Spatio-temporal distribution of beaked whales in southern California waters

Abstract

Cuvier’s beaked whales are the dominant beaked whales offshore of southern California. Their abundance, distribution, and seasonality are poorly understood. Insights on the spatio-temporal distribution of both Cuvier’s and a rare beaked whale with signal type BW43, likely Perrin’s beaked whale, have been derived from long-term autonomous recordings of beaked whale echolocation clicks. Acoustic recordings were collected at 18 sites offshore of southern California since 2006, resulting in a total of ~26 years of recordings. About 23,000 acoustic encounters with Cuvier’s beaked whales were detected. In contrast, there were ~100 acoustic encounters of the BW43 signal type. Cuvier’s beaked whales were predominantly detected at deeper, more southern, and farther offshore sites, and there appears to be a seasonal pattern to their presence, with lower probability of detection during summer and early fall. The BW43 signal type had higher detection rates in the central basins, indicating a possible difference in habitat preference and niche separation between the two species. Further investigation is needed to reveal if these distribution patterns are purely based on bathymetric preference, driven by water masses that determine prey species composition and distribution, or possibly by anthropogenic activity.