Biological and Behavioral Response Studies of Marine Mammals in southern California (SOCAL-10)

SOCAL‐10 was a scientific research project conducted in Aug‐Sept 2010 in the Southern California Bight. The overall objective was to provide a better understanding of marine mammal behavior, while providing direct scientific data for the Navy and regulatory agencies to estimate risk and minimize adverse effects of human sounds, particularly military sonar. SOCAL‐10 extended previous studies in the Bahamas (2007‐08) and Mediterranean Sea (2009) of whether and how marine mammals change their behavior when they hear different sounds; each effort integrated behavioral response studies (BRS) with ongoing research on diving, foraging, and social behavior. SOCAL‐10 was the first in a five‐year dedicated effort to study a variety of marine mammals in this area.

Like previous behavioral response studies (BRS) using controlled (sound) exposure experiment (CEE) methods, SOCAL‐10 involved an interdisciplinary collaboration of experts in marine mammal biology, behavior, and communication, as well as underwater acousticians and specialized field researchers1. During a preliminary scouting phase and two research legs on different research vessels, SOCAL‐10 observed, photographed, and/or tracked in detail, individuals of 21 different marine mammal species. Sixty‐three tags (of six different varieties) were successfully secured on 44 individual animals of at least eight different marine mammal species, including several for which little or no comparable tag data previously existed.

Researchers also conducted 28 controlled sound exposure experiments in which animals were monitored with acoustic and movement sensors (attached to animals with suction cups), remote listening devices and specialized observers with reticle binoculars. Sounds simulating military sonar (though several orders of magnitude less intense) and control stimuli were then played to the animals under specific protocols and protective measures (to ensure animals were not harmed) and changes in behavior were measured as a function of sound exposure. Preliminary results based primarily on clearly observable behavior in the field and from initial data assessment indicate variable responses, depending on species, type of sound, and behavioral state during the experiments. Some observations in certain conditions suggest avoidance responses, while in other cases subjects seemed to not respond, at least overtly.

Additional analysis and interpretation is underway of the ~400 hours of tag data, as well as thousands of marine mammal observations, photographs, tissue samples, and acoustic measurements. SOCAL‐10 was supported by several organizations within the U.S. Navy (below) seeking better data to inform decision‐making, and was closely coordinated with the U.S. National Oceanic and Atmospheric Administration (NOAA).


Southall, B. L.; Calambokidis, J.; Tyack, P.; Moretti, D.; Hildebrand, J.; Kyburg, C.; Carlson, R.; Friedlaender, A.; Falcone, E.; Schorr, G.; Douglas, A.; DeRuiter, S.; Goldbogen, J.; Pusser, T.; Barlow, J. 2011. Biological and Behavioral Response Studies of Marine Mammals in southern California (SOCAL-10). Abstract (Proceedings) 19th Biennial Conference on the Biology of Marine Mammals, Tampa, Florida, November 27-December 2, 2011.

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