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Hoggatt ML, Starbuck CA, O'Keefe JM. Acoustic monitoring yields informative bat population density estimates. Ecol Evol 2024; 14:e11051. [PMID: 38389998 PMCID: PMC10883235 DOI: 10.1002/ece3.11051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/24/2024] Open
Abstract
Bat population estimates are typically made during winter, although this is only feasible for bats that aggregate in hibernacula. While it is essential to measure summer bat population sizes for management, we lack a reliable method. Acoustic surveys should be less expensive and more efficient than capture surveys, and acoustic activity data are already used as indices of population size. Although we currently cannot differentiate individual bats by their calls, we can enter call counts, information on signal and detection angles, and weather data into generalized random encounter models to estimate bat density. We assessed the utility of generalized random encounter models for estimating Indiana bat (Myotis sodalis) population density with acoustic data collected at 51 total sites in six conservation areas in northeast Missouri, 2019-2021. We tested the effects of year, volancy period, conservation area, and their interactions on estimated density. Volancy period was the best predictor, with average predicted density increasing 60% from pre-volancy (46 bats/km2) to post-volancy (74 bats/km2); however, the magnitude of the effect differed by conservation area. We showed that passive acoustic surveys yield informative density estimates that are responsive to temporal changes in bat population size, which suggests this method may be useful for long-term monitoring. However, we need more information to choose the most appropriate values for the density estimation formula. Future work to refine this approach should include assessments of bat behavior and detection parameters and testing the method's efficacy in areas where population sizes are known.
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Affiliation(s)
- Meredith L Hoggatt
- Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign Urbana Illinois USA
| | - Clarissa A Starbuck
- Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign Urbana Illinois USA
| | - Joy M O'Keefe
- Department of Natural Resources and Environmental Sciences University of Illinois at Urbana-Champaign Urbana Illinois USA
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2
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Lewanzik D, Ratcliffe JM, Etzler EA, Goerlitz HR, Jakobsen L. Stealth echolocation in aerial hawking bats reflects a substrate gleaning ancestry. Curr Biol 2023; 33:5208-5214.e3. [PMID: 37898121 DOI: 10.1016/j.cub.2023.10.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 09/26/2023] [Accepted: 10/09/2023] [Indexed: 10/30/2023]
Abstract
Predator-prey co-evolution can escalate into an evolutionary arms race.1 Examples of insect countermeasures to bat echolocation are well-known,2 but presumptive direct counter strategies in bats to insect anti-bat tactics are rare. The emission of very low-intensity calls by the hawking Barbastella barbastellus to circumvent high-frequency moth hearing is the most convincing countermeasure known.2,3 However, we demonstrate that stealth echolocation did not evolve through a high-intensity aerial hawking ancestor becoming quiet as previously hypothesized2,3,4 but from a gleaning ancestor transitioning into an obligate aerial hawker. Our ancestral state reconstructions show that the Plecotini ancestor likely gleaned prey using low-intensity calls typical of gleaning bats and that this ability-and associated traits-was subsequently lost in the barbastelle lineage. Barbastelles did not, however, revert to the oral, high-intensity call emission that other hawking bats use but retained the low-intensity nasal emission of closely related gleaning plecotines despite an extremely limited echolocation range. We further show that barbastelles continue to emit low-intensity calls even under adverse noise conditions and do not broaden the echolocation beam during the terminal buzz, unlike other vespertilionids attacking airborne prey.5,6 Together, our results suggest that barbastelles' echolocation is subject to morphological constraints prohibiting higher call amplitudes and beam broadening in the terminal buzz. We suggest that an abundance of eared prey allowed the co-opting and maintenance of low-intensity, nasal echolocation in today's obligate hawking barbastelle and that this unique foraging behavior7 persists because barbastelles remain a rare, acoustically inconspicuous predator to eared moths. VIDEO ABSTRACT.
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Affiliation(s)
- Daniel Lewanzik
- Acoustic and Functional Ecology, Max Planck Institute for Biological Intelligence, Eberhard-Gwinner-Straße, 82319 Seewiesen, Germany; Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany
| | - John M Ratcliffe
- Department of Biology, University of Toronto, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Erik A Etzler
- Department of Biology, University of Toronto, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Holger R Goerlitz
- Acoustic and Functional Ecology, Max Planck Institute for Biological Intelligence, Eberhard-Gwinner-Straße, 82319 Seewiesen, Germany
| | - Lasse Jakobsen
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark.
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3
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Simon R, Dreissen A, Leroy H, Berg MP, Halfwerk W. Acoustic camouflage increases with body size and changes with bat echolocation frequency range in a community of nocturnally active Lepidoptera. J Anim Ecol 2023; 92:2363-2372. [PMID: 37882060 DOI: 10.1111/1365-2656.14016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 09/19/2023] [Indexed: 10/27/2023]
Abstract
Body size is an important trait in predator-prey dynamics as it is often linked to detection, as well as the success of capture or escape. Larger prey, for example, often runs higher risk of detection by their predators, which imposes stronger selection on their anti-predator traits compared to smaller prey. Nocturnal Lepidoptera (moths) vary strongly in body size, which has consequences for their predation risk, as bigger moths return stronger echoes for echolocating bats. To compensate for increased predation risk, larger moths are therefore expected to have improved anti-predator defences. Moths are covered by different types of scales, which for a few species are known to absorb ultrasound, thus providing acoustic camouflage. Here, we assessed whether moths differ in their acoustic camouflage in a size-dependent way by focusing on their body scales and the different frequency ranges used by bats. We used a sonar head to measure 3D echo scans of a total of 111 moth specimens across 58 species, from eight different families of Lepidoptera. We scanned all the specimens and related their echo-acoustic target strength to various body size measurements. Next, we removed the scales covering the thorax and abdomen and scanned a subset of specimens again to assess the sound absorptive properties of these scales. Comparing intact specimens with descaled specimens, we found almost all species to absorb ultrasound, reducing detection risk on average by 8%. Furthermore, the sound absorptive capacities of body scales increased with body size suggesting that larger species benefit more from acoustic camouflage. The size-dependent effect of camouflage was in particular pronounced for the higher frequencies (above 29 kHz), with moth species belonging to large-bodied families consequently demonstrating similar target strengths compared to species from small-bodied families. Finally, we found the families to differ in frequency range that provided the largest reduction in detection risk, which may be related to differences in predation pressure and predator communities of these families. In general, our findings have important implications for predator-prey interactions across eco-evolutionary timescales and may suggest that acoustic camouflage played a role in body size evolution of nocturnally active Lepidoptera.
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Affiliation(s)
- Ralph Simon
- Department of Ecological Sciences, Vrije Universiteit, Amsterdam, The Netherlands
- Behavioral Ecology and Conservation Lab, Nuremberg Zoo, Nuremberg, Germany
- Machine Learning and Data Analytics Lab, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Alrike Dreissen
- Department of Ecological Sciences, Vrije Universiteit, Amsterdam, The Netherlands
| | - Helene Leroy
- Department of Ecological Sciences, Vrije Universiteit, Amsterdam, The Netherlands
| | - Matty P Berg
- Department of Ecological Sciences, Vrije Universiteit, Amsterdam, The Netherlands
- Groningen Institute of Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Wouter Halfwerk
- Department of Ecological Sciences, Vrije Universiteit, Amsterdam, The Netherlands
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Brandt EE, Duke S, Wang H, Mhatre N. The ground offers acoustic efficiency gains for crickets and other calling animals. Proc Natl Acad Sci U S A 2023; 120:e2302814120. [PMID: 37934821 PMCID: PMC10655215 DOI: 10.1073/pnas.2302814120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 10/01/2023] [Indexed: 11/09/2023] Open
Abstract
Male crickets attract females by producing calls with their forewings. Louder calls travel further and are more effective at attracting mates. However, crickets are much smaller than the wavelength of their call, and this limits their power output. A small group called tree crickets make acoustic tools called baffles which reduce acoustic short-circuiting, a source of dipole inefficiency. Here, we ask why baffling is uncommon among crickets. We hypothesize that baffling may be rare because like other tools they offer insufficient advantage for most species. To test this, we modelled the calling efficiencies of crickets within the full space of possible natural wing sizes and call frequencies, in multiple acoustic environments. We then generated efficiency landscapes, within which we plotted 112 cricket species across 7 phylogenetic clades. We found that all sampled crickets, in all conditions, could gain efficiency from tool use. Surprisingly, we also found that calling from the ground significantly increased efficiency, with or without a baffle, by as much as an order of magnitude. We found that the ground provides some reduction of acoustic short-circuiting but also halves the air volume within which sound is radiated. It simultaneously reflects sound upwards, allowing recapture of a significant amount of acoustic energy through constructive interference. Thus, using the ground as a reflective baffle is an effective strategy for increasing calling efficiency. Indeed, theory suggests that this increase in efficiency is accessible not just to crickets but to all acoustically communicating animals whether they are dipole or monopole sound sources.
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Affiliation(s)
- Erin E. Brandt
- Department of Biology, Western University, London, ONN6A 3K7, Canada
| | - Sarah Duke
- Department of Biology, Western University, London, ONN6A 3K7, Canada
| | - Honglin Wang
- Department of Biology, Western University, London, ONN6A 3K7, Canada
| | - Natasha Mhatre
- Department of Biology, Western University, London, ONN6A 3K7, Canada
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Lin A, Li J, Hu Y, Zhong M, Yu M, Ma N, Wei T, Luo J, Feng J. Contrasting laboratory and field outcomes of bat-moth interactions. Mol Ecol 2023; 32:5864-5876. [PMID: 37789799 DOI: 10.1111/mec.17150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 09/19/2023] [Indexed: 10/05/2023]
Abstract
Predator-prey interactions are important but difficult to study in the field. Therefore, laboratory studies are often used to examine the outcomes of predator-prey interactions. Previous laboratory studies have shown that moth hearing and ultrasound production can help prey avoid being eaten by bats. We report here that laboratory behavioural outcomes may not accurately reflect the outcomes of field bat-moth interactions. We tested the success rates of two bat species capturing moths with distinct anti-bat tactics using behavioural experiments. We compared the results with the dietary composition of field bats using next-generation DNA sequencing. Rhinolophus episcopus and Rhinolophus osgoodi had a lower rate of capture success when hunting for moths that produce anti-bat clicks than for silent eared moths and earless moths. Unexpectedly, the success rates of the bats capturing silent eared moths and earless moths did not differ significantly from each other. However, the field bats had a higher proportion of silent eared moths than that of earless moths and that of clicking moths in their diets. The difference between the proportions of silent eared moths and earless moths in the bat diets can be explained by the difference between their abundance in bat foraging habitats. These findings suggest that moth defensive tactics, bat countertactics and moth availability collectively shape the diets of insectivorous bats. This study illustrates the importance of using a combination of behavioural experiments and molecular genetic techniques to reveal the complex interactions between predators and prey in nature.
