Great ears: functional comparisons of land and marine leviathan auditory systems

TitleGreat ears: functional comparisons of land and marine leviathan auditory systems
Publication TypeConference Paper
Year of Publication2005
AuthorsKetten, D. R., J. Shoshani, D. P. Domning, J. O'Malley, J. J. Arruda, C. O'Connell, and J. Meng
Conference NameInternational Mammalogical Congress
Date Published2005
Conference LocationSapporo, Japan
Keywordsauditory, baleen whale hearing, basilar membrane, cochlea, elephant, elephant hearing, elephants, impedance, infrasonic, inner ear, low frequency, mammal, mammalian, morphometry, mysticete, mysticeti, propagation, radii, signal, sound, structure, vocalizations, whale, whales

Elephants and baleen whales are massive creatures that respond to exceptionally low frequency signals. Although we have many elephant and whale vocalization recordings, little is known about their hearing. Playback experiments suggest hearing in both proboscideans and mysticetes is tuned similarly to low or even infrasonic signals. This raises several interesting issues. First, they emit and perceive signals in two media, air and water, with radically different physical acoustic properties: 4.5‐fold differences in sound speed, three‐fold magnitude difference in acoustic impedance, and, for common percepts, whales must accommodate 60‐fold acoustic pressures. Also, a commonly held tenet is that upper hearing limit is inversely correlated with body mass, implying there should be virtually no whale‐elephant hearing overlap given body mass differences. This study analyzed how inner ears in these groups are structured and specialized for low‐frequency hearing. Computerized tomography and celloidin histology sections were analyzed in six baleen whale (n=15) and two elephant species (n=7). The data show mysticetes have a substantially greater hearing range than elephants but that coiling and apical cochlear structures are similar, suggesting common mechanical underpinnings for LF hearing, including cochlear radii consistent with the Whispering Gallery propagation effect. (Work supported by ONR, NIH, WHOI OLI, Seaver Foundation.)