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A
Baumann-Pickering, S, Roch MA, Wiggins SM, Schnitzler HU, Hildebrand JA.  2015.  Acoustic behavior of melon-headed whales varies on a diel cycle. Behavioral Ecology and Sociobiology. 69:1553-1563.   10.1007/s00265-015-1967-0   AbstractWebsite

Many terrestrial and marine species have a diel activity pattern, and their acoustic signaling follows their current behavioral state. Whistles and echolocation clicks on long-term recordings produced by melon-headed whales (Peponocephala electra) at Palmyra Atoll indicated that these signals were used selectively during different phases of the day, strengthening the idea of nighttime foraging and daytime resting with afternoon socializing for this species. Spectral features of their echolocation clicks changed from day to night, shifting the median center frequency up. Additionally, click received levels increased with increasing ambient noise during both day and night. Ambient noise over a wide frequency band was on average higher at night. The diel adjustment of click features might be a reaction to acoustic masking caused by these nighttime sounds. Similar adaptations have been documented for numerous taxa in response to noise. Or it could be, unrelated, an increase in biosonar source levels and with it a shift in center frequency to enhance detection distances during foraging at night. Call modifications in intensity, directionality, frequency, and duration according to echolocation task are well established for bats. This finding indicates that melon-headed whales have flexibility in their acoustic behavior, and they collectively and repeatedly adapt their signals from day- to nighttime circumstances.

Bayless, AR, Oleson EM, Baumann-Pickering S, Simonis AE, Marchetti J, Martin S, Wiggins SM.  2017.  Acoustically Monitoring the Hawai‘i Longline Fishery for Interactions with False Killer Whales. Fisheries Research. 190:122-131.   10.1016/j.fishres.2017.02.006   Abstract

False killer whales (Pseudorca crassidens) feed primarily on several species of large pelagic fish, species that are also targeted by the Hawai‘i-permitted commercial deep-set longline fishery. False killer whales have been known to approach fishing lines in an attempt to procure bait or catch from the lines, a behavior known as depredation. This behavior can lead to the hooking or entanglement of an animal, which currently exceeds sustainable levels for pelagic false killer whales in Hawai‘i. Passive acoustic monitoring (PAM) was used to record false killer whales near longline fishing gear to investigate the timing, rate, and spatial extent of false killer whale occurrence. Acoustic data were collected using small autonomous recorders modified for deployment on the mainline of longline fishing gear. A total of 90 fishing sets were acoustically monitored in 2013 and 2014 on a chartered longline vessel using up to five acoustic recorders deployed throughout the fishing gear. Of the 102 odontocete click and/or whistle bouts detected on 55 sets, 26 bouts detected on 19 different fishing sets were classified as false killer whales with high or medium confidence based on either whistle classification, click classification, or both. The timing of false killer whale acoustic presence near the gear was related to the timing of fishing activities, with 57% of the false killer whale bouts occurring while gear was being hauled, with 50% of those bouts occurring during the first third of the haul. During three fishing sets, false killer whales were detected on more than one recorder, and in all cases the whales were recorded on instruments farther from the fishing vessel as the haul proceeded. Only three of the 19 sets with acoustically-confirmed false killer whale presence showed signs of bait or catch damage by marine mammals, which may relate to the difficulty of reporting depredation. PAM has proven to be a relatively inexpensive and efficient method for monitoring the Hawai‘i longline fishery for interactions with false killer whales.

Baumann-Pickering, S, Simonis AE, Wiggins SM, Brownell RL, Hildebrand JA.  2013.  Aleutian Islands beaked whale echolocation signals. Marine Mammal Science. 29(1):221-227.: Blackwell Publishing Inc   10.1111/j.1748-7692.2011.00550.x   AbstractWebsite

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Trickey, JS, Baumann-Pickering S, Hildebrand JA, Reyes Reyes MV, Melcón M, Iñíguez M.  2015.  Antarctic beaked whale echolocation signals near South Scotia Ridge. Marine Mammal Science. 31:1265–1274.   10.1111/mms.12216  
Hildebrand, JA, Frasier KE, Baumann-Pickering S, Wiggins SM, Merkens KP, Garrison LP, Soldevilla MS, McDonald MA.  2019.  Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico. Frontiers in Marine Science. 6(66):1-17.   10.3389/fmars.2019.00066   Abstract

