Select SEA Publications

Behavior and Ecology

Southall et al (2019) – Quantifying deep-sea predator–prey dynamics: Implications of biological heterogeneity for beaked whale conservation
Prey distribution and density drive predator habitat usage and foraging behavior. Understanding ecological relationships is necessary for effective management in any environment but can be challenging in certain contexts. While there has been substantial effort to quantify human disturbance for some protected, deep-diving marine mammals, there are virtually no direct measurements of deep-sea predator–prey dynamics.

Arranz et al (2019) – Diving Behavior and Fine-Scale Kinematics of Free-Ranging Risso’s Dolphins Foraging in Shallow and Deep-Water Habitats
Air-breathing marine predators must balance the conflicting demands of oxygen conservation during breath-hold and the cost of diving and locomotion to capture prey. However, it remains poorly understood how predators modulate foraging performance when feeding at different depths and in response to changes in prey distribution and type.

Arranz et al (2018) – Risso’s dolphins plan foraging dives
Humans remember the past and use that information to plan future actions. Lab experiments that test memory for the location of food show that animals have a similar capability to act in anticipation of future needs, but less work has been done on animals foraging in the wild. We hypothesized that planning abilities are critical and common in breath- hold divers who adjust each dive to forage on prey varying in quality, location and predictability within constraints of limited oxygen availability.

Friedlaender et al (2017) – Context-dependent lateralized feeding strategies in blue whales

Arranz et al (2016) – Discrimination of fast click-series produced by tagged Risso’s dolphins (Grampus griseus) for echolocation or communication
Early studies that categorized odontocete pulsed sounds had few means of discriminating signals used for biosonar-based foraging from those used for communication. This capability to identify the function of sounds is important for understanding and interpreting behavior; it is also essential for monitoring and mitigating potential disturbance from human activities.

Hazen et al (2015) – Blue whales (Balaenoptera musculus) optimize foraging efficiency by balancing oxygen use and energy gain as a function of prey density
Terrestrial predators can modulate the energy used for prey capture to maximize efficiency, but diving animals face the conflicting metabolic demands of energy intake and the minimization of oxygen depletion during a breath hold. It is thought that diving predators optimize their foraging success when oxygen use and energy gain act as competing currencies, but this hypothesis has not been rigorously tested because it has been difficult to measure the quality of prey that is targeted by free-ranging animals.

Stimpert et al (2015) – Sound production and associated behavior of tagged fin whales (Balaenoptera physalus) in the Southern California Bight
For marine animals, acoustic communication is critical for many life functions, yet individual calling behavior is poorly understood for most large whale species. These topics are important for understanding whale social behavior and can also serve as a baseline for behavioral studies assessing whale response to disturbance. Using a new technique for identifying the calling individual, we measured body orientation, dive behavior, and surface social behavior in relation to call production for tagged fin whales in Southern California.

Goldbogen (2014) – Using accelerometers to determine the calling behavior of tagged baleen whales
Low-frequency acoustic signals generated by baleen whales can propagate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals.

Friedlaender (2014) – Feeding performance by sympatric blue and fin whales exploiting a common prey resource
A major focus in macroecology is to understand the mechanisms that drive differences in habitat, morphology, and behavior in closely related species (Brown 1995). Within this paradigm, energy use and prey acquisition play a fundamental role in affecting behavior, especially with respect to foraging patterns and predator-prey interactions.

Goldbogen (2013) – Underwater acrobatics by the world’s largest predator: 360° rolling manoeuvres by lunge-feeding blue whales
The extreme body size of blue whales requires a high energy intake and therefore demands efficient foraging strategies. As an obligate lunge feeder on aggregations of small zooplankton, blue whales engulf a large volume of prey-laden water in a single, rapid gulp. The efficiency of this feeding mechanism is strongly dependent on the amount of prey that can be captured during each lunge, yet food resources tend to be patchily distributed in both space and time.

Behavioral Response Studies

Southall et al (2019) – Behavioral responses of individual blue whales (Balaenoptera musculus) to mid-frequency military sonar
This study measured the degree of behavioral responses in blue whales (Balaenoptera musculus) to controlled noise exposure off the southern California coast. High-resolution movement and passive acoustic data were obtained from non-invasive archival tags (n=42) whereas surface positions were obtained with visual focal follows. Controlled exposure experiments (CEEs) were used to obtain direct behavioral measurements before, during and after simulated and operational military mid-frequency active sonar (MFAS), pseudorandom noise (PRN) and controls (no noise exposure).

Ellison et al (2018) – An Acoustic Scene Perspective on Spatial, Temporal, and Spectral Aspects of Marine Mammal Behavioral Responses to Noise
Considering contextual factors in sound exposure scenarios when evaluating the probability and severity of behavioral responses of marine wild- life to sound is critically important. There is an increasingly strong scientific basis supporting the role of contextual variables and the need to con- sider these implications in regulatory assessments of potential impacts.

