Critical bandwidths in echolocating porpoises, dolphins and whales.

Abstract

Odontocete cetaceans may differ from most mammals in their response to noise. A close look at the published data [Popov et al. (2006)] of the critical bandwidths of two species of porpoises, the harbor porpoise (Phocaena phocoena) and the finless porpoise (Neophocaena phocaenoides), shows constant bandwidth critical bands in the high frequency area where echolocation signals are processed. A further look at harbor porpoise critical band data [Kastelein et al. (2009)] can be interpreted to show a mixture of constant Q bandwidths at lower frequencies and constant bandwidth data at higher frequencies. Data from Lemonds et al. [1997] indicate that the bottlenosed dolphin shows typical mammalian constant Q filters in lower frequency whistle areas but shifts to constant bandwidths in the areas of high frequency where echolocation discrimination processing is assumed to occur. Recent work (Kloepper et al.) has shown substantial loss in echolocation discrimination performance in the false killer whale with the loss of high frequency hearing. General high frequency hearing loss due to noise in the environment may particularly affect the echolocation processing capabilities of odontocetes and thus the foraging capabilities and fitness of odontocete echolocators. [Work funded by the Office of Naval Research.]