Echolocation is a biological sonar system used by certain animals, including some whales, to navigate and find food by interpreting reflected sound waves. This process involves producing a sound pulse and listening for the echo that returns. The time delay and characteristics of the returning echo provide information about the object’s distance, size, shape, and movement. While this ability is a hallmark of many marine mammals, not all whales use it.
The Whale Groups That Use Echolocation
The ability to echolocate serves as the fundamental biological difference between the two suborders of whales. The Odontocetes, or toothed whales, possess this active sonar system and include approximately 75 species, such as dolphins, porpoises, orcas, and sperm whales. Toothed whales are predators that hunt individual, fast-moving prey like fish and squid. They require a highly precise sensory tool to locate and track targets in low-visibility conditions, necessitating the evolution of complex anatomical structures to generate and receive high-frequency sound. Their acoustic strategy focuses on detailed, localized information about their immediate surroundings.
The other suborder, the Mysticetes, or baleen whales, do not echolocate. This group includes blue whales, humpback whales, and right whales. They lack the necessary organs to produce the high-frequency clicks used for biosonar.
The Mechanics of Active Sonar
The system begins with sound production in the nasal passage, not the larynx. The whale forces pressurized air through structures called phonic lips, which are folds of vibrating tissue located just below the blowhole. This vibration creates the characteristic, short, high-frequency sound pulses known as clicks. These clicks are then directed and focused into a narrow, intense beam by the melon, a large, fatty organ in the whale’s forehead. The melon acts as an acoustic lens, projecting the sound waves forward into the water.
When the sound wave strikes an object, the resulting echo travels back to the whale. The specialized mechanism for receiving this returning sound involves the lower jaw, or mandible, which contains an oil-filled channel that transmits the vibrations to the middle ear structure. The whale interprets the time it takes for the echo to return to accurately determine the distance to the object. As the whale closes in on its target, the clicks increase in frequency, often forming a rapid burst or “buzz” that provides a continuous stream of information for the final strike. This bio-sonar can discern the size, shape, and even the internal characteristics of an object.
Navigating Without Echolocation
Baleen whales, the Mysticetes, employ different sensory and acoustic strategies, relying on passive hearing rather than active sonar. Their foraging strategy of filter feeding—straining krill and plankton—does not require the high-resolution targeting necessary for hunting individual prey.
These whales produce powerful, extremely low-frequency sounds, including moans and rumbles, many of which are infrasonic (below the range of human hearing). Low-frequency sounds attenuate far less quickly than the high-frequency clicks of Odontocetes, allowing their vocalizations to travel hundreds, or even thousands, of miles. This long-distance acoustic communication is primarily used for finding mates and maintaining contact across vast ocean expanses. Their highly developed low-frequency hearing also assists them in broad-scale navigation, such as identifying large underwater features.