Pygmy sperm whales (Kogia breviceps) and dwarf sperm whales (Kogia sima) are deep diving cetaceans that commonly strand along the coast of the southeast US, but that are difficult to study visually at sea because of their elusive behavior. Conventional visual surveys are thought to significantly underestimate the presence of Kogia and they have proven difficult to approach for tracking and tagging. An approach is presented for density estimation of signals presumed to be from Kogia spp. based on passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period following the Deepwater Horizon oil spill (2010-2013). Both species of Kogia are known to inhabit the GOM, although it is not possible to acoustically separate the two based on available knowledge of their echolocation clicks. An increasing interannual density trend is suggested for animals near the primary zone of impact of the oil spill, and to the southeast of the spill. Densities were estimated based on both counting individual echolocation clicks and counting the presence of groups of animals during one-min time windows. Densities derived from acoustic monitoring at three sites are all substantially higher (4–16 animals/1000 km2) than those that have been derived for Kogia from line transect visual surveys in the same region (0.5 animals/1000 km2). The most likely explanation for the observed discrepancy is that the visual surveys are underestimating Kogia spp. density, due to the assumption of perfect detectability on the survey trackline. We present an alternative approach for density estimation, one that derives echolocation and behavioral parameters based on comparison of modeled and observed sound received levels at sites of varying depth.

Roch, MA, Brandes ST, Patel B, Barkley Y, Baumann-Pickering S, Soldevilla MS.  2011.  Automated extraction of odontocete whistle contours. Journal of the Acoustical Society of America. 130:2212-2223.   10.1121/1.3624821   AbstractWebsite

Many odontocetes produce frequency modulated tonal calls known as whistles. The ability to automatically determine time x frequency tracks corresponding to these vocalizations has numerous applications including species description, identification, and density estimation. This work develops and compares two algorithms on a common corpus of nearly one hour of data collected in the Southern California Bight and at Palmyra Atoll. The corpus contains over 3000 whistles from bottlenose dolphins, long- and short-beaked common dolphins, spinner dolphins, and melon-headed whales that have been annotated by a human, and released to the Moby Sound archive. Both algorithms use a common signal processing front end to determine time x frequency peaks from a spectrogram. In the first method, a particle filter performs Bayesian filtering, estimating the contour from the noisy spectral peaks. The second method uses an adaptive polynomial prediction to connect peaks into a graph, merging graphs when they cross. Whistle contours are extracted from graphs using information from both sides of crossings. The particle filter was able to retrieve 71.5% (recall) of the human annotated tonals with 60.8% of the detections being valid (precision). The graph algorithm's recall rate was 80.0% with a precision of 76.9%. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3624821]

B
Baumann-Pickering, S, Yack TM, Barlow J, Wiggins SM, Hildebrand JA.  2013.  Baird's beaked whale echolocation signals. The Journal of the Acoustical Society of America. 133:4321-4331.   10.1121/1.4804316   AbstractWebsite

Echolocation signals from Baird's beaked whales were recorded during visual and acoustic shipboard surveys of cetaceans in the California Current ecosystem and with autonomous, long-term recorders in the Southern California Bight. The preliminary measurement of the visually validated Baird's beaked whale echolocation signals from towed array data were used as a basis for identifying Baird's signals in the autonomous recorder data. Two distinct signal types were found, one being a beaked whale-like frequency modulated (FM) pulse, the other being a dolphin-like broadband click. The median FM inter-pulse interval was 230 ms. Both signal types showed a consistent multi-peak structure in their spectra with peaks at ∼9, 16, 25, and 40 kHz. Depending on signal type, as well as recording aspect and distance to the hydrophone, these peaks varied in relative amplitude. The description of Baird's echolocation signals will allow for studies of their distribution and abundance using towed array data without associated visual sightings and from autonomous seafloor hydrophones.