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Affiliation(s)
- Aiqing Lin
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
| | - Jiqian Li
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
| | - Yinli Hu
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
| | - Maojun Zhong
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
| | - Minglun Yu
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
| | - Nina Ma
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Tingting Wei
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Jinhong Luo
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, China
| | - Jiang Feng
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China
- College of Life Science, Jilin Agricultural University, Changchun, China
- Key Laboratory of Vegetation Ecology of Education Ministry, Institute of Grassland Science, Northeast Normal University, Changchun, China
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6
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Laeta M, Oliveira JA, Siciliano S, Lambert O, Jensen FH, Galatius A. Cranial asymmetry in odontocetes: a facilitator of sonic exploration? ZOOLOGY 2023; 160:126108. [PMID: 37633185 DOI: 10.1016/j.zool.2023.126108] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/31/2023] [Accepted: 08/04/2023] [Indexed: 08/28/2023]
Abstract
Directional cranial asymmetry is an intriguing condition that has evolved in all odontocetes which has mostly been associated with sound production for echolocation. In this study, we investigated how cranial asymmetry varies across odontocete species both in terms of quality (i.e., shape), and quantity (magnitude of deviation from symmetry). We investigated 72 species across all ten families of Odontoceti using two-dimensional geometric morphometrics. The average asymmetric shape was largely consistent across odontocetes - the rostral tip, maxillae, antorbital notches and braincase, as well as the suture crest between the frontal and interparietal bones were displaced to the right, whereas the nasal septum and premaxillae showed leftward shifts, in concert with an enlargement of the right premaxilla and maxilla. A clear phylogenetic signal related to asymmetric shape variation was identified across odontocetes using squared-change parsimony. The magnitude of asymmetry was widely variable across Odontoceti, with greatest asymmetry in Kogiidae, Monodontidae and Globicephalinae, followed by Physeteridae, Platanistidae and Lipotidae, while the asymmetry was lowest in Lissodelphininae, Phocoenidae, Iniidae and Pontoporiidae. Ziphiidae presented a wide spectrum of asymmetry. Generalized linear models explaining magnitude of asymmetry found associations with click source level while accounting for cranial size. Using phylogenetic generalized least squares, we reconfirm that source level and centroid size significantly predict the level of cranial asymmetry, with more asymmetric marine taxa generally consisting of bigger species emitting higher output sonar signal, i.e. louder sounds. Both characteristics theoretically support foraging at depth, the former by allowing extended diving and the latter being adaptive for prey detection at longer distances. Thus, cranial asymmetry seems to be an evolutionary pathway that allows odontocetes to devote more space for sound-generating structures associated with echolocation and thus increases biosonar search range and foraging efficiency beyond simple phylogenetic scaling predictions.
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Affiliation(s)
- Maíra Laeta
- Setor de Mastozoologia, Departamento de Vertebrados, Museu Nacional/Universidade Federal do Rio de Janeiro, 20941-160 Rio de Janeiro, RJ, Brazil.
| | - João A Oliveira
- Setor de Mastozoologia, Departamento de Vertebrados, Museu Nacional/Universidade Federal do Rio de Janeiro, 20941-160 Rio de Janeiro, RJ, Brazil
| | - Salvatore Siciliano
- Departamento de Ciências Biológicas, Escola Nacional de Saúde Pública Sergio Arouca/Fiocruz, 21040-360 Rio de Janeiro, RJ, Brazil; Grupo de Estudos de Mamíferos Marinhos da Região dos Lagos (GEMM-Lagos), Rua São José, 1.260, Praia Seca, 28970-000 Araruama, RJ, Brazil
| | - Olivier Lambert
- D.O. Terre et Histoire de la Vie, Institut royal des Sciences naturelles de Belgique, 1000 Brussels, Belgium
| | - Frants H Jensen
- Section for Marine Mammal Research, Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MA 02543, USA; Biology Department, Syracuse University, 107 College Place, Syracuse, NY 13244, USA
| | - Anders Galatius
- Section for Marine Mammal Research, Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark.
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Paulson OB, Schousboe A, Hultborn H. The history of Danish neuroscience. Eur J Neurosci 2023; 58:2893-2960. [PMID: 37477973 DOI: 10.1111/ejn.16062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 05/04/2023] [Accepted: 05/29/2023] [Indexed: 07/22/2023]
Abstract
The history of Danish neuroscience starts with an account of impressive contributions made at the 17th century. Thomas Bartholin was the first Danish neuroscientist, and his disciple Nicolaus Steno became internationally one of the most prominent neuroscientists in this period. From the start, Danish neuroscience was linked to clinical disciplines. This continued in the 19th and first half of the 20th centuries with new initiatives linking basic neuroscience to clinical neurology and psychiatry in the same scientific environment. Subsequently, from the middle of the 20th century, basic neuroscience was developing rapidly within the preclinical university sector. Clinical neuroscience continued and was even reinforced during this period with important translational research and a close co-operation between basic and clinical neuroscience. To distinguish 'history' from 'present time' is not easy, as many historical events continue in present time. Therefore, we decided to consider 'History' as new major scientific developments in Denmark, which were launched before the end of the 20th century. With this aim, scientists mentioned will have been born, with a few exceptions, no later than the early 1960s. However, we often refer to more recent publications in documenting the developments of initiatives launched before the end of the last century. In addition, several scientists have moved to Denmark after the beginning of the present century, and they certainly are contributing to the present status of Danish neuroscience-but, again, this is not the History of Danish neuroscience.
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Affiliation(s)
- Olaf B Paulson
- Neurobiology Research Unit, Department of Neurology, Rigshospitalet, 9 Blegdamsvej, Copenhagen, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hans Hultborn
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Moss CF, Ortiz ST, Wahlberg M. Adaptive echolocation behavior of bats and toothed whales in dynamic soundscapes. J Exp Biol 2023; 226:jeb245450. [PMID: 37161774 PMCID: PMC10184770 DOI: 10.1242/jeb.245450] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Journal of Experimental Biology has a long history of reporting research discoveries on animal echolocation, the subject of this Centenary Review. Echolocating animals emit intense sound pulses and process echoes to localize objects in dynamic soundscapes. More than 1100 species of bats and 70 species of toothed whales rely on echolocation to operate in aerial and aquatic environments, respectively. The need to mitigate acoustic clutter and ambient noise is common to both aerial and aquatic echolocating animals, resulting in convergence of many echolocation features, such as directional sound emission and hearing, and decreased pulse intervals and sound intensity during target approach. The physics of sound transmission in air and underwater constrains the production, detection and localization of sonar signals, resulting in differences in response times to initiate prey interception by aerial and aquatic echolocating animals. Anti-predator behavioral responses of prey pursued by echolocating animals affect behavioral foraging strategies in air and underwater. For example, many insect prey can detect and react to bat echolocation sounds, whereas most fish and squid are unresponsive to toothed whale signals, but can instead sense water movements generated by an approaching predator. These differences have implications for how bats and toothed whales hunt using echolocation. Here, we consider the behaviors used by echolocating mammals to (1) track and intercept moving prey equipped with predator detectors, (2) interrogate dynamic sonar scenes and (3) exploit visual and passive acoustic stimuli. Similarities and differences in animal sonar behaviors underwater and in air point to open research questions that are ripe for exploration.
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Affiliation(s)
- Cynthia F. Moss
- Johns Hopkins University, Departments of Psychological and Brain Sciences, Neuroscience and Mechanical Engineering, 3400 N. Charles St., Baltimore, MD 21218, USA
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Sara Torres Ortiz
- Marine Biological Research Center, University of Southern Denmark, Hindsholmvej 11, 5300 Kerteminde, Denmark
| | - Magnus Wahlberg
- Marine Biological Research Center, University of Southern Denmark, Hindsholmvej 11, 5300 Kerteminde, Denmark
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Luo J, Lu M, Luo J, Moss CF. Echo feedback mediates noise-induced vocal modifications in flying bats. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2023; 209:203-214. [PMID: 36266485 DOI: 10.1007/s00359-022-01585-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 10/01/2022] [Accepted: 10/05/2022] [Indexed: 02/07/2023]
Abstract
Diverse animal taxa are capable of rapidly modifying vocalizations to mitigate interference from environmental noise. Echolocating bats, for example, must frequently perform sonar tasks in the presence of interfering sounds. Numerous studies have documented sound production flexibility in echolocating bats; however, it remains unknown whether noise-induced vocal modifications (NIVMs) mitigate interference effects on echoes or calls. In this study, we leverage echo level compensation behavior of echolocating bats to answer this question. Using a microphone array, we recorded echolocation calls of Hipposideros pratti trained to approach and land on a perch in the laboratory under quiet and noise conditions. We found that H. pratti exhibited echo level compensation behavior during approaching flights, which depended critically on distance to the landing perch. Broadcast noise delayed and affected the rate of echo level compensation in H. pratti. Moreover, H. pratti increased vocalization amplitude, i.e., exhibited the Lombard effect, while also adjusting call duration and bandwidth with increasing noise levels. Quantitative analyses of the data show that H. pratti relies on echo feedback, not vocal feedback, to adjust signals in the presence of noise. These findings provide compelling evidence that NIVMs in echolocating animals and non-echolocating animals operate through different mechanisms.
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Affiliation(s)
- Jinhong Luo
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China.
| | - Manman Lu
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Jie Luo
- Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China
| | - Cynthia F Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA.
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Eitan O, Taub M, Boonman A, Zviran A, Tourbabin V, Weiss AJ, Yovel Y. Echolocating bats rapidly adjust their mouth gape to control spatial acquisition when scanning a target. BMC Biol 2022; 20:282. [PMID: 36527053 PMCID: PMC9758934 DOI: 10.1186/s12915-022-01487-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 11/30/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND As well known to any photographer, controlling the "field of view" offers an extremely powerful mechanism by which to adjust target acquisition. Only a few natural sensory systems can actively control their field of view (e.g., dolphins, whales, and bats). Bats are known for their active sensing abilities and modify their echolocation signals by actively controlling their spectral and temporal characteristics. Less is known about bats' ability to actively modify their bio-sonar field of view. RESULTS We show that Pipistrellus kuhlii bats rapidly narrow their sensory field of view (i.e., their bio-sonar beam) when scanning a target. On-target vertical sonar beams were twofold narrower than off-target beams. Continuous measurements of the mouth gape of free-flying bats revealed that they control their bio-sonar beam by a ~3.6 mm widening of their mouth gape: namely, bats open their mouth to narrow the beam and vice versa. CONCLUSIONS Bats actively and rapidly control their echolocation vertical beam width by modifying their mouth gape. We hypothesize that narrowing their vertical beam narrows the zone of ensonification when estimating the elevation of a target. In other words, bats open their mouth to improve sensory localization.
