Sayigh Laela S.

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Last Name
Sayigh
First Name
Laela S.
ORCID
0000-0001-8334-1326

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Now showing 1 - 20 of 23
  • Article
    Vocal copying of individually distinctive signature whistles in bottlenose dolphins
    (The Royal Society, 2013-02-20) King, Stephanie L. ; Sayigh, Laela S. ; Wells, Randall S. ; Fellner, Wendi ; Janik, Vincent M.
    Vocal learning is relatively common in birds but less so in mammals. Sexual selection and individual or group recognition have been identified as major forces in its evolution. While important in the development of vocal displays, vocal learning also allows signal copying in social interactions. Such copying can function in addressing or labelling selected conspecifics. Most examples of addressing in non-humans come from bird song, where matching occurs in an aggressive context. However, in other animals, addressing with learned signals is very much an affiliative signal. We studied the function of vocal copying in a mammal that shows vocal learning as well as complex cognitive and social behaviour, the bottlenose dolphin (Tursiops truncatus). Copying occurred almost exclusively between close associates such as mother–calf pairs and male alliances during separation and was not followed by aggression. All copies were clearly recognizable as such because copiers consistently modified some acoustic parameters of a signal when copying it. We found no evidence for the use of copying in aggression or deception. This use of vocal copying is similar to its use in human language, where the maintenance of social bonds appears to be more important than the immediate defence of resources.
  • Article
    The encoding of individual identity in dolphin signature whistles : how much information is needed?
    (Public Library of Science, 2013-10-23) Kershenbaum, Arik ; Sayigh, Laela S. ; Janik, Vincent M.
    Bottlenose dolphins (Tursiops truncatus) produce many vocalisations, including whistles that are unique to the individual producing them. Such “signature whistles” play a role in individual recognition and maintaining group integrity. Previous work has shown that humans can successfully group the spectrographic representations of signature whistles according to the individual dolphins that produced them. However, attempts at using mathematical algorithms to perform a similar task have been less successful. A greater understanding of the encoding of identity information in signature whistles is important for assessing similarity of whistles and thus social influences on the development of these learned calls. We re-examined 400 signature whistles from 20 individual dolphins used in a previous study, and tested the performance of new mathematical algorithms. We compared the measure used in the original study (correlation matrix of evenly sampled frequency measurements) to one used in several previous studies (similarity matrix of time-warped whistles), and to a new algorithm based on the Parsons code, used in music retrieval databases. The Parsons code records the direction of frequency change at each time step, and is effective at capturing human perception of music. We analysed similarity matrices from each of these three techniques, as well as a random control, by unsupervised clustering using three separate techniques: k-means clustering, hierarchical clustering, and an adaptive resonance theory neural network. For each of the three clustering techniques, a seven-level Parsons algorithm provided better clustering than the correlation and dynamic time warping algorithms, and was closer to the near-perfect visual categorisations of human judges. Thus, the Parsons code captures much of the individual identity information present in signature whistles, and may prove useful in studies requiring quantification of whistle similarity.
  • Dataset
    Temporal trends and effects of noise on upsweep calls of Eastern South Pacific southern right whales
    (Woods Hole Oceanographic Institution, 2022-03-30) Jacobs, Ellen ; Landea Briones, Rafaela ; Sayigh, Laela S.
