Near-Real-Time Acoustic Monitoring of Beaked Whales and Other Cetaceans Using a Seaglider™

Abstract

In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle – a glider – equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The glider was tested extensively off the west coast of the Island of Hawai'i, USA. The instrument covered approximately 390 km during three weeks at sea and collected a total of 194 h of acoustic data. Detections of beaked whales were successfully reported to shore in near-real time. Manual analysis of the recorded data revealed a high number of vocalizations of delphinids and sperm whales. Furthermore, the glider collected vocalizations of unknown origin very similar to those made by known species of beaked whales. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many endangered marine mammal species.

Validating the reliability of passive acoustic localisation: a novel method for encountering rare and remote Antarctic blue whales

“…Wade et al 2006, Clark et al 2010, Klinck et al 2012, Rone et al 2012, Baumgartner et al 2013. Real-time acoustic detection can be used along with adaptive survey designs in order to increase the amount of time spent with animals during studies that rely on visual observations and/or contact with animals (e.g.…”

“…Barlow & Taylor 2005, Baumgartner et al 2013, or it can comprise the primary means of locating cryptic or critically endangered animals that may be dispersed over large or rarely accessed areas (e.g. Wade et al 2006, Klinck et al 2012, Rone et al 2012). …”

Novel opportunities for wildlife conservation and research with real‐time monitoring

“…Successful implementation of such devices includes monitoring cattle-foraging behavior (Clapham et al 2011), characterizing activity budgets of wildlife (Lynch et al 2013), investigation of species communication (Payne et al 2003), or identifying the presence of marine mammals (Klinck et al 2012). Real-time directional tracking of sounds is also possible (Bergamo et al 2004) and gunshot detection (e.g., ''ShotSpotter,'' available online)…”

Marine mammal tracks from two-hydrophone acoustic recordings made with a glider

“…Given their mode of operation, gliders provide a platform that is acoustically very quiet, making them well-suited for passive acoustic monitoring of marine mammals. Increasing amounts of marine mammal recordings are being obtained by fitting gliders with hydrophones (e.g., Klinck et al, 2012;Baumgartner et al, 2013).…”

“…), sperm whales (Physeter macrocephalus), and delphinids (Delphinidae sp. ), which all produce highly broadband high-frequency echolocation clicks, were detected in real time from a glider off Hawai'i in 2009 in a study of habitats and vocalization behavior (Klinck et al, 2012). In addition, sei whale (Balaenoptera borealis) vocalizations were recorded by a glider to study their diel vocalization patterns (Baumgartner and Fratantoni, 2008).…”