Brownell, Robert L., J, Ralls K, Baumann-Pickering S, Poole MM.  2009.  Behavior of melon-headed whales, Peponocephala electra, near oceanic islands. Marine Mammal Science. 25:639-658.   10.1111/j.1748-7692.2009.00281.x   Abstract

Southall et al. (2006) concluded that a near mass stranding (MS) of melon-headed whales (MHWs), Peponocephala electra, in Hanalei Bay, Kauai, Hawaii, on 3-4 July 2004, was likely related to the operation of mid-frequency sonars (MFS). However, subsequent authors argued that the nearly simultaneous entry of MHWs into Sasanhaya Bay, Rota (similar to 5,740 km away) made this conclusion untenable. They suggested that both sightings, and other MSs of MHWs, could be related to lunar cycles. To resolve this question, we reviewed information on the biology and behavior of MHWs and compared the two sightings to observations of MHWs around Palmyra Atoll and Nuku Hiva, French Polynesia. We also tested for a relationship between observations and MSs of MHWs with lunar cycles. MHWs near many oceanic islands rest nearshore during the day and feed offshore in deeper water at night. The MHWs at Rota exhibited normal diurnal resting behavior as seen at Palmyra and Nuku Hiva, while those at Kauai showed milling behavior typically seen prior to MS events. Thus, these events were not similar. Neither observations nor MSs of MHWs were related to lunar cycles. Our review of MHW behavior strengthens the case that MFS use played a major role in the near MS in Hanalei Bay.

Kerosky, SM, Širović A, Roche LK, Baumann-Pickering S, Wiggins SM, Hildebrand JA.  2012.  Bryde's whale seasonal range expansion and increasing presence in the Southern California Bight from 2000 to 2010. Deep Sea Research Part I: Oceanographic Research Papers. 65:125-132.   10.1016/j.dsr.2012.03.013   AbstractWebsite

Bryde's whales (Balaenoptera edeni) are commonly found in tropical and subtropical regions of the Pacific Ocean, but few studies have explored the presence of Bryde's whales at the boundary of their distribution range. Such studies are increasingly relevant as climate impact models predict the range expansion of warm water species towards the poles in response to ocean warming. Like other baleen whales, Bryde's whales produce distinct low frequency (<60 Hz) calls, which can be used for long-term acoustic monitoring of whale presence in an area. Autonomous passive acoustic recorders deployed at five sites in the Southern California Bight (SCB) were used to investigate the presence of Bryde's whales in temperate waters from 2000 to 2010. Calling Bryde's whales were observed in the SCB from summer to early winter, indicating a seasonal poleward range expansion. There was a significant increase in the presence of calling Bryde's whales in the SCB between 2000 and 2010, but no significant correlation was found between Bryde's whale presence and local sea surface temperature. Bryde's whale occurrence is likely driven by prey availability within the California Current ecosystem, which is affected by seasonal and inter-annual changes in climate and oceanographic conditions. Continued monitoring of Bryde's whales and their prey in the eastern North Pacific is needed to provide a longer time series and determine the full effect of climate variability and ocean warming on the distribution of this species.

C
Roch, MA, Klinck H, Baumann-Pickering S, Mellinger DK, Qui S, Soldevilla MS, Hildebrand JA.  2011.  Classification of echolocation clicks from odontocetes in the Southern California Bight. Journal of the Acoustical Society of America. 129:467-475.   10.1121/1.3514383   Abstract

This study presents a system for classifying echolocation clicks of six species of odontocetes in the Southern California Bight: Visually confirmed bottlenose dolphins, short-and long-beaked common dolphins, Pacific white-sided dolphins, Risso's dolphins, and presumed Cuvier's beaked whales. Echolocation clicks are represented by cepstral feature vectors that are classified by Gaussian mixture models. A randomized cross-validation experiment is designed to provide conditions similar to those found in a field-deployed system. To prevent matched conditions from inappropriately lowering the error rate, echolocation clicks associated with a single sighting are never split across the training and test data. Sightings are randomly permuted before assignment to folds in the experiment. This allows different combinations of the training and test data to be used while keeping data from each sighting entirely in the training or test set. The system achieves a mean error rate of 22% across 100 randomized three-fold cross-validation experiments. Four of the six species had mean error rates lower than the overall mean, with the presumed Cuvier's beaked whale clicks showing the best performance (<2% error rate). Long-beaked common and bottlenose dolphins proved the most difficult to classify, with mean error rates of 53% and 68%, respectively. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3514383]

Roch, MA, Stinner-Sloan J, Baumann-Pickering S, Wiggins SM.  2015.  Compensating for the effects of site and equipment variation on delphinid species identification from their echolocation clicks. Journal of the Acoustical Society of America. 137:22-29.   10.1121/1.4904507   AbstractWebsite

