Introduction
Dolphins are fast-swimming aquatic mammal, belonging to the order Cetacea, including whales and porpoises. Dolphins are very powerful swimmers and are equally found in seas throughout the world, are dolphins mammals. Some Dolphines inhabit freshwater rivers and lakes.The characterizinf unique factors of most dolphins are; long snouts with rows of sharp teeth, and rounded foreheads with a nostril on top, known as the blowhole.
Physical description
Dolphins range in size approximately from the small tucuxi dolphin, which grows to about 1.2 m (4 ft) in length and weighs about 50 kg (110 lb), to the killer whale, which can grow to 9.8 m (32 ft) in length and weigh over 5,500 kg (12,100 lb). In most dolphins males grow slightly larger than females. Dolphins are commonly black, brown, or gray in color and are often marked with patterns of white or light colors. The dolphin body is streamlined and adapted to a life underwater. Two finlike flippers near the front of the body help stabilize and steer the animal as it swims. The flippers contain bones that are similar in arrangement to the bones in the human hand. Horizontal tail flukes, composed of tough connective tissue, are dolphins mammals move up and down to propel the animal through the water
Behavior
Studies of dolphins in captivity have taught scientists much about dolphin physiology and social behavior. In addition, since the late 1980s advances in the use of satellite tracking systems have broadened the opportunities for scientists to observe how dolphins behave in their natural habitat.
Some studies of captive dolphins from the 1960s suggested that the mental abilities of dolphins might rival those of primates, including humans. But scientists now agree that these early studies may have been overly optimistic, are dolphins mammals. Scientists have yet to develop intelligence tests for dolphins that can be comparable to intelligence tests used for humans, but more recent studies indicate that dolphins probably match or slightly exceed the intelligence of dogs.
Types of Dolphins
Scientists recognize at least 40 species of dolphins, and although there are different ways to classify these species, most authorities categorize dolphins into two groups: ocean dolphins and river dolphins. Ocean dolphins make up the family Delphinidae, which is the largest cetacean family, consisting of about 36 species. Members of this family include the bottlenose dolphin, the species that scientists have studied most extensively; and the spinner dolphin, named for its habit of leaping vertically out of the water and twirling. The largest member of this family is the killer whale, named for its voracious appetite for fish, seabirds, are dolphins mammals sea turtles, and some aquatic mammals. These and most other ocean dolphins are found in open seas, but several freshwater species inhabit rivers and lakes in Asia and South America. The small, graceful tucuxi dolphin, for example, has been sighted more than 2,000 km (more than 1,240 mi) up the Amazon River.