Heaviside's dolphins (Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Proceedings of the Royal Society B. Biological Sciences 285 (2018): 20181178, doi:10.1098/rspb.2018.1178.The costs of predation may exert significant pressure on the mode of communication used by an animal, and many species balance the benefits of communication (e.g. mate attraction) against the potential risk of predation. Four groups of toothed whales have independently evolved narrowband high-frequency (NBHF) echolocation signals. These signals help NBHF species avoid predation through acoustic crypsis by echolocating and communicating at frequencies inaudible to predators such as mammal-eating killer whales. Heaviside’s dolphins (Cephalorhynchus heavisidii) are thought to exclusively produce NBHF echolocation clicks with a centroid frequency around 125 kHz and little to no energy below 100 kHz. To test this, we recorded wild Heaviside’s dolphins in a sheltered bay in Namibia. We demonstrate that Heaviside’s dolphins produce a second type of click with lower frequency and broader bandwidth in a frequency range that is audible to killer whales. These clicks are used in burst-pulses and occasional click series but not foraging buzzes. We evaluate three different hypotheses and conclude that the most likely benefit of these clicks is to decrease transmission directivity and increase conspecific communication range. The expected increase in active space depends on background noise but ranges from 2.5 (Wenz Sea State 6) to 5 times (Wenz Sea State 1) the active space of NBHF signals. This dual click strategy therefore allows these social dolphins to maintain acoustic crypsis during navigation and foraging, and to selectively relax their crypsis to facilitate communication with conspecifics.This research was supported by a Fulbright U.S. Research Fellowship, the National Geographic Society’s Emerging Explorers Grant in conjunction with the Waitt Foundation (38115) and the University of Pretoria’s Zoology Department. TG was funded by the Claude Leon Foundation, and SE was funded by the South African National Research Foundation. FHJ acknowledges funding from the Office of Naval Research (N00014-1410410) and an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies

Editorial: Ecology and behaviour of free-ranging animals studied by advanced data-logging and tracking techniques

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wassmer, T., Jensen, F. H., Fahlman, A., & Murray, D. L. Editorial: Ecology and behaviour of free-ranging animals studied by advanced data-logging and tracking techniques. Frontiers in Ecology and Evolution, 8, (2020): 113, doi:10.3389/fevo.2020.00113.Many details of the behavior, life history and eco-physiology of animals, even among intensively-studied species, remain unknown. Direct observation is a laborious process only amenable for accessible and non-cryptic species, whereas traditional radio telemetry does not directly provide information on the diversity and complexity of animal physiology and behavior. Further, both methods are laborious and/or expensive, and may lead to biased data when physiology and/or behaviors are altered by marking or tracking (Boyer-Ontl and Pruetz, 2014; Nowak et al., 2014; Welch et al., 2018; see also Le Grand et al.). Ultimately, these methods provide only a fragmentary overview of animal behavior patterns during periods when individuals can be readily detected and surveyed while leaving activities during other times obscured. However, the ongoing miniaturization, sensor development, and increased affordability of data logging and advanced telemetric devices offers the potential for continuous and intensive data collection, thereby potentially allowing researchers to more rigorously investigate both physiology and behavior of animals that are difficult to study using traditional observational methods. Owing to these new technologies, we are at the cusp of a truly revolutionary opportunity to address important and longstanding knowledge gaps in animal eco-physiology. To that end, the special section entitled Ecology and Behaviour of Free-Ranging Animals Studied by Advanced Data-Logging and Tracking Techniques includes 22 papers that report on and quantify otherwise hidden aspects of the biology of a variety of mammals, birds, and even invertebrates, across diverse environments including land, water, and air. The highlighted studies focus on fields ranging from basic animal behavior and ecology to eco-physiology; several papers adopt an integrative approach, providing a rather comprehensive understanding of individual time budgets and their implications. Ultimately and collectively, these contributions serve as testament to the drastic improvement in the level of ecological inference that can be derived from research studies involving the use of data-logging and tracking devices that are currently available

Echolocation click source parameters of Australian snubfin dolphins (Orcaella heinsohni)

Author Posting. © Acoustical Society of America, 2018. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 143 (2018): 2564, doi: 10.1121/1.5034174.The Australian snubfin dolphin (Orcaella heinsohni) is endemic to Australian waters, yet little is known about its abundance and habitat use. To investigate the feasibility of Passive Acoustic Monitoring for snubfin dolphins, biosonar clicks were recorded in Cygnet Bay, Australia, using a four-element hydrophone array. Clicks had a mean source level of 200 ± 5 dB re 1 μPa pp, transmission directivity index of 24 dB, mean centroid frequency of 98 ± 9 kHz, and a root-mean-square bandwidth of 31 ± 3 kHz. Such properties lend themselves to passive acoustic monitoring, but are comparable to similarly-sized delphinids, thus requiring additional cues to discriminate between snubfins and sympatric species.We thank the Fitzroy Basin Association for funding fieldwork in Gladstone May 2013 as well as the Australian Marine Mammal Centre who funded J.N.S. with the Bill Dawbin Fellowship and provided fieldwork funding. P.T.M. was funded by a Sir Walter Murdoch Honorary Professorship from Murdoch University and frame grants from FNU. F.H.J. was supported by the office of naval research (N00014-1410410) and an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies, Aarhus University, under EU's FP7 programme (Agreement No. 609033)