A concern for applications of machine learning techniques to bioacoustics is whether or not classifiers learn the categories for which they were trained. Unfortunately, information such as characteristics of specific recording equipment or noise environments can also be learned. This question is examined in the context of identifying delphinid species by their echolocation clicks. To reduce the ambiguity between species classification performance and other confounding factors, species whose clicks can be readily distinguished were used in this study: Pacific white-sided and Risso's dolphins. A subset of data from autonomous acoustic recorders located at seven sites in the Southern California Bight collected between 2006 and 2012 was selected. Cepstral-based features were extracted for each echolocation click and Gaussian mixture models were used to classify groups of 100 clicks. One hundred Monte-Carlo three-fold experiments were conducted to examine classification performance where fold composition was determined by acoustic encounter, recorder characteristics, or recording site. The error rate increased from 6.1% when grouped by acoustic encounter to 18.1%, 46.2%, and 33.2% for grouping by equipment, equipment category, and site, respectively. A noise compensation technique reduced error for these grouping schemes to 2.7%, 4.4%, 6.7%, and 11.4%, respectively, a reduction in error rate of 56%-86%. (C) 2015 Acoustical Society of America.

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DeAngelis, AI, Stanistreet JE, Baumann-Pickering S, Cholewiak DM.  2018.  A description of echolocation clicks recorded in the presence of True's beaked whale (Mesoplodon mirus). The Journal of the Acoustical Society of America. 144(5):2691-2700.   10.1121/1.5067379   AbstractWebsite

True's beaked whales (Mesoplodon mirus) were encountered on two separate shipboard surveys on 24 July 2016 and 16 September 2017 in the western North Atlantic Ocean. Recordings were made using a hydrophone array towed 300 m behind the ship. In 2016, three different groups were sighted within 1500 m of the ship; clicks were recorded for 26 min. In 2017, a single group of five whales was tracked over the course of five hours in which the ship maintained a distance <4000 m from the group. A total of 2938 frequency-modulated (FM) clicks and 7 buzzes were recorded from both encounters. Plausible inter-click-intervals (ICIs) were calculated from 2763 clicks, and frequency and duration measurements were calculated from 2150 good quality FM clicks. The median peak frequencies were 43.1 kHz (2016, n = 718) and 43.5 kHz (2017, n = 1432). Median ICIs were 0.17 s (2016) and 0.19 s (2017). The spectra and measurements of the recorded clicks closely resemble Gervais's beaked whale clicks (Mesoplodon europaeus) and distinguishing between the two species in acoustic data sets proves difficult. The acoustic behavior of True's beaked whales was previously unknown; this study provides a description of echolocation clicks produced by this species.

Cholewiak, D, Baumann-Pickering S, Van Parijs S.  2013.  Description of sounds associated with Sowerby's beaked whales (Mesoplodon bidens) in the western North Atlantic Ocean. Journal of the Acoustical Society of America. 134:3905-3912.   10.1121/1.4823843   AbstractWebsite

Several groups of Sowerby's beaked whales (Mesoplodon bidens) were encountered on July 4, 2011, during a shipboard cetacean survey conducted off the eastern seaboard of the United States. Acoustic recordings were collected using a three-element towed hydrophone array. Many echolocation clicks were recorded during the encounter, but no tonal sounds were detected. A total of 2969 echolocation clicks were included in analyses of frequency and temporal characteristics. A Gaussian mixture model with four mixtures was fitted to the histogram of peak frequencies; four subsets of clicks were designated. The majority of clicks (n=2048) contained a median peak frequency of 33 kHz, while the others contained a median peak frequency of 25 kHz (n=324), 51 kHz (n=304), or 67 kHz (n=293). Most clicks did not contain a clear frequency-modulated upsweep, though some clicks exhibited a slight sweep from 30-36 kHz. Seven burst pulses were detected in the encounter, two of which were of high enough quality for detailed analysis. The acoustic characteristics of Sowerby's beaked whales have not previously been described; the current study will facilitate incorporation of these data into passive acoustic monitoring programs in the North Atlantic Ocean.

