LOMAC-MACNAIR, K.S., M.A. SMULTEA, T. YACK, M. LAMMERS, T.F. NORRIS, G. GREEN, K. DUNLEAVY, D. STECKLER, V. JAMES. 2018. Marine mammal visual and acoustic surveys near the Alaskan Colville River Delta. Polar Biology Online. DOI: 10.1007/s00300-018-2434-y
Information about the occurrence of marine mammals near the Colville River Delta (CRD), Beaufort Sea, Alaska is limited for most species expected to occur in this region. As part of marine mammal monitoring and mitigation for a seismic acquisition program August 25–September 30, 2014, we recorded marine mammal occurrence in a ~ 30 km2 survey area between the Spy Islands and Oliktok Point near Simpson Lagoon using a combination of visual and acoustic monitoring methods. Visual effort totaled 632 h, occurring 18–20 h/day during all daylight hours by observers aboard three small survey vessels. In addition, an Iñupiat observer and seal hunter from the village of Nuiqsut conducted a small-vessel survey to investigate locations of Phoca largha haul-out sites. A total of 102 individual marine mammals were recorded from five species: P. largha, Pusa hispida, Ursus maritimus, Erignathus barbatus, and Delphinapterus leucas. Over 400 h of acoustic data were recorded using second-generation Ecological Acoustic Recorders deployed on the seafloor at three locations. Calls were identified for D. leucas, Balaena mysticetus, E. barbatus, and P. hispida. Results provide valuable information on marine mammal occurrence for the Beaufort Sea CRD during summer/fall, an area proposed for potential offshore oil and gas development.
NORRIS, T.F., K.J. DUNLEAVY, T.M. YACK, E.L. FERGUSON. 2017. Estimation of minke whale abundance from an acoustic line transect survey of the Mariana Islands. Marine Mammal Science 33:574-592. Doi: 10.1 111/mms.12397
The minke whale is one of the most abundant species of baleen whales worldwide, yet is rarely sighted in subtropical waters. In the North Pacific, they produce a distinctive sound known as the “boing,” which can be used to acoustically localize individuals. A vessel‐based survey using both visual and passive acoustic monitoring was conducted during the spring of 2007 in a large (616,000 km2) study area encompassing the Mariana Islands. We applied line transect methods to data collected from a towed hydrophone array to estimate the abundance of calling minke whales in our study area. No minke whales were sighted, but there were hundreds of acoustic detections of boings. Computer algorithms were developed to localize calling minke whales from acoustic recordings, resulting in over 30 independent localizations, a six‐fold increase over those estimated during the survey. The two best estimates of abundance of calling minke whales were determined to be 80 and 91 animals (0.13 and 0.15 animals per 1,000 km2, respectively; CV = 34%). These are the first density and abundance estimates for calling minke whales using towed hydrophone array surveys, and the first estimates for this species in the Mariana Islands region. These are considered minimum estimates of the true number of minke whales in the study area.
OSWALD, J.N., T.F. NORRIS, T.M. YACK, E.L. FERGUSON, A. KUMAR, J. NISSEN, AND J. BELL. 2016. Patterns of occurrence and marine mammal acoustic behavior in relation to navy sonar activity off Jacksonville, Florida. In: A.N. Popper and A. Hawkins (eds). The effects of noise on aquatic life II, Springer, New York, pp. 791-799.
Passive acoustic data collected from marine autonomous recording units deployed off Jacksonville, FL (from 13 September to 8 October 2009 and 3 December 2009 to 8 January 2010), were analyzed for detection of cetaceans and Navy sonar. Cetaceans detected included Balaenoptera acutorostrata, Eubalaena glacialis, B. borealis, Physeter macrocephalus, blackfish, and delphinids. E. glacialis were detected at shallow and, somewhat unexpectedly, deep sites. P. macrocephalus were characterized by a strong diel pattern. B. acutorostrata showed the strongest relationship between sonar activity and vocal behavior. These results provide a preliminary assessment of cetacean occurrence off Jacksonville and new insights on vocal responses to sonar.
DEPARTMENT OF THE NAVY. 2015. From Clicks to Counts: Using Passive Acoustic Monitoring to Estimate the Density and Abundance of Cuvier’s Beaked Whales in the Gulf of Alaska (GoA). Prepared by T.M Yack, T. Norris, E. Ferguson, S. Coates, and B.K. Rone for Assistant Secretary of the Navy. Submitted to Naval Facilities Engineering Command Pacific, Pearl Harbor, Hawaii, under Contract No. N62470-10-3011, Task Order 22, issued to HDR, Inc., San Diego, CA. 31 August 2015. 43 pp.
The Gulf of Alaska (GoA) is home to three known species of beaked whales, Baird’s (Berardius bairdii), Cuvier’s (Ziphius cavirostris), and Stejneger’s (Mesoplodon stejnegeri). Beaked whale distribution and abundance is poorly understood with only limited sightings within the GoA (Allen and Angliss 2013). To address gaps in knowledge regarding the distribution and abundance of beaked whales and other marine mammals in the GoA, a 26-day visual and acoustic line- transect survey was conducted during the summer of 2013. One of the main objectives of the acoustic survey was to obtain acoustic-based density and abundance estimates for Cuvier’s beaked whales in the study area. The survey area was divided into four strata to reflect distinct marine mammal habitat types; ‘inshore’, ‘slope’, ‘offshore’ and ‘seamounts.’ Passive acoustic monitoring was conducted around the clock for 23 days over 6,304 kilometers (km) of trackline using a towed hydrophone array system. There were 93 acoustic encounters of beaked whales (32 Baird’s, 47 Cuvier’s and 14 Stejneger’s), of which 79 (85 percent) were localized during post-processing. Of these localized encounters, 18 Baird’s, 40 Cuvier’s and 10 Stejneger’s occurred during line-transect effort. Cuvier’s beaked whales were the only species of beaked whale with a sufficient sample size to reliably estimate density and abundance using line- transect distance sampling methods. Comparatively, visual survey methods resulted in only one sighting of Cuvier’s beaked whale (one individual), six sightings of Baird’s beaked whale (49 individuals) and five unidentified beaked whale encounters (nine individuals) during 4,155 km of visual effort. Line-transect distance sampling methods were used to estimate the density and abundance of Cuvier’s beaked whales using the acoustic data. Encounter rate varied by strata, and was highest in the seamount stratum (10 animals/1,000 km), followed by the offshore (7 animals/1,000 km) and slope strata (3 animals/1,000 km), respectively. An acoustic-based density and abundance estimate was obtained for each stratum. Results from this study represent the first estimates of density and abundance for Cuvier’s beaked whales within the GoA, and the first acoustic-based estimates for any species of beaked whales using a line- transect survey design.
