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Sympatric short- and long-beaked common dolphins in the Southern California Bight (Delphinus delphis and D. delphis bairdii) are challenging to identify acoustically because their whistles overlap in many time-frequency characteristics. We therefore asked whether frequency modulation patterns can help with species identification. Whistle contours from single-species encounters (short-beaked = 902 whistles, 14 schools, long-beaked = 872 whistles, 10 schools) were extracted and categorized based on frequency content and shape using dynamic time warping and artificial neural networks. This analysis resulted in 447 whistle types with 38% being produced by both species. Of the remaining species-specific whistle types, 22% (n = 60) were recorded from more than one school. Thirty-two of these were specific to short-beaked common dolphins and 28 were specific to long-beaked common dolphins. Almost half of the short-beaked common dolphin species-specific whistle types (47%) were oscillatory (contour shape containing at least two cycles with the maximum and minimum of each cycle separated by at least 1 kHz), while only 3% of long-beaked common dolphin species-specific types were oscillatory. Thus, oscillatory whistles appear to be diagnostic of short-beaked common dolphins in this area. More broadly, our findings suggest that repertoire-wide comparisons of acoustic features may overlook possible species recognition via specific signals.

In fall 2014 and spring 2015, passive acoustic data were collected via autonomous gliders east of Guam in an area that included the Mariana Trench Marine National Monument. A short (2-4 s), complex sound was recorded that features a ∼38 Hz moan with both harmonics and amplitude modulation, followed by broad-frequency metallic-sounding sweeps up to 7.5 kHz. This sound was recorded regularly during both fall and spring surveys. Aurally, the sound is quite unusual and most resembles the minke whale "Star Wars" call. It is likely this sound is biological and produced by a baleen whale.

A passive acoustic survey off Southern California is being conducted in summer–fall 2019 to estimate the distribution of beaked whale species. Two gliders are being flown to estimate the occurrence of Cuvier's, Blainville's, Stejneger's, Hubbs', and Baird's beaked whales in several regions: (1) near the Navy's Southern California Offshore Range (SCORE), in particular near fixed passive recorders there; (2) over the farther reaches of the continental shelf and shelf slope; and (3) over deep (>3000 m) waters offshore of the shelf slope up to 350 km from shore. The gliders collect passive acoustic data up to ca. 90 kHz, which should enable differentiation of these species of beaked whales in situations of reasonably high signal-to-noise ratios. Preliminary results of the glider flights and data analysis will be presented. [Funding from Navy NAVFAC.]

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.

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 the Northern Gulf of Mexico in the summers of 2015 and 2017 to study cetacean occurrence and behavior. Here, we summarize the virtues and hazards of glider PAM, and describe acoustic detection and classification of cetaceans in these recordings. [Research supported by GoMRI.]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...

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...

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...

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 (or lack thereof) from blue and fin whales exposed to simulated mid-frequency active sonar. The call behavior characterizations presented here will help with predicting calling behavior from surface behavior, informing interpretation of passive acoustic data, and further investigating effects of anthropogenic sound on baleen whales.

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...

A pilot study was conducted to evaluate the potential of animal-borne active and passive acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) using translocation experiments at Ano Nuevo State Park, CA, USA, in spring 2012. The principal scientific questions of this pilot study were (1) do low-intensity sounds emitted by an animal-borne tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g., threatening vs non-threatening)? Preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the study show the promise of this approach as a minimally invasive and cost-effective method to investigate animal responses to underwater sounds, as well as a method to develop mitigation strategies. We are currently in the process of improving the tag design for future field efforts with the goal to increase the sample size, range of acoustic stimuli, and age/sex classes of tagged seals. [Funding from NOAA/NMFS Ocean Acoustics Program.]

In 2011 a pilot study was begun to evaluate the potential of animal-borne active acoustic tags for conducting minimally-invasive behavioral response studies on pinnipeds. A basic prototype tag was developed and tested on juvenile northern elephant seals (Mirounga angustirostris) during translocation experiments at Ano Nuevo State Park, CA, USA in spring 2012. The principal scientific questions of this pilot study were these: (1) do sounds emitted from an animal-borne low acoustic intensity tag elicit behavioral responses, and (2) are potential animal responses related to signal content (e.g., threatening vs. non-threatening). Although the sample size was small, preliminary results indicate that (1) low-intensity sounds emitted by animal-borne tags elicit distinct behavioral responses, (2) these responses appear related to signal content, and (3) the responses may differ based on depth, bathymetry, and location. The results of the conducted study show the promise of this approach as a minimally-invasive an...