Long-term monitoring of Ziphius cavirostris behavior using 3D tracking from fixed hydrophone arrays off Southern California

Goose-beaked whales (Ziphius cavirostris) are a deep-diving toothed whale species and top predators in deep sea ecosystems. Much is yet to be learned about their social and foraging strategies due to their elusive behavior, but this information isincreasingly relevant given their demonstrated behavioral changes in association with anthropogenic sound. This study useddirection-of-arrival (DOA) localization to track the position of goose-beaked whales from echolocation clicks recorded onseafloor-mounted hydrophone arrays offshore Southern California. Overall, 2,738 tracks of diving goose-beaked whales wereprocessed from acoustic recordings collected at four long-term monitoring sites between 2018 and 2023. Results highlightdistinct spatial use patterns driven by bathymetric features at each site, with whales foraging closer to the seafloor at siteswith complex bathymetry and showing a preference for canyon slopes. Group sizes at depth ranged from 1 to 9 individualswith a mean of 2.34 and exhibited site-specific seasonal variability as well as a strong diel trend at one site. During manyof these encounters, individuals exhibited highly coordinated behaviors. This study demonstrates the value of long-termpassive acoustic tracking for studying elusive, deep-diving species and provides significant advancements in understandinggoose-beaked whale behavior at depth over long time scales.