The clicks are emitted from the melon of the dolphin in a narrow beam. The process of echolocation begins when dolphins emit very short sonar pulses called clicks, which are typically less than 50-70 millionth of a second long.
Such a capability is unparalleled in the annals of human sonar development. They have been observed digging as deep as 18 inches into the sand to secure a prey. Researchers, documenting the behavior of Atlantic bottlenose dolphins foraging for buried prey along the banks of Grand Bahama Island, have found that these dolphins, while swimming close to the bottom searching for prey, typically move their heads in a scanning motion, either swinging their snout back and forth or moving their heads in a circular motion as they emit sonar sounds. By using their sonar ability, dolphins are able to detect and recognize prey that have burrowed up to 1 ½ feet into sandy ocean or river bottoms – a talent that has stirred the imagination (and envy) of designers of manmade sonar. As a result, dolphins are especially good in finding and identifying prey in shallow and noisy coastal waters containing rocks and other objects. This ideal evolutionary adaptation has contributed to the success of cetacean hunting and feeding and their survival as a species overall. Synonymous with the term "sonar" (sound navigation and ranging) and used interchangeably, dolphin echolocation is considered to be the most advanced sonar capability, unrivaled by any sonar system on Earth, man-made or natural. With sound traveling better in water than electromagnetic, thermal, chemical, or light signals, it was advantageous for dolphins to evolve echolocation, a capability in which acoustic energy is used, in a sense, to see underwater. It is a process in which an organism probes its environment by emitting sounds and listening to echoes as the sounds bounce off objects in the environment. Millions of years ago, toothed whales developed echolocation, a sensory faculty that enabled them to survive in often murky and dark aquatic environments. (Dolphin Discovery: Bottlenose Dolphin Training and Interaction Sea World, 1999.) Movements of air in the trachea and nasal sacs probably produce sounds. Studies suggest that a tissue complex in the nasal region is most likely the site of all sound production. Technological advances in bio-acoustic research enable scientists to better explore the nasal region. Early studies suggested that "whistles" were generated in the larynx while "clicks" were produced in the nasal sac region. Bottlenose dolphins can produce clicks and whistles at the same time.Īs with all toothed whales, a dolphin’s larynx does not possess vocal cords, but researchers have theorized that at least some sound production originates from the larynx. Under these conditions, sight is of little use. Higher frequency clicks (40 to 150 kHz) are primarily used in echolocation.ĭolphins rely heavily on sound production and reception to navigate, communicate, and hunt in dark or murky waters. The lower frequency vocalizations (0.25 to 50 kHz) are likely used in social communication. Bottlenose dolphins produce sounds ranging from 0.25 to 150kHz. Sounds vary in volume, wavelength, frequency and pattern. They make these sounds at any time and at considerable depths.
Besides whistles, dolphins produce clicks and sounds that resemble moans, trills, grunts and squeaks.
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