Long-distance vocalizations of spotted hyenas contain individual, but not group, signatures

In animal societies, identity signals are common, mediate interactions within groups, and allow individuals to discriminate group-mates from out-group competitors. However, individual recognition becomes increasingly challenging as group size increases and as signals must be transmitted over greater distances. Group vocal signatures may evolve when successful in-group/out-group distinctions are at the crux of fitness-relevant decisions, but group signatures alone are insufficient when differentiated within-group relationships are important for decision-making. Spotted hyenas are social carnivores that live in stable clans of less than 125 individuals composed of multiple unrelated matrilines. Clan members cooperate to defend resources and communal territories from neighbouring clans and other mega carnivores; this collective defence is mediated by long-range (up to 5 km range) recruitment vocalizations, called whoops. Here, we use machine learning to determine that spotted hyena whoops contain individual but not group signatures, and that fundamental frequency features which propagate well are critical for individual discrimination. For effective clan-level cooperation, hyenas face the cognitive challenge of remembering and recognizing individual voices at long range. We show that serial redundancy in whoop bouts increases individual classification accuracy and thus extended call bouts used by hyenas probably evolved to overcome the challenges of communicating individual identity at long distance

Response to: the metabolic cost of whistling is low but measurable in dolphins

Author Posting. © Company of Biologists, 2020. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 223(11), (2020): jeb224915, doi: 10.1242/jeb.224915.Costs of sound production have been investigated only sparsely incetaceans, despite recent efforts to understand how increasinganthropogenic noise affects these animals that rely extensively onsound for communication and foraging. Theoretical estimates suggestthat metabolic costs of whistling for bottlenose dolphins should be<0.54% of resting metabolic rate (RMR) (Jensen et al., 2012),whereas empirical studies of a single whistling dolphin surprisinglyclaimed that sound production costs were around 20% of RMR (Holtet al., 2015; Noren et al., 2013). Addressing this discrepancy, wefound that costs of whistling were significantly less than 20% RMRand not statistically different from theoretical estimates (Pedersenet al., 2020). In their correspondence, Noren et al., 2020 argue thatthey did not claim whistling was‘costly’and questioned aspects ofour methods, and we address these points here.2021-06-0

Resting metabolic rate and lung function in wild offshore common bottlenose dolphins, Tursiops truncatus, near Bermuda

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Physiology 9 (2018): 886, doi:10.3389/fphys.2018.00886.Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O2 ⋅ min-1), tidal volume (VT, l), respiratory frequency (fR, breaths ⋅ min-1), respiratory flow (l ⋅ min-1), and dynamic lung compliance (CL, l ⋅ cmH2O-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30–49%), thus resulting in a greater O2 storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific CL (sCL, 0.30 ± 0.12 cmH2O-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O2 ⋅ min-1 ⋅ kg-1) nor VT (23.0 ± 3.7 ml ⋅ kg-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.Funding for this project was provided by the Office of Naval Research (ONR YIP Award No. N000141410563, and Dolphin Quest, Inc. FHJ was supported by the Office of Naval Research (Award No. N00014-1410410) and an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies under the FP7 program of the EU (Agreement No. 609033)

Ground-truthing daily and lunar patterns of coral reef fish call rates on a US Virgin Island reef

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ferguson, S., Jensen, F., Hyer, M., Noble, A., Apprill, A., & Mooney, T. Ground-truthing daily and lunar patterns of coral reef fish call rates on a US Virgin Island reef. Aquatic Biology, 31, (2022): 77–87, https://doi.org/10.3354/ab00755.Coral reefs comprise some of the most biodiverse habitats on the planet. These ecosystems face a range of stressors, making quantifying community assemblages and potential changes vital to effective management. To understand short- and long-term changes in biodiversity and detect early warning signals of decline, new methods for quantifying biodiversity at scale are necessary. Acoustic monitoring techniques have proven useful in observing species activities and biodiversity on coral reefs through aggregate approaches (i.e. energy as a proxy). However, few studies have ground-truthed these acoustic analyses with human-based observations. In this study, we sought to expand these passive acoustic methods by investigating biological sounds and fish call rates on a healthy reef, providing a unique set of human-confirmed, labeled acoustic observations. We analyzed acoustic data from Tektite Reef, St. John, US Virgin Islands, over a 2 mo period. A subset of acoustic files was manually inspected to identify recurring biotic sounds and quantify reef activity throughout the day. We found a high variety of acoustic signals in this soundscape. General patterns of call rates across time conformed to expectations, with dusk and dawn showing important and significantly elevated peaks in soniferous fish activity. The data reflected high variability in call rates across days and lunar phases. Call rates did not correspond to sound pressure levels, suggesting that certain call types may drive crepuscular trends in sound levels while lower-level critical calls, likely key for estimating biodiversity and behavior, may be missed by gross sound level analyses.This research was funded by the National Science Foundation Biological Oceanography award 1536782. The experiments were conducted under National Park Service Scientific Research and Collecting Permits VIIS-2016-SCI-0017-20, and we thank the Park staff for their support