Rankin, S, Baumann-Pickering S, Yack T, Barlow J.  2011.  Description of sounds recorded from Longman's beaked whale, Indopacetus pacificus. Journal of the Acoustical Society of America. 130:EL339-EL344.   10.1121/1.3646026   Abstract

Sounds from Longman's beaked whale, Inclopacetus pacificus were recorded during shipboard surveys of cetaceans surrounding the Hawaiian Islands archipelago; this represents the first known recording of this species. Sounds included echolocation clicks and burst pulses. Echolocation clicks were grouped into three categories, a 15 kHz click (11 = 106), a 25 kHz click (n = 136), and a 25 kHz pulse with a frequency-modulated upsweep (n = 70). The 15 and 25 kHz clicks were relatively short (181 and 144 ms, respectively); the longer 25 kHz upswept pulse was 288 ms. Burst pulses were long (0.5 s) click trains with approximately 240 clicks/s.

Gruden, P, White PR, Oswald JN, Barkley Y, Cerchio S, Lammers M, Baumann-Pickering S.  2015.  Differences in oscillatory whistles produced by spinner (Stenella longirostris) and pantropical spotted (Stenella attenuata) dolphins. Marine Mammal Science.   10.1111/mms.12280   AbstractWebsite

Acoustic recordings of two closely related species, spinner dolphin (Stenella longirostris) and pantropical spotted dolphin (Stenella attenuata), were investigated from four different geographic locations: two in the Central Tropical Pacific, one in the Eastern Tropical Pacific and one in the Indian Ocean. The two delphinid species occur in tropical and warm temperate waters, with overlapping ranges. They produce very similar vocalizations, but at the same time their calls exhibit a certain degree of intraspecific variation among different geographic locations as has been observed in other delphinid species. Oscillatory whistles (whistles with at least two oscillations in their frequency contours) were identified and manually extracted from the recordings. Whistles with four or more maxima (oscillations) occurred only in spinner dolphins and they were present in all geographic regions investigated. In addition, the oscillatory whistles with two and three maxima were significantly more frequent in spinner than in spotted dolphins. The differences in oscillatory whistles for these two species seem to be consistent across study areas and therefore, could be used in addition to other whistle features to help distinguish between them.

Baumann-Pickering, S, Wiggins SM, Hildebrand JA, Roch MA, Schnitz H-U.  2010.  Discriminating features of echolocation clicks of melon-headed whales (Peponocephala electra), bottlenose dolphins (Tursiops truncatus), and Gray's spinner dolphins (Stenella longirostris longirostris). Journal of the Acoustical Society of America. 128:2212-2224.   10.1121/1.3479549   Abstract

Spectral parameters were used to discriminate between echolocation clicks produced by three dolphin species at Palmyra Atoll: melon-headed whales (Peponocephala electra), bottlenose dolphins (Tursiops truncatus) and Gray's spinner dolphins (Stenella longirostris longirostris). Single species acoustic behavior during daytime observations was recorded with a towed hydrophone array sampling at 192 and 480 kHz. Additionally, an autonomous, bottom moored High-frequency Acoustic Recording Package (HARP) collected acoustic data with a sampling rate of 200 kHz. Melon-headed whale echolocation clicks had the lowest peak and center frequencies, spinner dolphins had the highest frequencies and bottlenose dolphins were nested in between these two species. Frequency differences were significant. Temporal parameters were not well suited for classification. Feature differences were enhanced by reducing variability within a set of single clicks by calculating mean spectra for groups of clicks. Median peak frequencies of averaged clicks (group size 50) of melon-headed whales ranged between 24.4 and 29.7 kHz, of bottlenose dolphins between 26.7 and 36.7 kHz, and of spinner dolphins between 33.8 and 36.0 kHz. Discriminant function analysis showed the ability to correctly discriminate between 93% of melon-headed whales, 75% of spinner dolphins and 54% of bottlenose dolphins. (c) 2010 Acoustical Society of America. [DOI: 10.1121/1.3479549]

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Baumann-Pickering, S, Wiggins SM, Roth EH, Roch MA, Schnitzler H-U, Hildebrand JA.  2010.  Echolocation signals of a beaked whale at Palmyra Atoll. Journal of the Acoustical Society of America. 127:3790-3799.   10.1121/1.3409478   Abstract

