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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.

McDonald, MA, Hildebrand JA, Wiggins SM, Johnston DW, Polovina JJ.  2009.  An acoustic survey of beaked whales at Cross Seamount near Hawaii (L). Journal of the Acoustical Society of America. 125:624-627.   10.1121/1.3050317   AbstractWebsite

An acoustic record from Cross Seamount, southwest of Hawaii, revealed sounds characteristic of beaked whale echolocation at the same relative abundance year-around (270 of 356 days), occurring almost entirely at night. The most common sound had a linear frequency upsweep from 35 to 100 kHz (the bandwidth of recording), an interpulse interval of 0.11 s, and duration of at least 932 mu s. A less common upsweep sound with shorter interpulse interval and slower sweep rate was also present. Sounds matching Cuvier's beaked whale were not detected, and Blainville's beaked whale sounds were detected on only one occasion. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3050317]

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   AbstractWebsite

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 Hawaii. 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. (C) 2017 Elsevier B.V. All rights reserved.

Baumann-Pickering, S, Simonis AE, Wiggins SM, Brownell RL, Hildebrand JA.  2012.  Aleutian Islands beaked whale echolocation signals. Marine Mammal Science. :-no.   10.1111/j.1748-7692.2011.00550.x   AbstractWebsite

Beaked whales are an elusive group of marine mammals. They are infrequently encountered as they are pelagic, deep diving foragers with short surface intervals between long dives (Tyack et al. 2006). In recent years, research has shown that beaked whales produce frequency modulated (FM) upsweep echolocation signals (Zimmer et al. 2005, Johnson et al. 2006, Gillespie et al. 2009, McDonald et al. 2009, Baumann-Pickering et al. 2010), which appear to be species specific in their spectral and temporal characteristics. Their typical echolocation behavior during foraging consists of FM pulses with very regular interpulse intervals (IPIs) while searching for prey, and discrete click series with short IPIs when closing in on a potential prey target, called a buzz (Johnson et al. 2004, Madsen et al. 2005).

Cranford, TW, McKenna MF, Soldevilla MS, Wiggins SM, Goldbogen JA, Shadwick RE, Krysl P, St Leger JA, Hildebrand JA.  2008.  Anatomic geometry of sound transmission and reception in Cuvier's beaked whale (Ziphius cavirostris). Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology. 291:353-378.   10.1002/ar.20652   AbstractWebsite

This study uses remote imaging technology to quantify, compare, and contrast the cephalic anatomy between a neonate female and a young adult male Cuvier's beaked whale. Primary results reveal details of anatomic geometry with implications for acoustic function and diving. Specifically, we describe the juxtaposition of the large pterygoid sinuses, a fibrous venous plexus, and a lipid-rich pathway that connects the acoustic environment to the bony ear complex. We surmise that the large pterygoid air sinuses are essential adaptations for maintaining acoustic isolation and auditory acuity of the ears at depth. In the adult male, an acoustic waveguide lined with pachyosteosclerotic bones is apparently part of a novel transmission pathway for outgoing biosonar signals. Substitution of dense tissue boundaries where we normally find air sacs in delphinoids appears to be a recurring theme in deep-diving beaked whales and sperm whales. The anatomic configuration of the adult male Ziphius forehead resembles an upside-down sperm whale nose and may be its functional equivalent, but the homologous relationships between forehead structures are equivocal. Anat Rec, 291:353-378, 2008. © 2008 Wiley-Liss, Inc.

Hildebrand, JA, Frasier KE, Baumann-Pickering S, Wiggins SM, Merkens KP, Garrison LP, Soklevilla 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   10.3389/fmars.2019.00066   AbstractWebsite

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 km(2)) than those that have been derived for Kogia from line transect visual surveys in the same region (0.5 animals/1000 km(2)). 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.

Frasier, KE, Roch MA, Soldevilla MS, Wiggins SM, Garrison LP, Hildebrand JA.  2017.  Automated classification of dolphin echolocation click types from the Gulf of Mexico. Plos Computational Biology. 13   10.1371/journal.pcbi.1005823   AbstractWebsite

Delphinids produce large numbers of short duration, broadband echolocation clicks which may be useful for species classification in passive acoustic monitoring efforts. A challenge in echolocation click classification is to overcome the many sources of variability to recognize underlying patterns across many detections. An automated unsupervised network-based classification method was developed to simulate the approach a human analyst uses when categorizing click types: Clusters of similar clicks were identified by incorporating multiple click characteristics (spectral shape and inter-click interval distributions) to distinguish within-type from between-type variation, and identify distinct, persistent click types. Once click types were established, an algorithm for classifying novel detections using existing clusters was tested. The automated classification method was applied to a dataset of 52 million clicks detected across five monitoring sites over two years in the Gulf of Mexico (GOM). Seven distinct click types were identified, one of which is known to be associated with an acoustically identifiable delphinid (Risso's dolphin) and six of which are not yet identified. All types occurred at multiple monitoring locations, but the relative occurrence of types varied, particularly between continental shelf and slope locations. Automatically- identified click types from autonomous seafloor recorders without verifiable species identification were compared with clicks detected on sea-surface towed hydrophone arrays in the presence of visually identified delphinid species. These comparisons suggest potential species identities for the animals producing some echolocation click types. The network-based classification method presented here is effective for rapid, unsupervised delphinid click classification across large datasets in which the click types may not be known a priori.

Wiggins, S.  2003.  Autonomous acoustic recording packages (ARPs) for long-term monitoring of whale sounds. Marine Technology Society Journal. 37:13-22.   10.4031/002533203787537375 pp.13-22   AbstractWebsite

Advancements in low-power and high-data capacity computer technology during the past decade have been adapted to autonomously record acoustic data from vocalizing whales over long time periods. Acoustic monitoring of whales has advantages over traditional visual surveys including greater detection ranges, continuous long-term monitoring in remote locations and in various weather conditions, and lower cost. An autonomous acoustic recording package (ARP) is described that uses a tethered hydrophone above a seafloor-mounted instrument frame. ARPs have been deployed to record baleen whale sounds in the Bering Sea, off the coast of southern California, near the West Antarctic Peninsula, and near Hawaii. ARP data have provided new information on the seasonal presence, abundance, call character, and patterns of vocalizing whales. Current development is underway for a broader-band, higher-data capacity system capable of recording odontocete whales, dolphins, and porpoises for long time periods.