@article {58230, title = {Bottlenose dolphin (Tursiops truncatus) calves appear to model their signature whistles on the signature whistles of community members}, year = {2005}, abstract = {

Bottlenose dolphins are unusual among non-human mammals in their ability to learn new sounds. This study investigates the importance of vocal learning in the development of dolphin signature whistles and the influence of social interactions on that process. We used focal animal behavioral follows to observe six calves in Sarasota Bay, Fla., recording their social associations during their first summer, and their signature whistles during their second. The signature whistles of five calves were determined. Using dynamic time warping (DTW) of frequency contours, the calves\’ signature whistles were compared to the signature whistles of several sets of dolphins: their own associates, the other calves\’ associates, Tampa Bay dolphins, and captive dolphins. Whistles were considered similar if their DTW similarity score was greater than those of 95\% of the whistle comparisons. Association was defined primarily in terms of time within 50 m of the mother/calf pair. On average, there were six dolphins with signature whistles similar to the signature whistles of each of the calves. These were significantly more likely to be Sarasota Bay resident dolphins than non-Sarasota dolphins, and (though not significantly) more likely to be dolphins that were within 50 m of the mother and calf less than 5\% of the time. These results suggest that calves may model their signature whistles on the signature whistles of members of their community, possibly community members with whom they associate only rarely.

}, keywords = {bottlenose dolphin, Social influences on learning, vocal learning, Whistle development}, doi = {10.1007/s10071-004-0225-z}, url = {http://link.springer.com/10.1007/s10071-004-0225-z}, author = {Fripp, Deborah and Owen, Caryn and Quintana-Rizzo, Ester and Shapiro, Ari and Buckstaff, Kara and Jankowski, Kristine and Wells, Randall and Tyack, Peter} } @article {58228, title = {Some results of studying the acoustics of dolphins}, journal = {Acoustical Physics}, volume = {50}, year = {2004}, month = {Jan-05-2004}, pages = {343 - 349}, abstract = {

An experimental study of the echolocation ability of dolphins (Tursiops truncatus) is performed in the presence of correlated and uncorrelated broadband noise acting on their organs of hearing. It is shown that, under such conditions, the echolocating pulses of a dolphin become noticeably modified: in the absence of noise, standard broadband pulses are produced, while in the presence of noise, the pulses acquire an oscillatory character (become narrowband). Sounds and air pressure that occur inside the respiratory tract of a dolphin when the animal produces whistles and pulsed signals are studied. Data testifying in favor of the pneumatic origin of sounds generated by dolphins are obtained.

}, issn = {1063-7710}, doi = {10.1134/1.1739503}, url = {http://link.springer.com/10.1134/1.1739503}, author = {Romanenko, E. V.} } @mastersthesis {57295, title = {Vocal Response of Bottlenose Dolphins (Tursiops truncatus) to a Novel Stimulus}, volume = {MA}, year = {2019}, school = {University of Southern Mississippi}, abstract = {

Bottlenose dolphins utilize acoustic signals as their primary mode of communication. Although some aspects of dolphin vocal behavior are well understood, less is known about vocalizations in different behavioral contexts and how these vocal behaviors may indicate habituation and sensitization. The focus of this study was to investigate how bottlenose dolphins respond vocally to a novel stimulus. Archival data from three populations of bottlenose dolphins (N = 20) living in a human-care facility were exposed to a novel apparatus (a mirror) for 10 trials, each lasting 20 minutes. Five of the trials presented the mirror covered with an opaque cloth whereas the other five trials left the mirror uncovered, exposing the reflective surface. Rates of two distinct vocal types (whistles and burst pulses) were calculated for each trial. Vocal rates were greater on the last (non-novel) trials versus novel trials\—a pattern of sensitization to the novel stimulus. Vocal rates and the degree of sensitization were greater on reflective trials than non-reflective trials. Finally, vocal rates were greater for whistles than burst pulses overall, but sensitization was most apparent with burst pulses. This study identifies how the production of two types of vocalizations change in response to a novel stimulus of varying reflectivity over repeated exposures thereby providing a greater understanding of the contexts in which these utterances are used.

