echolocation

Echolocation, also known as biosonar, is a biological sonar used by certain animals to navigate, locate prey, and identify objects in the environment by emitting calls and listening for the returning echoes. It is an active sensing system in which the animal generates sound and analyzes the information carried by the echoes.

The basic mechanism involves emitting rapid sound waves that travel through air or water and reflect off surrounding objects. The time delay between emission and echo indicates distance, while the pattern of frequencies in the returning echo provides information about size, shape, surface texture, and composition. Doppler shifts in the echoes reveal relative motion between the animal and the object. The processing of echo information occurs in specialized auditory and neural pathways.

Bats are the most well-known echolocators. They typically produce ultrasonic calls through the larynx, directed by the mouth or nostrils. Their calls can be frequency-modulated, wideband, or a combination, allowing fine-grained range estimation and the detection of small prey. Many bat species increase call rate as they close in on a target, producing a feeding buzz to improve prey capture.

Toothed whales, including dolphins and porpoises, echolocate underwater using clicks produced by the phonic lips and focused through the melon. Click frequencies commonly range from tens to over 100 kilohertz. They interpret echoes to determine distance, speed, and texture of objects, aiding navigation in dark or murky waters and in hunting.

Some terrestrial mammals, such as certain shrews and tenrecs, emit ultrasonic sounds for navigation and foraging, though their echolocation is less elaborate than in bats and whales.

Human research has leveraged echolocation principles in sonar, imaging, and signal-processing technologies.