    Eastern South Pacific southern right whales (ESPSRW) are a subpopulation of southern right whales (Eubalaena australis) off the coasts of Peru and Chile recognized by the International Union for the Conservation of Nature (IUCN) as critically endangered as a result of heavy whaling efforts in the late 18th to 20th centuries. Most recent population estimates put their numbers around 50 individuals. To test for the efficacy of passive acoustic monitoring of this population, we recorded five months of continuous acoustic data (January 2012-June 2012) off the southwestern tip of Isla de Chiloé. To test for trends in occurrence, we identified a total of 11,313 individual ESPSRW upsweep calls, which have been associated with maintaining contact with conspecifics. Calls increased over the course of the deployment and peaked between April and June, indicating an increase in use of the habitat consistent with the concurrent blue whale migration in the area. A clear diel pattern in which upsweep calls were predominately detected during dusk and night hours was identified, indicating that ESPSRW are likely foraging during daylight hours, as upsweep calls are known to be inversely related to foraging behavior. We also quantified noise levels in the frequency range of their communication (100 Hz third octave) to understand the change in active space whales may be experiencing. We measured noise levels from 90 dB re 1 µPa to 111 dB re 1 µPa (5th and 95th percentile), a 21 dB fluctuation that results in an order-of-magnitude decrease in active space area. We identified sources of high noise at or above the 75th percentile as predominately blue and humpback whale calls (occurring in 71.6% of total sampled minutes) and ship noise (occurring in 69.4% of total sampled minutes). Ship noise was responsible for outliers in excess of 140 dB re 1 µPa. In a population as diminished as ESPSRW, such disruptions of their communication range could result in significant barriers to maintaining contact with conspecifics. Passive acoustic monitoring is a powerful tool for monitoring populations as rarely sighted as ESPSRW. Understanding trends in presence and behavior as well as potential sources of disruption of their calling behavior is vital to determining conservation measures that will be most effective toward helping this critically endangered population.
  • Article
    Signal-specific amplitude adjustment to noise in common bottlenose dolphins (Tursiops truncatus)
    (Company of Biologists, 2019-11-08) Kragh, Ida M. ; McHugh, Katherine ; Wells, Randall S. ; Sayigh, Laela S. ; Janik, Vincent M. ; Tyack, Peter L. ; Jensen, Frants H.
    Anthropogenic underwater noise has increased over the past century, raising concern about the impact on cetaceans that rely on sound for communication, navigation and locating prey and predators. Many terrestrial animals increase the amplitude of their acoustic signals to partially compensate for the masking effect of noise (the Lombard response), but it has been suggested that cetaceans almost fully compensate with amplitude adjustments for increasing noise levels. Here, we used sound-recording DTAGs on pairs of free-ranging common bottlenose dolphins (Tursiops truncatus) to test (i) whether dolphins increase signal amplitude to compensate for increasing ambient noise and (ii) whether adjustments are identical for different signal types. We present evidence of a Lombard response in the range 0.1–0.3 dB per 1 dB increase in ambient noise, which is similar to that of terrestrial animals, but much lower than the response reported for other cetaceans. We found that signature whistles tended to be louder and with a lower degree of amplitude adjustment to noise compared with non-signature whistles, suggesting that signature whistles may be selected for higher output levels and may have a smaller scope for amplitude adjustment to noise. The consequence of the limited degree of vocal amplitude compensation is a loss of active space during periods of increased noise, with potential consequences for group cohesion, conspecific encounter rates and mate attraction.
  • Article
    Repeated call types in Hawaiian melon-headed whales (Peponocephala electra)
    (Acoustical Society of America, 2014-09) Kaplan, Maxwell B. ; Mooney, T. Aran ; Sayigh, Laela S. ; Baird, Robin W.
    Melon-headed whales are pantropical odontocetes that are often found near oceanic islands. While considered sound-sensitive, their bioacoustic characteristics are relatively poorly studied. The goal of this study was to characterize the vocal repertoire of melon-headed whales to determine whether they produce repeated calls that could assist in recognition of conspecifics. The first tag-based acoustic recordings of three melon-headed whales were analyzed. Tag records were visually and aurally inspected and all calls were individually extracted. Non-overlapping calls with sufficient signal-to-noise were then parameterized and visually grouped into categories of repeated call types. Thirty-six call categories emerged. Categories differed significantly in duration, peak and centroid frequency, and −3 dB bandwidth. Calls of a given type were more likely to follow each other than expected. These data suggest that repeated calls may function in individual, subgroup, or group recognition. Repeated call production could also serve to enhance signal detection in large groups with many individuals producing simultaneous calls. Results suggest that caution should be used in developing automatic classification algorithms for this species based on small sample sizes, as they may be dominated by repeated calls from a few individuals, and thus not representative of species- or population-specific acoustic parameters.
  • Preprint
    First observed wild birth and acoustic record of a possible infanticide attempt on a common bottlenose dolphin (Tursiops truncatus)
    ( 2015-06) Perrtree, Robin M. ; Sayigh, Laela S. ; Williford, Allison ; Bocconcelli, Alessandro ; Curran, Mary C. ; Cox, Tara M.
