Selene Fregosi

The acoustic signature of the male northern elephant seal: Individual variation supports recognition during competitive interactions

Northern elephant seals (Mirounga angustirostris) have a polygynous breeding system in which adult males establish dominance hierarchies that determine access to females. Acoustic signaling plays an important role in settling fights between males, as stereotyped displays elicit appropriate behavioral responses from individuals without contact during an energetically demanding breeding season. To determine whether reliable differences exist in the acoustic displays of individuals and whether these differences function to convey identity, we behaviorally and acoustically sampled male seals during the breeding season. Vocalizations were recorded during competitive interactions and analyzed for spectral, temporal, and amplitude characteristics. A cross-validated discriminant function analysis revealed small differences within—and significant differences between—the calls produced by 17 adult males of known dominance status. To determine whether acoustic displays serve as individual signatures that males learn...

Mobile Autonomous Platforms for Passive-Acoustic Monitoring of High-frequency Cetaceans

Increased human activities in coastal and offshore waters, including renewable energy efforts such as the deployment and operation of wind, wave, and tidal energy converters, leads to potential negative impacts on marine ecosystems. Efficient monitoring of marine mammals in these areas using stationary passive-acoustic technologies is challenging. Many recreational and commercial activities (e.g., fishing) can hinder long-term operation of moored listening devices. Further, these waters are often utilized by cetaceans such as porpoise species which produce high-frequency echolocation clicks (peak frequency ~130 kHz) for navigation, communication, and prey detection. Because these ultrasonic signals are strongly absorbed during propagation, the acoustic detection range is limited to a few 100 m, and therefore the spatial coverage of stationary recorders is relatively limited. In contrast, mobile passive-acoustic platforms could potentially be used to survey areas of concern for high-frequency cetacean vocalizations and provide increased temporal coverage and spatial resolution. In a pilot study, a commercially available acoustic recorder featuring sampling rates of up to 384 kHz was customized and implemented on an autonomous underwater vehicle (AUV) and an unmanned surface vehicle (USV) and tested in the field. Preliminary results indicate that these systems (a) are effective at detecting the acoustic presence of high-frequency cetaceans such as porpoises, and (b) could be a valuable tool to monitor potential negative impacts of renewable energy and other anthropogenic disturbances in the marine environment.

Baleen whale calling behavior and response to anthropogenic sound

Without a means of studying large whales in a controlled experimental environment, less is understood about their sound production mechanisms than is understood about those of smaller odontocetes. To describe call production behavior in fin whales, we used a recent technique that correlates fast-sampling accelerometer signals from tags with concurrently recorded acoustic signals to identify calls produced by the tagged animal. We tagged 18 fin whales as part of the Southern California Behavioral Response Study (SOCAL BRS), of which four were confirmed to be calling. We were then able to describe their kinematic and social behavior in relation to call production. Behaviors associated with elevated call rates included shallow maximum dive depths, little body movement, and negative pitch in body orientation, similar to some other calling baleen whale species. These are the first descriptions of body orientation and dive depths at which fin whales are most likely to call. We also describe calling responses (o...

Simultaneous recordings of marine mammal calls by a glider, float, and cabled hydrophone array

Recent advances in passive acoustic monitoring (PAM) technologies have led to development of mobile autonomous platforms for recording marine mammals. These instruments may allow greater spatial and temporal sampling than traditional towed or bottom moored systems. However, comparison of recording abilities of these instruments to traditional methods has yet to be performed. We deployed two types of commercially available platforms at the Southern California Offshore Range (SCORE) complex in late December 2015 through early January 2016. The QUEphone, based on the APEX float (Teledyne Webb Research, Falmouth, MA, USA), is a buoyancy driven device capable of descending to 2000 m where it drifts horizontally with the currents. The Seaglider (Kongsberg Underwater Technology, Lynwood, WA, USA) is also buoyancy driven, but dives repeatedly up to 1000 m following a flight path controlled via satellite. We deployed one glider and two floats, each equipped with identical acoustic sensors developed by Oregon State...

An animal-borne active acoustic tag for minimally invasive behavioral response studies on marine mammals

BackgroundThere is a variety of evidence that increased anthropogenic noise (e.g., shipping, explosions, sonar) has a measureable effect on marine mammal species. Observed impacts range in severity from brief interruptions of basic life functions to physiological changes, acute injury, and even death. New research tools are needed to better measure and understand the potential effects of anthropogenic noise on marine mammals. Current behavioral response studies typically utilize ship-based sound sources to study potential acute behavioral responses in tagged animals experimentally exposed to noise. Integrating the sound source within animal-mounted passive acoustic and motion-sensing tags provides a novel tool for conducting additional highly controlled response studies.ResultsWe developed and conducted pilot field trials of a prototype tag on five juvenile northern elephant seals, Mirounga angustirostris, using experimental exposures to both natural and anthropogenic noise stimuli. Results indicate behavioral responses were elicited in tagged individuals. However, no pattern was found in the occurrence and types of response compared to stimulus type. Responses during the ascending dive phase consisted of a dive inversion, or sustained reversal from ascending to descending (8 of 9 exposures). Dive inversions following exposure were 4–11 times larger than non-exposure inversions. Exposures received during the descending dive phase resulted in increased descent rates in 9 of 10 exposures. All 8 exposures during dives in which maximum dive depth was limited by bathymetry were characterized by increased flow noise in the audio recordings following exposure, indicating increased swim speed.ConclusionsResults of this study demonstrate the ability of an animal-mounted sound source to elicit behavioral responses in free-ranging individuals. Behavioral responses varied by seal, dive state at time of exposure, and bathymetry, but followed an overall trend of diving deeper and steeper and swimming faster. Responses did not consistently differ based on stimulus type, which may be attributable to the unique exposure context of the very close proximity of the sound source. Further technological development and focused field efforts are needed to advance and apply these tools and methods in subsequent behavioral response studies to address specific questions.

