Heterogeneity of Amazon River dolphin high-frequency clicks: Current Odontoceti bioacoustic terminology in need of standardization

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1 Heterogeneity of Amazon River dolphin high-frequency clicks: Current Odontoceti bioacoustic terminology in need of standardization Marie Trone, Hervé Glotin, Randall Balestriero, David E. Bonnett, and Jerry Blakefield Citation: Proc. Mtgs. Acoust. 22, (2014); View online: View Table of Contents: Published by the Acoustical Society of America Articles you may be interested in Vocalizations of Amazon river dolphins (Inia geoffrensis): Characterization, effect of physical environment and differences between populations The Journal of the Acoustical Society of America 139, 1285 (2016); / Automatic classification of whistles from coastal dolphins of the southern African subregion The Journal of the Acoustical Society of America 141, 2489 (2017); / Echolocation behavior of franciscana dolphins (Pontoporia blainvillei) in the wild The Journal of the Acoustical Society of America 131, EL448 (2012); /

2 Volume th Meeting of the Acoustical Society of America Indianapolis, Indiana October 2014 Underwater Acoustics: Paper 3aUW5 Heterogeneity of Amazon River dolphin highfrequency clicks: Current Odontoceti bioacoustics terminology in need of standardization Marie Trone Department of Math and Science, Valencia College, Kissimmee, FL; Hervé Glotin Aix Marseille Université, CNRS, ENSAM, LSIS UMR & Université de Toulon, CNRS, LSIS UMR & Institut Universitaire de France, Toulon, Var, France; Randall Balestriero Aix Marseille Université, CNRS, ENSAM, LSIS UMR & Université de Toulon, CNRS, LSIS UMR, Toulon, Var, France; David E. Bonnett Silverdale, WA; Jerry Blakefield Shelton, WA; The quality and quantity of acoustical data available to researchers are rapidly increasing with advances in technology. Recording cetaceans with a 500 khz sampling rate provides a more complete signal representation than traditional sampling at 96 khz and lower. Such sampling provides a profusion of data concerning various parameters, such as click duration, inter-click intervals, frequency, amplitude and phase. However, there is disagreement in the literature in the use and definitions of these acoustic terms and parameters. In this study, Amazon River dolphins (Inia geoffrensis) were recorded using a 500 khz sampling rate in the Peruvian Amazon River watershed. Subsequent spectral analyses, including time waveforms, fast Fourier transforms and wavelet scalograms, demonstrate acoustic signals with differing characteristics. These highfrequency, broadband signals are compared, and differences are highlighted, despite the fact that currently an unambiguous way to describe these acoustic signals is lacking. The need for standards in cetacean bioacoustics with regard to terminology is emphasized. Published by the Acoustical Society of America 2015 Acoustical Society of America [DOI: / ] Received 10 March 2015; Published 31 March 2015 Proceedings of Meetings on Acoustics, Vol (2015) Page 1

3 Introduction. The Amazon River dolphin (Inia sp.), also known as the boto, is distributed throughout the Amazon River watershed (Hrbek et al., 2014). Not only does this genus inhabit freshwater exclusively, it also differs from other odotocete species in several ways. Specifically, the Amazon River dolphin lacks a prominent dorsal fin that can be used for individual identification. Furthermore, these cetaceans are extremely flexible (Best and da Silva, 1993), such that a single animal at the surface can appear to be two individuals (Figure 1). What is more, these dolphins are characterized by shallow surfacing behavior, making it challenging to spot an individual when the surface chop of the river is only 15 cm. FIG. 1 A photograph of a single Amazon River dolphin that illustrates the indistinct and short dorsal fin, as well as its flexibility. Moreover, the Amazon River dolphin habitat differs from that of other cetaceans in many ways. First, the habitat is usually characterized by opaque water (Aliaga-Rossel, 2002), making it impossible to view the animal when it is below the surface. Water levels can fluctuate as much as 14 m between low and high water seasons in the Peruvian Amazon (Martin and da Silva, 2004), and has been observed to drop as much as 2 m within a 24 hour period (personal observation, 2007). During high water season the forest floods and the Amazon River dolphin expands its range into these flooded forests (da Silva, 2002; Gomez-Salazar et al., 2012). To our knowledge, no one has extensively investigated what these animals do when they disperse into the flooded forests. The complexity of this environment is increased by the large quantity of debris carried by the river, including logs, branches, and anthropogenic rubbish. Together, these unique characteristics of the Amazon River dolphin and its habitat render natural history studies of this genus using visual techniques exclusively inadequate (Martin and da Silva, 2004). Strong attempts have been made to obtain Amazon River dolphin population parameters using traditional visual techniques. Although this information is useful, it falls short of providing sufficient data needed to grant these animals the protection provided by endangered species status, as the International Union for the Conservation of Nature (IUCN) has listed the Inia species as data deficient in 2013 ( For example, McGuire & Henningson (2007) analyzed over 9000 photographs of the Amazon River dolphin, but were only able to use 136 of those photographs for individual identification and subsequent re-sighting data. A second study attempted to simply count the number of individual Amazon River dolphins using strip and line transects in selected rivers of Brazil, Bolivia, Colombia, Ecuador, Peru and Venezuela in the Amazon and Orinoco River basins from May 2006 to August Three well-qualified observers were positioned at the front of the survey vessel Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 2

