Great ears: Functional comparisons of land and marine leviathan ears Academic Article uri icon

abstract

  • 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.]

publication date

  • November 2006