se then they would suffocate. Dolphins have "solved" that by letting one half of their brain sleep at a time. This has been determined by doing EEG studies on dolphins. Dolphins sleep about 8 hours a day in this fashion. REM (Rapid Eye Movement) sleep, usually associated with dreaming has been recorded only very rarely. Some scientists claim dolphins do not have REM sleep at all. Dolphins reach sexual maturity at different ages. Males become sexually mature at 10 to 12 years, while females become sexually mature at 5 to 10 years. This is similar to the human. The female initiates courtship and breeding. The gestation period is roughly 12 months. Calves are born throughout the year. A dolphin can have a calf every two years, but normally wait three. Calves are born in the water. The calf is normally 42 to 52 inches long and 44 pounds, defering between species. The mother nurses the calf for up to 18 months. The calf normally stays with its mother for three to six years, or possibly longer. Sound and communication is one of the most important aspects of the dolphin. Dolphins identify themselves with a signature whistle. A mother dolphin will whistle to her calf over and over again so the young can identify the mother. Whistles are single-toned squeals that come from deeper in the larynx then clicks. Whistles communicate alarm, sexual excitement and other emotional states. Sound varies in volume, wavelength, frequency and pattern. The frequency of sound ranges from .25 to 150 kHz. The lower frequency is used mainly for social communication and take more energy. The higher frequency is used for the echolocation system. Dolphins produce clicks that resemble moans, trills, grunts, squeaks, or creaking doors. Clicks last about 50 to 128 microseconds. Clicks pass through the melon which consists of lipids(fats). The melon then acts as an acoustic lens to focus these sound waves into beams. Sound waves travel through the...