4 and two experienced observers were stationed at the rear. Despite this effort, 23% (141/611) of Inia sightings were missed by the observers positioned at the front of the vessel. At the completion of 2,704 linear kilometers of transects, 778 Inia geoffrensis and 1,323 Inia boliviensis were counted (Gomez-Salazar, Trujillo, Portocarrero-Aya & Whitehead, 2012). Due to the unique morphological features of the Amazon River dolphin, as well as the complexity of its habitat, visual methods seem to be inadequate in obtaining the population parameters necessary for river dolphin conservation. Furthermore, anthropogenic pressures are intensifying in the Amazon watershed due to increasing deforestation for timber and swidden agriculture, intentional and by-catch mortalities associated with fisheries, erosion, oil extraction, mercury facilitated gold mining, and pollution (Aliaga-Rossel, 2002; Fundación Omacha & WWF Colombia, 2008; Martin and da Silva, 2004; Martin, et al., 2004; McGuire and Henningsen, 2007). Our goals include improving Inia census accuracy using acoustical methods and identifying trends that may be correlated to anthropogenic stressors. Thus, we are exploring the possibility that there may be features in the acoustic emanations from Inia that would allow for more effective individual counting. However, there appears to be a need to formalize descriptors of Odontoceti sounds first. Published Odontoceti Acoustic Terminology. According to the American National Standards Institute S , a click is defined as an acoustic signal typically produced by exciting an earphone or speaker with a brief duration electrical pulse 1. For an appropriately brief pulse (e.g., 0.1 ms) the acoustic spectrum of a click is primarily determined by the transfer function of the transducer. 2. Click stimuli are commonly used to obtain auditory brainstem responses and otoacoustic emissions. See 4.16 and (ASA : 6.17, page 21) This definition is not helpful in describing Odontoceti high-frequency acoustical signals. In Au s book, The Sonar of Dolphins (1993), Evans (1967) is referenced for providing a dichotomous classification for Odontoceti acoustic signals. The first sound type is comprised of narrow-band frequency modulated continuous tonal sounds referred to as whistles. While the second type consists of broadband sonar clicks (page 77). Au (1993) explains further that a typical sonar signal resembles an exponentially damped sinusoidal wave with a duration between 40 and 70 μs and with 4-10 positive excursions (page 79). However, Kamminga & Wiersma (1981) refer to these positive excursions as ripples. Furthermore, they describe clicks as short broadband pulses that have durations between 50 & 200 μs (page 81). Thus, there is wide variation in the duration of a click, as well as what to call the phase fluctuations that form a wavepacket. What is more, Leighton et al., (2007) use the terms wavepacket and pulse interchangeably. Kamminga and Beitsma (1990) suggest that only the largest amplitude peak be considered as the authentic signal, and that the remaining phase fluctuations be excluded from analyses. They reason that these phase fluctuations/ripples contain only up to 15% of the signal s energy and should be considered as reverberations of the signal, possibly resulting from reflections within Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 3

