Publications

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2012
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.

2011
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]

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.

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]

2010
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]

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]

2009
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.