Heaviside's dolphins (Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range

The costs of predation may exert significant pressure on the mode of communication used by an animal, and many species balance the benefits of communication (e.g. mate attraction) against the potential risk of predation. Four groups of toothed whales have independently evolved narrowband high-frequency (NBHF) echolocation signals. These signals help NBHF species avoid predation through acoustic crypsis by echolocating and communicating at frequencies inaudible to predators such as mammal-eating killer whales. Heaviside's dolphins (Cephalorhynchus heavisidii) are thought to exclusively produce NBHF echolocation clicks with a centroid frequency around 125 kHz and little to no energy below 100 kHz. To test this, we recorded wild Heaviside's dolphins in a sheltered bay in Namibia. We demonstrate that Heaviside's dolphins produce a second type of click with lower frequency and broader bandwidth in a frequency range that is audible to killer whales. These clicks are used in burst-pulses and occasional click series but not foraging buzzes. We evaluate three different hypotheses and conclude that the most likely benefit of these clicks is to decrease transmission directivity and increase conspecific communication range. The expected increase in active space depends on background noise but ranges from 2.5 (Wenz Sea State 6) to 5 times (Wenz Sea State 1) the active space of NBHF signals. This dual click strategy therefore allows these social dolphins to maintain acoustic crypsis during navigation and foraging, and to selectively relax their crypsis to facilitate communication with conspecifics.Data Supplement: Martin et al. 2018 Supplementary Methods from Heaviside's dolphins (Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range - Supplementary Methods include detail on the statistical analyses conducted for classifying the pulsed signal types of Heaviside's dolphins. Also, these methods contain the relevant information, steps and figures used in the acoustic modelling of the detection range and active space of a NBHF click compared to a lower-frequency burst-pulse click.Data Supplement: Martin et al. 2018 Appendix S1 from Heaviside's dolphins (Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range - Appendix S1 contains the parameter measurements for all measured Heaviside's dolphin pulsed signals.A Fulbright U.S. Research Fellowship, the National Geographic Society's Emerging Explorers Grant in conjunction with the Waitt Foundation (38115) and the University of Pretoria's Zoology Department. T.G. was funded by the Claude Leon Foundation, and S.H.E. was funded by the South African National Research Foundation. F.H.J. acknowledges funding from the Office of Naval Research (N00014-1410410) and an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies.http://rspb.royalsocietypublishing.org2019-07-25hj2018Mammal Research InstituteZoology and Entomolog

Bottlenose dolphin mothers modify signature whistles in the presence of their own calves

PLT received support from ONR grants N00014-18-1-2062 and N00014-20-1-2709. Financial support for the whistle database project has come from the Protect Wild Dolphins fund at Harbor Branch Oceanographic Institute, Vulcan Machine Learning Center for Impact, Allen Institute for Artificial Intelligence, Adelaide M. & Charles B. Link Foundation, and Dolphin Quest, Inc.Human caregivers interacting with children typically modify their speech in ways that promote attention, bonding, and language acquisition. Although this “motherese,” or child-directed communication (CDC), occurs in a variety of human cultures, evidence among nonhuman species is very rare. We looked for its occurrence in a nonhuman mammalian species with long-term mother–offspring bonds that is capable of vocal production learning, the bottlenose dolphin (Tursiops truncatus). Dolphin signature whistles provide a unique opportunity to test for CDC in nonhuman animals, because we are able to quantify changes in the same vocalizations produced in the presence or absence of calves. We analyzed recordings made during brief catch-and-release events of wild bottlenose dolphins in waters near Sarasota Bay, Florida, United States, and found that females produced signature whistles with significantly higher maximum frequencies and wider frequency ranges when they were recorded with their own dependent calves vs. not with them. These differences align with the higher fundamental frequencies and wider pitch ranges seen in human CDC. Our results provide evidence in a nonhuman mammal for changes in the same vocalizations when produced in the presence vs. absence of offspring, and thus strongly support convergent evolution of motherese, or CDC, in bottlenose dolphins. CDC may function to enhance attention, bonding, and vocal learning in dolphin calves, as it does in human children. Our data add to the growing body of evidence that dolphins provide a powerful animal model for studying the evolution of vocal learning and language.Publisher PDFPeer reviewe

Creep resisting steels, nanoparticles, interparticles matrix stresses, mobile dislocations motion and creep rate

Development of improved equation for better accuracy of calculation of stationary creep rate of creep resisting steels. Effect of acting stress components in particles disjunction matrix. Effect of increase of number of ferrite lattice vacancies