    We observed the birth of a common bottlenose dolphin (Tursiops truncatus) followed immediately by a possible infanticide attempt in the estuary near Savannah, Georgia. Our report is unique in several ways: first, we witnessed the birth of the calf; second, we observed infanticidal behavior almost immediately afterward; and third, we obtained acoustic recordings concurrent with the possible infanticidal behavior. Our observations provide insight into aggressive, possible infanticidal, behavior in bottlenose dolphins.
  • Article
    What’s in a voice? Dolphins do not use voice cues for individual recognition
    (Springer, 2017-08-08) Sayigh, Laela S. ; Wells, Randall S. ; Janik, Vincent M.
    Most mammals can accomplish acoustic recognition of other individuals by means of “voice cues,” whereby characteristics of the vocal tract render vocalizations of an individual uniquely identifiable. However, sound production in dolphins takes place in gas-filled nasal sacs that are affected by pressure changes, potentially resulting in a lack of reliable voice cues. It is well known that bottlenose dolphins learn to produce individually distinctive signature whistles for individual recognition, but it is not known whether they may also use voice cues. To investigate this question, we played back non-signature whistles to wild dolphins during brief capture-release events in Sarasota Bay, Florida. We hypothesized that non-signature whistles, which have varied contours that can be shared among individuals, would be recognizable to dolphins only if they contained voice cues. Following established methodology used in two previous sets of playback experiments, we found that dolphins did not respond differentially to non-signature whistles of close relatives versus known unrelated individuals. In contrast, our previous studies showed that in an identical context, dolphins reacted strongly to hearing the signature whistle or even a synthetic version of the signature whistle of a close relative. Thus, we conclude that dolphins likely do not use voice cues to identify individuals. The low reliability of voice cues and the need for individual recognition were likely strong selective forces in the evolution of vocal learning in dolphins.
  • Article
    Temporal trends and effects of noise on upsweep calls of Eastern South Pacific southern right whales
    (Frontiers Media, 2022-08-30) Jacobs, Ellen Rose ; Landea-Briones, Rafaela ; Sayigh, Laela
    Eastern South Pacific southern right whales (ESPSRW) are a subpopulation of southern right whales (Eubalaena australis) off the coasts of Peru and Chile recognized by the International Union for the Conservation of Nature (IUCN) as critically endangered as a result of heavy whaling efforts in the late 18th to 20th centuries. Most recent population estimates put their numbers around 50 individuals. To test for the efficacy of passive acoustic monitoring of this population, we recorded 5 months of continuous acoustic data (January 2012-June 2012) off the southwestern tip of Isla de Chiloé. To test for trends in occurrence, we identified 11,313 individual ESPSRW upsweep calls, which have been associated with maintaining contact with conspecifics. Call occurrence increased over the course of the deployment and peaked between April and June, indicating an increase in use of this area. A clear diel pattern in which upsweep calls were predominately detected during dusk and night hours was identified, indicating ESPSRW are likely foraging during daylight hours, as upsweep calls are inversely related to foraging behavior. We quantified noise levels in the frequency range of their communication (100 Hz third octave) to understand the change in active space whales may be experiencing. We measured noise levels from 90 dB re 1 μPa to 111 dB re 1 µPa (5th and 95th percentile), a 21 dB fluctuation that results in an order-of-magnitude decrease in active space area. We identified sources of high noise at or above the 75th percentile as predominately blue whale calls (occurring in 71.6% of total sampled minutes) and ship noise (occurring in 69.4% of total sampled minutes). Ship noise was responsible for outliers in excess of 140 dB re 1 µPa. In a population as diminished as ESPSRW, such disruptions of their communication range could result in significant barriers to maintaining contact with conspecifics. Passive acoustic monitoring is a powerful tool for monitoring populations as rarely sighted as ESPSRW. Understanding trends in presence and behavior as well as potential sources of disruption to their calling behavior is vital to determining conservation measures that will be most effective toward helping this critically endangered population.
