NEW PAPER: Context-dependent feeding strategies in blue whales

We are proud to announce the publication of a new and exciting paper on context-dependent behavioral strategies in feeding blue whales, lead by SEA’s own Dr. Ari Friedlaender and co-authored by Dr. Brandon Southall. The article is entitled:

Friedlaender, A. S., Herbert-Read, J., Hazen, E. L., Cade, D. E., Calambokidis, J., Southall, B. L., Stimpert, A. K., and Goldbogen, J. A. (2017). Context-dependent lateralized feeding strategies in blue whales. Current Biology 27, R1–R3.

The article can be downloaded for a limited time at:

Here are links to some of the international media coverage of this exciting work:

Senior Scientist B. Southall presents results from first-ever experiments with high-power military sonar and whales

At the ongoing 22nd Biennial Conference on the Biology of Marine Mammals. Halifax, Nova Scotia, Canada, SEA Senior Scientist Dr. Brandon Southall presented results from the first-ever experimental study of the potential effects of high-power military sonar. This study involved measurements of behavioral responses of several marine mammal species exposed in controlled conditions to navy ships operating the highest-power, mid-frequency sonar systems. These kinds of sonar systems have been involved in a number of previous marine mammal stranding events. Navies around the world, most notably the U.S. Navy, have been supporting extensive research to try and understand what the potential risks from these systems may be and how they might be mitigated. Subject species included beaked whales, blue whales, fin whales, and Risso’s dolphins in studies spanning five years off of southern California.

Through the support of and logistical cooperation with the U.S. Navy (primarily the Living Marine Research Program along with the Office of Naval Research Marine Mammal Program), SEA scientists as well as research partners from many academic, private, and government research organizations worked together to carefully expose animals to realistic scenarios with operational, full-scale sonar systems using controlled experimental methods. The results indicated behavioral responses (changes in diving and feeding behavior) within some individuals, but that compared with the probability of responses for less powerful systems operated closer to animals the relative probability of response for the same sound levels was substantially reduced. This gives us some insight into the increasingly clear picture that contextual aspects of sound exposure, such as distance, relative motion, and familiarity of the noise animals are exposed to, may be as or even more important in terms of predicting response probability than simply how loud the sound is. These studies are helping us understand many basic aspects of behavior and context-dependencies, as well as applied questions about response probability for operational sources in the ocean.


Two Harbors, Catalina Island.

We wanted to provide a quick from-the-field update on our progress on the TAGLESS-BRS project ongoing off Catalina Island in southern California. We have encountered many groups of common, bottlenose, and Risso’s dolphins, with thousands of individuals seen from land, sea, and air, such as the group of common dolphins (Delphinus delphis) seen above (NMFS permit #19116; J. Calambokidis).

Our field teams have been collecting large amounts of data on group movement and behavior using theodolites and high powered binoculars from land stations, listening buoys deployed from small boats (above), and unmanned aerial systems with precise camera systems (below). These let us track the movements and behavior of groups of these animals in fine resolution for periods of time.

During carefully controlled periods and with experimental and safety protocols specified in our many federal, state, and institutional permit requirements (NMFS permit #19116), we deploy a sound source (below) that simulates military sonar for short (10 min) transmissions of experimental sonar signals relatively far from shore. Animals are continuously monitored by multiple observers from different stations to ensure that any behavioral responses that are measured do not pose any risk of harm to animals. We’ve conducted almost 10 experiments thus far monitoring animals from all stations, some involving experimental sonar signals and others serving as no-sound controls.

While we have been quite busy with all the field effort and data analysis, we have taken a little time to enjoy some of the great beauty that this special place has to offer.

An osprey with a freshly caught kelp bass in Two Harbors under a nice moon.

The reliable and capable M/V Magician, our home and base of field operations for the project.

Nice shot of a leaping common dolphin during the study (NMFS permit #19116; courtesy D. Alps).