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Affiliation(s)
- Ofri Eitan
- grid.12136.370000 0004 1937 0546School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel
| | - Mor Taub
- grid.12136.370000 0004 1937 0546School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel
| | - Arjan Boonman
- grid.12136.370000 0004 1937 0546School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel
| | - Amir Zviran
- grid.12136.370000 0004 1937 0546School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel ,grid.12136.370000 0004 1937 0546The School of Electrical Engineering, the Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, 6997801 Tel Aviv, Israel
| | - Vladimir Tourbabin
- grid.7489.20000 0004 1937 0511Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Anthony J. Weiss
- grid.12136.370000 0004 1937 0546The School of Electrical Engineering, the Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, 6997801 Tel Aviv, Israel
| | - Yossi Yovel
- grid.12136.370000 0004 1937 0546School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel ,grid.12136.370000 0004 1937 0546Sagol School of Neuroscience, Tel Aviv University, 6997801 Tel Aviv, Israel ,grid.12136.370000 0004 1937 0546School of Mechanical Engineering, the Iby and Aladar Fleischman Faculty of Engineering, Tel Aviv University, 6997801 Tel Aviv, Israel ,grid.12136.370000 0004 1937 0546The Steinhardt Museum of Natural History, National Research Center for Biodiversity Studies, Tel-Aviv University, Tel Aviv, Israel
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11
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Jespersen C, Docherty D, Hallam J, Albertsen C, Jakobsen L. Drone exploration of bat echolocation: A
UAV
‐borne multimicrophone array to study bat echolocation. Ecol Evol 2022; 12:e9577. [PMCID: PMC9719081 DOI: 10.1002/ece3.9577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 12/07/2022] Open
Affiliation(s)
| | - David Docherty
- Maersk McKinney Moller Institute University of Southern Denmark Odense M Denmark
| | - John Hallam
- Maersk McKinney Moller Institute University of Southern Denmark Odense M Denmark
| | - Carsten Albertsen
- Maersk McKinney Moller Institute University of Southern Denmark Odense M Denmark
| | - Lasse Jakobsen
- Department of Biology University of Southern Denmark Odense M Denmark
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Håkansson J, Mikkelsen C, Jakobsen L, Elemans CPH. Bats expand their vocal range by recruiting different laryngeal structures for echolocation and social communication. PLoS Biol 2022; 20:e3001881. [PMID: 36445872 PMCID: PMC9707786 DOI: 10.1371/journal.pbio.3001881] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/19/2022] [Indexed: 12/03/2022] Open
Abstract
Echolocating bats produce very diverse vocal signals for echolocation and social communication that span an impressive frequency range of 1 to 120 kHz or 7 octaves. This tremendous vocal range is unparalleled in mammalian sound production and thought to be produced by specialized laryngeal vocal membranes on top of vocal folds. However, their function in vocal production remains untested. By filming vocal membranes in excised bat larynges (Myotis daubentonii) in vitro with ultra-high-speed video (up to 250,000 fps) and using deep learning networks to extract their motion, we provide the first direct observations that vocal membranes exhibit flow-induced self-sustained vibrations to produce 10 to 95 kHz echolocation and social communication calls in bats. The vocal membranes achieve the highest fundamental frequencies (fo's) of any mammal, but their vocal range is with 3 to 4 octaves comparable to most mammals. We evaluate the currently outstanding hypotheses for vocal membrane function and propose that most laryngeal adaptations in echolocating bats result from selection for producing high-frequency, rapid echolocation calls to catch fast-moving prey. Furthermore, we show that bats extend their lower vocal range by recruiting their ventricular folds-as in death metal growls-that vibrate at distinctly lower frequencies of 1 to 5 kHz for producing agonistic social calls. The different selection pressures for echolocation and social communication facilitated the evolution of separate laryngeal structures that together vastly expanded the vocal range in bats.
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Affiliation(s)
- Jonas Håkansson
- Sound Communication and Behavior Group, Department of Biology, University of Southern Denmark, Odense M, Denmark,* E-mail: (JH); (CPHE)
| | - Cathrine Mikkelsen
- Sound Communication and Behavior Group, Department of Biology, University of Southern Denmark, Odense M, Denmark
| | - Lasse Jakobsen
- Sound Communication and Behavior Group, Department of Biology, University of Southern Denmark, Odense M, Denmark
| | - Coen P. H. Elemans
- Sound Communication and Behavior Group, Department of Biology, University of Southern Denmark, Odense M, Denmark,* E-mail: (JH); (CPHE)
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13
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Finger NM, Holderied M, Jacobs DS. Detection distances in desert dwelling, high duty cycle echolocators: A test of the foraging habitat hypothesis. PLoS One 2022; 17:e0268138. [PMID: 35588425 PMCID: PMC9119505 DOI: 10.1371/journal.pone.0268138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 04/24/2022] [Indexed: 11/18/2022] Open
Abstract
High Duty Cycle (HDC) echolocating bats use high frequency echolocation pulses that are clutter resistant, but their high frequencies give them limited range. Despite their unique ability to reject background clutter while simultaneously detecting fluttering prey, the frequency of their echolocation pulses has a strong correlation with level of environmental clutter, lower frequency pulses of HDC bats being associated with more open environments. The Foraging Habitat Hypothesis (FHH) proposes that the ecological significance of these lower frequency pulses in HDC bats in open environments is that they allow longer prey detection distances. To test the FHH, we compared the frequencies, Source Levels (SLs) and detection distances of Rhinolophus capensis, a HDC bat that has been shown to vary its call frequency in relation to habitat structure. As a further test of the FHH we investigated the SLs and detection distances of Rhinolophus damarensis (a heterospecific species that occurs in the same open desert environment as R. capensis but echolocates at a higher dominant pulse frequency). In the open desert, R. capensis emitted both lower frequency and higher SL pulses giving them longer detection distances than R. capensis in the cluttered fynbos. SL contributed more to differences in detection distances in both R. capensis and R. damarensis than frequency. In a few instances, R. damarensis achieved similar detection distances to desert–inhabiting R. capensis by emitting much higher SLs despite their average SLs being lower. These results suggest that lower frequency echolocation pulses are not a prerequisite for open desert living but may increase detection distance while avoiding energetic costs required for high SLs.
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Affiliation(s)
- Nikita M. Finger
- Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
| | - Marc Holderied
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - David S. Jacobs
- Department of Biological Sciences, University of Cape Town, Cape Town, South Africa
- * E-mail:
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14
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Leiser‐Miller LB, Santana SE. Functional differences in echolocation call design in an adaptive radiation of bats. Ecol Evol 2021; 11:16153-16164. [PMID: 34824818 PMCID: PMC8601877 DOI: 10.1002/ece3.8296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/18/2021] [Indexed: 11/15/2022] Open
Abstract
All organisms have specialized systems to sense their environment. Most bat species use echolocation for navigation and foraging, but which and how ecological factors shaped echolocation call diversity remains unclear for the most diverse clades, including the adaptive radiation of neotropical leaf-nosed bats (Phyllostomidae). This is because phyllostomids emit low-intensity echolocation calls and many inhabit dense forests, leading to low representation in acoustic surveys. We present a field-collected, echolocation call dataset spanning 35 species and all phyllostomid dietary guilds. We analyze these data under a phylogenetic framework to test the hypothesis that echolocation call design and parameters are specialized for the acoustic demands of different diets, and investigate the contributions of phylogeny and body size to echolocation call diversity. We further link call parameters to dietary ecology by contrasting minimum detectable prey size estimates (MDPSE) across species. We find phylogeny and body size explain a substantial proportion of echolocation call parameter diversity, but most species can be correctly assigned to taxonomic (61%) or functional (77%) dietary guilds based on call parameters. This suggests a degree of acoustic ecological specialization, albeit with interspecific similarities in call structure. Theoretical MDPSE are greatest for omnivores and smallest for insectivores. Omnivores significantly differ from other dietary guilds in MDPSE when phylogeny is not considered, but there are no differences among taxonomic dietary guilds within a phylogenetic context. Similarly, predators of non-mobile/non-evasive prey and predators of mobile/evasive prey differ in estimated MDPSE when phylogeny is not considered. Phyllostomid echolocation call structure may be primarily specialized for overcoming acoustic challenges of foraging in dense habitats, and then secondarily specialized for the detection of food items according to functional dietary guilds. Our results give insight into the possible ecological mechanisms shaping the diversity of sensory systems, and their reciprocal influence on resource use.
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Affiliation(s)
| | - Sharlene E. Santana
- Department of BiologyUniversity of WashingtonSeattleWashingtonUSA
- Burke Museum of Natural History and CultureUniversity of WashingtonSeattleWashingtonUSA
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15
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Malinka CE, Rojano-Doñate L, Madsen PT. Directional biosonar beams allow echolocating harbour porpoises to actively discriminate and intercept closely spaced targets. J Exp Biol 2021; 224:271830. [PMID: 34387665 DOI: 10.1242/jeb.242779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 06/28/2021] [Indexed: 10/20/2022]
Abstract
Echolocating toothed whales face the problem that high sound speeds in water mean that echoes from closely spaced targets will arrive at time delays within their reported auditory integration time of some 264 µs. Here, we test the hypothesis that echolocating harbour porpoises cannot resolve and discriminate targets within a clutter interference zone given by their integration time. To do this, we trained two harbour porpoises (Phocoena phocoena) to actively approach and choose between two spherical targets at four varying inter-target distances (13.5, 27, 56 and 108 cm) in a two-alternative forced-choice task. The free-swimming, blindfolded porpoises were tagged with a sound and movement tag (DTAG4) to record their echoic scene and acoustic outputs. The known ranges between targets and the porpoise, combined with the sound levels received on target-mounted hydrophones revealed how the porpoises controlled their acoustic gaze. When targets were close together, the discrimination task was more difficult because of smaller echo time delays and lower echo level ratios between the targets. Under these conditions, buzzes were longer and started from farther away, source levels were reduced at short ranges, and the porpoises clicked faster, scanned across the targets more, and delayed making their discrimination decision until closer to the target. We conclude that harbour porpoises can resolve and discriminate closely spaced targets, suggesting a clutter rejection zone much shorter than their auditory integration time, and that such clutter rejection is greatly aided by spatial filtering with their directional biosonar beam.
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Affiliation(s)
- Chloe E Malinka
- Zoophysiology, Department of Biology, Aarhus University, Aarhus 8000, Denmark
| | - Laia Rojano-Doñate
- Zoophysiology, Department of Biology, Aarhus University, Aarhus 8000, Denmark
| | - Peter T Madsen
- Zoophysiology, Department of Biology, Aarhus University, Aarhus 8000, Denmark
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16
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Gessinger G, Page R, Wilfert L, Surlykke A, Brinkløv S, Tschapka M. Phylogenetic Patterns in Mouth Posture and Echolocation Emission Behavior of Phyllostomid Bats. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.630481] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
While phyllostomid bats show an impressive range of feeding habits, most of them emit highly similar echolocation calls. Due to the presence of an often prominent noseleaf, it has long been assumed that all phyllostomids emit echolocation calls exclusively through the nostrils rather than through the mouth. However, photo evidence documents also phyllostomid bats flying with an opened mouth. We hypothesized that all phyllostomid species emit echolocation calls only through the nostrils and therefore fly consistently with a closed mouth, and that observations of an open mouth should be a rare and random behavior among individuals and species. Using a high-speed camera and standardized conditions in a flight cage, we screened 40 phyllostomid species. Behavior varied distinctly among the species and mouth posture shows a significant phylogenetic signal. Bats of the frugivorous subfamilies Rhinophyllinae and Carolliinae, the nectarivorous subfamilies Glossophaginae and Lonchophyllinae, and the sanguivorous subfamily Desmodontinae all flew consistently with open mouths. So did the animalivorous subfamilies Glyphonycterinae, Micronycterinae and Phyllostominae, with the notable exception of species in the omnivorous genus Phyllostomus, which consistently flew with mouths closed. Bats from the frugivorous subfamily Stenodermatinae also flew exclusively with closed mouths with the single exception of the genus Sturnira, which is the sister clade to all other stenodermatine species. Further, head position angles differed significantly between bats echolocating with their mouth closed and those echolocating with their mouths opened, with closed-mouth phyllostomids pointing only the nostrils in the direction of flight and open-mouth phyllostomids pointing both the nostrils and mouth gape in the direction of flight. Ancestral trait reconstruction showed that the open mouth mode is the ancestral state within the Phyllostomidae. Based on the observed behavioral differences, we suggest that phyllostomid bats are not all nasal emitters as previously thought and discuss possible reasons. Further experiments, such as selectively obstructing sound emission through nostrils or mouth, respectively, will be necessary to clarify the actual source, plasticity and ecological relevance of sound emission of phyllostomid bats flying with their mouths open.