  • Article
    Acoustic recordings of rough-toothed dolphin (Steno bredanensis) offshore Eastern Sicily (Mediterranean Sea)
    (Acoustical Society of America, 2019-09-25) Caruso, Francesco ; Sciacca, Virginia ; Parisi, Ignazio ; Viola, Salvatore ; de Vincenzi, Giovanni ; Bocconcelli, Alessandro ; Mooney, T. Aran ; Sayigh, Laela S. ; Li, Songhai ; Filiciotto, Francesco ; Moulins, Aurelie ; Tepsich, Paola ; Rosso, Massimiliano
    ough-toothed dolphin's abundance and distribution is largely unknown worldwide and evaluation of its conservation status in the Mediterranean Sea is necessary. A rough-toothed dolphin was sighted offshore Eastern Sicily (Mediterranean Sea) in July 2017 and acoustic data were acquired in the same area of Watkins, Tyack, Moore, and Notarbartolo di Sciara [(1987). Mar. Mamm. Sci. 3, 78–82]. An automatic detection algorithm was developed to identify the echolocation clicks recorded within both datasets and a recurrent inter-click interval value was identified during the new encounter. Distinctive whistle classes were also identified with similar contour shapes within both datasets.
  • Article
    Temporal and spatial distributions of delphinid species in Massachusetts Bay (USA) using passive acoustics from ocean gliders
    (Inter Research, 2019-11-21) Silva, Tammy L. ; Mooney, T. Aran ; Sayigh, Laela S. ; Baumgartner, Mark F.
    Knowledge about marine mammal habitat use is necessary for informing ecosystem-based management and mitigating human impacts. Massachusetts Bay is an important marine mammal foraging area in the Gulf of Maine and an area of substantial human activity, but delphinid habitat use is poorly understood. The goals of this work were to (1) document temporal and spatial occurrence of delphinid species in Massachusetts Bay using passive acoustic monitoring from ocean gliders and (2) explore the potential influences of environmental conditions on delphinid distributions. Gliders were deployed in late fall and early winter of 2014 and 2015-2016 and were equipped with a digital acoustic recorder and conductivity-temperature-depth instrument. Gliders surveyed an area of approximately 1000 km2. Delphinid whistles were detected on 93 of 128 (73%) deployment days. Animals were detected more often at night. Presence was consistent over 2 years, although detection rates showed annual and monthly variability. Spatial distribution differed between years, but most detections occurred close to Stellwagen Bank. Visual assessment of spectrograms suggests the presence of 2 species, Atlantic white-sided dolphins and common dolphins. The reoccurrence of 2 probable signature whistles over several weeks and consecutive winter seasons suggests prolonged occupancy during winter and possible annual site fidelity. These data show a consistent and frequent presence of delphinids near a known marine mammal foraging area (Stellwagen Bank) during late fall and winter and are a first step towards understanding both how odontocetes influence the Massachusetts Bay/Gulf of Maine ecosystem and how they may be impacted by human activities.
  • Preprint
    Identifying signature whistles from recordings of groups of unrestrained bottlenose dolphins (Tursiops truncatus)
    ( 2011-09-29) Janik, Vincent M. ; King, Stephanie L. ; Sayigh, Laela S. ; Wells, Randall S.
    Bottlenose dolphins (Tursiops truncatus) have individually-distinctive signature whistles. Each individual dolphin develops its own unique frequency modulation pattern and uses it to broadcast its identity. However, underwater sound localization is challenging, and researchers have had difficulties identifying signature whistles. The traditional method to identify them involved isolating individuals. In this context, the signature whistle is the most commonly produced whistle type of an animal. However, most studies on wild dolphins cannot isolate animals. We present a novel method, SIGID, that can identify signature whistles in recordings of groups of dolphins recorded via a single hydrophone. We found that signature whistles tend to be delivered in bouts with whistles of the same type occurring within 1-10 s of each other. Non-signature whistles occur over longer or shorter periods, and this distinction can be used to identify signature whistles in a recording. We tested this method on recordings from wild and captive bottlenose dolphins and show thresholds needed to identify signature whistles reliably. SIGID will facilitate the study of signature whistle use in the wild, signature whistle diversity between different populations, and potentially allow signature whistles to be used in mark-recapture studies.
