Spatio-Temporal Patterns of Beaked Whale Echolocation Signals in the North Pacific

Abstract

At least ten species of beaked whales inhabit the North Pacific, but little is known about their abundance, ecology, and behavior, as they are elusive and difficult to distinguish visually at sea. Six of these species produce known species-specific frequency modulated (FM) echolocation pulses: Baird’s, Blainville’s, Cuvier’s, Deraniyagala’s, Longman’s, and Stejneger’s beaked whales. Additionally, one described FM pulse (BWC) from Cross Seamount, Hawai’i, and three unknown FM pulse types (BW40, BW43, BW70) have been identified from almost 11 cumulative years of autonomous recordings at 24 sites throughout the North Pacific. Most sites had a dominant FM pulse type with other types being either absent or limited. There was not a strong seasonal influence on the occurrence of these signals at any site, but longer time series may reveal smaller, consistent fluctuations. Only the species producing BWC signals, detected throughout the Pacific Islands region, consistently showed a diel cycle with nocturnal foraging. By comparing stranding and sighting information with acoustic findings, we hypothesize that BWC signals are produced by ginkgo-toothed beaked whales. BW43 signal encounters were restricted to Southern California and may be produced by Perrin’s beaked whale, known only from Californian waters. BW70 signals were detected in the southern Gulf of California, which is prime habitat for Pygmy beaked whales. Hubb’s beaked whale may have produced the BW40 signals encountered off central and southern California; however, these signals were also recorded off Pearl and Hermes Reef and Wake Atoll, which are well south of their known range.

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

“…Temporal coverage was limited to a single year or included substantial gaps at several of our monitoring sites, and data from additional years may be necessary to reveal subtler seasonal or interannual trends. However, results from large-scale PAM in the North Pacific demonstrated a similar lack of temporal patterning in the detection of beaked whale acoustic signals (Baumann-Pickering et al 2014), and coordinated seasonal movements have not been documented in any beaked whale species. Studies utilizing photographic identification or animal-borne satellite telemetry tags have revealed a high degree of site fidelity within some beaked whale populations, including Cuvier's and Blainville's beaked whales in Hawai'i (McSweeney et al 2007;Schorr et al 2010), Blainville's beaked whales in the Bahamas (Claridge 2013), and northern bottlenose whales in Nova Scotia (Hooker et al 2002;Wimmer and Whitehead 2004).…”

“…Prior studies have shown that many beaked whale species produce a stereotyped echolocation signal type that is stable across geographic regions (Baumann-Pickering et al 2014). However, we acknowledge that scientific understanding of the acoustic behavior of most beaked whale species is far from complete, particularly for True's, Sowerby's, and Gervais' beaked whales in the Atlantic Ocean.…”

“…Many beaked whale species produce stereotypical echolocation clicks with unique temporal and spectral characteristics, and recent studies have made important progress in describing and attributing these click types to specific species . These advances, combined with innovations in recording technology that allow the collection of broadband acoustic recordings over long deployment periods, have facilitated the use of PAM to effectively study the spatiotemporal occurrence of beaked whale species (e.g., Baumann-Pickering et al 2014). PAM systems are not dependent on weather conditions and are a particularly useful method for monitoring remote regions and obtaining year-round data on species presence.…”

Acoustic Metadata Management and Transparent Access to Networked Oceanographic Data Sets

“…One manuscript on world-wide beaked whale descriptions was published (Baumann-Pickering et al, 2014), and three more have been submitted (Roch et al, submitted-a; Roch et al, submitted-b; Širović et al, submitted Roch et al (submitted-b) is an echolocation click classification study that examined the effects of equipment and site variability across a range of instruments and years in the Southern California Bight. Analyses conducted in the three studies were greatly simplified by the use of the Tethys Metadata Workbench.…”

Listening in on the deep sea

“…Back then, the researchers had to actually see a marine mammal to make recordings, dipping underwater microphones, called hydrophones, a few meters into the water. It wasn't until the 1990s that biologists started experimenting with autonomous recording devices that could be left out at sea (2).…”