Whales communicate through sound, yet they do not possess vocal cords like humans or other terrestrial mammals. These highly vocal creatures depend on sound for survival in the underwater environment. Their diverse vocalizations are fundamental to nearly every aspect of their marine lives.
Sound Production in Whales
Whales produce sound using specialized mechanisms that differ between toothed whales (Odontocetes) and baleen whales (Mysticetes). Toothed whales, including dolphins, porpoises, and sperm whales, generate high-frequency clicks and whistles using structures within their nasal passages. Air pushed through specialized soft tissues called phonic lips causes them to vibrate and create sound. These vibrations then travel through a fatty organ in the whale’s forehead, the melon, which acts as an acoustic lens to focus and direct sound waves. This system allows them to produce rapid sequences of clicks for echolocation and various whistles for communication, often recycling air to maintain continuous sound production underwater.
Baleen whales, such as humpbacks, blue whales, and minke whales, produce low-frequency sounds through a different laryngeal adaptation. Unlike toothed whales, they rely on unique structures within their voice box for resonant calls. Research indicates baleen whales possess a specialized U-shaped fold and associated cartilages, including modified arytenoids, that vibrate against a fat cushion within the larynx when air is pushed past them. This mechanism allows them to produce deep moans, grunts, and complex songs without exhaling air. These laryngeal adaptations were important for their evolution into aquatic environments, facilitating sound production without inhaling water.
The Purpose of Whale Sounds
Whales use sound for many functions, serving as a key sense for navigating and interacting underwater.
Communication
Communication is a core purpose, with whales employing clicks, whistles, and pulsed calls to socialize and maintain group cohesion. Vocalizations help individuals identify one another, warn of dangers, or coordinate activities within their pods. Some species, like orcas, exhibit distinct vocal “dialects” that distinguish family groups.
Navigation, Hunting, and Mating
Navigation and orientation are important functions for toothed whales, which use echolocation to construct an acoustic map of their surroundings. By emitting clicks and interpreting echoes, they discern the size, shape, distance, and movement of objects. This biological sonar system helps locate prey, avoid obstacles, and navigate in dark or murky waters. Beyond navigation, sound plays a role in hunting, with theories suggesting high-intensity sounds might disorient or stun prey. Male humpback whales are known for their elaborate, long-lasting songs, primarily associated with attracting mates during breeding seasons.
Conserving Their Acoustic World
Human-generated ocean noise poses a threat to whales, given sound’s central role in their lives. Activities like commercial shipping, sonar use, and seismic surveys introduce pervasive underwater noise that interferes with whale communication and navigation. This acoustic pollution masks their natural vocalizations, making it harder for whales to find food, locate mates, or stay connected with groups.
Studies indicate increased noise levels can lead to heightened stress, altered migratory patterns, and reduced foraging efficiency. Consequences range from behavioral disruptions, such as changes in diving patterns, to severe impacts like temporary hearing loss or strandings. For baleen whales, their evolved vocal structures limit sound production to a frequency range that overlaps with shipping noise.
To mitigate these impacts, conservation efforts focus on implementing noise reduction technologies on vessels, establishing quieter shipping routes, and regulating disruptive sonar and seismic activities. Protecting the acoustic environment of whales is important for their ability to thrive in the marine ecosystem.