The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Yossi Yovel - One of the best experts on this subject based on the ideXlab platform.
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the benefits of insect swarm hunting to echolocating Bats and its influence on the evolution of Bat Echolocation signals
PLOS Computational Biology, 2019Co-Authors: Arjan Boonman, Brock Fenton, Yossi YovelAbstract: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.
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the benefits of insect swarm hunting in echolocating Bats and its influence on the evolution of Bat Echolocation signals
bioRxiv, 2019Co-Authors: Arjan Boonman, Yossi Yovel, Brock FentonAbstract: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 intensity of insect swarms of different size and density. We show that swarm echo intensity 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 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.
Jiang Feng - One of the best experts on this subject based on the ideXlab platform.
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Patterns and causes of geographic variation in Bat Echolocation pulses.
Integrative zoology, 2015Co-Authors: Tinglei Jiang, Jiang FengAbstract:Evolutionary biologists have a long-standing interest in how acoustic signals in animals vary geographically, because divergent ecology and sensory perception play an important role in speciation. Geographic comparisons are valuable in determining the factors that influence divergence of acoustic signals. Bats are social mammals and they depend mainly on Echolocation pulses to locate prey, to navigate and to communicate. Mounting evidence shows that geographic variation of Bat Echolocation pulses is common, with a mean 5-10 kHz differences in peak frequency, and a high level of individual variation may be nested in this geographical variation. However, understanding the geographic variation of Echolocation pulses in Bats is very difficult, because of differences in sample and statistical analysis techniques as well as the variety of factors shaping the vocal geographic evolution. Geographic differences in Echolocation pulses of Bats generally lack latitudinal, longitudinal and elevational patterns, and little is known about vocal dialects. Evidence is accumulating to support the fact that geographic variation in Echolocation pulses of Bats may be caused by genetic drift, cultural drift, ecological selection, sexual selection and social selection. Future studies could relate geographic differences in Echolocation pulses to social adaptation, vocal learning strategies and patterns of dispersal. In addition, new statistical techniques and acoustic playback experiments may help to illustrate the causes and consequences of the geographic evolution of Echolocation pulse in Bats.
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different auditory feedback control for Echolocation and communication in horseshoe Bats
PLOS ONE, 2013Co-Authors: Jiang Feng, Ying Liu, Walter MetznerAbstract:Auditory feedback from the animal's own voice is essential during Bat Echolocation: to optimize signal detection, Bats continuously adjust various call parameters in response to changing echo signals. Auditory feedback seems also necessary for controlling many Bat communication calls, although it remains unclear how auditory feedback control differs in Echolocation and communication. We tackled this question by analyzing Echolocation and communication in greater horseshoe Bats, whose Echolocation pulses are dominated by a constant frequency component that matches the frequency range they hear best. To maintain echoes within this “auditory fovea”, horseshoe Bats constantly adjust their Echolocation call frequency depending on the frequency of the returning echo signal. This Doppler-shift compensation (DSC) behavior represents one of the most precise forms of sensory-motor feedback known. We examined the variability of Echolocation pulses emitted at rest (resting frequencies, RFs) and one type of communication signal which resembles an Echolocation pulse but is much shorter (short constant frequency communication calls, SCFs) and produced only during social interactions. We found that while RFs varied from day to day, corroborating earlier studies in other constant frequency Bats, SCF-frequencies remained unchanged. In addition, RFs overlapped for some Bats whereas SCF-frequencies were always distinctly different. This indicates that auditory feedback during Echolocation changed with varying RFs but remained constant or may have been absent during emission of SCF calls for communication. This fundamentally different feedback mechanism for Echolocation and communication may have enabled these Bats to use SCF calls for individual recognition whereas they adjusted RF calls to accommodate the daily shifts of their auditory fovea.
Christia C Voig - One of the best experts on this subject based on the ideXlab platform.
