Image: Maya Yamato, Woods Hole Oceanographic Institution)
We're all familiar with the songs of baleen whales from wildlife documentaries or piped through the speakers in new age shops. Their eerie calls are part of the underwater soundscape with radar and motors joining the biological throng. But if we were to join the whales in their own habitat we would probably make little sense of the noises because our ears are not adapted for underwater use.
Baleen whales, of course, have no trouble hearing underwater and new research has helped us understand how - specialist fat bodies associated with their ears.
Using MRI and CT imaging techniques as well as dissection, Maya Yamato and other scientists at Woods Hole Oceanographic Institution (WHOI), examined the anatomy of heads of seven minke whales. The computer image above was generated of a whale's skull using this data and shows the fat bodies in yellow leading to the whale's ear in purple deeper in its head.
Yamato and colleagues propose that the fat bodies provide a transmission pathway for sounds from the external environment to the auditory organ (see Anatomical Record). Baleen whales share this feature with toothed whales, where it was assumed the fat was part of the sophisticated echolocation system used in hunting. Because baleen whales graze rather than hunt, they do not need finely-tuned echolocation and the discovery of these fat bodies in their ears suggests it is a feature from the toothed and baleen whales' shared ancestor and is necessary for their hearing.
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