Echolocation
Echolocation is the ability to locate objects through the use of sound. Animals that echolocate form an image of their surroundings from returning echoes, allowing them to pick a path through vegetation or a cave system or to hone in on their prey in the dark. 18% of mammals echolocate.
Some of the animals that use echolocation
- Pygmy Shrew
- Leopard Seal
- Whippoorwill
- Minke Whale
- Brown Bat
- Orca
- Oilbird
- Bottle Nose Dolphin
- Swift
- Sperm Whale
- Egyptian Fruit Bat
- Porpoise
types of echolocation
There are three types:
Nasal
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Lingual
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Laryngeal
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How does echolocation work?
A sound is emitted and if there is an object nearby, it will reflect the sound back to the the echolocator. Echolocation is done by measuring the time delay between the animal's own sound emission and any echoes that return from their surroundings. The relative intensity of sound received at each ear provides information about the horizontal angle from which the reflected sound waves arrive. Unlike some sonar that relies on an extremely narrow beam to localize a target, animal echolocation relies on multiple receivers. Animals that use echolocation have two ears positioned slightly apart. The echoes returning to the two ears arrive at different times and at different loudness levels, depending on the position of the object generating the echoes. The time and loudness differences are used by the animals to perceive distance and direction. With echolocation, the animal can see not only where it is going but also how big another animal is, what kind of animal it is, and other features.
So to make it easy the animal sends out a signal, and depending on if the sound echos or not, it can get a sense for it's environment. If the sound doesn't return that would suggest there is an empty space.
So to make it easy the animal sends out a signal, and depending on if the sound echos or not, it can get a sense for it's environment. If the sound doesn't return that would suggest there is an empty space.
Comparative Anatomy
Dolphins
- Any Whale, Dolphin or Porpoise with teeth can echolocate.
- A dolphin is able to produce click sounds, which are sent out into the water. Once these sounds hit an object, echoes are created; the dolphin then listens to these echoes and is able to form a kind of mental image of the object.
- A dolphin produces these click sounds using a structure in its head called the phonic or sonic lips (the former nostrils).
- As dolphins evolved from land animals over millions of years they lost the function of their vocal cords. Instead what scientists call sonic lips, were evolved from what was once the dolphins nose.
- Now the dolphin breaths out of the blow howl located at the top of its head.
- The phonic lips are tucked just underneath the blowhole in the nasal cavity. By sending pressurized air past these lip-like structures, they are sent into vibration, and click sounds are produced.
- Although scientists are fairly sure that the lips are where the sound comes from they are still searching for the the answer to how the dolphins produce the actual clicks. Some guess that the lips slap against other fatty bodies in the dolphin's nasal cavity, which then transfer the sounds through the dolphin's head and out into the water. Since dolphins have two sets of phonic lips (having evolved from each of the two nostrils), they are able to produce two sets of click sounds simultaneously. This means that they can produce two sets of click sounds simultaneously, as well as whistle sounds which are produced in the larynx.
Bats
- Bats can fly using echolocation in complete darkness.
- A bats sonar is limited to a few feet in range
- This is why bats get so close to an object before they swiftly dive out of the way.
- If you have ever tried to get a bat out of your house this is easy to understand. Often the bat will be coming right for you with it's mouth open and then move out of the way right as it is about to hit you. The bats mouth is open because it is screaming at120dB SPL (which we cant hear).
- A bat screams in order to get information from the returning echos as to what might be in front of it.
- Bats have very large ears which allows them to collect and amplify very soft echoes coming from a particular direction.
- They flick their ears back and fort very quickly not unlike a hummingbird moves its wings. This allows bats to locate very small sounds bouncing back from small insects.
Shrew
- Shrews are noisy little mammals, and among their vocalizations are faint high-pitched twittering sounds. Some research has suggested that shrews might use these sounds for echolocation — like bats, only simpler.
- The findings suggest that the shrews may indeed use these calls for echolocation — sonically examining their surroundings and analyzing the reverberations to determine the nature of a particular location and how best to travel through it.
Echolocation in water vs. air
- Echolocation in water takes less energy, pulses travel further, reach target faster, echoes return faster
- Sound travels ~4x faster in water vs. air
- Intensity of a given frequency is higher in water vs. air
- Sound attenuates (loses intensity) more slowly in water
- Echolocation in water provides long range information
- Sperm whale >1,500 m
- Bats: ~2.5 - 62 m