  • Article
    Probable signature whistle production in Atlantic white-sided (Lagenorhynchus acutus) and short-beaked common (Delphinus delphis) dolphins near Cape Cod, Massachusetts
    (Wiley, 2022-09-15) Cones, Seth ; Dent, Molly ; Walkes, Sam ; Bocconcelli, Alessandro ; DeWind, Christianna ; Arjasbi, Kayla ; Rose, Kathryn S. ; Silva, Tammy L. ; Sayigh, Laela S.
    Some delphinids produce a learned, individually specific tonal whistle that conveys identity information to conspecifics (Janik & Sayigh, 2013). These whistles, termed signature whistles, were first described by Caldwell and Caldwell (1965) and have been studied intensively over the past several decades (Janik & Sayigh, 2013). In common bottlenose dolphins (Tursiops truncatus) and potentially other species, signature whistles facilitate many ecologically-important behaviors, including individual recognition and maintenance of group cohesion (Janik & Slater, 1998). Additionally, signature whistle contours, or patterns of frequency change over time, can remain stable for several decades, aiding in long-term social bonds (Sayigh et al., 1990). Signature whistles account for approximately 38%–70% of all whistle production in free-swimming animals (Buckstaff, 2004; Cook et al., 2004; Watwood et al., 2005); this percentage can be up to 100% for isolated individuals in captivity (Caldwell et al., 1990). Most of our knowledge on the function and use of signature whistles stems from Tursiops spp., and their use and presence in other delphinid taxa is less understood. Nonetheless, seven additional delphinid species have been reported to produce signature whistles: Indo-Pacific bottlenose dolphins (Tursiops aduncus; Gridley et al., 2014), common dolphins (D. delphis; Caldwell & Caldwell 1968; Fearey et al., 2019), Atlantic spotted dolphins (Stenella plagiodon; Caldwell et al., 1970), Pacific white-sided dolphins (Lagenorhynchus obliquidens; Caldwell & Caldwell, 1973), Pacific humpback dolphins (Sousa chinensis; Van Parijs & Corkeron, 2001), and Guiana dolphins (Sotalia guianensis; Duarte de Figueiredo & Simão, 2009).
  • Article
    Whistle characteristics and daytime dive behavior in pantropical spotted dolphins (Stenella attenuata) in Hawai‘i measured using digital acoustic recording tags (DTAGs)
    (Acoustical Society of America, 2016-07-19) Silva, Tammy L. ; Mooney, T. Aran ; Sayigh, Laela S. ; Tyack, Peter L. ; Baird, Robin W. ; Oswald, Julie N.
    This study characterizes daytime acoustic and dive behavior of pantropical spotted dolphins (Stenella attenuata) in Hawai‘i using 14.58 h of data collected from five deployments of digital acoustic recording tags (DTAG3) in 2013. For each tagged animal, the number of whistles, foraging buzzes, dive profiles, and dive statistics were calculated. Start, end, minimum, and maximum frequencies, number of inflection points and duration were measured from 746 whistles. Whistles ranged in frequency from 9.7 ± 2.8 to 19.8 ± 4.2 kHz, had a mean duration of 0.7 ± 0.5 s and a mean of 1.2 ± 1.2 inflection points. Thirteen foraging buzzes were recorded across all tags. Mean dive depth and duration were 16 ± 9 m and 1.9 ± 1.0 min, respectively. Tagged animals spent the majority of time in the upper 10 m (76.9% ± 16.1%) of the water column. Both whistle frequency characteristics and dive statistics measured here were similar to previously reported values for spotted dolphins in Hawai‘i. Shallow, short dive profiles combined with few foraging buzzes provide evidence that little spotted dolphin feeding behavior occurs during daytime hours. This work represents one of the first successful DTAG3 studies of small pelagic delphinids, providing rare insights into baseline bioacoustics and dive behavior.
  • Dataset
    Seasonal trends and diel patterns of downsweep and SEP calls in Chilean blue whales (Balaenoptera musculus)
    (Woods Hole Oceanographic Institution, 2022-01-13) Redaelli, Laura ; Mangia Woods, Sari ; Landea Briones, Rafaela ; Sayigh, Laela S.