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the use of automated identification of Bat Echolocation calls in acoustic monitoring a cautionary note for a sound analysis
Ecological Indicators, 2016Co-Authors: Danilo Russo, Christia C VoigAbstract:Abstract Bats are a species-rich order of mammals providing key ecosystem services. Because Bats are threatened by human action and also serve as important bioindicators, monitoring their populations is of utmost importance. However, surveying Bats is difficult because of their nocturnal habits, elusiveness and sensitivity to disturbance. Bat detectors allow echolocating Bats to be surveyed non-invasively and record species that would otherwise be difficult to observe by capture or roost inspection. Unfortunately, several Bat species cannot be identified confidently from their calls so acoustic classification remains ambiguous or impossible in some cases. The popularity of automated classifiers of Bat Echolocation calls has escalated rapidly, including that of several packages available on purchase. Such products have filled a vacant niche on the market mostly in relation to the expanding monitoring efforts related to the development of wind energy production worldwide. We highlight that no classifier has yet proven capable of providing correct classifications in 100% of cases or getting close enough to this ideal performance. Besides, from the literature available and our own experience we argue that such tools have not yet been tested sufficiently in the field. Visual inspection of calls whose automated classification is judged suspicious is often recommended, but human intervention a posteriori represents a circular argument and requires noticeable experience. We are concerned that neophytes – including consultants with little experience with Bats but specialized into other taxonomical groups – will accept passively automated responses of tools still awaiting sufficient validation. We remark that Bat call identification is a serious practical issue because biases in the assessment of Bat distribution or habitat preferences may lead to wrong management decisions with serious conservation consequences. Automated classifiers may crucially aid Bat research and certainly merit further investigations but the boost in commercially available software may have come too early. Thorough field tests need to be carried out to assess limitations and strengths of these tools.
Gareth Jones - One of the best experts on this subject based on the ideXlab platform.
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testing the performances of automated identification of Bat Echolocation calls a request for prudence
Ecological Indicators, 2017Co-Authors: Jens Rydell, Gareth Jones, Stefan Nyman, Johan S Eklof, Danilo RussoAbstract:Echolocating Bats are surveyed and studied acoustically with Bat detectors routinely and worldwide, yet identification of species from calls often remains ambiguous or impossible due to intraspecific call variation and/or interspecific overlap in call design. To overcome such difficulties and to reduce workload, automated classifiers of Echolocation calls have become popular, but their performance has not been tested sufficiently in the field. We examined the absolute performance of two commercially available programs (SonoChiro and Kaleidoscope) and one freeware package (BatClassify). We recorded noise from rain and calls of seven common Bat species with Pettersson real-time full spectrum detectors in Sweden. The programs could always (100%) distinguish rain from Bat calls, usually (68–100%) identify Bats to group (Nyctalus/Vespertilio/Eptesicus, Pipistrellus, Myotis, Plecotus, Barbastella) and usually (83–99%) recognize typical calls of some species whose Echolocation pulses are structurally distinct (Pipistrellus pygmaeus, Barbastella barbastellus). Species with less characteristic Echolocation calls were not identified reliably, including Vespertilio murinus (16–26%), Myotis spp. (4–93%) and Plecotus auritus (0–89%). All programs showed major although different shortcomings and the often poor performance raising serious concerns about the use of automated classifiers for identification to species level in research and surveys. We highlight the importance of validating output from automated classifiers, and restricting their use to specific situations where identification can be made with high confidence. For comparison we also present the result of a manual identification test on a random subset of the files used to test the programs. It showed a higher classification success but performances were still low for more problematic taxa.
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light emitting diode street lights reduce last ditch evasive manoeuvres by moths to Bat Echolocation calls
Royal Society Open Science, 2015Co-Authors: Andrew Wakefield, Gareth Jones, Emma Louise Stone, Stephen HarrisAbstract:The light-emitting diode (LED) street light market is expanding globally, and it is important to understand how LED lights affect wildlife populations. We compared evasive flight responses of moths to Bat Echolocation calls experimentally under LED-lit and -unlit conditions. Significantly, fewer moths performed ‘powerdive’ flight manoeuvres in response to Bat calls (feeding buzz sequences from Nyctalus spp.) under an LED street light than in the dark. LED street lights reduce the anti-predator behaviour of moths, shifting the balance in favour of their predators, aerial hawking Bats.