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17
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Voigt CC, Russo D, Runkel V, Goerlitz HR. Limitations of acoustic monitoring at wind turbines to evaluate fatality risk of bats. Mamm Rev 2021. [DOI: 10.1111/mam.12248] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Christian C. Voigt
- Department of Evolutionary Ecology Leibniz Institute for Zoo and Wildlife Research Alfred‐Kowalke‐Str. 1710315Berlin Germany
| | - Danilo Russo
- Wildlife Research Unit Dipartimento di Agraria Universita degli Studi di Napoli Federico II Portici Italy
- School of Biological Sciences University of Bristol Bristol Life Sciences Building, 24 Tyndall Avenue BristolBS8 1TQUK
| | - Volker Runkel
- Bundesverband für Fledermauskunde Deutschland e.V. Schmidtstedter Str. 30a99084Erfurt Germany
| | - Holger R. Goerlitz
- Acoustic and Functional Ecology Max Planck Institute for Ornithology Eberhard‐Gwinner‐Strasse 82319Seewiesen Germany
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18
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Loureiro LO, Engstrom MD, Lim BK. Does evolution of echolocation calls and morphology in Molossus result from convergence or stasis? PLoS One 2020; 15:e0238261. [PMID: 32970683 PMCID: PMC7514107 DOI: 10.1371/journal.pone.0238261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 08/12/2020] [Indexed: 11/20/2022] Open
Abstract
Although many processes of diversification have been described to explain variation of morphological traits within clades that have obvious differentiation among taxa, not much is known about these patterns in complexes of cryptic species. Molossus is a genus of bats that is mainly Neotropical, occurring from the southeastern United States to southern Argentina, including the Caribbean islands. Molossus comprises some groups of species that are morphologically similar but phylogenetically divergent, and other groups of species that are genetically similar but morphologically distinct. This contrast allows investigation of unequal trait diversification and the evolution of morphological and behavioural characters. In this study, we assessed the role of phylogenetic history in a genus of bat with three cryptic species complexes, and evaluated if morphology and behavior are evolving concertedly. The Genotype by Sequence genomic approach was used to build a species-level phylogenetic tree for Molossus and to estimate the ancestral states of morphological and echolocation call characters. We measured the correlation of phylogenetic distances to morphological and echolocation distances, and tested the relationship between morphology and behavior when the effect of phylogeny is removed. Morphology evolved via a mosaic of convergence and stasis, whereas call design was influenced exclusively through local adaptation and convergent evolution. Furthermore, the frequency of echolocation calls is negatively correlated with the size of the bat, but other characters do not seem to be evolving in concert. We hypothesize that slight variation in both morphology and behaviour among species of the genus might result from niche specialization, and that traits evolve to avoid competition for resources in similar environments.
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Affiliation(s)
- Livia O. Loureiro
- Hospital for Sick Children SickKids Learning Institute, The Centre for Applied Genomics, Toronto, Ontario, Canada
- Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Mark D. Engstrom
- Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Burton K. Lim
- Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada
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19
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Coombs EJ, Clavel J, Park T, Churchill M, Goswami A. Wonky whales: the evolution of cranial asymmetry in cetaceans. BMC Biol 2020; 18:86. [PMID: 32646447 PMCID: PMC7350770 DOI: 10.1186/s12915-020-00805-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/01/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Unlike most mammals, toothed whale (Odontoceti) skulls lack symmetry in the nasal and facial (nasofacial) region. This asymmetry is hypothesised to relate to echolocation, which may have evolved in the earliest diverging odontocetes. Early cetaceans (whales, dolphins, and porpoises) such as archaeocetes, namely the protocetids and basilosaurids, have asymmetric rostra, but it is unclear when nasofacial asymmetry evolved during the transition from archaeocetes to modern whales. We used three-dimensional geometric morphometrics and phylogenetic comparative methods to reconstruct the evolution of asymmetry in the skulls of 162 living and extinct cetaceans over 50 million years. RESULTS In archaeocetes, we found asymmetry is prevalent in the rostrum and also in the squamosal, jugal, and orbit, possibly reflecting preservational deformation. Asymmetry in odontocetes is predominant in the nasofacial region. Mysticetes (baleen whales) show symmetry similar to terrestrial artiodactyls such as bovines. The first significant shift in asymmetry occurred in the stem odontocete family Xenorophidae during the Early Oligocene. Further increases in asymmetry occur in the physeteroids in the Late Oligocene, Squalodelphinidae and Platanistidae in the Late Oligocene/Early Miocene, and in the Monodontidae in the Late Miocene/Early Pliocene. Additional episodes of rapid change in odontocete skull asymmetry were found in the Mid-Late Oligocene, a period of rapid evolution and diversification. No high-probability increases or jumps in asymmetry were found in mysticetes or archaeocetes. Unexpectedly, no increases in asymmetry were recovered within the highly asymmetric ziphiids, which may result from the extreme, asymmetric shape of premaxillary crests in these taxa not being captured by landmarks alone. CONCLUSIONS Early ancestors of living whales had little cranial asymmetry and likely were not able to echolocate. Archaeocetes display high levels of asymmetry in the rostrum, potentially related to directional hearing, which is lost in early neocetes-the taxon including the most recent common ancestor of living cetaceans. Nasofacial asymmetry becomes a significant feature of Odontoceti skulls in the Early Oligocene, reaching its highest levels in extant taxa. Separate evolutionary regimes are reconstructed for odontocetes living in acoustically complex environments, suggesting that these niches impose strong selective pressure on echolocation ability and thus increased cranial asymmetry.
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Affiliation(s)
- Ellen J Coombs
- Genetics, Evolution, and Environment Department, University College London, Gower Street, London, WC1E 6BT, UK.
- Department of Life Sciences, Natural History Museum, London, Cromwell Road, London, SW7 5BD, UK.
| | - Julien Clavel
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Travis Park
- Department of Life Sciences, Natural History Museum, London, Cromwell Road, London, SW7 5BD, UK
- Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK
| | - Morgan Churchill
- Department of Biology, University of Wisconsin-Oshkosh, Oshkosh, WI, 54901, USA
| | - Anjali Goswami
- Genetics, Evolution, and Environment Department, University College London, Gower Street, London, WC1E 6BT, UK
- Department of Life Sciences, Natural History Museum, London, Cromwell Road, London, SW7 5BD, UK
- Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK
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20
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Olsen MN, Surlykke A, Jakobsen L. The sonar beam of Macrophyllum macrophyllum implies ecological adaptation under phylogenetic constraint. J Exp Biol 2020; 223:jeb223909. [PMID: 32398318 DOI: 10.1242/jeb.223909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 05/05/2020] [Indexed: 11/20/2022]
Abstract
All animals are adapted to their ecology within the bounds of their evolutionary heritage. Echolocating bats clearly show such adaptations and boundaries through their biosonar call design. Adaptations include not only the overall time-frequency structure, but also the shape of the emitted echolocation beam. Macrophyllum macrophyllum is unique within the phyllostomid family, being the only species to predominantly hunt for insects in the open, on or above water, and as such it presents an interesting case for comparing the impact of phylogeny and ecology as it originates from a family of low-intensity, high-directionality gleaning bats, but occupies a niche dominated by very loud and substantially less-directional bats. Here, we examined the sonar beam pattern of M. macrophyllum in the field and in a flight room and compared it to closely related species with very different feeding ecology and to that of the niche-sharing but distantly related Myotis daubentonii Our results show that M. macrophyllum uses higher source levels and emits less-directional calls than other phyllostomids. In the field, its call directionality is comparable to M. daubentonii, but in the flight room, M. macrophyllum is substantially more directional. Hence our results indicate that ecology influences the emitted call, pushing the bats to emit a louder and broader beam than other phyllostomids, but that phylogeny does limit the emitted intensity and flexibility of the overall beam pattern.
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Affiliation(s)
| | - Annemarie Surlykke
- Department of Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Lasse Jakobsen
- Department of Biology, University of Southern Denmark, 5230 Odense, Denmark
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21
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López‐Cuamatzi IL, Vega‐Gutiérrez VH, Cabrera‐Campos I, Ruiz‐Sanchez E, Ayala‐Berdon J, Saldaña‐Vázquez RA. Does body mass restrict call peak frequency in echolocating bats? Mamm Rev 2020. [DOI: 10.1111/mam.12196] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Issachar L. López‐Cuamatzi
- Facultad de Ciencias Biológicas Benemérita Universidad Autónoma de Puebla Blvd, Valsequillo y Av, San Claudio, Edificio BIO 1, Ciudad Universitaria, Col. Jardines de San ManuelC.P. 72570 Puebla México
| | - Víctor H. Vega‐Gutiérrez
- Maestría en Ciencias Biológicas, Centro Tlaxcala de Biología de la Conducta Universidad Autónoma de Tlaxcala Carretera Tlaxcala‐Puebla Km. 1.5C.P. 90062Tlaxcala de Xicohténcatl Tlaxcala México
| | - Iván Cabrera‐Campos
- Maestría en Ciencias Biológicas, Centro Tlaxcala de Biología de la Conducta Universidad Autónoma de Tlaxcala Carretera Tlaxcala‐Puebla Km. 1.5C.P. 90062Tlaxcala de Xicohténcatl Tlaxcala México
| | - Eduardo Ruiz‐Sanchez
- Departamento de Botánica y Zoología Centro Universitario de Ciencias Biológicas y Agropecuarias Universidad de Guadalajara Camino Ing. Ramón Padilla Sánchez 2100, Nextipac45200Zapopán Jalisco México
| | - Jorge Ayala‐Berdon
- CONACyT Universidad Autónoma de Tlaxcala Carretera Tlaxcala‐Puebla Km. 1.5 C.P. 90062 Tlaxcala de Xicohténcatl Tlaxcala México
| | - Romeo A. Saldaña‐Vázquez
- Instituto de Investigaciones en Medio Ambiente Xavier Gorostiaga S.J. Universidad Iberoamericana Puebla Blvd. del Niño Poblano No. 2901, Col. Reserva Territorial Atlixcáyotl C. P. 72820 San Andrés Cholula Puebla México
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22
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Goerlitz HR, Hofstede HMT, Holderied MW. Neural representation of bat predation risk and evasive flight in moths: A modelling approach. J Theor Biol 2020; 486:110082. [PMID: 31734242 DOI: 10.1016/j.jtbi.2019.110082] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/05/2019] [Accepted: 11/13/2019] [Indexed: 11/16/2022]
Abstract
Most animals are at risk from multiple predators and can vary anti-predator behaviour based on the level of threat posed by each predator. Animals use sensory systems to detect predator cues, but the relationship between the tuning of sensory systems and the sensory cues related to predator threat are not well-studied at the community level. Noctuid moths have ultrasound-sensitive ears to detect the echolocation calls of predatory bats. Here, combining empirical data and mathematical modelling, we show that moth hearing is adapted to provide information about the threat posed by different sympatric bat species. First, we found that multiple characteristics related to the threat posed by bats to moths correlate with bat echolocation call frequency. Second, the frequency tuning of the most sensitive auditory receptor in noctuid moth ears provides information allowing moths to escape detection by all sympatric bats with similar safety margin distances. Third, the least sensitive auditory receptor usually responds to bat echolocation calls at a similar distance across all moth species for a given bat species. If this neuron triggers last-ditch evasive flight, it suggests that there is an ideal reaction distance for each bat species, regardless of moth size. This study shows that even a very simple sensory system can adapt to deliver information suitable for triggering appropriate defensive reactions to each predator in a multiple predator community.