}, author = {Johnson, Lindsey} } @article {53324, title = {Dolphins simplify their vocal calls in response to increased ambient noise}, journal = {Biology Letters}, volume = {14}, year = {2018}, month = {Sep-05-20182022}, pages = {20180484}, abstract = {

Ocean noise varies spatially and temporally and is driven by natural and anthropogenic processes. Increased ambient noise levels can cause signal masking and communication impairment, affecting fitness and recruitment success. However, the effects of increasing ambient noise levels on marine species, such as marine mammals that primarily rely on sound for communication, are not well understood. We investigated the effects of concurrent ambient noise levels on social whistle calls produced by bottlenose dolphins (Tursiops truncatus) in the western North Atlantic. Elevated ambient noise levels were mainly caused by ship noise. Increases in ship noise, both within and below the dolphins\&$\#$39; call bandwidth, resulted in higher dolphin whistle frequencies and a reduction in whistle contour complexity, an acoustic feature associated with individual identification. Consequently, the noise-induced simplification of dolphin whistles may reduce the information content in these acoustic signals and decrease effective communication, parent\–offspring proximity or group cohesion.

}, keywords = {acoustic communication, anthropogenic noise, bottlenose dolphin, vocal modification}, issn = {1744-9561}, doi = {10.1098/rsbl.2018.0484}, url = {http://rsbl.royalsocietypublishing.org/lookup/doi/10.1098/rsbl.2018.0484https://syndication.highwire.org/content/doi/10.1098/rsbl.2018.0484}, author = {Fouda, Leila and Wingfield, Jessica E. and Fandel, Amber D. and Garrod, Aran and Hodge, Kristin B. and Rice, Aaron N. and Bailey, Helen} } @article {53317, title = {Forward masking recovery in bottlenose dolphins ( Tursiops truncatus): Auditory brainstem responses to paired-click stimuli in high-pass masking noise}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1740 - 1740}, abstract = {

Adaptation is a fundamental process in the auditory system and underlies the automatic gain control system of echolocating bottlenose dolphins. As pulse-echo delay increases, auditory brainstem response (ABR) amplitudes to the echoes progressively increase. This study examined adaptation across cochlear frequency regions using a paired-click (i.e., forward masking) paradigm and high-pass masking noise. Bottlenose dolphins passively listened to paired click stimuli (20\–160 kHz \“pink\” spectra). A \“conditioning\” click was followed by a \“probe\” click with equal amplitude and a time delay ranging from 125 to 750 \μs. ABRs to click pairs were obtained with and without high-pass masking noise that precluded the basal turn of the cochlea from responding to the click stimuli. The ABR evoked by a single click (temporally aligned with the first click of the paired-click condition) was subtracted from the click-pair ABR to visualize the response evoked by the probe click. Probe ABR amplitudes recovered linearly with increasing delay relative to the conditioning click, and were approximately 70\% of full response amplitude at 750-\μs delay. Paired-click interval ABR amplitude recovery functions were similar for the unmasked and high-pass masked conditions. [Work sponsored by ONR.]

}, issn = {0001-4966}, doi = {10.1121/1.5067718}, url = {http://asa.scitation.org/doi/10.1121/1.5067718}, author = {Mulsow, Jason and Coffinger, Sean P. and Finneran, James J. and Burkard, Robert F.} } @article {53292, title = {Bottlenose dolphin ( Tursiops truncatus) vocal modifications in response to spectrally pink background noise}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1742 - 1742}, abstract = {