Acoustic recordings from Palmyra Atoll, northern Line Islands, central Pacific, showed upsweep frequency modulated pulses reminiscent of those produced by beaked whales. These signals had higher frequencies, broader bandwidths, longer pulse durations and shorter inter-pulse intervals than previously described pulses of Blainville's, Cuvier's and Gervais' beaked whales [Zimmer (2005). J. Acoust. Soc. Am. 117, 3919-3927; Johnson (2006). J. Exp. Biol. 209, 5038-5050; Gillespie (2009). J. Acoust. Soc. Am. 125, 3428-3433]. They were distinctly different temporally and spectrally from the unknown beaked whale at Cross Seamount, HI [McDonald (2009). J. Acoust. Soc. Am. 125, 624-627]. Genetics on beaked whale specimens found at Palmyra Atoll suggest the presence of a poorly known beaked whale species. Mesoplodon sp. might be the source of the FM pulses described in this paper. The Palmyra Atoll FM pulse peak frequency was at 44 kHz with a -10 dB bandwidth of 26 kHz. Mean pulse duration was 355 mu s and inter-pulse interval was 225 ms, with a bimodal distribution. Buzz sequences were detected with inter-pulse intervals below 20 ms and unmodulated spectra, with about 20 dB lower amplitude than prior FM pulses. These clicks had a 39 kHz bandwidth (-10 dB), peak frequency at 37 kHz, click duration 155 mu s, and inter-click interval between 4 and 10 ms. (C) 2010 Acoustical Society of America. [DOI: 10.1121/1.3409478]

Stanistreet, JE, Nowacek DP, Read AJ, Baumann-Pickering S, Moors-Murphy HB, Van Parijs SM.  2016.  Effects of duty-cycled passive acoustic recordings on detecting the presence of beaked whales in the northwest Atlantic. Journal of the Acoustical Society of America. 140(1):EL31-EL37.   10.1121/1.4955009   Abstract

This study investigated the effects of using duty-cycled passive acoustic recordings to monitor the daily presence of beaked whale species at three locations in the northwest Atlantic. Continuous acoustic records were subsampled to simulate duty cycles of 50%, 25%, and 10% and cycle period durations from 10 to 60 min. Short, frequent listening periods were most effective for assessing the daily presence of beaked whales. Furthermore, subsampling at low duty cycles led to consistently greater underestimation of Mesoplodon species than either Cuvier's beaked whales or northern bottlenose whales, leading to a potential bias in estimation of relative species occurrence.

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Baumann-Pickering, S, Simonis AE, Oleson EM, Baird RW, Roch MA, Wiggins SM.  2015.  False killer whale and short-finned pilot whale acoustic identification. Endangered Species Research. 28:97-108.   10.3354/esr00685   Abstract

False killer whales and short-finned pilot whales are known to interact with long-line fishing gear in Hawaiian waters, causing economic loss and leading to whale injuries and deaths. The main Hawaiian Islands insular population of false killer whales is listed as endangered and the offshore population is considered “strategic” under the Marine Mammal Protection Act due to relatively high bycatch levels. Discriminating between these species acoustically is problematic due to similarity in the spectral content of their echolocation clicks. We use passive acoustic monitoring along with data from satellite tags to distinguish signals from these two species. Acoustic encounters recorded with autonomous instruments offshore of the islands of Hawai‘i and Kaua‘i were matched with concurrent and nearby location information from satellite tagged individuals. Two patterns of echolocation clicks were established for the two species. The overall spectral click parameters were highly similar (22 kHz peak and 25 kHz center frequency), but false killer whales had shorter duration and broader bandwidth clicks than short-finned pilot whales (225 μs, 8 kHz (-3 dB bandwidth) and 545 μs, 4 kHz, respectively). Also, short-finned pilot whale clicks showed distinct spectral peaks at 12 and 18 kHz. Automated classification techniques using Gaussian mixture models had a 6.5% median error rate. Based on these findings for echolcoation clicks and prior published work on whistle classification, acoustic encounters of false killer whales and short-finned pilot whales on autonomous instruments should be identifiable to species level, leading to better long-term monitoring with the goal of mitigating bycatch.

