太平洋瓶鼻海豚 Pacific
Bottlenose Dolphins
新浪博客
Pacific Bottlenose Dolphins are warm blooded, air-breathing mammals that inhabit temperate and tropical waters throughout the world.
Thought to be one of the most intelligent and beautiful creatures in our oceans and rivers, dolphins also take on a persona that is adored worldwide. We see them jumping, playing, and even hear them laughing as they have fun in the ocean. Dolphins are some of the most highly intelligent creatures on earth. These warm-blooded mammals belong to a group of mammals called Cetaceans which also encompass all whales. Dolphins are referred to as 'toothed whales' or Odontocetes differentiated from Baleen whales which have horny plates connected to their upper jaw.
Dolphins come in many colors from the black and white Killer whale (which is actually in the dolphin family) to the False Killer whales and Pilot whales which are almost solid black. There are 67 total species of dolphins; 32 of them oceanic with River dolphins, Sperm whales, Beaked whales, Beluga, Narwhal and Porpoises rounding out the other 35 species. Porpoises are often confused with dolphins, but while dolphins have rounded interlocking teeth, porpoise teeth are squared. Pacific Bottlenose dolphins (Tursiops Truncatus) are the variety most commonly observed in and around the Pacific area.
Migration and Distribution
Bottlenose dolphins inhabit temperate and tropical waters throughout the world - from deep ocean waters to harbors, bays, lagoons, gulfs and estuaries. In general, the coastal ecotype seems to be adapted for warm, shallow waters. Its smaller body and larger flippers suggest increased maneuverability and heat dissipation. The offshore ecotype seems to be adapted for cooler, deeper waters, with a larger body that helps conserve heat and defend against predators.
Variations in water temperature, migration of food, fish and feeding habits account for the seasonal movements of some dolphins to and from certain areas. Some coastal animals stay within a limited home range (an area in which individuals or groups regularly move about during day-to-day activities). Home ranges may overlap although most dolphins undergo seasonal movements, probably as a response to variations in water temperature and food availability.
The worldwide population of Bottlenose dolphins is unknown. Specific Bottlenose dolphin populations have been approximated in a few areas, and based on those calculations the Bottlenose dolphin population worldwide is estimated to be near 125,000. Although protected by laws in many countries, Bottlenose dolphins are not endangered.
Reproduction
On the west coast of Mexico, calving generally happens in the fall months. Deliveries can be either tail or head first. 'Auntie' dolphins, either male or female may assist with the birth and are generally the only other dolphin allowed near the calf. Dolphins have a relatively close relationship with their offspring with a long period of parental care through maturation. Dolphins are birthed like most mammals via the birth canal in the female abdomen. Generally there is only a single offspring.
When a new baby dolphin is born, it immediately heads for the surface of the water with the help of its mother for its first breath. It is nursed on the surface as the mother turns on her side to allow the calf to breathe easily while nursing.
The baby will generally nurse for up to 18 months; while the milk, which is about 33% fats, helps the calf establish a thick layer of blubber for insulation. The rapid growth of the baby dolphin is related largely to the high fat, calcium and phosphorus content of the mother's milk. In zoological environs calves, can start to take a few fish at about 90 to 120 days. Mother-calf bonds are long-lasting with calves staying with their mother 3 to 6 years or more. An average bottlenose dolphin calf is a little over 3 feet at birth and can grow to eight or nine feet long after the gestation period that ranges from 9.5 to 17 months.
Where am I?
Although the dolphins have large eyes located near the corners of their mouths with acute vision both in and out of the water, a great deal of their location of food is done through echolocation. The term echolocation refers to an ability that dolphins possess that enables them essentially to 'see' with their ears by listening for echoes. Dolphins echo locate by producing clicking sounds and then receiving and interpreting the resulting echo. Dolphins produce directional clicks in trains. Each click lasts far less than a second.
The click trains pass through the melon (the rounded region of a dolphin's forehead), which is made up mostly of fatty tissue. The melon acts as an acoustical lens to focus these sound waves into a beam, which is projected forward into water in front of the animal. Sound waves travel through water at a speed of about one mile per second which is 4.5 times faster than sound traveling through air. These sound waves bounce off objects in the water and return to the dolphin in the form of an echo.
High frequency sounds don't travel far in water. Because of their longer wavelength and greater energy, low frequency sounds travel farther. Echolocation is most effective at about 5 to 200 m for objects about 2 to 6 inches in length. The returning sound is received in the fatty portions of the lower jaw where they are then sent to the ear and onto the brain. Through this echolocation dolphins are able to determine the size, shape, direction and speed of objects in the water. Many details of this ability in dolphins have yet to be understood fully by science.
Dolphin Talk
Bottlenose dolphins identify themselves with a signature whistle. However, scientists have found no evidence of a dolphin language. Sounds are probably produced by movements of air in the trachea and nasal sacs. During some vocalizations, Bottlenose dolphins actually release air from the blowhole, but scientists believe that these bubble trails and clouds are a visual display and not necessary for producing sound.
Bottlenose dolphins produce clicks and sounds that resemble moans, trills, grunts, squeaks, and creaking doors. They also produce whistles. They make these sounds at any time and at considerable depths. The sounds vary in volume, wavelength, frequency, and pattern. A mother dolphin may whistle to her calf almost continuously for several days after giving birth. This acoustic imprinting helps the calf learn to identify its mother.
The Senses
The dolphin's senses are very highly developed, with acute hearing, eyesight and sense of touch. Like all toothed whales dolphins have a limited sense of smell. Little is known about a dolphin's sense of taste, although they do have taste buds and show strong preferences for certain types of food fishes.
Going for a Swim
Bottlenose dolphins can often be found 'surfing' on the bow of a boat.
Although Bottlenose dolphins generally do not need to dive very deep to catch their food, they regularly dive to depths of up to 150 feet. Under experimental conditions a deep trained dive was made to over 1,700 feet. They can dive for up to 8 to ten minutes and maintain a slower heartbeat while diving to slow the metabolism of oxygen.
Dolphins are quite acrobatic and can be seen doing complex and artful aerial maneuvers that awe spectators both in marine parks and in the wild. They are able to execute spins and flips that place them well out of the water during mating, demonstrations of hierarchical dominance or even just while being playful.in the water. Many details of this ability in dolphins have yet to be understood fully by science.
Our Friend the Dolphin
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