Whales are highly vocal marine mammals, navigating their underwater world primarily through sound. Their acoustic landscape is complex and diverse, offering a fascinating area of study for scientists. The sounds whales produce are central to many aspects of their lives, from communication to locating food in the vast, dark ocean.
The Diverse Symphony of Whale Sounds
Whales produce a variety of sounds that can be broadly categorized based on their characteristics and the whale suborder that produces them.
Toothed whales (odontocetes), such as sperm whales and orcas, are known for high-frequency clicks and whistles. Sperm whales emit clicks for echolocation, often at about one click per second for searching, rapidly increasing to “creaks” or “buzzes” when homing in on prey. Whistles, pure-tone sounds, are also used by toothed whales for communication and social bonding, particularly at close ranges.
Baleen whales (mysticetes) produce lower-frequency sounds. These include moans, grunts, thumps, and knocks, with some sounds traveling for hundreds or even thousands of kilometers underwater. Humpback whales are known for their complex, structured “songs,” consisting of repeating themes that can last from five minutes to over 24 hours. Blue whale calls are typically between 10 and 40 Hz, with some populations producing songs with a four-note duration.
Why Whales Sing and Click
Whale sounds serve multiple purposes for their survival and social structures. Communication is a primary function, enabling whales to convey presence, identity, and even warning signals to others within their pods or species. Distinct vocal “dialects” can even exist between different groups, helping them differentiate between familiar whales and strangers.
Toothed whales rely on echolocation, using clicks to “see” their environment. By emitting clicks and interpreting the returning echoes, they can construct a three-dimensional acoustic map of their surroundings, essential for navigating in dark or murky waters and precisely locating prey. For baleen whales, complex songs, especially those of male humpbacks, are associated with mating and reproduction, attracting females.
The Unique Biology of Whale Sound Production
The biological mechanisms whales employ to create their diverse sounds differ significantly between the two suborders.
Toothed whales produce sound by moving air between specialized nasal sacs, past structures called “phonic lips” or “monkey lips” in the blowhole region. Vibrations are then focused and directed by the melon, a fatty organ in their forehead that acts like an acoustic lens for echolocation clicks. This system allows them to continuously generate clicks underwater without expelling air.
Baleen whales, despite lacking vocal cords similar to humans, produce sounds using an adapted larynx. They possess laryngeal structures, including modified cartilages called arytenoids, which form a U-shaped structure. When air from the lungs is pushed past a fatty cushion within the larynx, it vibrates, generating low-frequency underwater sounds. This adaptation allows them to vocalize while submerged by recycling air within their respiratory system.
Listening to the Deep: How Scientists Study Whale Sounds
Researchers employ specialized tools and techniques to study the complex world of whale sounds.
Hydrophones, underwater microphones, are used for passive acoustic monitoring. These devices allow scientists to listen for and record whale vocalizations, providing insights into their presence, distribution, and behavior.
To pinpoint vocalizing whales and track their movements, scientists deploy acoustic arrays, consisting of multiple hydrophones at different locations. By analyzing the slight differences in the time it takes for a sound to reach each hydrophone in the array, researchers can accurately determine the sound source. However, studying whale sounds in the ocean presents challenges, particularly due to increasing anthropogenic (human-made) noise from shipping, sonar, and oil exploration, which can interfere with whale communication and behavior.