5 the signaler s head. They illustrate this concept using a bottlenose dolphin (Tursiops truncatus) click. However, the confusion over what part of the acoustic signal is actual signal and what constitutes reverberation is exasperated by Figure 13 in Kamminga and Wiersma (1981). This figure is divided into two parts, each displaying the same illustration of a time waveform of a beluga whale click which consists of the initial, strongest amplitude wavepacket of phase fluctuations/ripples, and two other such wavepackets of lesser amplitude. The first part of this figure shows the waveform and is described as depicting the 3-parts of the echolocation click (page 57). Beneath this waveform an intensity versus frequency spectrum based upon these three wavepackets of phase fluctuations/ripples is displayed. The second part of this figure displays the same waveform, only this time it is described as displaying the spectrum from one reverberation (page 57). Beneath this time waveform is a different intensity versus frequency spectrum derived from the initial signal and only one of the two less intense wavepackets. Thus, the same wavepacket of phase fluctuations/ripples is described as being part of the echolocation click and as a reverberation in the same figure, leaving the reader confused. Kamming & Wiersma (1981) also describe a split-pulse phenomenon in certain clicks and occurs when the high-frequency component exists of two parts, with the second part being slightly higher in amplitude (page 50). They found this split-pulse phenomenon in clicks produced by harbour porpoises (Phocoena phocoena), a cetacean that is not known to whistle, as well as beluga whales (Delphinapterus leucas), which produce both clicks and whistles. Again, the time waveforms of the clicks that display this split-pulse phenomenon do not conform to the click definition provided by Au (1993). Another type of high-frequency, broadband signal has been identified by other researchers studying the finless porpoise (Neophcaena phocaena). This signal consist of two pulses separated by about 300 μs. Moreover, these pulses are practically identical in amplitude and quantity of ripples except that the second pulse is phase-reversed with respect to the first pulse. These researchers refer to such signals as twin inverted pulse sonar (TWIPS) and found that such signals provide enhanced target discrimination, especially when the signal path is occluded with millions of bubbles (Leighton, et al., 2007). Au (1993) also describes a series of clicks in quick succession as a click train. He illustrates a typical bottlenose dolphin click train in Figure 5.2 (page 78) and explains that the shape of the signals in a click train tends to be very repetitive and stereotypical (page 78). Each of these bottlenose dolphin clicks is characterized by peak frequencies ranging from khz. Au (1993) defines the peak frequency as the frequency of maximum energy (page 80). Finally, the inter-click interval (ICI) between each click within this click train remains relatively the same at approximately 128 ms. A burst pulse is another type of high-frequency, broadband signal produced by cetaceans. There are three major differences between burst pulse signals and echolocation clicks. First, burst pulse ICIs are much shorter than echolocation click ICIs, ranging from about 0.7 to 2.7 ms. Second, the amplitudes of burst pulse signals are between 12 and 20 db lower than the amplitudes of the higher echolocation clicks (page 427, Au & Hastings, 2008). Finally, burst pulse signals are highly directional, unlike most echolocation signals (Au & Hastings, 2008). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 4

6 Terminology related to frequency parameters can also be confusing. For example, Sanvito and Galimberti (2000) reference Miller and Murray (1995) when defining formants as parts of the frequency spectrum that are reinforced by resonant properties of the vocal tract (page 266). These investigators describe the vocalizations of elephant seals (Mirounga leonina) using fundamental formants, which are the minimum frequencies in Hertz at which a considerable part of the energy occurs (page 266). Formants have also been used to describe the acoustic emanations of other species as well (red deer, Cervus elaphus, Reby et al., 2005; dogs, Canis familiaris, Taylor et al., 2010; koalas, Phascolarctos cinereus, Charlton et al., 2012). Although not much is known about the ability of bottlenose dolphins to alter the resonant properties of their clicks, formant frequencies have also been used to characterize such clicks (Trone et al., 2013). However, cetacean clicks are generally described by their peak frequencies. Additionally, researchers describe clicks by referring to the centroid frequency, which is the center point of the spectral energy distribution which may lie between multiple peaks (Helweg et al., 1996). Methods. Acoustic recordings were made using two recording systems simultaneously in March of 2014, near Yanamono Island in the Peruvian Amazon (Figure 2). One system was custom made with the assistance of Cetacean Research Technologies (CRT), Inc and sampled at 500 khz (500,000 samples/second). A CR3 hydrophone was employed with this system. The sensitivity curve of this hydrophone is depicted in Figure 3. An I/O Tech A-to-D converter digitized the recordings with a 16-bit resolution. A second backup system employed a CRT-SQ 26-8 hydrophone feeding a Microtrack 24/96 recording unit and sampled at 96 khz (96,000 samples/second) with 24-bit resolution. These hydrophones were separated by approximately 2-3 m by suspending the hydrophones over the port and starboard sides of the recording platform. The hydrophones were suspended between 2 and 5 m below the surface. While recording, the vessel was maneuvered to drift with the local water column to reduce flow noise. FIG. 2a FIG. 2b FIG. 2a depicts a map indicating the study location, while FIG. 2b portrays the sampling site in greater detail. Recordings began when each system was manually initiated. For each pair of recordings the 500 khz system was deployed first, followed by the 96 khz system. As a result the 96 khz system lagged behind the 500 khz system by approximately 5 seconds. Each pair of recordings were 140 seconds in length. Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 5

