Comparison of whistle classification results for three overlapping false whale populations in the Hawaiian Islands

Abstract

The false killer whale (Pseudorca crassidens) is a globally distributed species found in temperate and tropical waters. The Hawaiian Archipelago is home to three genetically distinct populations of P. crassidens with overlapping distributions: two insular populations, one within the main Hawaiian Islands (MHI) and the other within the Northwestern Hawaiian Islands (NWHI), and a broadly distributed pelagic population. The mechanisms that created and maintain the separation between these populations are unknown, but previous studies have shown that acoustic diversity may reflect the genetic differences. For this study, whistles from 14 MHI, 11 NWHI, and 7 pelagic groups were extracted and measured to assess whether differences exist between the vocal repertoires of each population. Whistle measurements were tested for statistical differences and then used in two different classification methods: a random forest algorithm and Kullback-Leibler (KL) divergence calculations. Preliminary results suggest that the MHI and pelagic populations are vocally distinct, with up to 100% correct classification of whistles for some groups. A comparison of the classification results from the random forest and KL divergence studies will be discussed. Understanding the acoustic differences between these populations may open up new acoustic monitoring approaches for a difficult-to-study species.