Consistency of frequency dependent echolocation beam focus in an echolocating false killer whale (Pseudorca crassidens) performing a discrimination task.

Abstract

Tremendous variation in individual echolocation click parameters has been shown for odontocetes, making trend analysis of individual clicks within a click train necessary to understand their generalized echolocation behavior. The frequency dependent spatial echolocation beam profile of clicks for a single false killer whale (Pseudorca crassidens) performing a discrimination task was collected using a star shaped 16 hydrophone array. These spatial profiles were analyzed to compare the relative spatial location and focusing of various frequencies from click to click under different target exposures. Using a go/no go paradigm, the whale actively discriminated between objects of varying transmission reflectance properties. Very tight focusing and consistent spatial location was observed for frequencies near peak frequency but deteriorated for frequencies above peak frequency. This trend did not vary between targets, suggesting that the animal maintained a constant beam focus pattern regardless of the reflection characteristics of the target. Additionally, these patterns were consistent for all clicks within a train, suggesting that the animal employs a similar beam focus pattern throughout the entire click train.