7 Obtained recordings were subsequently analyzed using Gabor scalograms with customized algorithms (Trone et al., 2013), fast Fourier transforms (FFTs) with customized algorithms, Raven Pro software (Cornell Lab of Ornithology Bioacoustics Research Program), and Audacity open source software ( Acoustic parameters explored include the quantity of acoustical signals, the time intervals between acoustic signals, frequency, phase and amplitude. Amplitudes have been given in counts in the A-to-D converter because the system was not calibrated for sound pressure level. The resulting power spectrum amplitudes are in units of counts squared. FIG 3. The sensitivity curve for the CR3 hydrophone manufactured by Cetacean Research Technologies, Inc. Results and Discussion. Two recordings of Inia geoffrensis have been selected to illustrate aspects of Amazon River dolphin acoustic emanations which might benefit from a standardized set of descriptors. Each recording is approximately140 seconds in duration and has been analyzed in detail. The first recording is of a suspected adult female and a juvenile, while the second is of a solitary male. Adult males and females are sexually dimorphic, with males being larger and pinker in color than females (Martin and da Silva, 2006). Upon first examination the data collected provides examples of both whistles (Figure 4) and broadband sonar signals (Figure 5) as described by Au (1993) on page 77. However, upon closer examination the data does not conform to published bioacoustics standards, nor terminology encountered in the literature. Furthermore, Amazon River dolphins do not conform to the dichotomous classification of animals that only produce clicks and those that produce both clicks and whistles. Within this scheme, the former group of cetaceans only produce narrowband, higher-frequency clicks, while the latter produce broad-band, lower-frequency clicks (Au and Hastings, 2008) in addition to whistles. Amazon River dolphins produce clicks characteristic of both groups. Some exemplars from the collected data follow. Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 6

8 FIG. 4 A waveform and FFT of a narrow-band, frequency modulated tonal sound, or whistle, produced by I. geoffrensis (Raven software). FIG. 5 A waveform and FFT of a broadband click produced by I. geoffrensis (Raven software). Many of the high-frequency, broadband clicks seem to be comprised of two distinctly separated but related broadband elements referred to here as pulses. These pulses are separated by microseconds, while the intervals between each click are separated by milliseconds. These signals consisting of two pulses are referred to here as doublets. The generally accepted term for a series of clicks is click train (Au, 1993; Au and Hastings 2008), and is applied here to a series of doublets. In general, most of the second pulses within a click are phase reversed with respect to the first pulse, meaning that if the first pulse started out with a rise followed by a drop in voltage then the phase reversed pulse started out with a drop followed by a rise in voltage. However, some of the doublets are not phase reversed. Interestingly, the second pulse sometimes has a greater amplitude than the first. Figures 6 illustrates the waveform and FFT of a typical Inia click train, while Figure 7 displays a doublet where the second pulse is phase reversed and of greater amplitude than the first. At this time it is not known if these phase-reversed doublets are the result of surface reflections or if they are formed due to internal reflections within the animal. Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 7

9 FIG. 6 A time waveform and FFT of a click train produced by I. geoffrensis (Raven software). FIG. 7 A time waveform and FFT of a doublet produced by I. geoffrensis where the second pulse is phase reversed with respect to the first pulse of the click and is characterized by a greater amplitude than the first (Raven software). It may be possible that the phase reversed pulses are the result of the two pulses created at different times and places within the dolphin. Kamminga and Beitsma (1990) suggested that subsequent wavepackets that followed the initial broadband acoustic signal may be the result of reverberation within the head of the dolphin. Similarly, the phase reversed pulses produced by Amazon River dolphins may result from some internal reflection within the skull. Indeed, these doublets produced by Amazon River dolphins are similar to the TWIPS produced by finless porpoises (Leighton et al., 2008), a cetacean that is only known to produce clicks (Au and Hastings, 2008). Based upon the work of Leighton et al. (2005), the ability to produce two subsequent pulses that are phase reversed would provide additional fitness to dolphins inhabiting acoustically complex environments characterized by turbid and opaque water, such as that found in the Amazon River watershed. Through modeling, these researchers have determined that the ability to produce phase reversed pulses may greatly enhance detection of fish targets 330 mm in Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 8

