Abstract:

Exceptionally clear recordings of sperm whale (Physeter macrocephalus) codas reveal time and frequency properties, which show that clicks within a coda are remarkably similar to each other but that they can differ from clicks in other codas. This is consistent with the hypothesis that individual whales can be identified by the characteristics within their codas. Research has centered on the cluster analysis of these codas to help establish whether acoustic identification of individuals is possible. Recently the cluster analysis has been made more robust. This increases the confidence in the applicability of the approach. Data are now available to couple visual sightings and acoustic tracking with recordings for acoustic identification to give an independent verification of the analysis. Acoustic identification of individuals has also been attempted using isolated echolocation clicks of sperm and beaked whales (Mesoplodon densirostris and Ziphius cavirostris). Although this is a more difficult and problematic undertaking, there has been some promising cluster analysis. Again data for acoustic tracking and visual observations are now available with the recordings for acoustic identification using echolocation clicks to test and perhaps validate the method. [Research supported in part by SPAWAR.]