Echolocation was another interesting study from my Marine Biology class. We all know that bats use it, and of course dolphins and whales, but did you know that even shrews use a primitive type of echolocation?
Echolocation
Echolocation as defined in Marine
Biology written by Castro and Huber is the ability of some animals to sense
their surroundings by analyzing the reflection of sound waves, or clicks, they
emit. Another name for it is bio-sonar. Animals create sounds of different
pitches, and then listen for the echo. This helps them determine the distance,
and size of the object. It is usually used in place of vision. It helps with
navigating in their environment, and in the locating food. It can also be used
for social interaction. This is seen more in marine animals.
Echolocation is used by several animals.
It is used by Dolphins and Whales, bats, birds like Swiftlets and Oilbird’s,
Shrews and Tenrecs, and at times even by humans. People with vision impairments seem to be more
likely to benefit from echolocation. When one sense is disabled the other
senses become heightened which would seem to be the case with people without
vision. There are classes that can be attended to learn to use this ability. Of
course humans have found many uses for sonar.
Whales and Dolphin both depend on
echolocation for their survival. The sounds they make are different, but the
results are similar. Whales make high pitched groans and whistles while
dolphins make sounds from their nasal tissues that sound like clicks. They both
use it to navigate, locate food, communicate, and avoid predators. It is a very
sophisticated language.
Whales produce sound when air passes
through the phonic lips and there is a vibration. When it opens and closes it
produces a clack. This causes vibrations that pass sound waves to the melon
which is filled with fatty liquid and acts as an acoustic lens. From there it
is directed towards the target and emitted from the front of the forehead.
(Echolocation; pg3)
en.wikipedia.org/wiki/Animal_ecolocation
Sound waves travel better through water
then through the air, because it requires a high density medium to be
efficient. The sound is different in water in comparison to the way it sounds
in the air. Water is denser then air, so it transmits more efficiently.
Traveling through air it loses energy. It may sound louder under water, but it
isn’t. It has retained more of its energy. This makes echolocation a very
effective way for whales and dolphin to communicate.
There are terrestrial animals that use
echolocation. The Oilbird (Steatornis caripensis) is nocturnal, and rests in
caves during the day. It leaves to find food at night. It forages by sight, but
navigates by echolocation in poor light conditions. It uses a series of sharp
audible clicks for this purpose. Swiftlets also use echolocation. They use it
to locate their roost in a dark cave. Their clicking noise is well within human
hearing range. The clicks consist of two broadband pulses (3-10 KHz) separated
b y a slight pause (1-3 milliseconds). The interpulse periods are varied
depending on the level of light
Microbats also use echolocation. The
sounds that they emit are beyond human hearing. Bats are blind, and so
echolocation takes the place of their vision. They use it to navigate and
forage. It is emitted through the larynx and out the mouth. There are some bats
that emit the sound through their nose. They help keep the insect population
down. They emit a sound at a frequency of about 14,000 to over 100,000 Hz.
Different bat species echolocate within specific frequency ranges that suit
their environment and prey type.
A depiction of the ultrasound
signals emitted by a bat, and the echo from a nearby object.
en.wikipedia.org/wiki/Animal_ecolocation
Shrews and Tenrecs use echolocation, but their sound is a low amplitude,
broadband, multi-harmonic and frequency modulated. It seems to be used for
close range spatial orientation. They use it to investigate their habitat as
well as to search for food. They use the echoes to locate insects and other
prey They open and close their mouths rapidly to emit quick pulses of low
intensity sound as they get near their prey.
The terrestrial animals that use echolocation
have a more primitive version of echolocation, and use it for simpler purposes.
The marine animals that use it appear to have a more sophisticated system using
it not only for navigation and food searches, but for communication between
individuals.
Work sited
Animals That Use Echolocation/eHow.com. http://www.ehow.com/info_8576794_animals-use-echolocation.htlm
Animal echolocation-Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Animal_echolocation
Blind People’s Ability to Echolocate. http://www.disabled-world.com/disability/types/vision/echolocate.php
Can sound travel through water. http://wiki.answers.com/Q/Can_sound_travel_through_water
Echolocationand BioSonar/Sonography. http://www.sonargraphy.net/resources/echolocation-and-biosonar/
Microbats-Wikipedia,the free encyclopedia. http://en.wikipedia.org/wiki/Microchiroptera
Oilbird- Wikipedia, the free encyclopedia. http://en.wikipedia.org/wiki/oilbird
Swiftlet-Wikipedia, the free encyclopedia. http://wikipedia.org/wiki/Swiftlet
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