10 length surrounded by a bubble cloud consisting of 35 million bubbles (Leighton et al., 2005). Indeed, finless porpoises produce such phase-reversed signals (Leighton et al., 2007). Similar to the Amazon River dolphin, finless porpoises also inhabit shallow water (less than 50 m) and one population inhabits freshwater (Amano, 2002). Thus, there is a survival benefit to being able to produce phase reversed pulses. As stated previously, further investigation is needed to ascertain if these phase reversed pulses are due to surface reflections or are artefacts of signal production by the dolphin. Signals from the suspected female and juvenile recording have been further analyzed by calculating the time waveform and power spectra for each pulse within the clicks using customized algorithms. From these calculations 8 different click prototypes have been identified so far (Appendix A, Figures 12-19). Similarly, Houser et al. (1999) also uses patterns of frequency and energy to identify 7 distinct click types produced by bottlenose dolphins. As can be seen from the spectra presented in Appendix A, the clicks produced by these two Amazon River dolphins are not stereotypical like the ones described by Au (1993). Instead, these pulses vary with respect to amplitude, peak frequencies, and IPIs. This same recording has been further analyzed using Gabor scalograms (see Trone et al., 2013 for methods), providing enhanced information regarding peak frequencies when compared to the Fourier transform results. Fourier transforms use a sliding window that is associated with a time/frequency trade-off, such that shorter FFT windows portray better time resolutions but poorer frequency resolutions in the resulting spectrograms, and vice versa (Au & Hastings, 2008). However, the scattering algorithm uses a Gabor kernel to decompose the acoustic signal through wavelet transforms. Consequently, information regarding where frequency components are occurring in time is improved with the Gabor (Lelandais and Glotin, 2008; Lopatka et al., 2005). Furthermore, these scalogram analyses are able to detect more clicks than the STFT when the signal to noise ratio is low (Lelandais and Glotin, 2008; Lopatka et al., 2005). This new representation is enhanced by post-processing that emphasizes a specific frequency range, thus improving formant detection. Figure 8 displays a scalogram of the same click train depicted in Figure 6. The seven depicted doublets clearly demonstrate the temporal differences between the IPIs in the range of microseconds and the ICIs with ranges in milliseconds. Figure 8 also demonstrates that the peak frequencies differ between the pulses within each click, as indicated by the red bands of energy maxima, as well as between clicks. Even though the pulses are separated by microseconds, enhanced information regarding the energy at each frequency is available. The enhanced time and frequency details provided by the Gabor scalogram demonstrate that not only does the peak frequency differ between both successive pulses and clicks, but also the quantity of frequencies of maximum energies as well. Thus, the variety of click prototypes is most likely greater than what we have determined using Fourier analyses. Additional processing is needed to determine the extent of this variety. Furthermore, scalograms depict formants given the definition of formants as the frequencies at which a considerable part of the acoustic signal energy occurs (Sanvito and Galimberti, 2000). Thus, like other studies that have used formants to characterize animal acoustic emanations (Sanvito and Galimberti, 2000; Reby et al., 2005; Taylor et al., 2010; Charlton et al., 2012), using scalograms to ascertain formants may be a useful tool in categorize dolphin clicks. Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 9

11 This variation in frequency maxima is probably not due to pulses being recorded off-axis (Au, 1993), as the IPIs are so short that it seems dubious that a dolphin could move its head so quickly and precisely to produce the changes in the click frequency distributions observed in the spectra and scalograms. If the changes in frequency distributions are not attributable to being recorded off-axis, then the observed pulses do not conform to the previously described and published definitions of stereotypical clicks within a click train. We are currently analyzing these data to determine if there are any patterns in these data associated with individual dolphins, or if the observed spectra may result from off-axis click detection. FIG. 8 A Gabor scalogram from the suspected female and juvenile recording depicting 7 doublets displaying the difference between IPIs and ICIs. Bands of red within the pulses represent peak frequencies (customized algorithms). Furthermore, these high-frequency, broadband signals do not conform to the burst pulse definition either. Although some of the IPIs are brief enough to qualify as burst pulse signals, there are others that are longer and are more similar to the IPIs of clicks within click trains Figure 9). FIG. 9 A Gabor scalogram from the suspected female and juvenile recording depicting the temporal variability between clicks. These clicks do not conform to the published definitions of click train, or burst pulse. Bands of red within the pulses represent peak frequencies (customized algorithms). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 10

