Using passive acoustic monitoring to document the distribution of beaked whale species in the western North Atlantic Ocean

Abstract

Abstract:Little is known about the ecology of many beaked whale species, despite concerns raised by mass strandings linked to certain sources of anthropogenic noise. Here, we used passive acoustic monitoring to examine spatial and temporal patterns in beaked whale occurrence at six locations along the continental slope in the western North Atlantic Ocean. We analyzed 2642 days of recordings collected between 2011 and 2015, and identified echolocation signals from northern bottlenose whales (Hyperoodon ampullatus), Cuvier's (Ziphius cavirostris), Sowerby's (Mesoplodon bidens), Gervais', (Mesoplodon europaeus), and Blainville's (Mesoplodon densirostris) beaked whales, and one signal type of unknown origin. We recorded multiple species at each site, with detections generally occurring year-round, and observed latitudinal gradients and site-specific variation in relative species occurrence. Notably, we regularly detected Cuvier's beaked whales in a region where they have not been commonly observed, and discovered potential habitat partitioning among Cuvier's and Gervais' beaked whales within their overlapping ranges. This information on the distribution and seasonal occurrence of North Atlantic beaked whale species offers new insight into patterns of habitat use, and provides a year-round baseline from which to assess potential anthropogenic impacts.

Click characteristics of northern bottlenose whales (Hyperoodon ampullatus) and Sowerby's beaked whales (Mesoplodon bidens) off eastern Canada

“…The northern bottlenose whale clicks described in this study are consistent with clicks previously found in bottommounted recordings from the Gully (Martin and Moors-Murphy, 2013;Stanistreet et al, 2017) and Ireland (Kowarski et al, 2018). We found this click type in recordings made in the presence of northern bottlenose whales, not only in the Gully and other submarine canyons along the Scotian Shelf, but also off Newfoundland.…”

“…Other factors that can influence the variation in acoustic parameters are the specific environmental context in which they were recorded, such as the whale's range and orientation relative to the hydrophone, propagation effects, or differences in recording systems. However, the click parameters reported here are consistent with northern bottlenose clicks found in other large acoustic datasets from the Scotian Shelf and Ireland, which include both towed array and bottom-mounted recordings, suggesting that the frequency characteristics we describe are not unique to the environmental context or recorder characteristics of this study (Stanistreet et al, 2017;Kowarski et al, 2018). While we focused on describing the general characteristics of clicks produced by two beaked whale species, it is also important to consider intraspecific variation.…”

“…These on-axis clicks were characterized as having an FM upsweep structure with a center frequency of 43 6 7 kHz and an inter-click interval of 306 6 118 ms. This description is limited in sample size and not detailed enough for a full comparison, but it is not consistent with the northern bottlenose whales clicks typically recorded in the western North Atlantic (Moors-Murphy, 2012; Martin and Moors-Murphy, 2013;Stanistreet et al, 2017) or in the eastern north Atlantic, off Ireland (Kowarski et al, 2018).…”

“…Temporal and spectral characteristics of the FM clicks, such as the inter-click interval (ICI), peak frequency, center frequency, bandwidth and upsweep appear distinct between beaked whale species (Baumann-Pickering et al, 2013a). Detailed characterization of beaked whale acoustic signals allows species-specific classification and has informed the development of automated beaked whale click detectors resulting in significant improvements in the interpretation of PAM data for beaked whale monitoring (Dawson et al, 1998;Johnson et al, 2004;Zimmer et al, 2005;Johnson et al, 2006;Tyack et al, 2006;Gillespie et al, 2009;Baumann-Pickering et al, 2010;Rankin et al, 2011;Baumann-Pickering et al, 2013a;Baumann-Pickering et al, 2013b;Yack et al, 2013, Stanistreet et al, 2017, Kowarski et al, 2018.…”

“…In this study Cholewiak et al (2013) identified four different FM click types based on median peak frequencies, at 26, 33, 51, and 67 kHz. However, only one of these click types, with a 65-70 kHz peak frequency, has been found in other acoustic datasets, and therefore automated detectors, PAM programs, and analysts looking at data from bottom-mounted recorders have primarily relied on this high-frequency click type to detect and identify Sowerby's beaked whale clicks (Martin, 2016;Stanistreet et al, 2017, Kowarski et al, 2018.…”