    To learn more about occurrence and behavior of a recently discovered population of blue whales, passive acoustic data were collected for 15 consecutive months (January 2012 – April 2013) in the Chiloense ecoregion of southern Chile. Automatic detectors and manual auditing were used to detect blue whale songs (SEP calls) and D calls, which were then analyzed to gain insights into temporal calling patterns. We found a year-round acoustic presence of D calls, with the majority occurring during austral summer (December to April), with several sub-monthly peaks. On the other hand, no SEP calls were found during austral winter. Thus, our results support previous studies documenting austral summer residency of blue whales in the Chiloense ecoregion, although they suggest that some individuals remain in the area year-round, highlighting the importance of the Chiloense ecoregion as blue whale habitat. We also investigated daily occurrence of each call type and found that D calls occurred more frequently during dusk and night hours compared to dawn and day periods, whereas SEP calls did not show any significant diel differences. Overall, these findings contribute to a better understanding of occurrence and behavior of endangered Chilean blue whales, which can enhance our ability to develop conservation strategies in this important southern hemisphere habitat.
  • Article
    Seasonal trends and diel patterns of downsweep and SEP calls in Chilean blue whales
    (MDPI, 2022-02-23) Redaelli, Laura ; Mangia Woods, Sari ; Landea Briones, Rafaela ; Sayigh, Laela S.
    To learn more about the occurrence and behaviour of a recently discovered population of blue whales, passive acoustic data were collected between January 2012 and April 2013 in the Chiloense ecoregion of southern Chile. Automatic detectors and manual auditing were used to detect blue whale songs (SEP calls) and D calls, which were then analysed to gain insights into temporal calling patterns. We found that D call rates were extremely low during winter (June–August) but gradually increased in spring and summer, decreasing again later during fall. SEP calls were absent for most winter and spring months (July–November) but increased in summer and fall, peaking between March and April. Thus, our results support previous studies documenting the austral summer residency of blue whales in this region, while suggesting that some individuals stay longer, highlighting the importance of this area as a blue whale habitat. We also investigated the daily occurrence of each call type and found that D calls occurred more frequently during dusk and night hours compared to dawn and day periods, whereas SEP calls did not show any significant diel patterns. Overall, these findings help to understand the occurrence and behaviour of endangered Chilean blue whales, enhancing our ability to develop conservation strategies in this important Southern Hemisphere habitat.
  • Preprint
    Successful suction-cup tagging of a small delphinid species, Stenella attenuata : insights into whistle characteristics
    ( 2016-09) Silva, Tammy L. ; Mooney, T. Aran ; Sayigh, Laela S. ; Baird, Robin W. ; Tyack, Peter L.
    The Delphinidae is the most diverse family of cetaceans, with 38 species recognized. Small pelagic delphinids are also the most abundant cetaceans world-wide, yet their communication and behavior remain poorly understood. Many populations live in relatively remote habitats, which creates challenges in accessing study animals. Small odontocete species often face numerous anthropogenic stressors. For example, many pelagic delphinids incur significant interactions with fisheries (Gerrodette and Forcada 2005, Geijer and Read 2013). With a wide distribution, many delphinid populations utilize habitats that also are important for human seagoing activities that produce intense sound, such as seismic surveys or naval sonar exercises that may disturb or harm them. Many U.S. naval sonar exercises take place on naval training ranges such as those in in Hawai‘i (Baird et al. 2013), California (Carretta et al. 1995, Henderson et al. 2014), and the Bahamas (DeRuiter et al. 2013). At least one delphinid stranding event involving melon-headed whales (Peponocephala electra) was correlated with military activities (Southall et al. 2006); a mass stranding of melon-headed whales has also been associated with multi-beam echosounder operations as part of a seismic survey (Southall et al. 2013). Because many of these delphinid groups can number in the 100s to 1,000s, fisheries or sonar exposures can account for the highest estimates of marine mammal “takes” in related Environmental Impact Assessments (Department of the Navy 2013). Given the potential for anthropogenic interactions with large numbers of individual delphinids, improved methods of studying small delphinids are invaluable to understand, reduce, or mitigate potential human influences on these animals.
