The ethereal sounds produced by baleen whales, such as the humpback, have long captivated listeners across vast stretches of the ocean. However, the intricate process through which these colossal marine mammals generate their melodic compositions has remained a puzzle. Scientists have now unraveled this mystery by examining the anatomy of stranded and deceased whales. The findings, published in Nature on Wednesday, reveal that these filter-feeding marine mammals utilize a uniquely adapted larynx, or voice box, for underwater vocalization. Unlike toothed whales, which have a separate vocal organ, Mysticeti whales—encompassing baleen and beaked varieties—have evolved a distinctive structure involving a fat cushion that aids in sound production.
The researchers explain that when the land-dwelling ancestors of today’s whales returned to the sea, they needed to be able to inhale and expel air fast as they surfaced to breathe, the researchers explain in their paper in Nature. However, the vocal folds that serve as a human larynx could get in the way of this rapid cycling of air, so they developed a different mechanism.
The result is the baleen whale’s larynx, shaped like a U, and has long, rigid cylinder-like cartilages, a study author says in a press release. When air flows from the whale’s lungs through the larynx, it vibrates these internal structures and produces sounds distinctive to each baleen whale species. For example, humpback whales sing complex songs; minke whales quack like ducks, and sei whales create low-frequency sounds to help them navigate.
To study how these whales make their sounds, the researchers removed the larynges from three stranded whales: a sei, a humpback, and a minke. Using an air supply system to mimic the whale lung, they discovered that these leviathans produced sound by squeezing air between a fatty pad and the top of their paired laryngeal folds, which vibrated. This has never been seen in any other animal, the researchers say.
It’s a remarkable discovery, but it may also be a limitation. This mechanism allows whales to make sounds over a wide range of frequencies, but simultaneously, it makes them uniquely vulnerable to noise pollution, which masks their calls and drowns out their songs, the authors note.
The humpback song, for example, is the most well-known worldwide and is used to communicate with other whales and their environment. The study author, Coen Elemans of the University of Southern Denmark, says his research will help guide future studies into how baleen whales communicate.
However, one not involved in the research warns that this study is limited by its small sample size of just three whales. He suggests that studying more whales is essential to understanding how this bizarre anatomy enables the most amazing animals to inhabit the planet. This includes figuring out how the songs created by these giants of the ocean can be heard through the roar of ships, fishing gear, and other human activities.