Echolocation allows dolphins, bats to navigate without sight

Credit: Michael Setzer/Scitech Editor Credit: Michael Setzer/Scitech Editor

How do bats maneuver in the dark? How do dolphins make their way through the ocean? Echolocation is a biological sonar used by microchiropteran bats, odontocetes (toothed whales and dolphins), and some cave-dwelling bird species as a means of navigation in environments where vision is not very useful.

The basic concept behind echolocation is that the animal emits calls then listens to the echoes of its calls bouncing off nearby objects, the same way you might hear your own voice echo back in a cave or canyon. When the animal calls out, it causes vibrations in the air. These changes in the air affect surrounding particles and cause them to vibrate as well, resulting in a chain reaction, known as a sound wave, that can travel very long distances. When this sound wave hits another object, the particles are deflected in the opposite direction and the wave returns to the caller. explains how bats use this ability to find prey in the dark. Most bats make calls higher in pitch than humans can hear. When the echo returns to the bat, the time delay helps it process how far away the object is. Even more amazing, however, is the way bats can determine which direction the object is moving and how big it is. The bat can tell the direction the object is moving by comparing whether the sound reaches its right or left ear first — if the sound reaches the right ear first, for example, the object must be on the right side of the bat. In addition to the object’s horizontal position, the bat can determine if the object is above or below it by using special folds on its outer ear. These sensitive folds allow the bat to feel if the sound wave hits the lower or upper part of its ear.

The bat can also determine the size of the object by the intensity of the echo. Because a smaller object will reflect the sound wave less, the returning echo will be softer. If the echo is louder, the object is obviously larger. The bat can even use the Doppler effect to conclude if the object is moving away from or toward it. If the object is moving toward the bat, the peaks and troughs of the sound wave will seem closer together, causing the echo to have a higher pitch.

Similarly, if the object is moving away from the bat, the wave will appear to be more spread out, and the corresponding frequency will cause the echo's pitch to be lower.

Echolocation is a very important skill for whales and dolphins as well. According to the Australian government’s Department of the Environment, toothed whales — such as killer whales and dolphins — use echolocation for hunting and navigating. However, baleen whales, such as humpbacks and blue whales, use it as a form of communication.

According to the National Oceanic and Atmospheric Administration, sound is emitted in the head region of these sea mammals and is focused by the melon, a mass of adipose (fatty) tissue found in the forehead. The echo is then received through special tissue in the lower jawbone that is able to conduct sound. In both bats and odontocetes, characteristics of echolocation calls differ depending on the environment, hunting behavior, and type of prey.

While this kind of echolocation is not innate to humans, Smithsonian magazine confirmed that humans are also capable of echolocation and many vision-impaired individuals have actually developed the ability over time.
While humans lack the specialized anatomical structures that bats and odontocetes use to analyze echoes, the overall concept of echolocation is theoretically still possible. For example, humans are capable of making small click noises that echo back, have a left and right ear to distinguish the direction of the object, and are able to differentiate between volumes to determine the distance of the object.

Humans could potentially replicate echolocation — but they would need to determine the speed of sound in air, have a timer to measure how long it takes for the echo to return, and use physics equations to determine how an object is moving. Naturally echolocating animals can do all of these calculations purely by instinct.