Posted on October 10, 2012
This report summarizes the results from SOCAL-11, the second year of the research project Southern California Behavioral Response Study (SOCAL-BRS) conducted in the Southern California Bight. The study’s overall objective is to provide a better understanding of marine mammal behavior and a direct scientific basis to estimate the risk and minimize adverse effects of human sounds, particularly military sonar, on marine mammals. During a scouting phase and two operational legs of SOCAL-11, researchers observed, photographed, and/or tracked thousands of individuals of 18 marine mammal species. Thirty-eight tags were secured on 35 individual animals of four different marine mammal species, including many on focal species including blue whales, Risso’s dolphins, and Cuvier’s beaked whales. Eighteen controlled exposure experiments (CEEs) were conducted on eighteen individuals from three marine mammal species. Simulated military sonar signals and noise bands of comparable frequency were presented (under strict safety—for the animals—protocols) as stimuli. Changes in behavior from baseline conditions 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 (that range from none to apparent temporary avoidance) depending upon species, type of sound, and behavioral state during the experiments. Results of sound source testing and verification prior to the start of SOCAL-11 fieldwork are also presented. Finally, results of Passive Acoustic Monitoring (PAM) using towed hydrophone arrays to detect and track beaked and sperm whales in real-time using their echolocation clicks are presented. It is concluded that, although localization could still be improved, distinguishing Cuvier’s from Baird’s and Mesoplodon beaked whales is now fairly reliable in real-time.
For immediate access to this report, please visit NPS-OC-12-005CR