RANKIN, S., J.N. OSWALD, A.E. SIMONIS, AND J. BARLOW. 2015. Vocalizations of the rough-toothed dolphin, Steno bredanensis, in the Pacific Ocean. Marine Mammal Science. Doi: 10.1 111/mms.12226
The rough-toothed dolphin, Steno bredanensis, is found throughout tropical and warm-temperate waters worldwide (Miyazaki and Perrin 1994). Little is known of the habitat, ecology, or abundance of this species in most areas. The small group sizes and subtle surfacing behavior of S. bredanensis may lead to groups being missed by visual observers during shipboard line-transect population surveys, which would result in an underestimation of their abundance. It has been suggested that the use of passive acoustic methods may improve our ability to detect species that are difficult to observe using visual methods. This may be particularly true for S. bredanensis, as during 7 yr of combined visual and acoustic surveys in the tropical Pacific Ocean, this species was found to be one of the most vocal dolphin species (Rankin et al. 2008c). Like most other delphinids, S. bredanensis is known to produce whistles and broad- band click sounds (Busnell and Dziedzic 1966; Evans 1967; Watkins et al. 1987; Oswald et al. 2003, 2007; Rankin et al. 2008c; Baumann-Pickering et al. 2010b; Seabra de Lima et al. 2012). There are few descriptions of the full bandwidth of the echolocation clicks of S. bredanensis, and none that examine interclick interval (Norris and Evans 1967, Baumann-Pickering et al. 2010b). Here, we present a description of whistles and broadband clicks produced by S. bredanensis in the tropical Pacific Ocean to provide a more complete examination of its vocal repertoire and a foundation for improved acoustic species identification. The characterization of species-specific acoustic repertoires will aid in the improvement of automated techniques for acoustic species identification, which would allow for improved accuracy in abundance estimates resulting from shipboard surveys.
AZZOLIN, M., A. GANNIER, M.O. LAMMERS, J.N. OSWALD, E. PAPALE, G. BUSCAINO, G. BUFFA, S. MAZZOLA AND C. GIACOMA. 2014. Combining whistle acoustic parameters to discriminated Mediterranean odontocetes during passive acoustic monitoring. Journal of the Acoustical Society of America 135:502-512.
Acoustic observation can complement visual observation to more effectively monitor occurrence and distribution of marine mammals. For effective acoustic censuses, calibration methods must be determined by joint visual and acoustic studies. Research is still needed in the field of acoustic species identification, particularly for smaller odontocetes. From 1994 to 2012, whistles of four odontocete species were recorded in different areas of the Mediterranean Sea to determine how reliably these vocalizations can be classified to species. Recordings were attributed to species by simultaneous visual observation. The results of this study highlight that the frequency parameters, which are linked to physical features of animals, show lower variability than modulation parame- ters, which are likely to be more dependent on complex eco-ethological contexts. For all the studied species, minimum and maximum frequencies were linearly correlated with body size. DFA and Classification Tree Analysis (CART) show that these parameters were the most impor- tant for classifying species; however, both statistical methods highlighted the need for combining them with the number of contour minima and contour maxima for correct classification. Generally, DFA and CART results reflected both phylogenetic distance (especially for common and striped dolphins) and the size of the species.
RONE, B.K., A.B. DOUGLAS, T.M. YACK, A.N. ZERBINI, T.N. NORRIS, E. FERGUSON, AND J. CALAMBOKIDIS. 2014. Report for the Gulf of Alaska Line-Transect Survey (GOALS) II: Marine Mammal Occurrence in the Temporary Maritime Activities Area (TMAA). Submitted to Naval Facilities Engineering Command (NAVFAC) Pacific, Honolulu, Hawaii under Contract No. N62470-10-D-3011, Task Order 0022, issued to HDR Inc., San Diego, California. Prepared by Cascadia Research Collective, Olympia, Washington; Alaska Fisheries Science Center, Seattle, Washington; and Bio-Waves, Inc., Encinitas, California. April 2014.
The U.S. Navy periodically uses a Temporary Maritime Activities Area (TMAA) in the central Gulf of Alaska (GoA), east of Kodiak Island. Current scientific data on affected biological and environmental resources are necessary to conduct analyses required for Navy training, exercise, and technology-acquisition activities. In 2009, the Navy funded a vessel-based line-transect survey that provided density estimates for fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales in the TMAA. However, additional data on marine mammal species were necessary to obtain the regionalized population-density data that Navy and other participating Federal agencies like the Bureau of Ocean Energy Management need to meet their environmental stewardship obligations. In the summer of 2013, the Navy funded a second survey to fill in the gaps of knowledge on distribution, movements, and densities of marine mammals within this training area.During this survey, the visual team surveyed 4,504 kilometers (km) of ‘full-effort,’ which included 349 km of ‘transit-effort.’ There was an additional 375 km of ‘fog-effort’ (transect and transit). Based on total effort, there were 802 sightings (1,998 individuals) of 13 confirmed marine mammal species, with an additional 162 sightings (228 individuals) of unidentified cetaceans and pinnipeds (including those recorded on transit and during off-effort mode).