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Affiliation(s)
- Holger R Goerlitz
- Max Planck Institute for Ornithology, Acoustic and Functional Ecology Group, 82319 Seewiesen, Germany; University of Bristol, School of Biological Sciences, Bristol, BS8 1UG, UK.
| | - Hannah M Ter Hofstede
- Dartmouth College, Department of Biological Sciences, Hanover, NH 03755, USA; University of Bristol, School of Biological Sciences, Bristol, BS8 1UG, UK
| | - Marc W Holderied
- University of Bristol, School of Biological Sciences, Bristol, BS8 1UG, UK
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23
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Milchram M, Suarez‐Rubio M, Schröder A, Bruckner A. Estimating population density of insectivorous bats based on stationary acoustic detectors: A case study. Ecol Evol 2020; 10:1135-1144. [PMID: 32076503 PMCID: PMC7029071 DOI: 10.1002/ece3.5928] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 11/18/2019] [Accepted: 11/22/2019] [Indexed: 11/24/2022] Open
Abstract
Automated recording units are commonly used by consultants to assess environmental impacts and to monitor animal populations. Although estimating population density of bats using stationary acoustic detectors is key for evaluating environmental impacts, estimating densities from call activity data is only possible through recently developed numerical methods, as the recognition of calling individuals is impossible.We tested the applicability of generalized random encounter models (gREMs) for determining population densities of three bat species (Common pipistrelle Pipistrellus pipistrellus, Northern bat Eptesicus nilssonii, and Natterer's bat Myotis nattereri) based on passively collected acoustical data. To validate the results, we compared them to (a) density estimates from the literature and to (b) Royle-Nichols (RN) models of detection/nondetection data.Our estimates for M. nattereri matched both the published data and RN-model results. For E. nilssonii, the gREM yielded similar estimates to the RN-models, but the published estimates were more than twice as high. This discrepancy might be because the high-altitude flight of E. nilssonii is not accounted for in gREMs. Results of gREMs for P. pipistrellus were supported by published data but were ~10 times higher than those of RN-models. RN-models use detection/nondetection data, and this loss of information probably affected population estimates of very active species like P. pipistrellus.gREM models provided realistic estimates of bat population densities based on automatically recorded call activity data. However, the average flight altitude of species should be accounted for in future analyses. We suggest including flight altitude in the calculation of the detection range to assess the detection sphere more accurately and to obtain more precise density estimates.
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Affiliation(s)
- Markus Milchram
- Institute of ZoologyDepartment of Integrative Biology and Biodiversity ResearchUniversity of Natural Resources and Life Sciences ViennaViennaAustria
| | - Marcela Suarez‐Rubio
- Institute of ZoologyDepartment of Integrative Biology and Biodiversity ResearchUniversity of Natural Resources and Life Sciences ViennaViennaAustria
| | - Annika Schröder
- Institute of ZoologyDepartment of Integrative Biology and Biodiversity ResearchUniversity of Natural Resources and Life Sciences ViennaViennaAustria
| | - Alexander Bruckner
- Institute of ZoologyDepartment of Integrative Biology and Biodiversity ResearchUniversity of Natural Resources and Life Sciences ViennaViennaAustria
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24
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Boonman A, Fenton B, Yovel Y. The benefits of insect-swarm hunting to echolocating bats, and its influence on the evolution of bat echolocation signals. PLoS Comput Biol 2019; 15:e1006873. [PMID: 31830029 PMCID: PMC6907744 DOI: 10.1371/journal.pcbi.1006873] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 10/14/2019] [Indexed: 11/20/2022] Open
Abstract
Predation on swarms of prey, especially using visual information, has drawn much interest in studies of collective movement. Surprisingly, in the field of biosonar this aspect of prey detection, which is probably very common, has received little to no attention. Here, we combine computer simulations and actual echo measurements to accurately estimate the echo sound pressure of insect swarms of different size and density. We show that swarm echo sound pressure increases with 3dB for every doubling of insect number, irrespective of swarm density. Thus swarms will be much easier to detect than single insects. Many of the insects bats eat are so small that they are only detectable by echolocation at very short distances. By focusing on detection of swarms of insects, a bat may increase its operating range and diversify its diet. Interestingly, interference between the sound waves reflected from a swarm of insects can sometimes result in echoes that are much weaker than echoes from single insects. We show that bats can reduce this problem by increasing the bandwidth of their echolocation calls. Specifically, a bandwidth of 3–8 kHz would guarantee receiving loud echoes from any angle relative to the swarm. Indeed, many bat species, and specifically bats hunting in open spaces, where swarms are abundant, use echolocation signals with a bandwidth of several kHz. Our results might also explain how the first echolocating bats that probably had limited echolocation abilities, could detect insects through swarm hunting. When bats hunt, they often encounter insects that fly in swarms. Echolocating bats emit sonar signals to search for prey and it is currently unknown what such swarms look like to a bat. Unlike vision, sonar senses the delay or distance to objects directly. We show that when bats hunt for insects in the sky, the echoes from the insects in a swarm will most of the time sum up and therefore become much louder than the echo of a single insect. Every time an insect swarm would double in number, a bat would hear an echo that is 3dB stronger. This could enable a bat to detect prey from longer distances and some bats might thus profit from swarm hunting. However, the echoes reflected from the many insects in the swarm also create acoustic interference so that sometimes the summed echo is actually weak at a certain frequency. We show how bats could deal with this drawback. It is known that most bats do not use sonar signals with a single tone but that they modulate their tones. Our analysis shows that this modulation can solve the problem of spectral interference ensuring that the swarm-echo is always loud.
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Affiliation(s)
- Arjan Boonman
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University, Israel
- * E-mail:
| | - Brock Fenton
- Dpt of Biology, Western University, London, Ontario, Canada
| | - Yossi Yovel
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University, Israel
- School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Israel
- Sagol School of Neuroscience, Tel Aviv University, Israel
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Lee H, Roan MJ, Ming C, Simmons JA, Wang R, Müller R. High-frequency soundfield microphone for the analysis of bat biosonar. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:4525. [PMID: 31893689 DOI: 10.1121/1.5139652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 11/20/2019] [Indexed: 06/10/2023]
Abstract
Numerous bat species emit wideband frequency-modulated signals for echolocation to hunt prey and avoid obstacles. Research investigating the behavioral and physiological responses of bats to echoes typically includes analysis of acoustic signals from microphones and/or microphone arrays, using time difference of arrival between array elements or the microphones to locate flying bats (azimuth and elevation). This has provided insight into transmission adaptations such as pulse duration and duty cycle with respect to target distance, clutter, and interferers. Microphones recording transmitted signals and echoes near a stationary bat provide sound pressure as a function of time but no directional information. In this work, the authors propose a spatial audio/soundfield microphone array to both track bats in flight and pinpoint the directions of echoes received by a bat. The authors introduce an ultrasonic (20-80 kHz) tetrahedral soundfield microphone to capture bat sounds up to 80 kHz. A spatial audio decoding technique called high angular resolution planewave expansion (HARPEx) supplies angle and elevation estimates, either for a flying bat based on the bat pulses or for targets based on echoes. Experiments using the soundfield microphone and HARPEx show that the approach accurately estimates the sound direction of arrival in both scenarios.
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Affiliation(s)
- Hyeon Lee
- Department of Mechanical Engineering, Virginia Tech, 460 Old Turner Street, Blacksburg, Virginia 24061, USA
| | - Michael J Roan
- Department of Mechanical Engineering, Virginia Tech, 460 Old Turner Street, Blacksburg, Virginia 24061, USA
| | - Chen Ming
- Department of Neuroscience, Brown University, 185 Meeting Street, Providence, Rhode Island 02912, USA
| | - James A Simmons
- Department of Neuroscience, Brown University, 185 Meeting Street, Providence, Rhode Island 02912, USA
| | - Ruihao Wang
- Department of Mechanical Engineering, Virginia Tech, 460 Old Turner Street, Blacksburg, Virginia 24061, USA
| | - Rolf Müller
- Department of Mechanical Engineering, Virginia Tech, 460 Old Turner Street, Blacksburg, Virginia 24061, USA
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Bou Mansour C, Koreman E, Steckel J, Peremans H, Vanderelst D. Avoidance of non-localizable obstacles in echolocating bats: A robotic model. PLoS Comput Biol 2019; 15:e1007550. [PMID: 31856162 PMCID: PMC6941896 DOI: 10.1371/journal.pcbi.1007550] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 01/03/2020] [Accepted: 11/17/2019] [Indexed: 12/02/2022] Open
Abstract
Most objects and vegetation making up the habitats of echolocating bats return a multitude of overlapping echoes. Recent evidence suggests that the limited temporal and spatial resolution of bio-sonar prevents bats from separately perceiving the objects giving rise to these overlapping echoes. Therefore, bats often operate under conditions where their ability to localize obstacles is severely limited. Nevertheless, bats excel at avoiding complex obstacles. In this paper, we present a robotic model of bat obstacle avoidance using interaural level differences and distance to the nearest obstacle as the minimal set of cues. In contrast to previous robotic models of bats, the current robot does not attempt to localize obstacles. We evaluate two obstacle avoidance strategies. First, the Fixed Head Strategy keeps the acoustic gaze direction aligned with the direction of flight. Second, the Delayed Linear Adaptive Law (DLAL) Strategy uses acoustic gaze scanning, as observed in hunting bats. Acoustic gaze scanning has been suggested to aid the bat in hunting for prey. Here, we evaluate its adaptive value for obstacle avoidance when obstacles can not be localized. The robot's obstacle avoidance performance is assessed in two environments mimicking (highly cluttered) experimental setups commonly used in behavioral experiments: a rectangular arena containing multiple complex cylindrical reflecting surfaces and a corridor lined with complex reflecting surfaces. The results indicate that distance to the nearest object and interaural level differences allows steering the robot clear of obstacles in environments that return non-localizable echoes. Furthermore, we found that using acoustic gaze scanning reduced performance, suggesting that gaze scanning might not be beneficial under conditions where the animal has limited access to angular information, which is in line with behavioral evidence.
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Affiliation(s)
- Carl Bou Mansour
- Department of Psychology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Elijah Koreman
- Department of Computer Science, Cornell University, Ithaca, New York, United States of America
| | - Jan Steckel
- Constrained Systems Lab, University of Antwerp, Antwerp, Belgium
| | - Herbert Peremans
- Department of Engineering Management, University of Antwerp, Antwerp, Belgium
| | - Dieter Vanderelst
- Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio, United States of America
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Smith AB, Pacini AF, Nachtigall PE, Laule GE, Aragones LV, Magno C, Suarez LJA. Transmission beam pattern and dynamics of a spinner dolphin (Stenella longirostris). THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 145:3595. [PMID: 31255135 DOI: 10.1121/1.5111347] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
Toothed whales possess a sophisticated biosonar system by which ultrasonic clicks are projected in a highly directional transmission beam. Beam directivity is an important biosonar characteristic that reduces acoustic clutter and increases the acoustic detection range. This study measured click characteristics and the transmission beam pattern from a small odontocete, the spinner dolphin (Stenella longirostis). A formerly stranded individual was rehabilitated and trained to station underwater in front of a 16-element hydrophone array. On-axis clicks showed a mean duration of 20.1 μs, with mean peak and centroid frequencies of 58 and 64 kHz [standard deviation (s.d.) ±30 and ±12 kHz], respectively. Clicks were projected in an oval, vertically compressed beam, with mean vertical and horizontal beamwidths of 14.5° (s.d. ± 3.9) and 16.3° (s.d. ± 4.6), respectively. Directivity indices ranged from 14.9 to 27.4 dB, with a mean of 21.7 dB, although this likely represents a broader beam than what is normally produced by wild individuals. A click subset with characteristics more similar to those described for wild individuals exhibited a mean directivity index of 23.3 dB. Although one of the broadest transmission beams described for a dolphin, it is similar to other small bodied odontocetes.
