Animals also use a form of sonar called echolocation. Echolocation has several uses much like human's uses of sonar, including:
- communication
- hunting
- defense (to avoid danger)
- aids in navigation
Echolocation is primarily used by toothed whales such as dolphins, porpoises and killer whales. It is considered to be one of the most advanced sensory skills in nature.
These whales are able to emit sounds by "clicking". In dolphins these clicks are produced by the sphincter muscles within the blowhole, and are produced at frequencies of 0.25 to 200 kHz. The high pitched clicks are then focused into a beam by the whale. This beam spreads out from the whale through the sea water and bounces off any object in its path. The sound waves are then reflected back as echoes usually to the animal. The dolphins pick up these echoes by the fat organ of their lower jaw called the mandibular fat body and by the bulbous forehead. The brain then deciphers this information and tells the dolphin the object's texture, density, internal structure, speed and the direction it is moving.
Animals have similar problems of absorption, spreading, reflection, refraction, and scattering as humans do, but they also have the problem of humans! The military has been causing constant underwater noise which disrupts and inhibits the ability for underwater animals to communicate and listen for the returning echoes.
Humans take advantage of the dolphin's ability. The navy has formed four operational Marine Mammal Systems (MMS). They use both bottlenose dolphins and sea lions who are specially trained to perform certain tasks. These tasks include:
1. to hunt for mines and neutralize them,
2. pingered (acoustic sound used to locate metal objects) object recover,
3. Swimmer detection and defense for harbours, anchorages and individual ships, and
4. for mine detection and location of buried mines.