The acoustic team conducted round-the-clock monitoring with a towed-hydrophone array for 6,304 km of line-transect effort totaling 426 hours of ‘standard’ monitoring, with an additional 374 km of ~30 hours of ‘non-standard’ and ‘chase’ effort. There were 379 acoustic detections and 267 localizations of six confirmed cetacean species. Additionally, 186 sonobuoys were deployed (success rate of 93.5 percent) with seven confirmed cetacean species detected. Two satellite transmitter tags were attached to monitor movements of cetaceans. One was deployed on a blue whale (B. musculus), which transmitted for 9 days, and the other was deployed on a Baird’s beaked whale (Berardius bairdii), which transmitted for 15 days. Based on photo-identification matches, the tagged blue whale had been previously identified off Baja California, Mexico, in 2005. Photographs of five cetacean species were collected for photo- identification purposes: fin, humpback, blue, killer (Orcinus orca) and Baird’s beaked whales.
Density and abundance estimates (uncorrected for proportion of animals missed on the transect line) were estimated from line-transect data for six cetacean and one pinniped species. The abundance of large whales not identified to species was computed and allocated to blue, fin, and humpback whales proportionally within each stratum. Pooled density (D) and abundance (N) estimates for the survey area were: blue whales (N = 78; D = 0.0005; CV = 1.22), fin whales (N = 3,581; D = 0.0217; CV = 0.28), humpback whales (N = 3,054; D = 0.0185; CV = 0.71), killer whales (N = 950; D = 0.0058; CV = 0.73), sperm whales (Physeter macrocephalus; N = 296; D = 0.0018; CV(N) = 0.57), Dall’s porpoise (Phocoenoides dalli; N = 11,924; D = 0.0722; CV = 0.28), and northern fur seals (Callorhinus ursinus; N = 1,770; D = 0.0107; CV = 0.23). A second density and abundance estimate was obtained for sperm whales using acoustic localizations from the towed-hydrophone array (N = 215; D = 0.0013; CV = 0.18). The estimates of abundance and density for five species were obtained for the first time for this region. New information on movements and habitat use were documented using data collected from the first satellite tag deployments on either blue or Baird’s beaked whales within this region. Photographic data contributed to knowledge on seasonal presence of individuals. Overall, this survey provides one of the most comprehensive datasets on marine mammal occurrence, abundance, and distribution within the central GoA, an area rarely surveyed.
BAUMANN-PICKERING , S., MCDONALD, M.A., SIMONIS, A.E., SOLSONA BERGA, S., MERKENS, K P. B. ,OLESON, E. M., ROCH, M.A.,WIGGINS, S.M. , RANKIN, S.M, YACK, T.M., HILDEBRAND, J.A. 2013. Species-specific beaked whale echolocation signals. Journal of the Acoustical Society of America. 134(3): pp. 2293-2301.
Beaked whale echolocation signals are mostly frequency-modulated (FM) upsweep pulses and appear to be species specific. Evolutionary processes of niche separation may have driven differentiation of beaked whale signals used for spatial orientation and foraging. FM pulses of eight species of beaked whales were identified, as well as five distinct pulse types of unknown species, but presumed to be from beaked whales. Current evidence suggests these five distinct but unidentified FM pulse types are also species-specific and are each produced by a separate species. There may be a relationship between adult body length and center frequency with smaller whales producing higher frequency signals. This could be due to anatomical and physiological restraints or it could be an evolutionary adaption for detection of smaller prey for smaller whales with higher resolution using higher frequencies. The disadvantage of higher frequencies is a shorter detection range. Whales echolocating with the highest frequencies, or broadband, likely lower source level signals also use a higher repetition rate, which might compensate for the shorter detection range. Habitat modeling with acoustic detections should give further insights into how niches and prey may have shaped species-specific FM pulse types.
HANNAY, D.E., J. DELARUE, X. MOUY, B.S. MARTIN, D. LEARY , J.N. OSWALD, AND J. VALLARTA. 2013. Marine mammal acoustic detections in the northeastern Chukchi Sea, September 2007- July 2011. Continental Shelf Research 127-146.
Several cetacean and pinniped species use the northeastern Chukchi Sea as seasonal or year-round habitat. This area has experienced pronounced reduction in the extent of summer sea ice over the last decade, as well as increased anthropogenic activity, particularly in the form of oil and gas exploration. The effects of these changes on marine mammal species are presently unknown. Autonomous passive acoustic recorders were deployed over a wide area of the northeastern Chukchi Sea off the coast of Alaska from Cape Lisburne to Barrow, at distances from 8 km to 200 km from shore: up to 44 each summer and up to 8 each winter. Acoustic data were acquired at 16 kHz continuously during summer and on a duty cycle of 40 or 48 min within each 4-h period during winter. Recordings were analyzed manually and using automated detection and classification systems to identify calls.
Bowhead (Balaena mysticetus) and beluga (Delphinapterus leucas) whale calls were detected primarily from April through June and from September to December during their migrations between the Bering and Beaufort seas. Summer detections were rare and usually concentrated off Wainwright and Barrow, Alaska. Gray (Eschrichtius robustus) whale calls were detected between July and October, their occurrence decreasing with increasing distance from shore. Fin (Balaenoptera physalus), killer (Orcinus orca), minke (Balaenoptera acutorostrata), and humpback (Megaptera novaeangliae) whales were detected sporadically in summer and early fall. Walrus (Odobenus rosmarus) was the most commonly detected species between June and October, primarily occupying the southern edge of Hanna Shoal and haul-outs near coastal recording stations off Wainwright and Point Lay. Ringed (Pusa hispida) and bearded (Erignathus barbatus) seals occur year-round in the Chukchi Sea. Ringed seal acoustic detections occurred throughout the year but detection numbers were low, likely due to low vocalization rates. Bearded seal acoustic detections peaked in April and May during their breeding season, with much lower detection numbers in July and August, likely as a result of reduced calling rates after breeding season. Ribbon seals (Histriophoca fasciata) were only detected in the fall as they migrated south through the study area toward the Bering Sea. These results suggest a regular presence of marine mammals in the Chukchi Sea year-round, with species-dependent seasonal and spatial density variations.
LAMMERS, M.O., M. CASTELLOTE, R. SMALL, S. ATKINSON, J. JENNINGS, A. ROSINSKI, J.N. OSWALD, AND C. GARNER. 2013. Passive acoustic monitoring of Cook Inlet beluga whales (Delphinapterus leucas). Journal of the Acoustical Society of America 134:2497-2504.