The increase of oceanic shipping is a global predicament. The resulting proliferation of underwater noise levels is a serious concern for marine mammal welfare, as it has the potential to interfere with the communicative signals of bottlenose dolphins (Tursiops truncatus). The Lombard effect and other noise-induced vocal modifications may be employed to compensate for reduced signal-to-noise ratios. This study aimed to determine which vocal modifications dolphins use during experimentally controlled background noise conditions. Three dolphins (ages 30\–52) participated in behavioral hearing tests using an adaptive up-down staircase, go/no-go procedure with 15 or 40 kHz tones. Tones decreased by 3 dB increments if a dolphin responded to the tone with a conditioned whistle, and increased by 3 dB if they did not. Dolphins performed this task during ambient noise (control) conditions, as well as three elevated bandpass noise (experimental) conditions: 0.6\–5 kHz (115 dB re 1 \μPa) and 0.6\–10 kHz (115 and 125 dB re 1 \μPa). The acoustic parameters of the dolphins\’ response whistles and victory squeals, such as duration, frequency, amplitude, and response latency, were analyzed and compared between control and noise conditions. These data provide a complement to field studies of odontocete noise-induced vocal modifications in the wild.

}, issn = {0001-4966}, doi = {10.1121/1.5067724}, url = {http://asa.scitation.org/doi/10.1121/1.5067724}, author = {Zapetis, Maria and Mulsow, Jason and Schlundt, Carolyn E. and Finneran, James J. and Lyn, Heidi} } @article {53281, title = {Dependence of bottlenose dolphin (Tursiops truncatus) auditory brainstem responses on noise burst rise time, amplitude, and envelope shape}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1741 - 1741}, abstract = {

A series of experiments examined the dependence of dolphin auditory brainstem response (ABR) peak amplitudes and latencies by stimulus level, rise times, and envelope shape. Stimuli were spectrally \“pink\” noise bursts with frequency content from 10 to 160 kHz, rise times that varied from 32 \μs to 4 ms, and plateau sound pressure levels from 102 to 138 dB re 1 \μPa. Cosine and cosine-cubed rise (and fall) envelopes were tested, and results were compared to those obtained for dolphins using noise bursts with linear rise envelopes [Finneran et al., J. Acoust. Soc. Am. 143, 2914\–2921 (2018)]. Results for the cosine and cosine-cubed envelopes showed that ABR peak amplitudes were a function of envelope sound pressure at the end of a fixed integration window of approximately 260 \μs. This is congruent with the previous findings for linear envelopes. The ABR peak latencies for the cosine and cosine-cubed envelopes were dependent on the second derivative of the envelope pressure function, as opposed to the first derivative of the pressure function for linear envelopes. These data are consistent with single-unit and nearfield response data for terrestrial mammals. [Work supported by Navy Living Marine Resources and SSC Pacific Naval Innovative Science and Engineering Programs.]

}, issn = {0001-4966}, doi = {10.1121/1.5067722}, url = {http://asa.scitation.org/doi/10.1121/1.5067722}, author = {Jones, Ryan A. and Finneran, James J. and Mulsow, Jason and Burkard, Robert F.} } @article {53278, title = {Passive echo detection and discrimination in bottlenose dolphins}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1741 - 1741}, abstract = {

Echolocation in bottlenose dolphins (Tursiops truncatus) is an active process involving outgoing signal transmission and echo reception. Transmitted echolocation \“clicks\” interact with a target to produce echoes that contain representative information about the target. Echolocation allows dolphins to detect, discriminate, and identify complex targets using only their hearing. However, it is unclear whether dolphins capitalize on an internal representation of echolocation clicks for matched filter processing or whether the same information (and performance) can be obtained through passive echo reception (i.e., without a corresponding ensonifying click). Here, we investigate the passive echo discrimination ability of a bottlenose dolphin by embedding a target echo in a stream of distractor echoes with similar spectral and time-domain characteristics. Initial testing has demonstrated excellent echo-discrimination ability in the light of multiple distractor echoes of similar amplitude. Additional testing is underway with expanded distractor sets and echo-ordering complexity. The paradigm specifically investigates the plausibility of perceptual identification without the potential for matched filter processing. If representational identity is attainable via a passive process and not degraded relative to active echolocation, then the function of the echolocation click might not serve in matched filter processing, though it would remain important for ensonification and in determining target location.

