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Marine Species Monitoring

Assessment of Marine Mammal Vocal Response to Sonar

Introduction & Objectives

Passive acoustic monitoring using autonomous recorders deployed on the seafloor is an effective method for long-term monitoring of marine mammals (Mellinger et al. 2007, Van Parijs et al. 2009). Autonomous recorders have been used to investigate the distribution, occurrence, and acoustic behaviors of a variety of marine mammals in diverse habitats and geographic locations (Clark et al. 2002, Clark and Clapham 2004, Baumgartner et al. 2008, Johnston et al. 2008, Sousa-Lima et al. 2013). Recently, researchers have analyzed autonomous recorder data to investigate the effects of anthropogenic noise, such as seismic airguns and sonar, on the calling behavior of baleen whales (Nieukirk et al. 2004, Di Iorio and Clark 2010, Castellote et al. 2012, Melcón et al. 2012, Risch et al. 2012). Changes in vocal behavior in response to anthropogenic noise have been studied in several species of odontocetes. For example, beluga whales (Delphinapterus leucas), killer whales (Orcinus orca)and Pacific humpback dolphins (Sousa chinensis)have been documented to change call rates and time‑frequency characteristics of their calls in response to vessel noise (Au et al. 1985, Lesage et al. 1999, Van Parijs and Corkeron 2001, Foote et al. 2004). Much less is known about the behavioral responses of odontocetes to mid-frequency active sonar (MFAS).

This study is a collaborative effort involving researchers at Cornell University, Bio-Waves, Inc., and St. Andrews University to develop robust statistical methods that can be used to analyze vocal behavior before, during, and MFAS activities on a species-by-species basis when possible. The primary objectives were to develop analytic methods to evaluate vocal responses based on passive acoustic monitoring techniques, and evaluate behavioral responses by cetaceans exposed to MFAS from U.S. Navy training and testing activities.

Technical Approach

In order to further investigate potential changes in behavior in response to MFAS exposure, sounds of marine mammals were recorded in the vicinity of three U.S. Navy training exercises before, during, and after the use of MFAS in Onslow Bay, North Carolina (July 2008), and near Jacksonville, Florida (September–October, and December 2009). The resulting passive acoustic data were analyzed using automated signal-detection software to detect individual sonar transmissions (“pings”), and sounds from a variety of cetaceans including striped dolphin , short-beaked common dolphin, bottlenose, Atlantic spotted dolphins, short-finned pilot whales, sperm whales, minke whales, fin whales, and North Atlantic right whales. Statistical analysis and methods development was performed using generalized estimating equations (GEEs), and the other used hidden Markov models (HMM).

 

Progress & Results

Initial methods development has been completed.  The results obtained from the initial methods development and analyses provide a good foundation for the further development of statistical methods for evaluating changes in cetacean acoustic behavior in response to MFA sonar, however larger sample sizes and the inclusion of covariates representing a cumulative effect of sonar on vocalization behaviors are necessary to make these analyses more robust. Methods and results are detailed in two final reports and continued model development and analysis is being conducted through the incorporation of additional data.  A final report covering the results from this continued work is now available.

 
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