The endangered beluga whale (Delphinapterus leucas) population in Cook Inlet, AK faces threats from a variety of anthropogenic factors, including coastal development, oil and gas exploration, vessel traffic, and military activities. To address existing gaps in understanding about the occurrence of belugas in Cook Inlet, a project was developed to use passive acoustic monitoring to document the yearround distribution of belugas, as well as killer whales (Orcinus orca), which prey on belugas. Beginning in June 2009, ten moorings were deployed throughout the Inlet and refurbished every two to eight months. Despite challenging conditions consisting of strong tidal currents carrying debris and seasonal ice cover, 83% of mooring deployments were successfully recovered. Noise from water flow, vessel traffic, and/or industrial activities was present at several sites, potentially masking some signals. However, belugas were successfully detected at multiple locations. Detections were relatively common in the upper inlet and less common or absent atmiddle and lower inlet locations. Killer whale signals were also recorded. Some seasonal variability in the occurrence of both belugas and killer whales was evident.
PAPALE, E., M. AZZOLIN, I. CASCAO, A. GANNIER, M.O. LAMMERS, V.M. MARTIN, J.N. OSWALD, M. PEREZ-GIL, R. PRIETO, M.A. SILVA, AND C. GIACOMA. 2013. Geographic variability in the acoustic parameters of striped dolphin’s (Stenella coeruleoalba) whistles. Journal of the Acoustical Society of America 133:1126-1134.
Geographic variation in the acoustic features of whistles emitted by the striped dolphin (Stenella coeruleoalba) from the Atlantic Ocean (Azores and Canary Islands) and the Mediterranean was investigated. Ten parameters (signal duration, beginning, end, minimum and maximum frequency, the number of inflection points, of steps, of minima and maxima in the contour and the frequency range) were extracted from each whistle. Discriminant function analysis correctly classified 73% of sounds between Atlantic Ocean and Mediterranean Sea. A cline in parameters was apparent from the Azores to the Mediterranean, with a major difference between the Canaries and the Mediterranean than between Azores and Canaries. Signal duration, maximum frequency, and frequency range measured in the Mediterranean sample were significantly lower compared to those measured in the Atlantic. Modulation parameters played a considerable role in area discrimination and were the only parameters contributing to highlight the differences within the Atlantic Ocean. Results suggest that the acoustic features constrained by structural phenotype, such as whistle’s frequency parameters, have a major effect on the Atlantic and Mediterranean separation while behavioral context, social, and physical environment may be among the main factors contributing to local distinctiveness of Atlantic areas. These results have potential passive acoustic monitoring applications.
PAPALE, E., M. AZZOLIN, I. CASCAO, A. GANNIER, M.O. LAMMERS, V.M. MARTIN, J.N. OSWALD, M. PEREZ-GIL, R. PRIETO, M.A. SILVA AND C. GIACOMA. 2013. Macro and micro geographic variation of short-beaked common dolphin’s whistles in the Mediterranean Sea and Atlantic Ocean. Ethology, Ecology and Evolution, ahead of print.
Genetic studies have shown that there are small but significant differences between the short-beaked common dolphin populations in the Atlantic Ocean and those in the Mediterranean Sea. The short-beaked common dolphin is a highly vocal species with a wide sound production repertoire including whistles. Whistles are continuous, narrowband, frequency-modulated signals that can show geographic variation in dolphin species. This study tests whether the differences, highlighted by genetic studies, are recognisable in the acoustic features of short-beaked common dolphin’s whistles in the two adjacent areas of the Atlantic Ocean and the Mediterranean Sea. From a selected sample of good quality whistles (514 recorded in the Atlantic and 193 in the Mediterranean) 10 parameters of duration, frequency and frequency modulation were measured. Comparing data among basins, differences were found for duration and all frequency parameters except for minimum frequency. Modulation parameters showed the highest coefficient of variation. Through discriminant analysis we correctly assigned 75.7% of sounds to their basins. Furthermore, micro-geographic analysis revealed similarity between the sounds recorded around the Azores and the Canary archipelagos and between the Bay of Biscay and the Mediterranean Sea. Results are in agreement with the hypothesis proposed by previous genetic studies that two distinct populations are present, still supposing a gene flow between the basins. This study is the first to compare short-beaked common dolphin’s whistles of the Atlantic Ocean and the Mediterranean areas.
SOUSA-LIMA, R. S., T. F. NORRIS, J. N. OSWALD, and D. P. FERNANDES. 2013. A Review and Inventory of Fixed Autonomous Recorders for Passive Acoustic Monitoring of Marine Mammals. Aquatic Mammals 39: In press.
Fixed autonomous acoustic recording devices (autonomous recorders [ARs]) are defined as any electronic recording system that acquires and stores acoustic data internally (i.e., without a cable or radio link to transmit data to a receiving station), is deployed semi-permanently underwater (via a mooring, buoy, or attached to the sea floor), and must be retrieved to access the data. More than 30 ARs were reviewed. They varied greatly in capabilities and costs, from small, hand-deployable units for detecting dolphin and porpoise clicks in shallow water to larger units that can be deployed in deep water and can record at high-frequency bandwidths for over a year, but must be deployed from a large vessel. The capabilities and limitations of the systems reviewed herein are discussed in terms of their effectiveness in monitoring and studying marine mammals.
NORRIS, T., T. YACK, J.N. OSWALD, S. MARTIN, L. THOMAS, V. JANIK. 2012. Boing! Acoustic localization, characterisation and comparison of minke whale songs from the Hawaiian islands and other areas in the North Pacific Ocean. Bioacoustics 21 (1): 77
The minke whale (Balaenoptera acutorostrata) is a small, elusive baleen whale that is rarely sighted in tropical waters of the North Pacific Ocean. During winter and spring, they produce songs, also known as ‘boings’, that are commonly detected at deep water hydrophones located around the Hawaiian Islands. We acoustically monitored minke whales using a fixed seafloor hydrophone array encompassing a large ( >2000 km2), deep-water area off the island of Kauai. Simultaneous visual-acoustic surveys of the same region were conducted from a quiet motor-sailing vessel. The combination of the towed and fixed hydrophone arrays allowed animals to be localized and tracked in near real-time. Using both methods, we were able to visually confirm the location of a minke whale initially detected and localized using the fixed hydrophone array, and later with the towed hydrophone array. These data are being collected to help validate statistical methods that are being developed to estimate densities of marine mammals using acoustic signals they produce. In a related study, boings recorded in the Hawaiian Islands (central North Pacific) were acoustically characterised and compared to boings recorded in the western and eastern North Pacific. These results are discussed in relation to the behaviour and population biology of this species. We provide recommendations for tracking, monitoring behaviours and estimating the distribution and distribution of these vocally active, but visually elusive whales.
