by the curvature of its mouth. The killer whale, or orca, is the largest member of dolphin family.

Physical features

Dolphins have a sleek body shape, so as to offer the least resistance for swimming. The two flippers located underside help the dolphin steer its course. The bones in these flippers resemble human hand! The tail with flukes provides the main swimming force.

As mammals, dolphins have to breathe air. They do so through a single blowhole on the top of the head. It has a muscular plug to keep water out of the lungs while diving. The head has a long snout. Dolphins have a long row of conical teeth that are used for catching and tearing prey - not for chewing.

Different dolphin species vary a lot in size. The smallest one, tucuxi dolphin, is about 4 feet (1.2m) long and weighs about 110 pounds (50kg), whereas the enormous killer whales is over 30 feet (9-10m) long and weighs 12,000 pounds (5 500 kg).

You've seen the gray ones, but dolphins can also be black or brown, and can have patterns of white or light colors.

In the middle of their back, many dolphins have what is called a dorsal fin. It helps them to keep their balance. Furthermore, each dolphin's dorsal fin is shaped differently from the others. It's like an identification mark. In some ocean dolphins, the dorsal fin is hooked-shape instead of like a triangle. The male killer whales have very tall dorsal fins whereas in river dolphins it scarcely forms a ridge on the back.

Besides using eyes, dolphins can find their way by making clicking sounds, and listening to the sounds that echo or bounce back to them from their surroundings. This is called echolocation.

Under their skin, dolphins have a layer of fat called blubber. It insulates the dolphin so it can keep warm even in cold water. The colder the water is where the dolphin lives, the thicker the layer of blubber.

Behavior

Dolphins are social animals that live in schools of varying size; some only have 2-5 dolphins while enormous schools of 1,000 or more have been found as well. A typical school of bottlenose dolphins might be 10-20 individuals.

For food, dolphins hunt fish, squid and other invertebrates; killer whales also feed on other marine mammals, sea turtles, and birds. Dolphins often hunt together, trying to catch schools of fish. They can use echolocation to find prey in deep, dark waters.

Dolphins make whistles, clicks, and screeching sounds to communicate with each other, and for echolocation. In many species each individual dolphin makes a unique 'signature whistle'. Human-made underwater sounds, such as used with sonar images, can interfere with dolphins' communication, and even injure tissues used for hearing and air intake.

Dolphins also help each other in various ways. If a dolphin is sick and can't raise to the surface to get air, another one supports it at the surface so it can breathe. Or, a dolphin may stay near an injured or sick one as a companion. Dolphins also defend an injured one against a threat such as a boat.

Male and female dolphin take part in courtship, which involves playing, caressing, and 'songs'. Gestation lasts about a year, and then a single calf is born. Calving usually occurs once every two years. Dolphin mother produces very high-fat milk for her young. The calf is weaned aroud 6 months to two years.

Certain dolphin species live quite long, 50 years or more, while the bottlenose dolphin and common dolphin typically live around 20-25 years.

Dolphin Classification:

Class Mammalia

Order Cetacea

Suborder Odontoceti

Names:

male: bull

female: cow

young: calf

group: pod

Sources:

Microsoft ® Encarta ® Reference Library 2005

Encyclopedia Britannica

About the author:

SeaWorldAdventurePa rk.info is a website filled with photos from SeaWorld, Orlando, Florida, plus information, reviews, and a po ll .