Insights into acoustic behavior of false killer whales

Abstract

The Hawaiian Archipelago is home to three distinct populations of false killer whales (Pseudorca crassidens), including one currently listed as endangered. These delphinids are known to interact with fishing gear, leading to whale mortality or injury. Hence, it is critical to assess the abundance of these populations typically achieved through visual-based sighting surveys. However, these surveys are complicated by a number of biases and uncertainties specific to this species. Passive acoustics could aid in monitoring of their population status, but the knowledge is limited about the patterns in their acoustic repertoire and behavior, which hinders our ability to derive reliable acoustics-based abundance estimates. Here, we discuss insights into the acoustic behaviour of false killer whales in the wild, gained by simultaneous tracking of both narrowband whistles and broadband echolocation clicks from towed hydrophone arrays. The results indicate a diverse acoustic behaviour between different subgroups within the same encounter, where 23.8% of subgroups (N total = 408) only echolocate, 18.9% only whistle, and 57.3% emit both types of vocalizations. Such increased understanding of false killer whale vocal behavior can contribute information from passive acoustic data for management and conservation purposes.