Detection probability of Cuvier’s beaked whale clicks from a glider and a deep-water float

Work is being conducted to estimate marine mammal density and abundance from slow-moving, passive acoustically equipped underwater gliders and deep-water floats. We deployed five drifting acoustic spar buoy recorders (DASBRs) simultaneously with a seaglider and QUEphone float in the Catalina Basin of Southern California in 2016 to estimate the probability of detecting Cuvier’s beaked whale echolocation clicks from the glider and float. The DASBRs successfully localized and tracked individual whales, though a limited number of encounters prohibited estimation of detection probability through a trial-based method. We explored using a spatially explicit capture recapture (SECR) approach. The SECR analysis was modified to account for the non-static array and we explored sample size requirements for SECR using simulations. During tracked dives, over 200 one-minute time bins contained echolocation clicks on at least one DASBR. Of these, 10 and 34 bins contained clicks recorded on the glider and float, respectively, and were used to make preliminary estimates of detection probability as a function of range. Detection probability estimation is a key step towards animal density estimation; other information such as encounter rate and click production rates are required to estimate animal density, which will form the next part of this work.

Passive acoustic monitoring in the Northern Gulf of Mexico using ocean gliders

Although George Ioup did not use ocean gliders for passive acoustic monitoring, he recognized their value as platforms for PAM and encouraged others to use them. They function well as PAM platforms because (1) they move slowly, minimizing flow noise; (2) they have no propeller or continuously running machinery, minimizing motor noise; (3) they collect acoustic data nearly continuously; (4) they traverse the upper water column every few hours, measuring temperature and salinity as needed for calculating sound speed profiles and enabling accurate modeling of long-range acoustic propagation; (5) they can cover hundreds to thousands of kilometers in distance during a deployment, enabling them to monitor a large area and/or repeatedly monitor a smaller area; and (6) some models can dive to 1000 m, the depth at which some deep-diving cetaceans—sperm and beaked whales, frequent targets of PAM operations—forage and vocalize. Two models of gliders equipped with passive acoustic recording systems were deployed in t...

Evaluating autonomous underwater vehicles as platforms for animal population density estimation

AFFOGATO (A Framework For Ocean Glider-based Acoustic density estimation) is a multi-year project (2015—2018) funded by the Office of Naval Research. Its main goal is to investigate the utility of slow-moving marine vehicles, particularly ocean gliders and profiling floats, for animal density or abundance estimation, using the passive acoustic data that these vehicles can collect. In this presentation, we will (1) provide a project overview and (2) share results from the initial stages of the project. As part of one task, existing deployments in the Gulf of Alaska, Hawaii, and the Mariana Islands have been used to investigate the capability of gliders to adhere to planned survey tracks. Simulations were also conducted to assess whether realized glider survey track lines could produce unbiased density estimates using two hypothetical animal distributions and assuming so-called design-based analysis methods (the standard, and also simplest, approach). Five deployments were assessed and deviances of up to 20...

Simultaneous operation of mobile acoustic recording systems off the Washington coast for cetacean studies

Acoustic monitoring of cetaceans was conducted using two buoyancy-driven AUVs in a deep-water canyon north of the Navys QUTR range off the Washington coast in April 2015. The two AUVs operated were the acoustically-equipped QUEphone, which is an APEXTM-based acoustic profiler float from Teledyne Webb, and the SeagliderTM from Kongsberg. A passive acoustic monitoring device, WISPR, from Embedded Ocean Systems (EOS) was installed on both AUVs. With one 512GB CF card and level-2 Free Lossless Audio Codec (FLAC), WISPR recorded sound continuously for 12 days at a 125 kHz sampling rate with 16-bit resolution. The Sealiders record showed high levels of flow noise below 100 Hz during ascent, 16 dB higher than during the descent. The Seagliders CTD generated 1-sec long line noise at 53.37 kHz at 5 to 10 sec intervals, while the Seagliders mass shifter generated 3-sec long band-limited noise below 10 kHz. The QUEphones acoustic record was generally quieter than the Seaglider primarily due to the fact that it is nearly stationary platform with less mechanical and electrical components to generate system noise. Despite higher system noise levels, the Seaglider detected twice as many calls/clicks resulting from its ability to actively stay in the target area where the population density of marine mammals was higher, while the QUEphone drifted away from the target area with the prevailing ocean currents.

High-frequency observations from mobile autonomous platforms

With increased human use of US coastal waters—including use by renewable energy activities such as the deployment and operation of wind, wave, and tidal energy converters—the issue of potential negative impacts on coastal ecosystems arises. Monitoring these areas efficiently for marine mammals is challenging. Recreational and commercial activities (e.g., fishing) can hinder long-term operation of fixed moored instruments. Additionally these shallow waters are often utilized by high-frequency cetaceans (e.g., harbor porpoises) which can only be acoustically detected over short distances of a few hundred meters. Mobile acoustic platforms are a useful tool to survey these areas of concern with increased temporal and spatial resolution compared to fixed systems and towed arrays. A commercially available acoustic recorder (type Song Meter SM2 + , Wildlife Acoustics, Inc.) featuring sampling rates up to 384 kHz was modified and implemented on an autonomous underwater vehicle (AUV) as well as an unmanned surface...