WHALE SENSES – ECHOLOCATION
Echolocation is a fascinating ability that is only found in very few animal species known to mankind. These include bats, dolphins and some whale species. In the case of whales, echolocation is an important means of finding their way, tracking and seizing prey, and perceiving threats in the water around them. Because the ocean depths are murky and dark, whales are not readily able to use sight to give them an accurate idea of what is around them. Therefore, the hunters of this species require an additional sense to aid them. There are more than 60 known whale species, the toothed whales, that use echolocation. In addition to cetaceans, some bats and dolphins also make use of this incredible adaptation.
Echolocation, as its name implies, works on an echo basis. High-pitched sounds (some of which are perceived by us as clicks) are emitted by the animal in the direction in which the head is pointing. These sound waves travel through the water until they hit an object (whether moving or stationery). They bounce off the object and echo back towards the whale. The animal receives the echoed impulse and then interprets it.
The sound emitted is generated by air passing from the bony nares (or nostrils) through the phonic lips (a structure that has a similar function to the nasal cavities in human beings). The sound is then reflected by the cranium (which is a dense bone that is concave in shape) and an air sac that lies at the base of the cranium. The beam of sound is controlled by the melon of the whale, which is a large fatty organ on the front of the head. The melon contains fatty tissues of different densities, which act as a flexible acoustic lens.
Usually, whales will emit a number of clicks in succession, forming a click-train. Some, however, may emit clicks individually. A burst pulse refers to a click-train that exceeds 600 clicks per second!
Using the reflected feedback, the whale can determine the size, distance, shape, speed of movement, and even the texture of the object off which the sounds bounced. The echo is received using the structures that surround the lower jaw, which are made up of complex fatty tissue. These are the primary reception paths of the echo. From here, the sound is transmitted to the middle ear of the whale.
Because of the effectiveness of this technique, engineers have designed a number of submarines to make use of the same “technology” to negotiate the dark waters.
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