  • Article
    Characterizing Chilean blue whale vocalizations with DTAGs : a test of using tag accelerometers for caller identification
    (Company of Biologists, 2017-09-07) Saddler, Mark R. ; Bocconcelli, Alessandro ; Hickmott, Leigh S. ; Chiang, Gustavo ; Landea Briones, Rafaela ; Bahamonde, Paulina A. ; Howes, Gloria ; Segre, Paolo S. ; Sayigh, Laela S.
    Vocal behavior of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile, was analysed using both audio and accelerometer data from digital acoustic recording tags (DTAGs). Over the course of three austral summers (2014, 2015 and 2016), seventeen tags were deployed, yielding 124 h of data. We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations and timing consistent with previous recordings made using towed and moored hydrophones. We also describe tonal downswept (D) calls, which have not been previously described for this population. As being able to accurately assign vocalizations to individual whales is fundamental for studying communication and for estimating population densities from call rates, we further examine the feasibility of using high-resolution DTAG accelerometers to identify low-frequency calls produced by tagged blue whales. We cross-correlated acoustic signals with simultaneous tri-axial accelerometer readings in order to analyse the phase match as well as the amplitude of accelerometer signals associated with low-frequency calls, which provides a quantitative method of determining if a call is associated with a detectable acceleration signal. Our results suggest that vocalizations from nearby individuals are also capable of registering accelerometer signals in the tagged whale's DTAG record. We cross-correlate acceleration vectors between calls to explore the possibility of using signature acceleration patterns associated with sounds produced within the tagged whale as a new method of identifying which accelerometer-detectable calls originate from the tagged animal.
  • Preprint
    Quantifying parameters of bottlenose dolphin signature whistles
    ( 2009-01-06) Esch, H. Carter ; Sayigh, Laela S. ; Wells, Randall S.
    Bottlenose dolphins (Tursiops truncatus) produce individually distinctive vocalizations called signature whistles, first described by Melba and David Caldwell (1965). The Caldwells observed that isolated, captive dolphins produced whistles with individually distinctive frequency contours, or patterns of frequency changes over time, and hypothesized that these whistles were used to transmit identity information (Caldwell and Caldwell 1965; Caldwell et al. 1990). Since the Caldwell’s work with isolated, captive dolphins, several studies have documented signature whistles in a variety of contexts, including free-swimming captive dolphins (e.g., Janik and Slater 1998; Tyack 1986), briefly restrained wild dolphins (e.g., Sayigh et al. 1990, 2007, Watwood et al. 2005), and free-ranging wild dolphins (e.g., Watwood 2003; Watwood et al. 2004, 2005; Buckstaff 2004; Cook et al. 2004). Janik and Slater (1998) demonstrated that signature whistles are used to maintain group cohesion, thus supporting the Caldwells’ hypothesis. Janik et al. (2006) verified experimentally that bottlenose dolphins respond to signature whistles produced by familiar conspecifics even after voice featured have been removed, reinforcing the notion that the contour of a signature whistle carries identity information.
  • Article
    Sounding the call for a global library of underwater biological sounds
    (Frontiers Media, 2022-02-08) Parsons, Miles J. G. ; Lin, Tzu-Hao ; Mooney, T. Aran ; Erbe, Christine ; Juanes, Francis ; Lammers, Marc O. ; Li, Songhai ; Linke, Simon ; Looby, Audrey ; Nedelec, Sophie L. ; Van Opzeeland, Ilse ; Radford, Craig A. ; Rice, Aaron N. ; Sayigh, Laela S. ; Stanley, Jenni A. ; Urban, Edward ; Di Iorio, Lucia
    Aquatic environments encompass the world’s most extensive habitats, rich with sounds produced by a diversity of animals. Passive acoustic monitoring (PAM) is an increasingly accessible remote sensing technology that uses hydrophones to listen to the underwater world and represents an unprecedented, non-invasive method to monitor underwater environments. This information can assist in the delineation of biologically important areas via detection of sound-producing species or characterization of ecosystem type and condition, inferred from the acoustic properties of the local soundscape. At a time when worldwide biodiversity is in significant decline and underwater soundscapes are being altered as a result of anthropogenic impacts, there is a need to document, quantify, and understand biotic sound sources–potentially before they disappear. A significant step toward these goals is the development of a web-based, open-access platform that provides: (1) a reference library of known and unknown biological sound sources (by integrating and expanding existing libraries around the world); (2) a data repository portal for annotated and unannotated audio recordings of single sources and of soundscapes; (3) a training platform for artificial intelligence algorithms for signal detection and classification; and (4) a citizen science-based application for public users. Although individually, these resources are often met on regional and taxa-specific scales, many are not sustained and, collectively, an enduring global database with an integrated platform has not been realized. We discuss the benefits such a program can provide, previous calls for global data-sharing and reference libraries, and the challenges that need to be overcome to bring together bio- and ecoacousticians, bioinformaticians, propagation experts, web engineers, and signal processing specialists (e.g., artificial intelligence) with the necessary support and funding to build a sustainable and scalable platform that could address the needs of all contributors and stakeholders into the future.
