What Does a Whale's Ear Look Like?

This week I've been talking a bit about deafness and human hearing. A human cochlea is tiny, and is located in a bony stucture near in the skull called the bulla of the temporal bone. The temporal bone is oft said to be the hardest bone in the body. Predictably, almost all other mammals share this structure (the bulla), as a protective shield around the inner ear. Humans' bulla are quite small, about the size of a large marble, but that of a whale's (and especially, a blue whale) is enornous, reaching sizes of a Nerf football. (See picture below the fold of bulla taken from a 20 ft humpback whale.)

i-715d390786afa543467ac99ac9203d29-whale ear drum.jpg

Unlike humans, whose bullae (and middle/inner ear) is inside the skull, whale's bulla is located inside their jaw. Incoming auditory information enters their head straight-on and travels through their fat-filled jawbone to the bulla. Their bulla is curved, like a seashell, which aids in collecting and amplifying sounds.

i-d9d5724a08213a230ee00d496fe0aeb6-whale hearing diagram.jpg

Apparently sound brings the tympanic bone (located inside the bulla), and especially its thin tympanic plate, into vibration. The ossicles in the air-filled middle ear cavity form a bridge from the tympanic plate to the periotic bone connecting the vibrating plate to the oval window and the whale's cochlea. The equivalent of the tympanic plate in humans is the eardrum (the tympanic membrane).

If you're interested in the evolution of the whale ear (quite fascinating, as it catalogs their travels from sea to land to sea), PZ has written an informative post here. Afarensis also has an article on whale semicircular canals (part of the vestibular system) here.

More like this

does a whale have a peanus?

Stephanie Wang(^_^)

By Stephanie (not verified) on 09 Jun 2009 #permalink

Interesting, but consider the semicirclar canals [SCC]:
"Cetaceans ... have unique semicircular canals that allow them to be highly acrobatic swimmers without becoming dizzy ... living cetaceans the semicircular canals are much smaller than in any other mammal of the same body size. In fact, the semicircular canals of the huge blue whale are smaller than those of humans ..."

I can recall seeing either a NOVA, Nature or National Geographic special on African cats. A cat missed a large bird when attacking by vision, but heard the bird land, and then successfully attacked by acoustics. I think it was the "... caracal is also well known for using its agility and superior jumping ability to catch birds just after take-off ..."

Scientific American, special issue 12 DEC 2006 has a fascinating article by Masakazu Konishi on how owls combine two hearing signals "into a single spatial perception" in "Listening with two ears". [Originally in SCIAM April 1993]

There are two sensory articles in NATURE - issue: Volume 445 Number 7126 pp339-458 that appear to relate other sensory modalities to dynamic game theory:

1 - Fish can infer social rank by observation alone p429
Logan Grosenick, Tricia S. Clement and Russell D. Fernald

2 - 'Infotaxis' as a strategy for searching without gradients p406
Massimo Vergassola, Emmanuel Villermaux and Boris I Shraiman

I suspect that the SCC are important in location and balance for pursuit-evasion games.

You may want discuss with your advisor, including the SCC with the cochlea.
Best wishes for your research.

Interesting, but not the direction I'm going in!

By afarensis (not verified) on 07 Feb 2007 #permalink