Habitat utilization by beaked whales in the western North Atlantic Ocean using passive acoustics

Beaked whales (family Ziphiidae) are cryptic, deep-diving cetaceans found offshore. Passive acoustic monitoring of this family allows identification to species level and is instrumental in expanding knowledge of their behavior, distribution, and habitat use. From 28 June to 25 August 2016, 2 broadscale shipboard surveys towed a hydrophone array in the western North Atlantic. Concurrently, 11 bottom-mounted recorders collected continuous passive acoustic data along the 1000 m contour during July and August 2016. Five beaked whale species (goose-beaked, Ziphius cavirostris ; Gervais’, Mesoplodon europaeus ; True’s, M. mirus ; Sowerby’s, M. bidens ; and Blainville’s, M. densirostris ) were present in both data sets. Beaked whales were commonly detected at the bottom-mounted sites (71% total days present), with sites off the US Mid-Atlantic Bight containing the greatest species diversity. Overall, daily co-occurrence was uncommon (35% of study period). Using the towed array, Blainville’s and Gervais’ beaked whales were found in the Gulf Stream, True’s beaked whales were more common in abyssal waters, and Sowerby’s beaked whales were more common on the continental slope. Goose-beaked whales were present throughout. Using multipath reflections, click depths were examined for 192 beaked whale detection events. Among 3 species tested (goose-beaked, Gervais’, and True’s), only goose-beaked whales were found to significantly forage in proximity to the seafloor. This is the first study of its kind to provide a comprehensive overview of how these whales utilize their habitat across latitudes, longitudes, and depths.