The ocean is a world of sound where marine mammals communicate through complex acoustic signals known collectively as whalesong. This term encompasses the long, patterned melodies of Mysticetes (baleen whales) and the rapid clicks, whistles, and pulsed calls of Odontocetes (toothed whales). Sound travels nearly five times faster in water than in air, making acoustics the primary sense for navigation and social interaction. These intricate vocalizations are integral to the survival of these massive creatures.
The Biological Mechanics of Sound Generation
Whales cannot produce sound using the same vocal cord mechanism as land mammals, requiring two distinct anatomical solutions for underwater acoustics. Baleen whales, such as humpbacks and blue whales, utilize a specialized laryngeal structure to generate their characteristic low-frequency sounds without exhaling air. This structure includes a U-shaped fold of tissue that vibrates against a large fatty cushion within the larynx.
The vibration of this apparatus generates deep, resonant calls that can travel hundreds of miles through the ocean. The whale recycles air between its lungs and a laryngeal air sac, allowing it to produce sound continuously while submerged. This air-recycling system prevents water from entering the respiratory system and enables the production of long, sustained songs without surfacing for breath.
Toothed whales, including dolphins and sperm whales, evolved an entirely different, nasal-based system for sound production. They generate sounds using a pair of structures called “phonic lips” located within the nasal passages beneath the blowhole. Air is forced across these lips, causing them to vibrate rapidly to produce high-frequency clicks for echolocation and whistles for social communication.
These sound waves are channeled forward and focused by the melon, a specialized organ composed of fatty tissue in the whale’s forehead. The melon acts as an acoustic lens, shaping the clicks into a narrow, concentrated beam projected into the water. In many species, the right phonic lip pair is responsible for powerful echolocation clicks, while the left is used for producing social whistles, demonstrating a functional asymmetry.
The Diverse Functions of Vocalization
Whales employ their varied vocal repertoire for behaviors ranging from finding a mate to locating prey. The complex, long-duration songs produced primarily by male humpback whales during the breeding season are a well-studied example of a reproductive display. These elaborate melodies, which can last up to 30 minutes, function as an advertisement of competitive fitness directed toward other males.
The songs may also serve to attract females to a communal display area, or “lek,” signaling a male’s quality and readiness to mate. However, the exact purpose is still debated, with some studies suggesting the primary audience is other males who may be deterred or challenged. The presence of these songs is highly seasonal, occurring mostly on the tropical breeding grounds rather than the feeding grounds.
Toothed whales rely heavily on echolocation clicks for navigation and foraging. By emitting high-frequency clicks and listening for the returning echoes, the whales construct a detailed acoustic map of their surroundings. This biological sonar allows them to determine the distance, size, shape, and movement of objects, which is effective for locating fast-moving prey like squid and fish.
Beyond mating and hunting, vocalizations are used year-round for social cohesion and coordination within the pod. Orcas, for example, use complex calls and whistles to coordinate cooperative hunting strategies, such as herding fish or stunning seals. Certain baleen whales, like humpbacks, employ a distinctive “feeding call”—a long, low-frequency sound—to synchronize their bubble-net feeding maneuvers.
Dialects, Structure, and Cultural Transmission
The humpback whale song possesses a structured complexity that rivals human music and poetry. This vocalization is organized hierarchically, beginning with the smallest element, the “unit,” which is a single sound like a moan or a grunt. Units are grouped into “phrases,” and repeated phrases form a “theme.”
A full “song” is a sequence of multiple themes, always sung in a specific, fixed order, and this sequence may be repeated for hours. All males within a single population or ocean basin sing the same song at any given time, demonstrating cultural conformity.
This conformity is not static; the songs are constantly evolving, with small changes incorporated by all singers in a process known as cultural transmission. Humpback populations sometimes undergo a “song revolution,” where the existing song is replaced by a new, novel song type. This new song often originates from a neighboring population and spreads rapidly across the entire population within a few seasons.
In toothed whales, evidence of cultural learning is seen in geographic and clan-specific dialects. Sperm whales communicate using rhythmic patterns of clicks called “codas,” and different family groups, or clans, maintain distinct coda patterns. These identity codas function as regional “accents,” allowing whales to recognize and differentiate members of their own clan from others.
Monitoring and Conservation of Whalesong
Scientists rely on specialized instruments to capture and study the ocean soundscape, a process known as passive acoustic monitoring. Hydrophones, or underwater microphones, are deployed in fixed locations or towed behind ships in large-scale acoustic arrays. These arrays allow researchers to detect, localize, and track vocalizing whales in three dimensions for estimating population sizes and studying behavior.
The acoustic environment is under increasing threat from human activity. Anthropogenic noise from commercial shipping, seismic surveys for oil and gas, and military sonar creates a constant, low-frequency background hum. This noise causes “masking,” effectively drowning out the whales’ own calls and drastically reducing their communication range.
This continuous disruption impairs the whales’ ability to find a mate, coordinate feeding maneuvers, and maintain contact with their young. For some species, the distance over which they can communicate has been reduced by as much as 90 percent in noisy areas. Exposure to intense sound sources, such as naval sonar, can lead to behavioral changes, increased stress hormones, and mass stranding events.