Papers by Douglas Nowacek
OCEANS 2016 MTS/IEEE Monterey, 2016
The Journal of experimental biology, Jan 12, 2018
The risk of predation is often invoked as an important factor influencing the evolution of social... more The risk of predation is often invoked as an important factor influencing the evolution of social organization in cetaceans, but little direct information is available about how these aquatic mammals respond to predators or other perceived threats. We used controlled playback experiments to examine the behavioral responses of short-finned pilot whales () off Cape Hatteras, NC, USA, and Risso's dolphins () off the coast of Southern California, USA, to the calls of a potential predator, mammal-eating killer whales. We transmitted calls of mammal-eating killer whales, conspecifics and baleen whales to 10 pilot whales and four Risso's dolphins equipped with multi-sensor archival acoustic recording tags (DTAGs). Only playbacks of killer whale calls resulted in significant changes in tagged animal heading. The strong responses observed in both species occurred only following exposure to a subset of killer whale calls, all of which contained multiple non-linear properties. This fin...
PeerJ, 2017
Repetitive species-specific sound enables the identification of the presence and behavior of soni... more Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1,408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2,600 Hz and a majority of the energy below 4,000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times t...
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
The overall goal of this project is to increase the longevity of suction cup attachments for shor... more The overall goal of this project is to increase the longevity of suction cup attachments for short term archival tags such as the DTAG. Specifically, we are working to extend the routine attachment duration for suction-cup tags to multiple days, if not weeks. OBJECTIVES 1) Examine and identify forces and failure modes in suction cup attachments. 2) Assess the impact of tags and non-invasive surface attachments on cetaceans. 3) Take the knowledge gained from objectives 1) and 2) and engineer suction cups and surface treatments for improved attachment. 4) Examine on-animal performance of engineered attachments and tags.
Scientific Reports, 2017
Diving behaviour of short-finned pilot whales is often described by two states; deep foraging and... more Diving behaviour of short-finned pilot whales is often described by two states; deep foraging and shallow, non-foraging dives. However, this simple classification system ignores much of the variation that occurs during subsurface periods. We used multi-state hidden Markov models (HMM) to characterize states of diving behaviour and the transitions between states in short-finned pilot whales. We used three parameters (number of buzzes, maximum dive depth and duration) measured in 259 dives by digital acoustic recording tags (DTAGs) deployed on 20 individual whales off Cape Hatteras, North Carolina, USA. The HMM identified a four-state model as the best descriptor of diving behaviour. The state-dependent distributions for the diving parameters showed variation between states, indicative of different diving behaviours. Transition probabilities were considerably higher for state persistence than state switching, indicating that dive types occurred in bouts. Our results indicate that subsurface behaviour in short-finned pilot whales is more complex than a simple dichotomy of deep and shallow diving states, and labelling all subsurface behaviour as deep dives or shallow dives discounts a significant amount of important variation. We discuss potential drivers of these patterns, including variation in foraging success, prey availability and selection, bathymetry, physiological constraints and socially mediated behaviour. Cetaceans live most of their lives underwater and thus engage in a great variety of subsurface behaviour. Classification of any repertoire of diving behaviour requires identification of objective criteria that allow an observer to discriminate among various dive types; several methods have been used to identify such categories in odontocetes, see ref. 1 for review. These methods range from subjective grouping of dives based on a certain characteristic (e.g. maximum depth) to the more objective use of statistical techniques. Analysis of diving in cetaceans has been improved by the development of animal-borne tags that provide high resolution data on kinematic and acoustic behaviour 2. However, analysing complex, non-independent, time series data and quantifying the likelihood of an individual type of behaviour based on a series of observed data points from a tag record presents a particular set of challenges. Inherent differences among individual animals, motivational states and environmental factors may all contribute to observed behaviour. Furthermore, it is difficult to scale up from an individual tag record to a population-level behavioural model. The use of non-invasive digital acoustic recording tags (DTAGs), attached via suction cups 3 , has provided detailed records of diving behaviour in a number of deep-diving cetaceans, including sperm whales Physeter macrocephalus 4 , beaked whales 5-7 , short-finned pilot whales Globicephala macrorhynchus 8,9 and long-finned pilot whales Globicephala melas 10,11. DTAGs record kinematic and depth measurements of subsurface behaviour, together with a synchronized acoustic record, providing a rich data series of variables that can be associated with diving behaviour. Pilot whales are social toothed whales found worldwide in tropical and subtropical waters of the shelf break and continental slope 12. Two species exist, and both (long-finned and short-finned) are capable of performing foraging dives to hundreds of meters 8,9,13-17. Temporal clustering, or bouts, of dives has been suggested for long-finned pilot whales, with periods of shallow diving followed by bouts of deep diving 10,11. For short-finned
The Journal of the Acoustical Society of America, Jul 1, 2016
This study investigated the effects of using duty-cycled passive acoustic recordings to monitor t... more 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.