OSWALD, J.N., W.W.L. AU, AND F. DUENNEBIER. 2011. Minke whale (Balaenoptera acutorostrata) boings detected at the Station ALOHA Cabled Observatory. Journal of the Acoustical Society of America 129:3353-3360.
Minke whales (Balaenoptera acutorostrata) in the tropical North Pacific are elusive and difficult to detect visually. The recent association of a unique sound called the “boing” to North Pacific minke whales has made it possible to use passive acoustics to investigate the occurrence of this species in Hawaiian waters. One year of recordings (17 February 2007–18 February 2008) made at the Station ALOHA Cabled Observatory were examined to investigate the characteristics of boings and temporal patterns in their occurrence at this site, located 100 km north of Oahu. Characteristics of boings exhibited low variability. Pulse repetition rate and duration measurements matched those for “central” or “Hawaii” boing types. Boings were detected from October until May, with a peak in March. Although no boings were detected from June to September, the absence of boings does not necessarily indicate the absence of minke whales. Significant diel variation in boing rate was not observed. The absence of a diel pattern in boing production suggests that day- or night-time acoustic surveys are equally acceptable methods for studying minke whale occurrence. Future research should include efforts to determine what other sounds are produced by minke whales in this area, and which age/sex classes produce boings.
GANNIER, A., S. FUCHS, P. QUEBRE, AND J.N. OSWALD. 2010. Performance of a contour-based classification method for whistles of Mediterranean delphinids. Applied Acoustics 71:1063-1069.
Whistles from five delphinid species in the western Mediterranean Sea (Stenella coeruleoalba, Grampus griseus, Delphinus delphis, Tursiops truncatus, Globicephala melas) were taken from GREC sound archives. FFT contours (window size 512, Hanning, sampling frequency 44.1 kHz) were extracted with custom developed Matlab software: 277 samples of striped dolphins (Sc), 158 whistles of Risso’s dolphins (Gg), 120 of common dolphins (Dd), 76 of bottlenose dolphins (Tt), and 66 of pilot whales (Gm) were selected. Seafox software extracted 15 variables from the digitized contours, including: duration, initial, final, maximal and minimal frequency slopes, frequency range, number of frequency extrema, beginning, ending, maximal and minimal frequencies, presence of harmonics. Four of five species were significantly different (Mann–Whitney test) for average durations (respectively 0.73, 0.65, 0.47 and 0.89 s for Sc, Gg, Dd, Gm) while the average duration of bottlenose dolphins was 0.71 s. Frequency ranges (respectively 7.3,6.3, 4.6, 3.2 and 6.3 kHz) were significantly different for all species pairs, with the exception of bottlenose and Risso’s dolphins. From a global point of view, pilot whale calls were the most distinct, with 43 significant pair-wise tests out of a total of 52, followed by the common dolphins. Risso’s dolphins were closest to other species whistles. A CART classification method achieved a global classification rate of 62.9%.
YACK, T. M., J. BARLOW, M. A. ROCH, H. KLINCK, S. MARTIN, D. K. MELLINGER and D. GILLESPIE. 2010. Comparison of beaked whale detection algorithms. Applied Acoustics 71: 1043-1049.
Due to recent advances in passive acoustic monitoring techniques, beaked whales are now more effectively detected acoustically than visually during vessel-based (e.g. line-transect) surveys. Beaked whales signals can be discriminated from those of other cetaceans by the unique characteristics of their echolocation clicks (e.g. duration >175 ls, center frequencies between 30 and 40 kHz, inter-click intervals between 0.2 and 0.4 s and frequency upsweeps). Furthermore, these same characteristics make these signals ideal candidates for testing automated detection and classification algorithms. There are several different beaked whale automated detectors currently available for use. However, no comparative analysis of detectors exists. Therefore, comparison between studies and datasets is difficult. The purpose of this study was to test, validate, and compare algorithms for detection of beaked whales in acoustic line-transect survey data. Six different detection algorithms (XBAT, Ishmael, PAMGUARD, ERMA, GMM and FMCD) were evaluated and compared. Detection trials were run on three sample days of towed-hydrophone array recordings collected by NOAA Southwest Fisheries Science Center (SWFSC) during which were confirmed visual sightings of beaked whales (Ziphius cavirostris and Mesoplodon peruvianus). Detections also were compared to human verified acoustic detections for a subset of these data. In order to measure the probabilities of false detection, each detector was also run on three sample recordings containing clicks from another species: Risso’s dolphin (Grampus griseus). Qualitative and quantitative comparisons and the detection performance of the different algorithms are discussed.
OSWALD, J. N., S. RANKIN and J. BARLOW. 2008. To Whistle or Not to Whistle? Geographic Variation in the Whistling Behavior of Small Odontocetes. Aquatic Mammals 34: 288-302.
Whistles are used by odontocetes to varying degrees. During a visual and acoustic survey of dolphin abundance in the eastern tropical Pacific Ocean (ETP), whistles were heard from 66% of single species schools and from 98% of mixed species schools. In contrast, whistles were heard from only 24% of single species schools and 23% of mixed species schools during a survey of temperate waters off the western United States. The most common species encountered in the ETP were Stenella coeruleoalba, S. attenuata, and Tursiops truncatus, all of which whistled frequently. The most common species encountered in the temperate study area were Delphinus delphis, Phocoenoides dalli, Lissodelphis borealis, and Phocoena phocoena, only one of which whistled (D. delphis). Why do small odontocete species living in the ETP whistle more frequently than those living in colder waters farther north? Six hypotheses are explored: (1) predator avoidance, (2) group size, (3) school composition, (4) behavior state, (5) temporal variation, and (6) anatomical differences. Multivariate logistic regression with whistling as the dependent variable and group size, school composition, time of day, presence of a beak, and study area as independent variables showed that all variables were significant (p < 0.001). An explanation of the aggregation of whistling species in the tropical study area and nonwhistling species in the temperate study area is likely found in some combination of the hypotheses discussed.
