Echolocation Facts: Know The Meaning Of High Frequencies Of Sounds

Do you know how bats locate objects even in complete darkness or how whales detect prey underwater?

Some organisms of the animal kingdom, such as bats and whales, possess a remarkable ability to locate invisible or distant objects and navigate their surroundings using sound waves. Surprisingly, even some humans can detect objects in their environment with the help of sound waves.

While it sounds extraordinary, echolocation is a common physiological process most notable in bats, whales, and dolphins. Apart from these well-known mammals, some birds, tenrecs, and shrews have also been reported to echolocate. Echolocation helps these animal species to determine the location of objects, detect food or prey, avoid obstacles, and even interact with each other.

Read on to know more interesting facts about echolocation in animals.

Meaning Of Echolocation

Echolocation is a physiological process that helps some animals determine the location of objects in their surroundings by using reflected sound.

Echolocation is like nature's very own sonar system. Animals that echolocate emit ultrasonic sounds beyond the range of human hearing. These ultrasonic calls range in frequency between 20-200 kHz (kilohertz), while humans cannot hear sounds beyond 20 kHz. Apart from the frequency of the sound wave, the echolocation calls are distinctive for their intensity and duration. While intensity is measured in decibels (dB), the time duration is in the millisecond (ms) scale. Echolocating animals emit ultrasonic calls, and the reflected sound or echo from the surroundings enables them to locate any object in their immediate environment. Thus, the term echolocation comes from the fact that the phenomenon involves sound and its echo to find objects.

Bats, dolphins, porpoises, and toothed whales are widely known for their ability to echolocate. In the case of toothed whales and dolphins, echolocation helps find food sources in the ocean. Apart from these animals, birds such as the cave swiftlet of Southeast Asia, the oilbird of South America, the tenrec of Madagascar, and some shrews are known to use echoes to navigate and detect objects. Surprisingly, some blind people have reportedly used echolocation to determine their surroundings. Such individuals produce clicking sounds with their mouths, stomp their feet, snap fingers, or even tap their canes to create sounds and hear the resulting echoes to detect surrounding objects.

Principle Of Echolocation

Echolocation is based on the simple principle of reflection of sound.

The basic principle of echolocation is pretty straightforward. There is a source that produces the sound waves, which, in this case, is an animal like a bat or whale. The sound waves travel through air (or water) and bounce back from any object that falls in its path. The sound-producing animals can sense the time duration separating the successive echoes and figure out the distance of the respective object in its surroundings. If the target object is moving, the echolocating organism will even detect its speed from the reflected sound waves.

Did you know that scientists experimented with echolocation as early as the 18th century? In 1793, Italian researcher Lazzaro Spallanzani showed that while blind bats could navigate their way around an enclosure, deaf bats had no sense of direction. Later, in 1938, zoologist Donald R. Griffin listened to bats using a microphone sensitive to ultrasound. Also, Griffin was the one to coin the term echolocation.

How does echolocation work?

Echolocation is the ability to localize any object based on how well it reflects sound. While many mammals and birds can echolocate, bats are the perfect subjects to understand how echolocation works!

Just like we depend on reflected light to see our surroundings, bats rely on reflected sound to navigate their way through the dark. While they fly, these nocturnal animals produce various squeaking and chirping sounds and hear the echoes. Now, it's pretty evident that sound reflected from a nearby object will be louder and reach the bats' ears more quickly than the sound waves that hit a more distant obstacle. It doesn't end there. Bats' ears can also sense the change in phase of an echo to make out the type of surface the sound source has. So, while hard targets like a wall produce a sharp echo, the sound reflected from softer targets such as vegetation will be less sharp.

Bats have fascinating physical adaptations that help in echolocation. For example, bats run the risk of being temporarily deafened by the intensity of their own calls. Therefore, the bats' middle ear muscles contract about 19.6 ft per second (6 m per second) before the larynx contracts to produce ultrasonic sounds. The ear muscles relax about 6.5-26 ft per second (2-8 m per second) later, and by that time, the bat is ready to hear the echo from the target. In addition, the size and shape of the bats' external ears help in receiving and directing sound waves emitted from targets. Moreover, bats' brain cells and ears are adapted to the frequency of sound waves they emit and the resulting echoes, while specialized cells in their ear are susceptible to frequency changes.

What bats perceive also depends on the frequency of their echolocation call. For instance, high-frequency calls give bats detailed information such as the position, size, range, speed, and even the direction of the target's flight. Therefore, bats mostly use high-frequency sound to echolocate even though low-frequency calls travel further.

Purpose Of Echolocation In Bats

Bats are well-known for their echolocating abilities, and they do so by producing sounds beyond the range of human hearing.

Echolocation is no less than a survival mechanism for bats. The animals use echolocation to locate food in their surroundings, primarily insects that fly in the air. Besides, echolocation also helps bats detect obstacles during flight even when their surroundings are dark. When bats detect insects via echolocation, they energize their calls and produce a rapid series of sounds to pinpoint the prey and close in on the kill. Moreover, these flying mammals can change their calls depending on the purpose, such as hunting, searching, or social interactions. Also, different species of bats have unique call patterns. While most bats use their voice box or larynx to produce calls, some make clicking noises with their tongues. Still others, such as the Old World leaf-nosed bats and horseshoe bats, give off echolocation calls through nostrils.

Despite the evident benefits of echolocation, there are some downsides to this physiological process. To begin with, echolocation has a limited range. Moreover, it may lead to information leakage. Although bats can hear echolocation calls from their kind, it isn't equivalent to communication unless the information transfer is intentional. Therefore, it ends up as eavesdropping.