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Soldevilla, MS, Baumann-Pickering S, Cholewiak DM, Hodge LEW, Oleson EM, Rankin S.  2017.  Geographic variation in Risso’s dolphin echolocation click spectra. Journal of the Acoustical Society of America. 142:599-617.   10.1121/1.4996002   Abstract

Discrimination of bioacoustic signals to the species or population level is critical for using passive acoustic monitoring to study cetacean ecology. Risso's dolphins off southern California have distinctive peaks and notches in their echolocation clicks, but it was unknown whether Risso's dolphins from other geographic areas have similarly distinctive click spectra and whether populations are acoustically distinct. This study investigates using clicks for species and population identification by characterizing the spectral structure of Risso's dolphin echolocation clicks recorded over wide-ranging geographic regions including the U.S. waters of the North Atlantic Ocean, Gulf of Mexico, and North Pacific Ocean; and international waters of the Eastern Tropical Pacific. All recordings with Risso's dolphin clicks exhibited the spectral peak and notch pattern described off southern California, indicating the presence of peak banding patterns is useful for species discrimination. Geographic regions were a significant explanatory factor for variability in the frequencies of click spectral peaks, with relatively higher frequency peaks and notches found off Hawaii compared to California waters and off the southeast U.S. compared to the Gulf of Mexico. In the North Atlantic Ocean, a latitudinal cline in frequencies was evident. Potential causes of acoustic variation within and among acoustic encounters are evaluated.

Levin, LA, Bett BJ, Gates AR, Heimbach P, Howe BM, Janssen F, McCurdy A, Ruhl HA, Snelgrove P, Stocks KI, Bailey D, Baumann-Pickering S, Beaverson C, Benfield MC, Booth DJ, Carreiro-Silva M, Colaço A, Eblé MC, Fowler AM, Gjerde KM, Jones DOB, Katsumata K, Kelley D, Le Bris N, Leonardi AP, Lejzerowicz F, Macreadie PI, McLean D, Meitz F, Morato T, Netburn A, Pawlowski J, Smith CR, Sun S, Uchida H, Vardaro MF, Venkatesan R, Weller RA.  2019.  Global Observing Needs in the Deep Ocean. Frontiers in Marine Science. 6:241.   10.3389/fmars.2019.00241   AbstractWebsite

The deep ocean below 200 m water depth is the least observed, but largest habitat on our planet by volume and area. Over 150 years of exploration has revealed that this dynamic system provides critical climate regulation, houses a wealth of energy, mineral, and biological resources, and represents a vast repository of biological diversity. A long history of deep-ocean exploration and observation led to the initial concept for the Deep-Ocean Observing Strategy (DOOS), under the auspices of the Global Ocean Observing System (GOOS). Here we discuss the scientific need for globally integrated deep-ocean observing, its status, and the key scientific questions and societal mandates driving observing requirements over the next decade. We consider the Essential Ocean Variables (EOVs) needed to address deep-ocean challenges within the physical, biogeochemical, and biological/ecosystem sciences according to the Framework for Ocean Observing (FOO), and map these onto scientific questions. Opportunities for new and expanded synergies among deep-ocean stakeholders are discussed, including academic-industry partnerships with the oil and gas, mining, cable and fishing industries, the ocean exploration and mapping community, and biodiversity conservation initiatives. Future deep-ocean observing will benefit from the greater integration across traditional disciplines and sectors, achieved through demonstration projects and facilitated reuse and repurposing of existing deep-sea data efforts. We highlight examples of existing and emerging deep-sea methods and technologies, noting key challenges associated with data volume, preservation, standardization, and accessibility. Emerging technologies relevant to deep-ocean sustainability and the blue economy include novel genomics approaches, imaging technologies, and ultra-deep hydrographic measurements. Capacity building will be necessary to integrate capabilities into programs and projects at a global scale. Progress can be facilitated by Open Science and Findable, Accessible, Interoperable, Reusable (FAIR) data principles and converge on agreed to data standards, practices, vocabularies, and registries. We envision expansion of the deep-ocean observing community to embrace the participation of academia, industry, NGOs, national governments, international governmental organizations, and the public at large in order to unlock critical knowledge contained in the deep ocean over coming decades, and to realize the mutual benefits of thoughtful deep-ocean observing for all elements of a sustainable ocean.