RANKIN, S., J.N. OSWALD, AND J. BARLOW. 2008. Acoustic behavior of dolphins in the Pacific Ocean: implications for using passive acoustic methods for population studies. Canadian Journal of Acoustics 36:88-92.
The Southwest Fisheries Science Center has been conducting shipboard visual line-transect cetacean surveys for over 30 years, and combined visual and acoustic surveys for seven years. Full incorporation of passive acoustics as a tool for population assessment requires an understanding of the acoustic behavior of cetaceans as well as the limitations of the methods used in these surveys. Our research summarizes data collected during seven years of combined visual and acoustic surveys throughout the central and eastern North Pacific Ocean, ranging from the Aleutian Island chain in the north, to Peru in the south. Phonations from 2,034 dolphin schools were examined to better understand the acoustic behavior of cetaceans. Equally important are the cetacean schools that were seen but not heard, and this analysis includes an examination of these groups by species, group size, geographic location, and time of day. The results of this analysis allow us to take the first steps to incorporate passive acoustics into line-transect cetacean surveys.
RANKIN, S., J.N. OSWALD, J. BARLOW AND M.O. LAMMERS. 2007b. Patterned burst-pulse vocalizations of the northern right whale dolphin, Lissodelphis borealis. Journal of the Acoustical Society of America 121:1213-1218.
Vocalizations from the northern right whale dolphin, Lissodelphis borealis, were recorded during a combined visual and acoustic shipboard survey of cetacean populations off the west coast of the United States. Seven of twenty single-species schools of L. borealis produced click and pulsed vocalizations. No whistles were detected during any of the encounters. Clicks associated with burst-pulse vocalizations were lower in frequency and shorter in duration than clicks associated with echolocation. All burst-pulse sounds were produced in a series containing 6–18 individual burst-pulses. These burst-pulse series were stereotyped and repeated. A total of eight unique burst-pulse series were detected. Variation in the temporal characteristics of like units compared across repeated series was less than variation among all burst-pulses. These stereotyped burst-pulse series may play a similar communicative role as do stereotyped whistles found in other delphinid species.
OSWALD, J. N., S. RANKIN, J. BARLOW and M. O. LAMMERS. 2007b. A tool for real-time acoustic species identification of delphinid whistles. Journal of the Acoustical Society of America 122: 587-595.
The ability to identify delphinid vocalizations to species in real-time would be an asset during shipboard surveys. An automated system, Real-time Odontocete Call Classification Algorithm (ROCCA), is being developed to allow real-time acoustic species identification in the field. This Matlab-based tool automatically extracts ten variables (beginning, end, minimum and maximum frequencies, duration, slope of the beginning and end sweep, number of inflection points, number of steps, and presence/absence of harmonics) from whistles selected from a real-time scrolling spectrograph (ISHMAEL). It uses classification and regression tree analysis (CART) and discriminant function analysis (DFA) to identify whistles to species. Schools are classified based on running tallies of individual whistle classifications. Overall, 46% of schools were correctly classified for seven species and one genus (Tursiops truncatus, Stenella attenuata, S. longirostris, S. coeruleoalba, Steno bredanensis, Delphinus species, Pseudorca crassidens, and Globicephala macrorhynchus), with correct classification as high as 80% for some species. If classification success can be increased, this tool will provide a method for identifying schools that are difficult to approach and observe, will allow species distribution data to be collected when visual efforts are compromised, and will reduce the time necessary for post-cruise data analysis.
OSWALD, J. N., S. RANKIN and J. BARLOW. 2007a. First description of whistles of pacific fraser’s dolphins Lagenodelphis hosei. Bioacoustics-the International Journal of Animal Sound and Its Recording 16: 99-111.
Acoustic recordings were made in the presence of four single-species schools of Fraser’s Dolphin Lagenodelphis hosei during combined acoustic and visual shipboard line-transect cetacean abundance surveys. Recordings were made using a towed hydrophone array and sonobuoys. Echolocation clicks were detected during only one recording session and no burst pulses were detected. Whistles were present in all four recording sessions. Fourteen variables were measured from the fundamental frequencies of 60 whistles. The whistles were generally simple, with few inflection points or steps. Whistles ranged from 6.6 kHz to 23.5 kHz, with durations ranging from 0.06 to 0.93 see. Whistle characteristics closely match those reported for L. hosei recorded in the Gulf of Mexico (Leatherwood et al. 1993) and the Caribbean (Watkins et al. 1994), although, in general, the Pacific dolphins were less vocally active than the Caribbean dolphins described by Watkins et al. (1994). This difference may be related to the orientation of the hydrophone array relative to the dolphins. It may also be due to behaviour, as the Caribbean dolphins were engaged in feeding activities and the Pacific dolphins were fast travelling to evade the approaching vessel.
RANKIN, S., T. F. NORRIS, M. A. SMULTEA, C. OEDEKOVEN, A. M. ZOIDIS, E. SILVA and J. RIVERS. 2007a. A visual sighting and acoustic detections of Minke whales, Balaenoptera acutoroshata (Cetacea : Balaenopteridae), in nearshore Hawaiian waters’. Pacific Science 61: 395-398.
