Dolphins and Whales Use Sounds to Identify Obstacles in the Ocean
Why are sounds in the ocean important? Dolphins and toothed whales rely heavily on sound production and reception to navigate, communicate, hunt, and avoid predators in dark or limited vision waters.
Echolocation in Dolphins and Toothed Whales
Echolocation refers to an ability that dolphins, toothed whales and most bats possess, that enables them to locate and discriminate objects by projecting high-frequency sound waves and receiving and interpreting the echoes as the sound waves reflect off objects. Dolphins and toothed whales will also use echolocation to identify, locate, and hunt their prey. However, baleen whales like the blue whale is not found to have the ability of echolocating. They hunt by using filter feeding instead.
Other Sounds Made by Dolphins
In general, dolphins make two kinds of sounds, “whistles” and “clicks”. Clicks are used to sense their surroundings through echolocation, while they use whistles to communicate with other members of their species and very likely, with other species too. It is also thought that each dolphin has a unique whistle called a ‘signature whistle’, which is used to identify an individual. Signature whistles are so distinct that scientists can identify individual dolphins by looking at their whistle shapes on a sonogram. They use these unique whistles to communicate, identity, location and, potentially, emotional state. Dolphins have been observed using signature whistles to cooperate with one another, address other individuals, facilitate mother-calf reunions and, possibly, to broadcast affiliation with other individuals. For example, a mother dolphin may whistle to her newborn for days, apparently to imprint a signature whistle upon her baby that will enable it to recognize her.
Navigation Using Echolocation
Echolocation works similarly to ultrasound. It gives a dolphin the capacity to explore their environment 3-dimensionally and aids in navigation and hunting in low light and low visibility environments. In front of the dolphin's blowhole, in the area we call our forehead is their melon. The melon serves as the lens, through which sound is focused during echolocation. Sound waves or clicks are created in dolphins’ nasal sacs and focused through their melons at various frequencies, allowing them to "see" with sound. The sound waves travel through their melons and into the water and bounce off of objects of interest. The sound waves then travel back to the dolphins and are received by their lower jaw as an echo. The sound waves travel from the jaw to the inner ear, to the nerves connected directly to the brain, where they translate the sound into an image. Echolocation is so efficient that bottlenose dolphins are capable of distinguishing an object the size of a ping-pong ball from a football field away.
