All About Dolphins - Page 2

Reproduction

Dolphin pairOn 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.

Continued......