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Affiliation(s)
- Adam B Smith
- Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, Hawaii 96744, USA
| | - Aude F Pacini
- Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, Hawaii 96744, USA
| | - Paul E Nachtigall
- Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Kaneohe, Hawaii 96744, USA
| | - Gail E Laule
- Ocean Adventure, Camayan Wharf, West Ilanin Forest, Subic Bay Freeport Zone, Philippines
| | - Lemnuel V Aragones
- Institute of Environmental Science and Meteorology, University of the Philippines, Diliman, Quezon City, Philippines
| | - Carlo Magno
- Ocean Adventure, Camayan Wharf, West Ilanin Forest, Subic Bay Freeport Zone, Philippines
| | - Leo J A Suarez
- Ocean Adventure, Camayan Wharf, West Ilanin Forest, Subic Bay Freeport Zone, Philippines
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Amichai E, Tal S, Boonman A, Yovel Y. Ultrasound Imaging Reveals Accelerated In-utero Development of a Sensory Apparatus in Echolocating Bats. Sci Rep 2019; 9:5275. [PMID: 30918299 PMCID: PMC6437157 DOI: 10.1038/s41598-019-41715-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 03/14/2019] [Indexed: 11/16/2022] Open
Abstract
Organ development, both in-utero and after birth, follows a different path for every organ depending upon how early the newborn will use it. Perception of the environment using echolocation occurs very early in the life of neonatal bats. In nostril-emitting echolocating bats of the families Hipposideridae and Rhinolophidae, the shape and area of the nasal-horseshoe is crucial for echolocation emission. We therefore hypothesized that most of this organ’s ontogeny will be completed in-utero while skull and wings will develop slower and continue their growth after birth. We used intrauterine ultrasonography of pregnant females, and measured newborn Asellia tridens (Hipposideridae) to test our hypothesis at different stages of ontogeny. We found that horseshoe development is completed in-utero and neonates begin emitting precursor echolocation calls already two days after birth. In contrast, skull and forearm only develop to 70% and 40% of adult size (respectively), and continue development after birth.
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Affiliation(s)
- Eran Amichai
- School of Zoology, Tel Aviv University, Tel Aviv-Yafo, Israel.
| | - Smadar Tal
- School of Zoology, Tel Aviv University, Tel Aviv-Yafo, Israel.,Koret School of Veterinary Medicine, The Hebrew University, Jerusalem, Israel
| | - Arjan Boonman
- School of Zoology, Tel Aviv University, Tel Aviv-Yafo, Israel
| | - Yossi Yovel
- School of Zoology, Tel Aviv University, Tel Aviv-Yafo, Israel. .,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv-Yafo, Israel.
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30
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Bat Pass Duration Measurement: An Indirect Measure of Distance of Detection. DIVERSITY 2019. [DOI: 10.3390/d11030047] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Few reports have been published on detection distances of bat calls because the evaluation of detection distance is complicated. Several of the approaches used to measure detection distances are based on the researcher’s experience and judgment. More recently, multiple microphones have been used to model flight path. In this study, the validity of a low-cost and simple detectability metric was tested. We hypothesize that the duration of an echolocating-bat-pass within the area of an ultrasonic bat detector is correlated with the distance of detection. Two independent datasets from a large-scale acoustic bat survey—a total of 25,786 bat-passes from 20 taxa (18 species and two genera)—were measured. We found a strong relationship between these measures of bat-pass duration and published detection distances. The advantages of bat-pass duration measures are that, for each study, experimenters easily produce their own proxy for the distance of detection. This indirect measure of the distance of detection could be mobilized to monitor the loss in microphone sensitivity used to monitor long-term population trends. Finally, the possibility of producing an index for distance of detection provides a weight for each bat species’ activity when they are aggregated to produce a bat community metric, such as the widely used “total activity”.
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Gordon R, Ivens S, Ammerman LK, Fenton MB, Littlefair JE, Ratcliffe JM, Clare EL. Molecular diet analysis finds an insectivorous desert bat community dominated by resource sharing despite diverse echolocation and foraging strategies. Ecol Evol 2019; 9:3117-3129. [PMID: 30962885 PMCID: PMC6434550 DOI: 10.1002/ece3.4896] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 12/12/2018] [Accepted: 12/13/2018] [Indexed: 01/05/2023] Open
Abstract
Interspecific differences in traits can alter the relative niche use of species within the same environment. Bats provide an excellent model to study niche use because they use a wide variety of behavioral, acoustic, and morphological traits that may lead to multi-species, functional groups. Predatory bats have been classified by their foraging location (edge, clutter, open space), ability to use aerial hawking or substrate gleaning and echolocation call design and flexibility, all of which may dictate their prey use. For example, high frequency, broadband calls do not travel far but offer high object resolution while high intensity, low frequency calls travel further but provide lower resolution. Because these behaviors can be flexible, four behavioral categories have been proposed: (a) gleaning, (b) behaviorally flexible (gleaning and hawking), (c) clutter-tolerant hawking, and (d) open space hawking. Many recent studies of diet in bats use molecular tools to identify prey but mainly focus on one or two species in isolation; few studies provide evidence for substantial differences in prey use despite the many behavioral, acoustic, and morphological differences. Here, we analyze the diet of 17 sympatric species in the Chihuahuan desert and test the hypothesis that peak echolocation frequency and behavioral categories are linked to differences in diet. We find no significant correlation between dietary richness and echolocation peak frequency though it spanned close to 100 kHz across species. Our data, however, suggest that bats which use both gleaning and hawking strategies have the broadest diets and are most differentiated from clutter-tolerant aerial hawking species.
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Affiliation(s)
- Rowena Gordon
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonUK
| | - Sally Ivens
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonUK
| | | | - M. Brock Fenton
- Department of BiologyUniversity of Western OntarioLondonOntarioCanada
| | - Joanne E. Littlefair
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonUK
- Department of BiologyMcGill UniversityMontréalQuébecCanada
| | - John M. Ratcliffe
- Department of BiologyUniversity of Toronto MississaugaMississaugaOntarioCanada
| | - Elizabeth L. Clare
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonUK
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Jensen FH, Johnson M, Ladegaard M, Wisniewska DM, Madsen PT. Narrow Acoustic Field of View Drives Frequency Scaling in Toothed Whale Biosonar. Curr Biol 2018; 28:3878-3885.e3. [DOI: 10.1016/j.cub.2018.10.037] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 09/12/2018] [Accepted: 10/12/2018] [Indexed: 11/27/2022]
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Gupta AK, Webster D, Müller R. Entropy analysis of frequency and shape change in horseshoe bat biosonar. Phys Rev E 2018; 97:062402. [PMID: 30011434 DOI: 10.1103/physreve.97.062402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Indexed: 11/07/2022]
Abstract
Echolocating bats use ultrasonic pulses to collect information about their environments. Some of this information is encoded at the baffle structures-noseleaves (emission) and pinnae (reception)-that act as interfaces between the bats' biosonar systems and the external world. The baffle beam patterns encode the direction-dependent sensory information as a function of frequency and hence represent a view of the environment. To generate diverse views of the environment, the bats can vary beam patterns by changes to (1) the wavelengths of the pulses or (2) the baffle geometries. Here we compare the variability in sensory information encoded by just the use of frequency or baffle shape dynamics in horseshoe bats. For this, we use digital and physical prototypes of both noseleaf and pinnae. The beam patterns for all prototypes were either measured or numerically predicted. Entropy was used as a measure to compare variability as a measure of sensory information encoding capacity. It was found that new information was acquired as a result of shape dynamics. Furthermore, the overall variability available for information encoding was similar in the case of frequency or shape dynamics. Thus, shape dynamics allows the horseshoe bats to generate diverse views of the environment in the absence of broadband biosonar signals.
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Affiliation(s)
- Anupam K Gupta
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Dane Webster
- School of Visual Arts, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Rolf Müller
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA.,Shandong University-Virginia Tech International Laboratory, Shandong University, Jinan 250100, China
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A fully autonomous terrestrial bat-like acoustic robot. PLoS Comput Biol 2018; 14:e1006406. [PMID: 30188901 PMCID: PMC6126821 DOI: 10.1371/journal.pcbi.1006406] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 07/29/2018] [Indexed: 12/16/2022] Open
Abstract
Echolocating bats rely on active sound emission (echolocation) for mapping novel environments and navigating through them. Many theoretical frameworks have been suggested to explain how they do so, but few attempts have been made to build an actual robot that mimics their abilities. Here, we present the ‘Robat’—a fully autonomous bat-like terrestrial robot that relies on echolocation to move through a novel environment while mapping it solely based on sound. Using the echoes reflected from the environment, the Robat delineates the borders of objects it encounters, and classifies them using an artificial neural-network, thus creating a rich map of its environment. Unlike most previous attempts to apply sonar in robotics, we focus on a biological bat-like approach, which relies on a single emitter and two ears, and we apply a biological plausible signal processing approach to extract information about objects’ position and identity. Many animals are able of mapping a new environment even while moving through it for the first time. Bats can do this by emitting sound and extracting information from the echoes reflected from objects in their surroundings. In this study, we mimicked this ability by developing a robot that emits sound like a bat and analyzes the returning echoes to generate a map of space. Our Robat had an ultrasonic speaker mimicking the bat’s mouth and two ultrasonic microphones mimicking its ears. It moved autonomously through novel out-doors environments and mapped them using sound only. It was able to negotiate obstacles and move around them, to avoid dead-ends and even to recognize if the object in front of it is a plant or not. We show the great potential of using sound for future robotic applications.
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Penone C, Kerbiriou C, Julien JF, Marmet J, Le Viol I. Body size information in large-scale acoustic bat databases. PeerJ 2018; 6:e5370. [PMID: 30155347 PMCID: PMC6110253 DOI: 10.7717/peerj.5370] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 07/13/2018] [Indexed: 12/03/2022] Open
Abstract
Background Citizen monitoring programs using acoustic data have been useful for detecting population and community patterns. However, they have rarely been used to study broad scale patterns of species traits. We assessed the potential of acoustic data to detect broad scale patterns in body size. We compared geographical patterns in body size with acoustic signals in the bat species Pipistrellus pipistrellus. Given the correlation between body size and acoustic characteristics, we expected to see similar results when analyzing the relationships of body size and acoustic signals with climatic variables. Methods We assessed body size using forearm length measurements of 1,359 bats, captured by mist nets in France. For acoustic analyses, we used an extensive dataset collected through the French citizen bat survey. We isolated each bat echolocation call (n = 4,783) and performed automatic measures of signals, including the frequency of the flattest part of the calls (characteristic frequency). We then examined the relationship between forearm length, characteristic frequencies, and two components resulting from principal component analysis for geographic (latitude, longitude) and climatic variables. Results Forearm length was positively correlated with higher precipitation, lower seasonality, and lower temperatures. Lower characteristic frequencies (i.e., larger body size) were mostly related to lower temperatures and northern latitudes. While conducted on different datasets, the two analyses provided congruent results. Discussion Acoustic data from citizen science programs can thus be useful for the detection of large-scale patterns in body size. This first analysis offers a new perspective for the use of large acoustic databases to explore biological patterns and to address both theoretical and applied questions.