12 Although we sampled at 500 khz, some of our high-frequency, broadband signals demonstrated a ceiling effect at 250 khz, suggesting that these animals produce acoustic signals of even higher frequencies (see Figure 5). Some would negate this finding, stating that the hearing range of the Amazon River dolphin has only been demonstrated to extend to 105 khz via behavioral testing (Jacobs & Hall, 1972). However, these results are based upon data obtained from one captive individual four decades ago. Furthermore, Penner and Murchison (1970) have recorded Amazon River dolphin acoustic signals in a pool setting as well, and found these signals ranging up to 200 khz. It is assumed that cetacean hearing ranges extend as high as their acoustic emanations (Houser and Moore, 2014). Results showing that bottlenose dolphins, a beluga whale (Delphinapterus leucas) and a false killer whale (Pseudorca crassidens) produce clicks of higher frequencies and amplitudes in noisier environments (Au, 1993) provides additional credence to our data, given that our data were recorded in the acoustically complex Amazon environment, and not a pool. Similarly, bottlenose dolphins have also been documented to produce highfrequency, broadband acoustical signals up to 500 khz (Toland, 1998), even though both physiological and behavioral tests only detect a hearing threshold to 150 khz (Johnson, 1966, 1967; Houser & Finneran, 2006). Another type of high-frequency broadband acoustic signal that has been recorded is characterized by high intensities in the lower frequency ranges from khz (Figure 10). These acoustic signals are percussive and very intense when compared with the other clicks that are recorded simultaneously. These signals are characterized by lower frequencies and higher amplitudes, like the clicks produced by cetaceans that whistle and click (Au and Hastings, 2008). However, these signals also seem to only extend over a range of about 60 khz, and thus are narrow-band, like the signals produced by cetaceans that only emit clicks (Au and Hastings, 2008). Once again, these data demonstrate that Amazon River dolphin bioacoustics do not fit into the previously established dichotomous classification. Furthermore, these low frequency, percussive clicks have been recorded when Amazon River dolphins have been observed to be fishing. Thus, it is possible that these clicks may be used to stun prey. However, further study is needed to clarify the function of this signal. FIG. 10 A time waveform and FFT of the low-frequency, highly percussive clicks that have been documented when I. geoffrensis is fishing (Raven software). Amazon River dolphins occasionally produce narrow-band, frequency modulated acoustic signals (May-Collado and Wartzok 2007). In addition to broadband signals, we have also recorded whistles (Figure 4) and squeals (Figure 11) from this species. It is believed that Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 11

13 cetaceans that do not produce whistles, produce clicks that are of high frequency, narrow bandwidth, and low intensity (Au and Hastings, 2008). However, Inia produces both low and high-frequency signals of varying intensities and bandwidths. Thus, once again this species appears to differ acoustically from other odontocetes. FIG. 11 A time waveform and FFT of a squeal produced by I. geoffrensis (Raven software). Conclusion. There is a tremendous need for standards in cetacean bioacoustics with regard to terminology due to a lack of operational definitions and multiplicity of terms. Furthermore, this terminology needs to be expanded to be able to unambiguously reference the variety of parameters documented in broadband, high-frequency acoustical signals. Not only will this aid in describing future studies of Inia bioacoustics, but will also enhance other odontocete studies as well. The data in this investigation demonstrate that Amazon River dolphins produce a variety of high frequency, broadband acoustic signals and that this species differs bioacoustically from oceanic odonotocetes. Future studies of Inia bioacoustics should utilize a fixed hydrophone array in order to clarify whether phase reversed pulses are the result of surface reflections or animal sound production. However, the use of fixed arrays is complicated by the large and copious amounts of debris carried by the strong currents of Amazonian waterways. Furthermore, future studies should explore any possible correlations between click prototypes, pulse duration, IPIs, ICIs, bandwidth and peak frequencies. Gabor scalograms may enhance such an investigation given the lack of the time-frequency trade off experienced in FFTs. Data derived from future studies may be used to explore the possibility of individually identifying dolphins acoustically to obtain robust population data and correlating various acoustic parameters with behavior. In order to achieve these goals, concise operational definitions for the differing high-frequency, broadband signals and their characteristics need to be established. Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 12