Minke whales, Balaenoptera acutorostrata (Lacepede), have been considered a rare species in Hawaiian waters due to limited sightings during visual and aerial surveys. However, Our research suggests that they are more common than previously considered. In spring 2005, a combined visual-acoustic survey, of cetaceans in Hawaiian waters resulted in the sighting of a minke whale within 22 kin of Kaua’i. Minke whale vocalizations were also detected at several other locations near Kaua’i and O’ahu. These 2005 reports are the first from nearshore (<50 kin) Hawaiian waters despite years of previous shipboard and aerial surveys. The lack of historical sightings is likely due to misidentification or the inability to detect these animals during poor sighting conditions. We recommend that future cetacean surveys in Hawaiian waters include a passive acoustic component to increase the likelihood of detecting minke whales.
BRANCH, T. A., K. M. STAFFORD, D. M. PALACIOS, C. ALLISON, J. L. BANNISTER, C. L. K. BURTON, E. CABRERA, C. A. CARLSON, B. G. VERNAZZANI, P. C. GILL, R. HUCKE-GAETE, K. C. S. JENNER, M. N. M. JENNER, K. MATSUOKA, Y. A. MIKHALEV, T. MIYASHITA, M. G. MORRICE, S. NISHIWAKI, V. J. STURROCK, D. TORMOSOV, R. C. ANDERSON, A. N. BAKER, P. B. BEST, P. BORSA, R. L. BROWNELL, JR., S. CHILDERHOUSE, K. P. FINDLAY, T. GERRODETTE, A. D. ILANGAKOON, M. JOERGENSEN, B. KAHN, D. K. LJUNGBLAD, B. MAUGHAN, R. D. MCCAULEY, S. MCKAY, T. F. NORRIS, S. RANKIN, F. SAMARAN, D. THIELE, K. VAN WAEREBEEK and R. M. WARNEKE. 2007. Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean. Mammal Review 37: 116-175.
1. Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of >= 8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings. 2. Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar. 3. Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering. 4. Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic. 5. Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales. 6. South-east Pacific blue whales have a discrete distribution and high sighting rates compared with the Antarctic. Further work is needed to clarify their subspecific status given their distinctive genetics, acoustics and length frequencies. 7. Antarctic blue whales numbered 1700 (95% Bayesian interval 860-2900) in 1996 (less than 1% of original levels), but are increasing at 7.3% per annum (95% Bayesian interval 1.4-11.6%). The status of other populations in the Southern Hemisphere and northern Indian Ocean is unknown because few abundance estimates are available, but higher recent sighting rates suggest that they are less depleted than Antarctic blue whales.
OSWALD, J. N., S. RANKIN and J. BARLOW. 2004. The effect of recording and analysis bandwidth on acoustic identification of delphinid species. Journal of the Acoustical Society of America 116: 3178-3185.
Because many cetacean species produce characteristic calls that propagate well under water, acoustic techniques can be used to detect and identify them. The ability to identify cetaceans to species using acoustic methods varies and may be affected by recording and analysis bandwidth. To examine the effect of bandwidth on species identification, whistles were recorded from four delphinid species (Delphinus delphis, Stenella attenuata, S. coeruleoalba, and S. longirostris) in the eastern tropical Pacific ocean. Four spectrograms, each with a different upper frequency limit (20, 24, 30, and 40 kHz), were created for each whistle (n = 484). Eight variables (beginning, ending, minimum, and maximum frequency; duration; number of inflection points; number of steps; and presence/absence of harmonics) were measured from the fundamental frequency of each whistle. The whistle repertoires of all four species contained fundamental frequencies extending above 20 kHz. Overall correct classification using discriminant function analysis ranged from 30% for the 20-kHz upper frequency limit data to 37% for the 40-kHz upper frequency limit data. For the four species included in this study, an upper bandwidth limit of at least 24 kHz is required for an accurate representation of fundamental whistle contours.
OSWALD, J. N., J. BARLOW and T. F. NORRIS. 2003. Acoustic identification of nine delphinid species in the eastern tropical Pacific Ocean. Marine Mammal Science 19: 20-37.
Acoustic methods may improve the ability to identify cetacean species during shipboard surveys. Whistles were recorded from nine odontocete species in the eastern tropical Pacific to determine how reliably these vocalizations can be classified to species based on simple spectrographic measurements. Twelve variables were measured from each whistle (n = 908). Parametric multivariate discriminant function analysis (DFA) correctly classified 41.1% of whistles to species. Non-parametric classification and regression tree (CART) analysis resulted in 51.4% correct classification. Striped dolphin whistles were most difficult to classify. Whistles of bottlenose dolphins, false killer whales, and pilot whales were most distinctive. Correct classification scores may be improved by adding prior probabilities that reflect species distribution to classification models, by measuring alternative whistle variables, using alternative classification techniques, and by localizing vocalizing dolphins when collecting data for classification models.
CERCHIO, S., J. K. JACOBSEN and T. F. NORRIS. 2001. Temporal and geographical variation in songs of humpback whales, Megaptera novaeangliae: synchronous change in Hawaiian and Mexican breeding assemblages. Animal Behaviour 62: 313-329.
Humpback whale song, a male breeding display, shows a remarkable degree of similarity among distant breeding assemblages, despite constant progressive change. It has been hypothesized that whales maintain continuity through cultural transmission via migratory movements of mates. We examined songs of whales breeding off Hawaii and Mexico to determine whether they changed similarly in both areas during the course of a breeding season. Songs recorded off Kauai, Hawaii (11 individuals) and Isla Socorro, Mexico (13 individuals) during winter and spring of 1991, were compared qualitatively and quantitatively. We measured 44 acoustic variables describing all known levels of song structure for each singer and we grouped these variables into six categories. We used two-factor analyses of variance to assess change across the season in each area, comparing the two regions and two 3-week periods (January/February and April). Twenty-seven variables changed significantly during the 12-week study in at least one area. Variables within categories displayed similar trends of change. Time and frequency characteristics describing the structure of song elements (units and phrases) changed synchronously in each area, with 21 of 25 variables displaying significant differences between periods and no interaction with region. Structures of song patterns, as defined by frequency of occurrence and number of unit and phrase types, changed differently in each area, with five of 12 variables indicating a significant interaction between region and period. Our results may suggest cultural transmission during the season, since many variables changed in similar manners. We propose an alternative hypothesis, that whales may be predisposed to gradually change certain features of song independently of cultural influences; change of structural elements may be governed by a discrete set of rules, or according to an innate template. Therefore, continuity of song patterns across the ocean basin may be due to a combination of mechanisms, only partially involving cultural transmission. We assess these hypotheses in relation to humpback whale behaviour and population structure, and cultural transmission and evolution of avian song.