Fall Phase of Tagless-BRS study begins off Catalina Island

The SOCAL Tagless-BRS project is back on the water! SEA is partnering with Cascadia Research, Kelp Marine Research, and NOAA’s Southwest Fisheries Science Center and the talented crew of the M/V Magician (above) on an exciting technology integration collaboration conducting novel studies on the basic behavior and behavioral responses to noise in several dolphin species. Common, bottlenose, and Risso’s dolphins have proven challenging to study with high-resolution tag sensors, but there are important scientific and conservation reasons to understand how they behave and respond to potential disturbances. We described our overall objectives and methodology during our initial effort this spring – please see the below link for more details:

We made major progress in the spring effort described there in understanding how to integrate shore-based visual tracking, unmanned aerial systems to track and quantify spatial orientation of animals, and underwater listening buoys to measure group calling behavior. We collected tens of thousands of images, tracks, and recordings of baseline behavioral patterns of all three species tracked in controlled, experimental conditions. By design owing to the novelty and challenges in doing this in these species, we did not include sound exposure in the spring effort, however. Careful analysis of the approaches used and data collected resulted in a number of adaptations and refinement of the methods to ensure we can succeed in collecting the most meaningful data on responses of animals to meet the project objectives. With those useful lessons, we are now moving carefully forward with the experimental aspects of the study using controlled exposure experiments using simulated military sonar signals.

We’ve just started up our fall field effort over the next two weeks and have had several successful baseline focal follow monitoring sequences with all teams. We have specific protocols and requirements (NMFS permit #19116) to ensure we can successfully and safely complete the experiments involving sound exposure and today the Catalina fog monster (below) limited our ability to conduct an experimental sound sequence. We will provide some subsequent updates on our progress and findings here. Many thanks to all our collaborators and thanks for the support of the Office of Naval Research for this project. For more information or interest in this project, contact



NEW PUBLICATION – New insights into prey aggregation in ocean scattering layers

SEA’s Senior Scientist Dr. Brandon Southall was proud to co-author a recent paper providing new insights into the aggregation of marine organisms into ocean scattering layers – a basic principle of life in the ocean. This paper was lead by our colleague Dr. Kelly Benoit-Bird of MBARI and Oregon State University. The citation and abstract are provided below. A courtesy copy of the paper is available on request from

Benoit-Bird, K. J., Moline, M. A., and Southall, B. L. (2017). Prey in oceanic sound scattering layers organize to get a little help from their friends. Limnology and Oceanography. DOI:10.1002/lno.10606

Group formation in animals is a widespread phenomenon driven by food acquisition, reproduction, and

defense. Life in the ocean is characteristically aggregated into horizontally extensive layers as a result of

strong vertical gradients in the environment. Each day, animals in high biomass aggregations called “deep

scattering layers” migrate vertically, comprising the largest net animal movement on earth. This movement

is commonly thought of as a predator avoidance tactic, however, the aggregation of animals into layers has

been viewed as an incidental outcome of similar responses by many individuals to the risk of visual predation

coupled with the location of resources including food and oxygen rather than active, socially mediated

congregation for defense purposes. Here, using a newly adapted autonomous vehicle to measure individual

characteristics, we provide the first measures of the internal layer structure, demonstrating that these features

are made up of many topologically scaled, mono-specific aggregations, or “schools” rather than an indiscriminate

mix of sizes and species. Schools responded to predators using behavior much like flash compression

while neighboring aggregations increased their spacing to maintain coherent layers. Rather than simply an

incidental outcome, the formation of layers of life in the sea is a highly organized process driven, at least in

part, by biotic pressures for cohesion with broad adaptive significance for the myriad species that inhabit

these ubiquitous features. These observations highlight the range of spatial scales we must examine in order

to understand the strong impacts these high-biomass layers have on ecological and biogeochemical processes

in the sea.

NEW PUBLICATION – Shipping Noise and Marine Mammals

SEA’s Senior Scientist Dr. Brandon Southall recently authored a chapter within the Encyclopedia of Maritime and Offshore Engineering (Wiley). This publication traces a decade-long collaboration among several governmental, non-governmental, academic, and industry partners to begin to tackle the global issue of shipping noise in the ocean and it’s potential effects on marine mammals. Beginning with simply identifying this issue as a broad consideration, to proposing some international partnerships, and ultimately the implementation of voluntary guidelines for vessel-quieting, this was both a great accomplishment and a great example of how cross-sectoral partnerships can work in addressing difficult issues. The chapter is currently featured on the Wiley site and available to view online at:

The citation for this chapter and the abstract is available below:

Southall, B. L., Scholik-Schlomer, A., Hatch, L., Bergmann, T., Jasny, M., Metcalf, K., Weilgart, L. and Wright, A. J. (2017). Underwater Noise from Large Commercial Ships – International Collaboration for Noise Reduction in Encyclopedia of Maritime and Offshore Engineering (J. Carlton, P. Jukes, Y. S. Choo, eds). Wiley & sons Publishing, New York, NY). DOI: 10.1002/9781118476406.emoe056. ISBN: 978-1-118-47635-2