14 Acknowledgments. We thank the following for their support of this research: -SABIOD.ORG Scaled Acoustic Biodiversity Project of MI CNRS MASTODONS -Explorama Lodges -International Expeditions References. Aliaga-Rossel, E. (2002). Distribution and abundance of the river dolphin (Inia geoffrensis) in the Tijamuchi River, Beni, Bolivia. Aquatic Mammals, 28(3), American National Standards Institute S Amano, M. (2002). Finless porpoise. In W.F. Perrin, B. Wursig, and J.G.M. Thewissen (Eds.), Encyclopedia of Marine Mammals, pp Academic Press, San Diego. Audacity Open Source Software: Au, W.W.L. (1993). The Sonar of Dolphins. Springer, New York. Au, W.W.L and Hastings, M.C. (2008). Principles of Marine Bioacoustics. Springer, New York. Best, R.C. and da Silva, V.M.F. (1993). Mammalian Species, No. 426, Inia geoffrensis, American Society of Mammalogists, pp Stable URL: Charlton, B.D., Ellis, W.A.H., Larkin, R. and Fitch, W.T. (2012). Perception of size-related formant information in male koalas (Phascolarctos cinereus). Animal Cognition, 15, DOI: /s Cornell Lab of Ornithology Bioacoustics Program da Silva, V.M.F. (2002). Amazon River dolphin. In W.F. Perrin, B. Wursig, and J.G.M. Thewissen (Eds.), Encyclopedia of Marine Mammals, pp Academic Press, San Diego. Fundación Omacha & WWF Colombia. (2008). First evaluation of abundance of the three river dolphin species (Inia geoffrensis, I. boliviensis, and Sotalia fluviatilis) in the Orinoco and Amazon River Basins, South America (February-March). Gomez-Salazar, C., Trujillo, F., Portocarrero-Aya, M., & Whitehead, H. (2012). Population, density estimates, and conservation of river dolphins (Inia and Sotalia) in the Amazon and Orinoco river basins. Marine Mammal Science, 28(1), DOI: /j x Helweg, D.A., Au, W.W.L., Roitblat, H.L. and Nachtigall, P.E. (1996). Acoustic basis for recognition of aspect-dependent three-dimensional targets by an echolocating bottlenose dolphin. Journal of the Acoustical Society of America, 99(4), Pt. 1, Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 13

15 Houser, D. S., and Finneran, J. J. (2006). Variation in the hearing sensitivity of a dolphin population determined through the use of evoked potential audiometry. Journal of the Acoustical Society of America, 120, Houser, D.S., Helweg, D.A., and Moore, P.W. (1999). Classification of dolphin echolocation clicks by energy and frequency distributions. Journal of the Acoustical Society of America, 106(3), Houser, D.S and Moore, P.W. (2014). Report on the current status and future of underwater hearing research. Report NMMF National Marine Mammal Foundation, San Diego, CA, Hrbek, T., da Silva, V.M.F., Dutra, N., Gravena, W., Martin, A.R., and Farias, I.P. (2014). A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity PLoS ONE, (9)1: e83623 DOI: /journal.pone Jacobs, D. W., and Hall, J. D. (1972). Auditory thresholds of a freshwater dolphin, Inia geoffrensis Blainville. The Journal of the Acoustical Society of America, 51, Johnson, C. S. (1966). Auditory Thresholds of the Bottlenosed Porpoise (Tursiops truncatus, Montagu). U.S. Naval Ordnance Test Station, China Lake, CA. pp Johnson, C. S. (1967). Sound detection thresholds in marine mammals. In W. N. Tavolga (Ed.), Marine Bioacoustics, pp Pergamon Press, New York. Kamminga, C. and Beitsma, G.R. (1990). Investigations on cetacean sonar IV. Remarks on dominant sonar frequencies from Tursiops truncatus. Aquatic Mammals, 16(1), Kamminga, C. and Wiersma, H. (1981). Investigations on cetacean sonar II. Acoustical similarities and differences in odontocete sonar signals. Aquatic Mammals, 8(2), Leighton, T.G., Finfer, D.C. and White, P.R. (2005). Bubble acoustics in shallow water: Possible applications in nature. In N.G. Pace and P. Blondel, (Eds.), Boundary Influences in High Frequency, Shallow Water Acoustics, pp , University of Bath, UK, 5th-9th September Leighton, T.G., Finfer, D.C. and White, P.R. (2007). Sonar which penetrates bubble clouds, 2nd International Conference & Exhibition on Underwater Acoustic Measurements: Technologies & Results, Lelandais, F. & Glotin, H. (2008). Mallat's matching pursuit of sperm whale clicks in real-time using Daubechies 15 wavelets. In New Trends for Environmental Monitoring Using Passive Systems. IEEE conf. Passive DOI: /PASSIVE Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 14

