Biodiversity

Monday, May 15, 2006

ECHOLOCATION IN BATS AND WHALES

Bats and whales use high frequency sounds like sonar and radar to locate objects in the surrounding environment (echolocation) (2).

Whales use sound to sense objects especially when they are hunting. Whales make a high-pitched click sound which bounces off the object. Whale starts by producing a series of low-frequency click sounds before they can be able to produce a high-pitched sound. The frequencies pass through the “melon of the whale” (1). The click sound is focused into a ray of sounds and some of the sound bounces off and then returns to the whale. The sound waves which come back are received by the fat-filled cavities of the lower jaw-bone of the whale. The sounds are interpreted through the bone of the ear and the brain. The whales interpret the sound and determine how the object looks, how far and how far the object is (1).

Bats are active during the night so they look for food at night. Bats also use the same process as the whales when hunting (echolocation). Bats produce the sound by speeding up air from their lungs; through their vibrating vocal chords. These vibrations cause fluctuations in the speed of the air, which forms sound wave (3). The change in air pressure pushes surrounding air particles out and then pulls some of them back in. These particles then "push and pull the particles next to them, passing on the energy and pattern of the sound" (3). In this way, sound can travel long distances through the air. The pitch and tone of the sound are determined by the frequency of the air-pressure fluctuations, which is determined by the way they move their vocal chords (3).

Some bats emit the sounds through their mouth and others emit sound through their nose (3). It's not fully understood how the bat's sound production works, but scientists believe that the way the nose of a bat is structured serves to focus the noise for more accurate pin-pointing of insects and other prey. The sounds that bats realise range from 14,000 to 100,000 hertz in frequency (4). In the case of most bats, the sound that they produce is very loud. The sound travels through the air as waves, and the energy of this waves bounces off any object it comes across. A bat listens carefully to the sounds that return to it and interprets information/sounds in its brain. It determines how long it takes for a noise or sound to return to its ears. Then the bats use their brain to figure out how far away is an object, also the shape of an object (3).

The bat can also determine where the object is, how big it is and in what direction it is moving. The bat can tell whether its victim is to the right or left by comparing how fast the sound reaches the right or left ear first: for example if the sound reaches the right ear before it reaches the left ear, then the bat knows that its victim is on the right and vice versa. The bat's ears have a "complex collections of folds that help it determine an insect's vertical position" (3). Echoes coming from below will hit the folds of the "outer ear at a different point than sounds coming from above, and so will sound different when they reach the bat's inner ear" (3). A bat can tell how big its victim is; based on the power of the echo. Small object will reflect fewer sound waves then produce a less powerful resound and bigger objects will produce very powerful resound (3).

Whales use their tooth to locate their objects by producing a click sound while bats use their lungs to make the sounds which is released through the mouth or nose. The mechanism that these animals are using is safer because they can sense how far an object is and they can also tell the direction in which the object is travelling. The mechanism that both the whales and bats are using requires them to listen attentively. They should have good listening skills so if it happens that they become deaf what are they going to do because they depends mostly on their listening skills. If they loss their ability to make sounds or their listening skills does this mean that they are no longer going to eat because they hunt animals by making sounds and listening to the echo.

Reference:

1. Anon .Echolocation –Whale Glossary. [Internet] Updated 2006. Cited 2006 May 16. Available from: http://www.enchantedlearning.com/subjects/whales/glossary/Echolocation.shtml
2. The Georgia Museum of Natural History. Google definition: [Internet] Updated 2000 Jun 30. Cited 2006 May 16. Available from: http://museum.nhm.uga.edu/gawildlife/glossary/gawwglossary.html
3. Anon. How stuff works “How Bats Work”. [Internet] Updated 2006. Cited 2006 May 16. Available from: http://science.howstuffworks.com/bat2.htm
4. Anon. Answers.com. Animal echolation. [Internet] Updated 2006. Cited 2006 May 25. Available from: http://www.answers.com/topic/animal-echolocation

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
Mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

1 Comments:

  • Hi there

    You seem to have some trouble with the concept of referencing, and when to paraphrase or rather to quote directly. There are also some grammar problems, and general confusion throughout. Your concluding paragraph, especially, is confused, and very repetitive.

    Nick

    By Blogger NcK, at May 29, 2006 10:35 AM  

Post a Comment

Links to this post:

Create a Link

<< Home