2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2015
In this paper, we apply the Weyl transform to represent the vocalization of marine mammals. In co... more In this paper, we apply the Weyl transform to represent the vocalization of marine mammals. In contrast to other popular representation methods, such as the MFCC and the Chirplet transform, the Weyl transform captures the global information of signals. This is especially useful when the signal has low order polynomial phase. We can reconstruct the signal from the coefficients obtained from the Weyl transform, and perform classification based on these coefficients. Experimental results show that classification using features extracted from the Weyl transform outperforms the MFCC and the Chirplet transform on our collected whales data.
Frontiers in Ecology and the Environment, 2015
Marine seismic surveys use intense (eg ≥ 230 decibel [dB] root mean square [RMS]) sound impulses ... more Marine seismic surveys use intense (eg ≥ 230 decibel [dB] root mean square [RMS]) sound impulses to explore the ocean bottom for hydrocarbon deposits, conduct geophysical research, and establish resource claims under the United Nations Convention on the Law of the Sea. The expansion of seismic surveys necessitates greater regional and international dialogue, partnerships, and planning to manage potential environmental risks. Data indicate several reasons for concern about the negative impacts of anthropogenic noise on numerous marine species, including habitat displacement, disruption of biologically important behaviors, masking of communication signals, chronic stress, and potential auditory damage. The sound impulses from seismic surveys-spanning temporal and spatial scales broader than those typically considered in environmental assessments-may have acute, cumulative, and chronic effects on marine organisms. Given the international and transboundary nature of noise from marine seismic surveys, we suggest the creation of an international regulatory instrument, potentially an annex to the existing International Convention on the Prevention of Pollution from Ships, to address the issue.
Journal of Cetacean Research and Management
Three unusual mortalities events involving bottlenose dolphins (Tursiops truncatus Montagu 1821) ... more Three unusual mortalities events involving bottlenose dolphins (Tursiops truncatus Montagu 1821) occurred along Florida's northern Gulf of Mexico coast between 1999 and 2006. The causes of these events, in which over 300 bottlenose dolphins are known to have died, are still under investigation. The impact of these mortality events cannot be fully evaluated, because little prior information on bottlenose dolphin abundance and distribution patterns exist in this region. Thus, the goals of this study were to estimate seasonal abundance, develop site-fidelity indices, and describe distribution patterns of bottlenose dolphins in St. Joseph Bay, Gulf County, Florida, USA. This study site was chosen because it was impacted by all three unusual mortality events and was the geographic focus of the 2004 event. Mark-recapture photo-identification surveys were conducted across multiple seasons from February 2005 through July 2007. Site-fidelity indices were calculated for each identifiable ...
Cetacean Research and Management, defined and utilized dolphin residency patterns and variations ... more Cetacean Research and Management, defined and utilized dolphin residency patterns and variations in habitat use to identify and differentiate between dolphins whose ranging patterns overlap within the estuaries of southern Georgia. Three residency patterns, based upon previous studies, were defined utilizing the total number of years and seasons that individual dolphins were sighted throughout all photo-identification effort in the region. Transients were defined as individuals that were sighted in only one season for one year, seasonal visitors were sighted in one or two seasons for greater than one year, and residents were sighted in three or four seasons for greater than one year. For each residency pattern, the total number of sightings within each SSO tributary was determined to identify differences in habitat use among residency patterns. Residents were primarily sighted across all seasons and all SSO tributaries. These individuals are likely members of the estuarine stock(s) for this region. Seasonal visitors and transients were sighted predominantly in summer or seasons adjacent to summer and in larger SSO tributaries. The majority of these individuals are likely members of the South Carolina/Georgia Coastal Stock that enter the larger estuarine tributaries as they travel along the coast. The results of this chapter provided insight into the appropriate survey effort required to assist with future stock assessments in other estuaries along the U.S. Atlantic and Gulf of Mexico coasts. A minimum of two years of seasonal CR photo-identification surveys were required to group individuals into the residency patterns defined in this chapter. This survey methodology initially requires an
The Anatomical Record, 2015
Odontocete echolocation clicks are generated by pneumatically driven phonic lips within the nasal... more Odontocete echolocation clicks are generated by pneumatically driven phonic lips within the nasal passage, and propagated through specialized structures within the forehead. This study investigated the highly derived echolocation structures of the pygmy (Kogia breviceps) and dwarf (K. sima) sperm whales through careful dissections (N 5 18 K. breviceps, 6 K. sima) and histological examinations (N 5 5 K. breviceps). This study is the first to show that the entire kogiid sound production and transmission pathway is acted upon by complex facial muscles (likely derivations of the m. maxillonasolabialis). Muscles appear capable of tensing and separating the solitary pair of phonic lips, which would control echolocation click frequencies. The phonic lips are enveloped by the "vocal cap," a morphologically complex, connective tissue structure unique to kogiids. Extensive facial muscles appear to control the position of this structure and its spatial relationship to the phonic lips. The vocal cap's numerous air crypts suggest that it may reflect sounds. Muscles encircling the connective tissue case that surrounds the spermaceti organ may change its shape and/or internal pressure. These actions may influence the acoustic energy transmitted from the phonic lips, through this lipid body, to the melon. Facial and rostral muscles act upon the length of the melon, suggesting that the sound "beam" can be focused as it travels through the melon and into the environment. This study suggests that the kogiid echolocation system is highly tunable. Future acoustic studies are required to test these hypotheses and gain further insight into the kogiid echolocation system.