16 Lopatka, M., Adam, O., Laplanche, C., Zarzycki, J. & Motsch, J.F. (2005). An attractive alternative for sperm whale click detection using the wavelet transform in comparison to the Fourier spectrogram. Aquatic Mammals, 31(4), DOI: /AM Martin, A.R. & da Silva, V.F.M. (2006). Sexual dimorphism and body scarring in the boto (Amazon River dolphin) Inia geoffrensis. Marine Mammal Science, 22(1): Martin, A.R. & Da Silva, V.F.M. (2004). Number, seasonal movements, and residency characteristics of river dolphins in an Amazonian floodplain lake system. Canadian Journal of Zoology, 82, Martin, A.R., Da Silva, V.F.M., & Salmon, D.L. (2004). Riverine habitat preferences of botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the central Amazon. Marine Mammal Science, 20(2), May-Collado, L.J. and Wartzok, D. (2007). The freshwater dolphin Inia geoffrensis geoffrensis produces high frequency whistles. Journal of the Acoustical Society of America, 121(2), DOI: / McGuire, T.L. & Henningsen, T. (2007). Movement patterns and site fidelity of river dolphins (Inia geoffrensis and Sotalia fluviatilis) in the Peruvian Amazon as determined by photoudentification. Aquatic Mammals, 33(3), DOI /AM Penner, R.H. and Murchison, A.E. (1970). Experimentally demonstrated echolocation in the Amazon River porpoise, Inia geoffrensis (Blainville). Naval Undersea Research and Development Centers, San Diego, CA. PDF URL: AD Reby, D, McComb, K., Cargnelutti, B., Darwin, C., Fitch, W.T. and Clutton-Brock, T. (2005). Red deer stags use formants as assessment cues during intrasexual agonistic interactions. Proceedings of Biological Science, 272(1566), Sanvito, S. and Galimberti, F. (2000). Bioacoustics of southern elephant seals. I. Acoustic structure of male aggressive vocalizations. Bioacoustics, 10, Taylor,A.M., Reby, D. and McComb, K. (2010). Size communication in domestic dog, Canis familiaris, growls. Animal Behaviour, 79, DOI: /j.anbehav Trone, M., Balestriero, R., & Glotin, H. (2013). Gabor scalogram extracts dolphin click formants. In: Proceedings of International Symposium: Neural Information Scaled for Bioacoustics, sabiod.org/nips4b, joint to NIPS, Nevada, December 2013 Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 15

17 Appendix A Prototype 1 FIG. 12 The time waveforms and energy spectra for the two pulses comprising click prototype 1 produced by suspected dolphin A in the recording of the suspected female and juvenile (customized algorithms). Prototype 2 FIG. 13 The time waveforms and energy spectra for the two pulses comprising click prototype 2 produced by suspected dolphin A in the recording of the suspected female and juvenile (customized algorithms). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 16

18 Prototype 3 FIG. 14 The time waveforms and energy spectra for the two pulses comprising click prototype 3 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Prototype 4 FIG. 15 The time waveforms and energy spectra for the two pulses comprising click prototype 4 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 17

19 Prototype 5 FIG. 16 The time waveforms and energy spectra for the two pulses comprising click prototype 5 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Prototype 6 FIG. 17 The time waveforms and energy spectra for the two pulses comprising click prototype 6 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 18

20 Prototype 7 FIG. 18 The time waveforms and energy spectra for the two pulses comprising click prototype 7 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Prototype 8 FIG. 19 The time waveforms and energy spectra for the two pulses comprising click prototype 8 produced by suspected dolphin B in the recording of the suspected female and juvenile (customized algorithms). Proceedings of Meetings on Acoustics, Vol. 22, (2015) Page 19