}, issn = {0001-4966}, doi = {10.1121/1.5067721}, url = {http://asa.scitation.org/doi/10.1121/1.5067721}, author = {Coffinger, Sean P. and Houser, Dorian S. and Finneran, James J. and Mulsow, Jason} } @article {53272, title = {Directional hearing sensitivity for 2{\textendash}30 kHz sounds in the bottlenose dolphin (Tursiops truncatus)}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1741 - 1741}, abstract = {

Bottlenose dolphins (Tursiops truncatus) depend on sounds with frequencies \<30 kHz for social communication and foraging, but little information on the directional dependence of hearing thresholds for these sounds exists. This study measured behavioral hearing thresholds for 2, 10, 20, and 30-kHz tones projected from eight different angular positions around the dolphin in both the horizontal and vertical planes to determine whether the receiving beam at these frequencies was directional. Omni-directional hearing was hypothesized for sounds below 30 kHz, but this hypothesis was rejected. Results from two bottlenose dolphins demonstrated a positive relationship between directivity and the frequency of the test tone, with asymmetric beam patterns. Directional hearing sensitivity declined most dramatically between 10 kHz and 2 kHz. The results suggest that dolphins\’ directional hearing is more pronounced for lower frequencies than previously predicted.

}, issn = {0001-4966}, doi = {10.1121/1.5067720}, url = {http://asa.scitation.org/doi/10.1121/1.5067720}, author = {Accomando, Alyssa W. and Mulsow, Jason and Branstetter, Brian K. and Finneran, James J. and Jenkins, Keith} } @article {52565, title = {Bottlenose dolphins that forage with artisanal fishermen whistle differently}, journal = {Ethology}, volume = {123}, year = {2017}, month = {Jan-12-2017}, pages = {906 - 915}, abstract = {

Acoustic communication is a taxonomically widespread phenomenon, crucial for social animals. We evaluate social sounds from bottlenose dolphins (Tursiops truncatus) of Laguna, southern Brazil, whose social structure is organized around a cooperative foraging tactic with artisanal fishermen. This tactic involves stereotyped and coordinated behaviour by dolphins and fishermen and is performed by a subset of the dolphin population, splitting it into two distinct social communities. We compared the acoustic parameters and type of whistles emitted by dolphins of the \“non-cooperative\” and \“cooperative\” communities, both during their interactions with fishermen and in times where dolphins were engaged in other types of foraging. Our findings show how dolphins\’ social sounds differ between foraging tactics and social communities. The frequencies of six whistle types (ascending, descending, concave, convex, multiple, flat) were significantly dependent on tactics and communities. Ascending whistles were more common than expected during foraging without fishermen, and among dolphins of the non-cooperative community. Whistle acoustic parameters (duration, number of inclination changes and inflection points, and initial, final, maximum, minimum frequencies) also varied between social communities. In general, whistles emitted by cooperative dolphins, mainly when not interacting with fishermen, tended to be shorter, had higher frequency and more inflections than those emitted by non-cooperative dolphins. These results suggest that different whistles may convey specific information among dolphins related to foraging, which we hypothesize promote social cohesion among members of the same social community. These differences in acoustic repertoires add a new dimension of complexity to this unique human\–animal interaction.

}, doi = {10.1111/eth.2017.123.issue-1210.1111/eth.12665}, url = {http://doi.wiley.com/10.1111/eth.2017.123.issue-12}, author = {Romeu, Bianca and Cantor, Mauricio and Bezamat, Carolina and Sim{\~o}es-Lopes, Paulo C. and Daura-Jorge, F{\'a}bio G.}, editor = {Ebensperger, L.} }