Journal of Experimental Biology, 2006
SUMMARY The passive listening hypothesis proposes that dolphins and whales detect acoustic signal... more SUMMARY The passive listening hypothesis proposes that dolphins and whales detect acoustic signals emitted by prey, including sound-producing (soniferous)fishes. Previous work showed that bottlenose dolphins (Tursiops truncatus) behaviorally orient toward the sounds of prey, including the advertisement calls of male Gulf toadfish (Opsanus beta). In addition, soniferous fishes constitute over 80% of Tursiops diet, and toadfishes alone account for approximately 13% of the stomach contents of adult bottlenose dolphins. Here, we used both behavioral (vocalizations) and physiological (plasma cortisol levels) parameters to determine if male Gulf toadfish can, in turn, detect the acoustic signals of bottlenose dolphins. Using underwater playbacks to toadfish in their natural environment, we found that low-frequency dolphin sounds (`pops') within the toadfish's range of hearing dramatically reduce toadfish calling rates by 50%. Highfrequency dolphin sounds (whistles) and low-frequen...
Marine Mammal Science, 2004
Large predators should have difficulty catching small prey because small animals demonstrate grea... more Large predators should have difficulty catching small prey because small animals demonstrate greater maneuverability and agility compared to large animals. The ability of a predator to capture small prey indicates locomotor strategies to compensate for inequities in maneuverability. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida feed on fish at least one order of magnitude smaller than themselves. To examine the locomotor strategies involved in prey capture, the foraging movements of these dolphins were videotaped from overhead using a remotely-controlled camera suspended from a helium-filled aerostat, which was tethered to an observation vessel. Dolphins were observed to rapidly maneuver during chases of fish in open water or around patches of rooted vegetation. Video analysis of the chase sequences indicated that the dolphins could move the rostrum through small radius turns with a mean value of 0.20 body lengths and with a minimum value of 0.08 body lengths. Mean rate of turn was 561.68/sec with a maximum rate measured at 1,372.08/sec. High turning rates
The Journal of the Acoustical Society of America, 2003
Recordings of manatee ͑Trichechus manatus spp.͒ vocalizations were made in Florida and Belize to ... more Recordings of manatee ͑Trichechus manatus spp.͒ vocalizations were made in Florida and Belize to quantify both intraspecific and geographic variation. Manatee vocalizations were relatively stereotypical in that they were short tonal harmonic complexes with small frequency modulations at the beginning and end. Vocalizations ranged from almost pure tones to broader-band tones that had a raspy quality. The loudest frequency was typically the second or third harmonic, with average received levels of the peak frequency of about 100 dB re 1 Pa. Signal parameters measured from these calls showed the manatees from Belize and Florida have overlapping distributions of sound duration, peak frequency, harmonic spacing, and signal intensity, indicating no obvious distinguishing characteristics between these isolated populations.
The Journal of the Acoustical Society of America, 1998
me ecology of the odontocete echolocation system is not well understood despite a solid understan... more me ecology of the odontocete echolocation system is not well understood despite a solid understanding of the system's operation. To gain insight into the functional uses of dolphin biosorrsr we have developed an acoustic data logger which utilizes a miniature DAT recorder and two suction-cup hydrophores. The first hydrophore is located 10 cm posterior of the blowhole, and (he second 20 cm below the lateral base of the dorssf fin. The anterior 'high-frequency' hydrophore, designed specifically to record echolocation signals, has unity gain and a one-pole 10 kHz high pass filter. The 'ambient' hydrophore located at the base of the dorsal fin has +18 dB gain and has a one-pole I kHz high pass filter. To obtain echolocation recordings the 'high-frequency' hydrophore was filtered through a simple demodulator in one of the deployments, The package was attached to temporarily restrained animals which, after release, were followed to record behavioral data. During (he two successful deployments to date the logger recorded animal vocalizations, surfacing events, the sounds of passing boats, and hydrodynamic sounds produced by the animal's fluke strokes.
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Papers by Douglas Nowacek