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Hodge, LEW, Baumann-Pickering S, Hildebrand JA, Bell JT, Cummings EW, Foley HJ, McAlarney RJ, McLellan WA, Pabst DA, Swaim ZT, Waples DM, Read AJ.  2018.  Heard but not seen: Occurrence of Kogia spp. along the western North Atlantic shelf break. Marine Mammal Science. 34:1141-1153.   10.1111/mms.12498   AbstractWebsite
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Simonis, AE, Baumann-Pickering S, Oleson E, Melcon ML, Gassmann M, Wiggins SM, Hildebrand JA.  2012.  High-frequency modulated signals of killer whales (Orcinus orca) in the North Pacific. Journal of the Acoustical Society of America. 131:EL295-EL301.   10.1121/1.3690963   Abstract

Killer whales in the North Pacific, similar to Atlantic populations, produce high-frequency modulated signals, based on acoustic recordings from ship-based hydrophone arrays and autonomous recorders at multiple locations. The median peak frequency of these signals ranged from 19.6-36.1 kHz and median duration ranged from 50-163 ms. Source levels were 185-193 dB peak-to-peak re: 1 mu Pa at 1 m. These uniform, repetitive, down-swept signals are similar to bat echolocation signals and possibly could have echolocation functionality. A large geographic range of occurrence suggests that different killer whale ecotypes may utilize these signals. (C) 2012 Acoustical Society of America

Reyes Reyes, MV, Baumann-Pickering S, Simonis AE, Trickey JS, Melcón M, Hildebrand JA, Iñíguez M.  2017.  High-frequency modulated signals recorded off the Antarctic Peninsula area: are killer whales emitting them? Acoustics Australia.   10.1007/s40857-017-0103-x   Abstract

High-frequency modulated signals with a stereotyped down-swept contour were recorded in the northwestern Antarctic Peninsula using an autonomous recorder and a towed hydrophone array. Signals have a mean start frequency at 21.6 kHz, end frequency at 15.7 kHz, −10 dB bandwidth of 5.9 kHz, and duration of 65.2 ms. Bouts of signals were generally recorded with a median inter-signal interval of 2.1 s. HFM signals partially modulated in the non-ultrasonic range similar to the ones described in this paper have already been reported for killer whales in the North Pacific, Western South Atlantic and Western Australian coast. The HFM signals were recorded in the presence of other odontocete sounds such as whistles, echolocation clicks and burst-pulsed sounds. The similarities of these sounds with vocalizations described for killer whales in the Western Australian coast lead us to strongly believe that the described HFM signals were produced by Antarctic killer whales. This paper described for the first time HFM signals in Antarctica and discussed evidence suggesting that Antarctic type A killer whales are the most probable candidates to produce such signals. However, a visual confirmation is still needed and the function of the HFM signals remains unknown.

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Young, HS, Nigro K, McCauley DJ, Ballance LT, Oleson EM, Baumann-Pickering S.  2017.  Limited trophic partitioning among sympatric delphinids off a tropical oceanic atoll. PLoS ONE. 12(8):e0181526.   10.1371/journal.pone.0181526   Abstract

Understanding trophic relationships among marine predators in remote environments is challenging, but it is critical to understand community structure and dynamics. In this study, we used stable isotope analysis of skin biopsies to compare the isotopic, and thus, trophic niches of three sympatric delphinids in the waters surrounding Palmyra Atoll, in the Central Tropical Pacific: the melon-headed whale (Peponocephala electra), Gray’s spinner dolphin (Stenella longirostris longirostris), and the common bottlenose dolphin (Tursiops truncatus). δ15N values suggested that T. truncatus occupied a significantly higher trophic position than the other two species. δ13C values did not significantly differ between the three delphinds, potentially indicating no spatial partitioning in depth or distance from shore in foraging among species. The dietary niche area—determined by isotopic variance among individuals—of T. truncatus was also over 30% smaller than those of the other species taken at the same place, indicating higher population specialization or lower interindividual variation. For P. electra only, there was some support for intraspecific variation in foraging ecology across years, highlighting the need for temporal information in studying dietary niche. Cumulatively, isotopic evidence revealed surprisingly little evidence for trophic niche partitioning in the delphinid community of Palmyra Atoll compared to other studies. However, resource partitioning may happen via other behavioral mechanisms, or prey abundance or availability may be adequate to allow these three species to coexist without any such partitioning. It is also possible that isotopic signatures are inadequate to detect trophic partitioning in this environment, possibly because isotopes of prey are highly variable or insufficiently resolved to allow for differentiation.