  • Thesis
    Development and functions of signature whistles of free-ranging bottlenose dolphins, Tursiops truncatus
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1992-09) Sayigh, Laela S.
    This thesis presents data on the development and functions of individually distinctive signature whistles of free-ranging bottlenose dolphins, Tursiops tnmcatus. Research was conducted at a study site near Sarasota, Florida, where a resident community of bottlenose dolphins have been the focus of a long-term, ongoing study. Through observations and censuses, researchers have gained information on home ranges and association patterns among individuals. A temporary capture and release program has provided opportunities to collect basic information regarding age, sex, genetic relationships, and life history of individuals, as well as to record vocalizations of known individuals. During the periods 1975-1976 and 1984-1992, 134 different individuals were recorded during temporary capture. More than half of these were recorded on two or more (up to 10) different occasions. These recordings demonstrate that free-ranging dolphins produce individually distinctive signature whistles, as was previously documented for captive dolphins. Each dolphin produced a distinctive frequency contour, or pattern of frequency changes over time, and this whistle comprised a large portion of all whistles produced. Comparisons of whistles recorded from the same individuals over periods of more than a decade indicate that these signature whistle contours are markedly stable. This extensive database of recordings of signature whistles produced by known individuals formed the basis for much of the work described in this thesis. Playback experiments conducted during temporary capture-release projects indicated that free-ranging dolphins were able to discriminate among signature whistles of familiar individuals. When these results are taken in the context of what is known about dolphin societies, which are characterized by stable individual associations intermixed with fluid patterns of association among many individuals, it appears highly likely that dolphins use signature whistles to recognize one another as individuals. Sex differences in whistle production were documented through analysis of whistles recorded during temporary capture. Naive judges rated the similarity of signature whistle contours of 42 Sarasota calves and their mothers, and found that males were more likely than females to produce signature whistle contours highly similar to those of their mothers. Conversely, females were more likely than males to produce contours highly distinct from those of their mothers. In addition, preliminary results indicated that male calves were more likely than female calves to produce whistles other than the signature whistle (called "variant" whistles). It was hypothesized that these sex differences may relate to the different roles males and females play in the social structure of the community. Comparisons of whistle contours of parents and offspring, both in the wild (Sarasota) and in captivity (Miami Seaquarium), do not indicate that signature whistle structure is strictly inherited. Instead, it appears that learning plays a role in determining whistle structure. This contrasts with other non-human mammalian species, where learning does not appear to be involved in vocal development. Focal observations and acoustic recordings of four free-ranging Sarasota mother-calf pairs were conducted in order to examine the effects of the early social and auditory environment on signature whistle development. Although there was considerable individual variability among these four calves, this study provided some preliminary insights into factors affecting the time course and outcome of signature whistle development in the wild. Two calves which exhibited relatively rapid whistle development and produced contours that resembled those of their mothers also heard proportionately more of their mothers' signature contours than did the other two calves. The other two calves exhibited more prolonged whistle development and produced contours that did not resemble those of their mothers. Preliminary data indicated that these two mothers may have actively taught their calves to produce a distinctive whistle contour by producing "model" contours while their calves were very young. Strength of the mother-calf association, number of associates other than the mother, overall number of whistles heard, and number of whistles produced by the mother all may affect the time course of whistle development and whether or not a calf develops a contour similar to that of its mother.