Guan et al (2017) – Sonar Inter-Ping Noise Field Characterization During Cetacean Behavioral Response Studies off Southern California
The potential negative effects of sound, particularly active sonar, on marine mammals has received considerable attention in the past decade. Numerous behavioral response studies are ongoing around the world to examine such direct exposures. However, detailed aspects of the acoustic field (beyond simply expo- sure level) in the vicinity of sonar operations both during real operations and experimental exposures have not been regularly measured.

Southall et al (2017) – Mitigation of harm during a novel behavioural response study involving active sonar and wild cetaceans
Some studies of how human activities can affect wild free-ranging animals may be considered to have potential negative outcomes too severe to be ethically studied. This creates a societal dilemma involving choices between continuing risky activities with high uncertainty about their potential effects on wildlife, often with considerable associated precaution or undertaking focused research to reduce uncertainty, but with some risk of harm from either strong response leading to potential stranding or direct physical injury from sound exposure.

DeRuiter et al (2017) – A Multivariate Mixed Hidden Markov Model for Blue Whale Behaviour and Responses to Sound Exposure
Characterization of multivariate time series of behaviour data from animal-borne sensors is challenging. Biologists require methods to objectively quantify baseline behaviour, and then assess behaviour changes in response to environmental stimuli. Here, we apply hidden Markov models (HMMs) to characterize blue whale movement and diving behaviour, identifying latent states corresponding to three main underlying behaviour states: shallow feeding, travelling, and deep feeding.

Friedlaender et al (2016) – Prey-mediated behavioral responses of feeding blue whales in controlled sound exposure experiments
Behavioral response studies provide significant insights into the nature, magnitude, and consequences of changes in animal behavior in response to some external stimulus. Controlled exposure experiments (CEEs) to study behavioral response have faced challenges in quantifying the importance of and interaction among individual variability, exposure conditions, and environmental covariates.

Southall et al (2016) – Experimental field studies to measure behavioral responses of cetaceans to sonar
Substantial recent progress has been made in directly measuring behavioral responses of free-ranging marine mammals to sound using controlled exposure experiments. Many studies were motivated by concerns about observed and potential negative effects of military sonar, including stranding events. Well-established experimental methods and increasingly sophisticated technologies have enabled fine-resolution measurement of many aspects of baseline behavior and responses to sonar.

Stimpert et al (2014) – Acoustic and foraging behavior of a Baird’s beaked whale, Berardius bairdii, exposed to simulated sonar
Beaked whales are hypothesized to be particularly sensitive to anthropogenic noise, based on previous strandings and limited experimental and observational data. However, few species have been studied in detail. We describe the underwater behavior of a Baird’s beaked whale (Berardius bairdii) from the first deployment of a multi-sensor acoustic tag on this species. The animal exhibited shallow (23 6 15 m max depth), intermediate (324 6 49 m), and deep (1138 6 243 m) dives.

DeRuiter et al (2013) – First direct measurements of behavioural responses by Cuvier’s beaked whales to mid-frequency active sonar
Most marine mammal strandings coincident with naval sonar exercises have involved Cuvier’s beaked whales (Ziphius cavirostris). We recorded animal movement and acoustic data on two tagged Ziphius and obtained the first direct measurements of behavioural responses of this species to mid-frequency active (MFA) sonar signals.

Goldbogen (2013) – Blue whales respond to simulated mid-frequency military sonar
Mid-frequency military (1–10 kHz) sonars have been associated with lethal mass strandings of deep-diving toothed whales, but the effects on endangered baleen whale species are virtually unknown. Here, we used controlled exposure experiments with simulated military sonar and other mid-frequency sounds to measure behavioural responses of tagged blue whales (Balaenoptera musculus) in feeding areas within the Southern California Bight.

Southall et al (2012) – Marine Mammal Behavioral Response Studies in Southern California: Advances in Technology and Experimental Methods
Behavioral response studies (BRS) are increasingly being conducted to better understand basic behavioral patterns in marine animals and how underwater sounds, including from human sources, can affect them. These studies are being enabled and enhanced by advances in both acoustic sensing and transmission technologies.

Hearing and Noise Impacts

Southall et al (2019) – Marine Mammal Noise Exposure Criteria: Updated Scientific Recommendations for Residual Hearing Effects
This article evaluates Southall et al. (2007) in light of subsequent scientific findings and proposes revised noise exposure criteria to predict the onset of auditory effects in marine mammals. Estimated audiograms, weighting functions, and underwater noise exposure criteria for temporary and permanent auditory effects of noise are presented for six species groupings, including all marine mammal species.

