A humpback whale, like the one seen here in Monterey Bay, is a type of baleen whale. Photo: Mike Doherty
New research that maps the functions of baleen whale anatomy has provided a new level of understanding of how these filter-feeding behemoths produce their bellowing songs. The research also highlights why the shipping industry is problematic for their communication.
An article published in Nature detailed the findings of examinations done on the carcasses of three types of baleen whales: humpback, minke, and sei. The whales, whose cause of death are believed to range from bacterial infections to drowning from fishing nets, had their sound-producing larynxes (also known as a “voice box”) removed for study.
Until now, the processes by which baleen whales produce sound was not well-understood. However, by examining the larynxes and blowing air through them the researchers were able to understand how the whale anatomy produces its songs. Interestingly, the whales have adapted to recycle air – not having to inhale and exhale to make noise like humans – which passes over a large U-shaped cushion of fat in the larynx and creates the vibrations that we know as whale songs. The research also illustrates the evolution of whales when their ancestors left land, returned to the ocean, and adapted to be able to communicate great distances in a medium of water.
Another key finding was further understanding about the frequency levels within which the baleen whales are capable of operating. As it turns out, the narrow frequencies in which these whales are able to produce sound overlaps with the frequency given off by shipping vessels. In theory, the sound could hinder whales from communicating with each other from long distances, information that could become crucial for the animals’ conservation. The paper says that most baleen whales “are severely masked by vessel noise, from which their specialized and unique vocal production system allows them no escape.”
“Sound is absolutely crucial for their survival, because it’s the only way they can find each other to mate in the ocean,” said the study leader, Prof Coen Elemans, of the University of Southern Denmark.
Six of the 14 species of baleen whales – blue, bowhead, fin, humpback, right, and sei – are protected under the U.S. Endangered Species Act. Their protection is primarily due to reduced numbers that occurred during the time when commercial whaling was widely practiced.
Baleen whales are different from their toothed counterparts in that their mouths feature plates of baleen that filter prey, such as krill and small fish, out of the ocean water.
