SEA is proud to partner with Cascadia Research Collective, NOAA/NMFS Southwest Fisheries Science Center, and Kelp Marine Research on a new marine mammal research project beginning off southern California.

“Integrating remote sensing methods to measure social delphinid baseline behavior and responses to Navy sonar”

This new research collaboration is being supported by the Office of Naval Research Marine Mammals and Biology Program. It builds on several recent and ongoing research efforts to provide high-resolution measurements of behavior and behavioral response of marine mammals to human noise in their environment using controlled exposure experiments. All research is authorized under NMFS permits #16111, 19091, and 19116 as well as numerous Institutional Animal Care and Use Committee and other federal, state, and local authorizations. All research is conducted with explicit monitoring and mitigation requirements in order to ensure studies are conducted safely and ethically while providing vitally needed information on understanding and managing the effects of noise on marine mammals. An initial evaluation of monitoring methods for this project will occur over the next several weeks with experimental work occurring in the fall and next summer. We will provide updates both here and through our research partners. Below is a simple summary of the project and more information is available on request from the project chief scientist at


Oceanic delphinids are generally not endangered or threatened, have typically not been observed in mass-stranding events associated with Navy sonar. Potential responses of these species are often inferred from laboratory measurements or from anecdotal observations in uncontrolled contexts, each of which has significant limitations in predicting responses in these common species for realistic sonar exposures. To date there have been no direct experimental studies of the potential responses of these animals in known, controlled conditions.

Building on related studies in a number of field sites, we will develop and utilize a novel integration of several established remote-sensing methods to quantify behavior and biopsy sampling to measure stress hormone levels in three delphinid species that are common and frequently exposed to Navy mid-frequency active sonar (MFAS) off California. We will evaluate potential responses to simulated mid-frequency active sonar (MFAS) using controlled exposure experiments (CEEs). The nature of the resulting data will be necessarily and categorically different from previous response studies involving tagging of single individuals. Beyond the fact that getting tags to stay on individuals has proven infeasible to date, these social species typically occur in groups and group members likely interact in their response to external stimuli. As such, the group, or part of the group, is likely the more relevant unit of analysis.


I.Develop integrated, cross-disciplinary methods to simultaneously track group movement and behavior using shore- or vessel-based visual observers, aerial photogrammetry, and remote-deployed acoustic recorders.

II.Apply group-sampling methods using integrated technologies to better characterize typical (undisturbed) behavioral parameters for these species.

III.Obtain biopsy samples for use in a collaborative research project to measure stress hormone levels

IV.Obtain direct measurements of group behavioral changes and stress hormone responses, if any, resulting from experimentally controlled simulated Navy MFAS for three delphinid species that occur in large numbers in Navy range areas, including common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus), and Risso’s dolphin (Grampus griseus).


Building on our recent and ongoing research, we will develop and utilize a novel integration of three different complementary systems to measure aspects of baseline behavior and potential behavioral responses to simulated mid-frequency active sonar (MFAS) using controlled exposure experiments (CEEs) in three delphinid species. Standard biopsy sampling procedures will be used to obtain tissue samples. A custom vertical line array sound source will project simulated MFAS signals at much lower power than real military sonar systems during CEEs. These studies are intended to identify the nature of behavioral responses to potential disturbance from sonar signals and the onset of responses using carefully controlled methods, in order to inform our evaluation of potential responses to more realistic and louder exposures that may occur off California during regular authorized sonar training events.

Remote sensing methods include:

(1) Shore- and vessel-based visual sampling;

(2) Unmanned aerial systems (UAS) for photogrammetry;

(3) Remote-deployed passive acoustic sensors