Ambient noise in broad areas of the ocean has increased significantly over the last half-century from the introduction of tens of thousands of commercial ships continuously transiting the sea.  Ship-radiated noise is predominately low frequency (<1000 Hz) other than close to vessels, and aggregate noise can dominate low-frequency bands, even well outside shipping lanes. Such sounds add to an already noisy background and can affect marine animals in various ways. This includes reducing the areas over which they can communicate, particularly for species that rely on low-frequency sounds like baleen whales, seals, and fishes. An international community of researchers, environmental groups, government agencies, and sectors of the shipping industry has recognized shipping noise as an important marine conservation issue, as have various international bodies, notably the United Nation’s International Maritime Organization (IMO). Reducing potential impacts from aggregate vessel noise is challenging given the nature and magnitude of the issue and the historical lack of regulation. But substantial recent progress has been made by proactive collaborations among environmentalists, regulators, scientists, and industry, leading to progress in the IMO in the development of guidelines for the reduction of underwater noise from commercial shipping. This chapter discusses low-frequency noise incidentally radiated from ships and its potential effects on marine life, with an emphasis on marine mammals. We also trace the formation and evolution of efforts to address environmental and economic costs and benefits of ship-quieting efforts. The authors represent a range of governmental, scientific, industry, and conservation organizations centrally engaged in the IMO effort.

New Marine Mammal Research Project – Integrating Visual and Acoustic Sensors to Study Behavior and Behavioral Response in Small Cetaceans

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

Brandon Southall Leads Ocean Acoustics Panel at Capital Hill Oceans Weeks

This week is Capital Hill Oceans Week in Washington D.C. Organized by the National Marine Sanctuaries Program, this event brings together ocean policy makers and scientists from around the U.S. to discuss cutting edge issues in marine science and conservation. (please see:

The session is entitled “Cacophony: The decline of silent seas” and it take place on Wednesday, June 14, 2017 from 9:30 am to 10:30 am at the Ronald Reagan Building and International Trade Center (1300 Pennsylvania Ave NW, Washington, DC). The session will be led by SEA’s Dr Brandon Southall. Panelists include experts in marine noise reduction, commercial shipping operations, oil and gas exploration, and marine conservation. A summary of the session is given below.

NOTE: A full video of this panel discussion is now available online


“Diving under the waves often elicits images of a quiet and serene place, but the sea is no longer silent. As use of technology for everything from shipping to energy exploration and production, to military activity increases, our use of the ocean brings with it noise that travels long distances and has lasting effects throughout the marine environment. Numerous marine animals from invertebrates to mammals rely on sound for survival. We are just beginning to understand the full range of how sound is used by these animals – finding prey, mating, avoiding predators, navigating, and communicating – and how anthropogenic noise impacts these functions. This session will explore the current information that exists on ocean noise and its mitigation, with a focus on the development and implementation of noise reduction technology within industry.”


Public Outreach on Marine Acoustics in Monterey Bay

Dr. Brandon Southall will appear with colleagues from MBARI and the Monterey Bay National Marine Sanctuary this Friday March 3rd at 5pm for a First Friday public event entitled:

“Sounds in the Sanctuary: An Opportunity to Listen Beneath the Waves”

Recordings of sounds from animals and people recorded on a new passive acoustics listening system in Monterey Bay will be displayed and explained with an interactive exhibit.

Dr. Brandon Southall serves on United Nations ocean acoustics panel

An international group of ocean scientists and leaders from a range of international research and environmental organizations, government agencies, and industry partners (pictured below) participated in a special session on ship noise and ship strike issues related to marine conservation at a recent preparatory meeting for the United Nations Oceans Conference. SEA’s Brandon Southall was among the invited panelists, which also included the President of the General Assembly of the United Nations.

A summary of the concept note developed for this meeting and a summary of the event is available at the Oceans Conference website: and

Edited video and all the various documents available (including our final WG summary is also available at:


This event lead to the formation of a working group in preparation for the June UN Oceans Conference which has developed a set of voluntary commitments on the reduction of noise in the oceans, for which SEA is proud to be a participating member:


SOCAL-BRS is a study of basic behavior and responses to controlled sound exposures in a variety of marine mammal species.

Southall Environmental Associates, Inc.

Reducing environmental impacts from essential human activities requires unique approaches to meet challenging conservation objectives in the 21st century. SEA, Inc. works globally with diverse scientific teams and cutting-edge technologies to provide real-world solutions. Learn more about SEA