Sills et al (2016) – Listening for signals in seismic noise: A case study of masking in Arctic seals
When considering the effects of noise on hearing in marine mammals, standard audiometric data are commonly applied to predict how a noise source will influence an individual or species. With regard to auditory masking, critical ratio measurements and average noise spectral density levels can be used to obtain masked threshold predictions. However, the extent to which this method is appropriate varies based on the features of the noise source in question.

Reichmuth (2016) – Low-frequency temporary threshold shift not observed in spotted or ringed seals exposed to single air gun impulses
Underwater hearing thresholds were measured at 100 Hz in trained spotted (Phoca largha) and ringed seals (Pusa hispida) before and immediately following voluntary exposure to impulsive noise from a seismic air gun. Auditory responses were determined from psychoacoustic data and behavioral responses were scored from video recordings.

Sills (2015) – Amphibious hearing in ringed seals (Pusa hispida): underwater audiograms, aerial audiograms and critical ratio measurements
Ringed seals (Pusa hispida) are semi-aquatic marine mammals with a circumpolar Arctic distribution. In this study, we investigate the amphibious hearing capabilities of ringed seals to provide auditory profiles for this species across the full range of hearing. Using psychophysical methods with two trained ringed seals, detection thresholds for narrowband signals were measured under quiet, carefully controlled environmental conditions to generate aerial and underwater audiograms.

Nowacek (2015) – Marine seismic surveys and ocean noise: time for coordinated and prudent planning
Marine seismic surveys use intense (eg 230 decibel [dB] root mean square [RMS]) sound impulses to explore the ocean bottom for hydrocarbon deposits, conduct geophysical research, and establish resource claims under the United Nations Convention on the Law of the Sea. The expansion of seismic surveys necessitates greater regional and international dialogue, partnerships, and planning to manage potential environmental risks. 

Sills (2014) – Amphibious hearing in spotted seals (Phoca largha): underwater audiograms, aerial audiograms and critical ratio measurements
Spotted seals (Phoca largha) inhabit Arctic regions that are facing both rapid climate change and increasing industrialization. While little is known about their sensory capabilities, available knowledge suggests that spotted seals and other ice seals use sound to obtain information from the surrounding environment. To quantitatively assess their auditory capabilities, the hearing of two young spotted seals was tested using a psychophysical paradigm.

Southall et al (2003) – Auditory masking in three pinnipeds: Aerial critical ratios and direct critical bandwidth measurements
This study expands the limited understanding of pinniped aerial auditory masking and includes measurements at some of the relatively low frequencies predominant in many pinniped vocalizations. Behavioral techniques were used to obtain aerial critical ratios CRs within a hemianechoic chamber for a northern elephant seal Mirounga angustirostris, a harbor seal Phoca vitulina, and a California sea lion Zalophus californianus.

Science-Policy Interface

Calambokidis et al (2019) – Differential Vulnerability to Ship Strikes Between Day and Night for Blue, Fin, and Humpback Whales Based on Dive and Movement Data From Medium Duration Archival Tags
We examine the dive and movement behavior of blue, fin, and humpback whales along the US West Coast in regions with high ship traffic where ship strikes have been identified as a major concern. All three species are known to feed in coastal waters near areas of high ship traffic.

Southall et al (2017) – Underwater Noise from Large Commercial Ships—International Collaboration for Noise Reduction
Underwater noise introduced by ships into the ocean environment originates from a number of sources, both deliberately produced for navigational purposes and incidentally emitted as a function of mechanical operations. The focus of this article, however, is on propulsion systems, which are the predominant sources of overall radiated noise from individual ships.

Forney et al (2017) – Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity
As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses, including injury and mortality, to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increased gradually. Recent experiences demonstrate that this approach is inadequate or even counterproductive for small, localized marine mammal populations, for which displacement of animals may itself cause harm.

Nowacek, Southall (2016) – Effective planning strategies for managing environmental risk associated with geophysical and other imaging surveys
This document is a practical guide to the responsible and effective planning of offshore geophysical surveys and other forms of environmental imaging. It will be useful for both understanding the impacts of imaging surveys on managed resources and planning future activities.

Ellison et al (2012) – A New Context-Based Approach to Assess Marine Mammal Behavioral Responses to Anthropogenic Sounds
Acute effects of anthropogenic sounds on marine mammals, such as from military sonars, energy development, and offshore construction, have received considerable international attention from scientists, regulators, and industry. Moreover, there has been increasing recognition and concern about the potential chronic effects of human activities (e.g., shipping). It has been demonstrated that increases in human activity and background noise can alter habitats of marine animals and potentially mask communications for species that rely on sound to mate, feed, avoid predators, and navigate.