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Affiliation(s)
- Caterina Penone
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Christian Kerbiriou
- CESCO UMR7204 MNHN-UPMC-CNRS-Sorbonne Université, Université Pierre et Marie Curie (Paris VI), Paris, France.,Marine Station, Muséum national d'Histoire naturelle, Concarneau, France
| | - Jean-François Julien
- CESCO UMR7204 MNHN-UPMC-CNRS-Sorbonne Université, Muséum national d'Histoire naturelle, Paris, France
| | - Julie Marmet
- CESCO UMR7204 MNHN-UPMC-CNRS-Sorbonne Université, Muséum national d'Histoire naturelle, Paris, France
| | - Isabelle Le Viol
- Marine Station, Muséum national d'Histoire naturelle, Concarneau, France.,CESCO UMR7204 MNHN-UPMC-CNRS-Sorbonne Université, Muséum national d'Histoire naturelle, Paris, France
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Volodin IA, Panyutina AA, Abramov AV, Ilchenko OG, Volodina EV. Ultrasonic bouts of a blind climbing rodent (Typhlomys chapensis): acoustic analysis. BIOACOUSTICS 2018. [DOI: 10.1080/09524622.2018.1509374] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Ilya A. Volodin
- Department of Vertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
- Scientific Research Department, Moscow Zoo, Moscow, Russia
| | | | - Alexei V. Abramov
- Zoological Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Joint Vietnam–Russian Tropical Research and Technological Centre, Nguyen Van Huyen, Hanoi, Vietnam
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Vanderelst D, Peremans H. Modeling bat prey capture in echolocating bats: The feasibility of reactive pursuit. J Theor Biol 2018; 456:305-314. [PMID: 30102889 DOI: 10.1016/j.jtbi.2018.07.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 07/07/2018] [Accepted: 07/22/2018] [Indexed: 10/28/2022]
Abstract
Echolocating bats are the only mammals engaging in airborne pursuit. In this paper, we implement a reactive model of sonar based prey pursuit in bats. Our simulations include a realistic prey localization mechanism as well as a model of the bat's motor behavior. In contrast to previous work, our model incorporates bats' ability to execute rapid saccadic scanning motions keeping the prey within its field of view. Decoupling the flight direction from the gaze direction allows our model to capture erratically moving prey using reactive control. We conclude that the rapid shifts in gaze direction allow bats to deal with the narrow field of view provided by their sonar system.
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38
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Martin MJ, Gridley T, Elwen SH, Jensen FH. Heaviside's dolphins ( Cephalorhynchus heavisidii) relax acoustic crypsis to increase communication range. Proc Biol Sci 2018; 285:rspb.2018.1178. [PMID: 30051842 DOI: 10.1098/rspb.2018.1178] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 06/26/2018] [Indexed: 11/12/2022] Open
Abstract
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.
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Affiliation(s)
- Morgan J Martin
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, c/o Sea Search Research and Conservation NPC, 4 Bath Rd, Cape Town 7945, South Africa
| | - Tess Gridley
- Centre for Statistics in Ecology, Environment and Conservation, Department of Statistical Sciences, University of Cape Town, c/o Sea Search Research and Conservation NPC, 4 Bath Rd, Cape Town 7945, South Africa
| | - Simon H Elwen
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, c/o Sea Search Research and Conservation NPC, 4 Bath Rd, Cape Town 7945, South Africa
| | - Frants H Jensen
- Aarhus Institute of Advanced Studies, Aarhus University, 8000 Aarhus C, Denmark.,Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543, USA
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39
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Ratcliffe J, Jakobsen L. Don’t believe the mike: behavioural, directional, and environmental impacts on recorded bat echolocation call measures. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0219] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Echolocation calls produced by bats in their larynges allow these flying, nocturnal mammals to orient and find food at night. The acoustic signals are not like bird song, and even individual bats exhibit great flexibility in call design and between-species overlap is common. As a result, identifying bats to species by their echolocation calls even in communities with few bat species can be difficult. Unfortunately, the situation is worse still. As a result of several factors — some to do with microphones, some with environment, some with bats, and the calls themselves — acoustic information transmitted to and transduced by microphones can be dramatically different from the actual signal produced by the bat and as would be recorded on axis, close to its mouth using ideal microphones under ideal conditions. We outline some of these pitfalls and discuss ways to make the best of a bad situation. Overall, however, we stress that many of these factors cannot be ignored and do impact our recordings.
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Affiliation(s)
- J.M. Ratcliffe
- Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, ON L5L 1C6, Canada
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
| | - L. Jakobsen
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark
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Jakobsen L, Hallam J, Moss CF, Hedenström A. Directionality of nose-emitted echolocation calls from bats without a nose leaf ( Plecotus auritus). ACTA ACUST UNITED AC 2018; 221:jeb.171926. [PMID: 29222128 DOI: 10.1242/jeb.171926] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 12/06/2017] [Indexed: 11/20/2022]
Abstract
All echolocating bats and whales measured to date emit a directional bio-sonar beam that affords them a number of advantages over an omni-directional beam, i.e. reduced clutter, increased source level and inherent directional information. In this study, we investigated the importance of directional sound emission for navigation through echolocation by measuring the sonar beam of brown long-eared bats, Plecotus auritusPlecotus auritus emits sound through the nostrils but has no external appendages to readily facilitate a directional sound emission as found in most nose emitters. The study shows that P. auritus, despite lacking an external focusing apparatus, emits a directional echolocation beam (directivity index=13 dB) and that the beam is more directional vertically (-6 dB angle at 22 deg) than horizontally (-6 dB angle at 35 deg). Using a simple numerical model, we found that the recorded emission pattern is achievable if P. auritus emits sound through the nostrils as well as the mouth. The study thus supports the hypothesis that a directional echolocation beam is important for perception through echolocation and we propose that animals with similarly non-directional emitter characteristics may facilitate a directional sound emission by emitting sound through both the nostrils and the mouth.
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Affiliation(s)
- Lasse Jakobsen
- Centre for BioRobotics, Department of Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - John Hallam
- Centre for BioRobotics, Maersk McKinney Moller Institute, University of Southern Denmark, DK-5230 Odense M, Denmark
| | | | - Anders Hedenström
- Centre for Animal Movement Research, Department of Biology, Lund University, 223 62 Lund, Sweden
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Russo D, Ancillotto L, Jones G. Bats are still not birds in the digital era: echolocation call variation and why it matters for bat species identification. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0089] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The recording and analysis of echolocation calls are fundamental methods used to study bat distribution, ecology, and behavior. However, the goal of identifying bats in flight from their echolocation calls is not always possible. Unlike bird songs, bat calls show large variation that often makes identification challenging. The problem has not been fully overcome by modern digital-based hardware and software for bat call recording and analysis. Besides providing fundamental insights into bat physiology, ecology, and behavior, a better understanding of call variation is therefore crucial to best recognize limits and perspectives of call classification. We provide a comprehensive overview of sources of interspecific and intraspecific echolocation call variations, illustrating its adaptive significance and highlighting gaps in knowledge. We remark that further research is needed to better comprehend call variation and control for it more effectively in sound analysis. Despite the state-of-art technology in this field, combining acoustic surveys with capture and roost search, as well as limiting identification to species with distinctive calls, still represent the safest way of conducting bat surveys.
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Affiliation(s)
- Danilo Russo
- Wildlife Research Unit, Dipartimento di Agraria, Università degli Studi di Napoli Federico II, 80055 Portici, Italy
- School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, United Kingdom
| | - Leonardo Ancillotto
- Wildlife Research Unit, Dipartimento di Agraria, Università degli Studi di Napoli Federico II, 80055 Portici, Italy
| | - Gareth Jones
- School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, United Kingdom
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Müller R. Quantitative approaches to sensory information encoding by bat noseleaves and pinnae. CAN J ZOOL 2018. [DOI: 10.1139/cjz-2017-0117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The biosonar systems of horseshoe bats (Rhinolophidae) and Old World round leaf-nosed bats (Hipposideridae) incorporate a pervasive dynamic at the interfaces for ultrasound emission (noseleaves) and reception (pinnae). Changes in the shapes of these structures alter the acoustic characteristics of the biosonar system and could hence influence the encoding of sensory information. The focus of the present work is on approaches that can be used to investigate the hypothesis that the interface dynamic effects sensory information encoding. Mutual information can be used as a metric to quantify the extent to which the different ultrasonic emission and reception characteristics (beampatterns) provide independent views of the environment. Two different quantitative approaches have been taken to evaluate the relationship between dynamically encoded additional sensory information and sensing performance in finding the direction of a biosonar target. The first approach is to determine an upper bound on the number of different directions that can be distinguished by virtue of distinct spectral signatures. The second approach is based on a lower bound (Cramér–Rao) on the variance of direction estimates. All these different metrics demonstrate that the peripheral dynamics seen in bats result in the encoding of additional sensory information that is suitable for enhancing biosonar performance.
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Affiliation(s)
- Rolf Müller
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA; Shandong University – Virginia Tech International Laboratory, Shandong University, Jinan, People’s Republic of China
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA; Shandong University – Virginia Tech International Laboratory, Shandong University, Jinan, People’s Republic of China
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Todd BD, Müller R. A comparison of the role of beamwidth in biological and engineered sonar. BIOINSPIRATION & BIOMIMETICS 2017; 13:016014. [PMID: 29130894 DOI: 10.1088/1748-3190/aa9a0f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Sonar is an important sensory modality for engineers as well as in nature. In engineering, sonar is the dominating modality for underwater sensing. In nature, biosonar is likely to have been a central factor behind the unprecedented evolutionary success of bats, a highly diverse group that accounts for over 20% of all mammal species. However, it remains unclear to what extent engineered and biosonar follow similar design and operational principles. In the current work, the key sonar design characteristic of beamwidth is examined in technical and biosonar. To this end, beamwidth data has been obtained for 23 engineered sonar systems and from numerical beampattern predictions for 151 emission and reception elements (noseleaves and ears) representing bat biosonar. Beamwidth data from these sources is compared to the beamwidth of a planar ellipsoidal transducer as a reference. The results show that engineered and biological both obey the basic physical limit on beamwidth as a function of the ratio of aperture size and wavelength. However, beyond that, the beamwidth data revealed very different behaviors between the engineered and the biological sonar systems. Whereas the beamwidths of the technical sonar systems were very close to the planar transducer limit, the biological samples showed a very wide scatter away from this limit. This scatter was as large, if not wider, than what was seen in a small reference data set obtained with random aluminum cones. A possible interpretation of these differences in the variability could be that whereas sonar engineers try to minimize beamwidth subject to constraints on device size, the evolutionary optimization of bat biosonar beampatterns has been directed at other factors that have left beamwidth as a byproduct. Alternatively, the biosonar systems may require beamwidth values that are larger than the physical limit and differ between species and their sensory ecological niches.