THODE, A., T. NORRIS and J. BARLOW. 2000. Frequency beamforming of dolphin whistles using a sparse three-element towed array. Journal of the Acoustical Society of America 107: 3581-3584.
Acoustic bearings are obtained from dolphin whistles using frequency-domain (FD) beamforming techniques on signals recorded on a three-element 9-m aperture towed array. Due to the wide element separation, the high-frequency (kHz range) signals generate numerous grating lobes, but these lobes shift bearing with beamformed frequency, allowing identification of the true bearing whenever the whistles have over 1 kHz bandwidth. This method was validated by matching a sighting of a compact group of dolphins with acoustic bearing estimates. The system was subsequently used to detect and determine bearings from animals at least 3 km away and in Beaufort 5+ conditions. Frequency-domain beamforming has advantages over temporal cross correlation when the signals are faint and/or overlapping.
NORRIS, T. F., M. MC DONALD and J. BARLOW. 1999. Acoustic detections of singing humpback whales (Megaptera novaeangliae) in the eastern North Pacific during their northbound migration. Journal of the Acoustical Society of America 106: 506-514.
Numerous (84) acoustic detections of singing humpback whales were made during a spring (08 March-09 June 1997) research cruise to study sperm whales in the central and eastern North Pacific. Over 15000 km of track-line was surveyed acoustically using a towed hydrophone array. Additionally, 83 sonobuoys were deployed throughout the study area. Detection rates were greatest in late March, near the Hawaiian Islands, and in early April, northeast of the islands. Only one detection was made after April. Detection rates for sonobuoys were unequal in three equally divided longitudinal regions of the study area. Two high density clusters of detections occurred approximately 1200-2000 km northeast of the Hawaiian Islands and were attributed to a large aggregation of migrating animals. The distribution of these detections corroborates findings of previous studies. It is possible that these animals were maintaining acoustic contact during migration. Two unexpected clusters of singing whales were detected approximately 900 to 1000 km west of central and southern California. The location of these detections may indicate a previously undocumented migration route between an offshore breeding area, such as the Revillagigedo Islands, Mexico, and possible feeding areas in the western North Pacific or Bering Sea.
CERCHIO, S., C. M. GABRIELE, T. F. NORRIS and L. M. HERMAN. 1998. Movements of humpback whales between Kauai and Hawaii: implications for population structure and abundance estimation in the Hawaiian Islands. Marine Ecology-Progress Series 175: 13-22.
Identification photographs of individual humpback whales Megaptera novaeangliae were used to investigate movements of whales between Kauai and Hawaii (approximately 500 km apart; the Hawaiian Islands, USA) during the winter and spring months of 1989, 1990 and 1991. A total of 1072 individuals were identified with 40 individuals being sighted off both islands. There were 15 documented transits between islands within seasons; 9 whales traveled northwest (from Hawaii to Kauai), whereas 6 whales traveled southeast (Kauai to Hawaii). Simulation data indicated that these transit-direction proportions did not deviate from random expectations (p = 0.76); therefore, there was no directional trend to movement between the islands. The shortest observed transit was 8 d, indicating that whales can move throughout the island chain in short periods. Males were significantly overrepresented in inter-island recaptures (p much less than 0.001), and we suggest that males actively engaged in courtship behaviors are more wide-ranging. Whales did not show a significant trend to be captured off the same island in different years (p = 0.08 for Kauai, p = 0.12 for Hawaii); however, recaptures were few, power was relatively low, and 1 test approached significance. The observed number of within-season, between-island recaptures was significantly less than expected as determined by random simulations (p = 0.013 for Kauai, p = 0.008 for Hawaii), indicating that, during a season, whales are more Likely to be recaptured off the island of initial capture. There was also evidence suggesting that sub-groups of whales moved among the islands in loose aggregations: within seasons, the number of pairs of individuals captured off both islands within 7 d of each other was significantly greater than expected in random simulations (p = 0.038). We conclude that complete random mixing of whales among the islands is unlikely, and should not be assumed in the context of mark-recapture abundance estimation. Larger samples with greater coverage of the Hawaiian Islands and higher recapture probability will be needed to elucidate movement patterns of the population.
MOBLEY, J. R., JR., M. SMULTEA, T. NORRIS and D. WELLER. 1996. Fin whale sighting north of Kaua’i, Hawai’i. Pacific Science 50: 230-233.
A rare fin whale (Balaenoptera physalus) sighting occurred on 26 February 1994 during an aerial survey of waters north of the Hawaiian island of Kauai. The sighting occurred ca. 24 nm north of Makaha Point, at 22 degree 31.5′ N, 159 degree 44.5′ W. The fin whale was accompanied by an adult humpback whale (Megaptera novaeangliae) during the entire 25 min of observation. Fin whales are not unknown in Hawaiian waters, but the most recent confirmed sighting on record for Hawaiian waters was 16 February 1979.
NORRIS, T. 1995. Effects of boat noise on the singing behavior of humpback whales (Megaptera novaeangliae).Thesis (MS), Moss Landing Marine Laboratories, San Jose State University: 75pp.
Songs from humpback whales (Megaptera novaeangliae) were recorded when noise from a small (5.5 m) boat was experimentally introduced, and when large (10-35 m) vessels passed nearby. Twelve variables characterizing the structure and patterns of humpback whale song were compared for periods before and during exposure to boat noise. Generally, singing humpback whales decreased the duration of song units (notes) resulting in an increase in the “tempo” of songs. The frequency structures of some song units were affected by noise from large boats. Statistical power analyses indicated that phrase and theme patterns probably were not affected. Spectral analysis of humpback whale song and noise produced by large and small boats indicated that masking of songs is more severe from noise by large boats than noise by small boats. Changes in song tempo may indicate disturbance in singing whales. The significance of these effects on the behavioral biology of humpback whales remains uncertain.