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.
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.
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. 2007. 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.