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Affiliation(s)
- Bryan D Todd
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, United States of America
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Lee WJ, Falk B, Chiu C, Krishnan A, Arbour JH, Moss CF. Tongue-driven sonar beam steering by a lingual-echolocating fruit bat. PLoS Biol 2017; 15:e2003148. [PMID: 29244805 PMCID: PMC5774845 DOI: 10.1371/journal.pbio.2003148] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Revised: 01/19/2018] [Accepted: 11/22/2017] [Indexed: 11/19/2022] Open
Abstract
Animals enhance sensory acquisition from a specific direction by movements of head, ears, or eyes. As active sensing animals, echolocating bats also aim their directional sonar beam to selectively “illuminate” a confined volume of space, facilitating efficient information processing by reducing echo interference and clutter. Such sonar beam control is generally achieved by head movements or shape changes of the sound-emitting mouth or nose. However, lingual-echolocating Egyptian fruit bats, Rousettus aegyptiacus, which produce sound by clicking their tongue, can dramatically change beam direction at very short temporal intervals without visible morphological changes. The mechanism supporting this capability has remained a mystery. Here, we measured signals from free-flying Egyptian fruit bats and discovered a systematic angular sweep of beam focus across increasing frequency. This unusual signal structure has not been observed in other animals and cannot be explained by the conventional and widely-used “piston model” that describes the emission pattern of other bat species. Through modeling, we show that the observed beam features can be captured by an array of tongue-driven sound sources located along the side of the mouth, and that the sonar beam direction can be steered parsimoniously by inducing changes to the pattern of phase differences through moving tongue location. The effects are broadly similar to those found in a phased array—an engineering design widely found in human-made sonar systems that enables beam direction changes without changes in the physical transducer assembly. Our study reveals an intriguing parallel between biology and human engineering in solving problems in fundamentally similar ways. It is well known that animals move their eyes, ears, and heads towards stimuli of interest to selectively gather information in complex environments. Interestingly, lingual-echolocating fruit bats, which generate sonar signals for object localization by clicking their tongues, can rapidly switch the direction of the sonar beam without changing head aim or mouth shape. The mechanism underlying this capability has intrigued scientists and engineers alike. In this study, we used a combination of experimental measurements and theoretical modeling to solve this mystery. We discovered that the focus of this bat’s sound beam shifts systematically across a range of angles as the sonar frequency increases. This unusual multi-frequency structure can be captured by modeling the sound emission as an array of sound sources located along the side of the mouth and driven by the clicking tongue. Changing only the position of the tongue in this model can steer the sonar beam in different directions, showing an effect broadly similar to that found in a human-made sonar phased array—a design that enables changing beam direction without changing the physical transducer assembly. Our study thus reveals an intriguing parallel between biology and human engineering, which arrived at fundamentally similar solutions to the same problem.
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Affiliation(s)
- Wu-Jung Lee
- Applied Physics Laboratory, University of Washington, Seattle, Washington, United States of America
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
| | - Benjamin Falk
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Chen Chiu
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Anand Krishnan
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
- Indian Institute of Science Education and Research (IISER) Pune, Pune, Maharashtra, India
| | - Jessica H. Arbour
- Department of Biology, University of Washington, Seattle, Washington, United States of America
| | - Cynthia F. Moss
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
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Greif S, Zsebők S, Schmieder D, Siemers BM. Acoustic mirrors as sensory traps for bats. Science 2017; 357:1045-1047. [PMID: 28883074 DOI: 10.1126/science.aam7817] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 08/01/2017] [Indexed: 11/02/2022]
Abstract
Sensory traps pose a considerable and often fatal risk for animals, leading them to misinterpret their environment. Bats predominantly rely on their echolocation system to forage, orientate, and navigate. We found that bats can mistake smooth, vertical surfaces as clear flight paths, repeatedly colliding with them, likely as a result of their acoustic mirror properties. The probability of collision is influenced by the number of echolocation calls and by the amount of time spent in front of the surface. The echolocation call analysis corroborates that bats perceive smooth, vertical surfaces as open flyways. Reporting on occurrences with different species in the wild, we argue that it is necessary to more closely monitor potentially dangerous locations with acoustic mirror properties (such as glass fronts) to assess the true frequency of fatalities around these sensory traps.
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Affiliation(s)
- Stefan Greif
- Sensory Ecology Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany. .,Department of Zoology, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Sándor Zsebők
- Sensory Ecology Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | - Daniela Schmieder
- Sensory Ecology Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | - Björn M Siemers
- Sensory Ecology Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
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Thiagavel J, Santana SE, Ratcliffe JM. Body Size Predicts Echolocation Call Peak Frequency Better than Gape Height in Vespertilionid Bats. Sci Rep 2017; 7:828. [PMID: 28400604 PMCID: PMC5429766 DOI: 10.1038/s41598-017-00959-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 03/20/2017] [Indexed: 11/09/2022] Open
Abstract
In most vocalizing vertebrates, lighter animals tend to produce acoustic signals of higher frequency than heavier animals. Two hypotheses propose to explain this negative relationship in vespertilionid bats: (i) mass-signal frequency allometry and (ii) emitter-limited (maximum gape) signal directionality. The first hypothesis, that lighter bats with smaller larynges are constrained to calls with higher frequencies, is supported at the species level. The second hypothesis proposes that in open space, small bats use higher frequencies to achieve narrow sonar beams, as beam directionality increases with both emitter size (maximum gape) and signal frequency. This hypothesis is supported within a comparative context but remains untested beyond a few species. We analyzed gape, body mass, and echolocation data under a phylogenetic comparative framework to test these hypotheses, and considered forearm length as both a proxy for wing design and an alternative measure of bat size. Controlling for mass, we found no support for the directionality hypothesis. Body mass and relative forearm length were negatively related to open space echolocation call peak frequency, reflecting species-specific size differences, but also the influence of wing design and preferred foraging habitat on size-independent species-specific differences in echolocation call design.
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Affiliation(s)
- Jeneni Thiagavel
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Sharlene E Santana
- Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, USA
| | - John M Ratcliffe
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada.
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48
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Yamada Y, Hiryu S, Watanabe Y. Species-specific control of acoustic gaze by echolocating bats, Rhinolophus ferrumequinum nippon and Pipistrellus abramus, during flight. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2016; 202:791-801. [PMID: 27566319 PMCID: PMC5061877 DOI: 10.1007/s00359-016-1121-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 08/13/2016] [Accepted: 08/18/2016] [Indexed: 12/19/2022]
Abstract
Based on the characteristics of the ultrasounds they produce, echolocating bats can be categorized into two main types: broadband FM (frequency modulated) and narrowband CF (constant frequency) echolocators. In this study, we recorded the echolocation behavior of a broadband FM (Pipistrellus abramus) and a narrowband CF echolocator species (Rhinolophus ferrumequinum nippon) while they explored an unfamiliar space in a laboratory chamber. During flight, P. abramus smoothly shifted its acoustic gaze in relation to its flight direction, whereas R. ferrumequinum nippon frequently shifted its acoustic gaze from side to side. The distribution of the acoustic gazes of R. ferrumequinum nippon was twice as wide as that of P. abramus. Furthermore, R. ferrumequinum nippon produced double pulses twice as often as P. abramus. Because R. ferrumequinum nippon has a horizontal beam width (−6 dB off-axis angle) half as wide (±20.8 ± 6.0°) as that of P. abramus (±38.3 ± 6.0°), it appears to double the width of its acoustical field of view by shifting its acoustic gaze further off-axis and emitting direction-shifted double pulses. These results suggest that broadband FM and narrowband CF bats actively control their acoustic gazes in a species-specific manner based on the acoustic features of their echolocation signals.
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Affiliation(s)
- Yasufumi Yamada
- Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, 610-0321, Japan
| | - Shizuko Hiryu
- Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, 610-0321, Japan. .,JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan.
| | - Yoshiaki Watanabe
- Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, 610-0321, Japan
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Vanderelst D, Steckel J, Boen A, Peremans H, Holderied MW. Place recognition using batlike sonar. eLife 2016; 5:e14188. [PMID: 27481189 PMCID: PMC4970868 DOI: 10.7554/elife.14188] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 06/20/2016] [Indexed: 11/28/2022] Open
Abstract
Echolocating bats have excellent spatial memory and are able to navigate to salient locations using bio-sonar. Navigating and route-following require animals to recognize places. Currently, it is mostly unknown how bats recognize places using echolocation. In this paper, we propose template based place recognition might underlie sonar-based navigation in bats. Under this hypothesis, bats recognize places by remembering their echo signature - rather than their 3D layout. Using a large body of ensonification data collected in three different habitats, we test the viability of this hypothesis assessing two critical properties of the proposed echo signatures: (1) they can be uniquely classified and (2) they vary continuously across space. Based on the results presented, we conclude that the proposed echo signatures satisfy both criteria. We discuss how these two properties of the echo signatures can support navigation and building a cognitive map.
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Affiliation(s)
- Dieter Vanderelst
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
- Active Perception Lab, University of Antwerp, Antwerp, Belgium
| | - Jan Steckel
- Active Perception Lab, University of Antwerp, Antwerp, Belgium
- Constrained Systems Lab, Faculty of Applied Engineering, University of Antwerp, Antwerp, Belgium
| | - Andre Boen
- Active Perception Lab, University of Antwerp, Antwerp, Belgium
| | | | - Marc W Holderied
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
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Treitler JT, Heim O, Tschapka M, Jung K. The effect of local land use and loss of forests on bats and nocturnal insects. Ecol Evol 2016; 6:4289-97. [PMID: 27386075 PMCID: PMC4930980 DOI: 10.1002/ece3.2160] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/31/2016] [Accepted: 04/13/2016] [Indexed: 12/04/2022] Open
Abstract
Land‐use intensification at local and landscape level poses a serious threat to biodiversity and affects species interactions and ecosystem function. It is thus important to understand how interrelated taxa respond to land‐use intensification and to consider the importance of different spatial scales. We investigated whether and how local land‐use intensity and landscape features affect the predator–prey interaction of bats and insects. Bats and nocturnal insects were assessed on 50 grassland sites in the Schorfheide‐Chorin. We analyzed the effect of local land use and distance to forested areas as a proxy for site accessibility on bats and insects and their biological interaction measured in bat's feeding activity. Insect abundance increased with higher land‐use intensity, while size and diversity of insects decreased. In contrast, bat activity, diversity, and species composition were determined by the distance to forested areas and only slightly by land‐use intensity. Feeding attempts of bats increased with higher insect abundance and diversity but decreased with insect size and distance to forested areas. Finally, our results revealed that near forested areas, the number of feeding attempts was much lower on grassland sites with high, compared to those with low land‐use intensity. In contrast, far from forests, the feeding attempts did not differ significantly between intensively and extensively managed grassland sites. We conclude that the two interrelated taxa, bats and insects, respond to land‐use intensification on very different scales. While insects respond to local land use, bats are rather influenced by surrounding landscape matrix. Hereby, proximity to forests reveals to be a prerequisite for higher bat species diversity and a higher rate of feeding attempts within the area. However, proximity to forest is not sufficient to compensate local high land‐use intensity. Thus, local land‐use intensification in combination with a loss of forest remnants weakens the interaction of bats and insects.
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Affiliation(s)
- Julia T Treitler
- Evolutionary Ecology and Conservation Genomics University Ulm Ulm Germany; Present address: RG Ecology and Environmental Education Institute of Biology and Chemistry University of Hildesheim Hildesheim Germany
| | - Olga Heim
- Evolutionary Ecology and Conservation Genomics University Ulm Ulm Germany; Present address: Leibniz Institute for Zoo- and Wildlife Research (IZW) Berlin Germany
| | - Marco Tschapka
- Evolutionary Ecology and Conservation Genomics University Ulm Ulm Germany; Smithsonian Tropical Research Institute Balboa Panama
| | - Kirsten Jung
- Evolutionary Ecology and Conservation Genomics University Ulm Ulm Germany
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