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using Echolocation calls to identify thai Bat species vespertilionidae emballonuridae nycteridae and megadermatidae
Acta Chiropterologica, 2011Co-Authors: Alice C Hughes, Gareth Jones, Chutamas Satasook, Paul J J Bates, Pipat Soisook, Tuanjit Sritongchuay, Sara BumrungsriAbstract:Variation in the acoustic structure of Bat Echolocation calls can often provide sufficient information for reliable and efficient species identification. The aim of this study was to investigate the use of Echolocation call structure to identify a number of Bats in the families Vespertilionidae, Emballonuridae, Nycteridae and Megadermatidae from Thailand. These species typically emit Echolocation calls with a frequency-modulated (FM) sweep dominating part or all of their calls. A total of 510 Echolocation calls from free-flying individuals were recorded throughout Thailand. According to the frequency-time spectra, these calls were categorized into four types: broadband FM (eight species), narrowband FM (seven species), long multiharmonic (four species) and short multiharmonic (three species). Discriminant function analysis was used to classify calls from individual Bats to species. Correct classification levels were 85.9% for individuals emitting broadband FM calls (six species with adequate sample sizes)...
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moth wing scales slightly increase the absorbance of Bat Echolocation calls
PLOS ONE, 2011Co-Authors: Jinyao Zeng, Gareth Jones, Ning Xiang, Lei Jiang, Yongmei Zheng, Bingwan Liu, Shuyi ZhangAbstract:Coevolutionary arms races between predators and prey can lead to a diverse range of foraging and defense strategies, such as countermeasures between nocturnal insects and echolocating Bats. Here, we show how the fine structure of wing scales may help moths by slightly increasing sound absorbance at frequencies typically used in Bat Echolocation. Using four widespread species of moths and butterflies, we found that moth scales are composed of honeycomb-like hollows similar to sound-absorbing material, but these were absent from butterfly scales. Micro-reverberation chamber experiments revealed that moth wings were more absorbent at the frequencies emitted by many echolocating Bats (40–60 kHz) than butterfly wings. Furthermore, moth wings lost absorbance at these frequencies when scales were removed, which suggests that some moths have evolved stealth tactics to reduce their conspicuousness to echolocating Bats. Although the benefits to moths are relatively small in terms of reducing their target strengths, scales may nonetheless confer survival advantages by reducing the detection distances of moths by Bats by 5–6%.
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The communicative potential of Bat Echolocation pulses
Journal of Comparative Physiology A, 2011Co-Authors: Gareth Jones, Björn M. SiemersAbstract:Ecological constraints often shape the Echolocation pulses emitted by Bat species. Consequently some (but not all) Bats emit species-specific Echolocation pulses. Because Echolocation pulses are often intense and emitted at high rates, they are potential targets for eavesdropping by other Bats. Echolocation pulses can also vary within species according to sex, body size, age, social group and geographic location. Whether these features can be recognised by other Bats can only be determined reliably by playback experiments, which have shown that Echolocation pulses do provide sufficient information for the identification of sex and individual in one species. Playbacks also show that Bats can locate conspecifics and heterospecifics at foraging and roost sites by eavesdropping on Echolocation pulses. Guilds of echolocating Bat species often partition their use of pulse frequencies. Ecology, allometric scaling and phylogeny play roles here, but are not sufficient to explain this partitioning. Evidence is accumulating to support the hypothesis that frequency partitioning evolved to facilitate intraspecific communication. Acoustic character displacement occurs in at least one instance. Future research can relate genetic population structure to regional variation in Echolocation pulse features and elucidate those acoustic features that most contribute to discrimination of individuals.
Hannah M Ter Hofstede - One of the best experts on this subject based on the ideXlab platform.
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from understory to canopy in situ behavior of neotropical forest katydids in response to Bat Echolocation calls
Frontiers in Ecology and Evolution, 2018Co-Authors: Laurel B Symes, Sharon J Martinson, Larsolaf Hoeger, Rachel A Page, Hannah M Ter HofstedeAbstract:Predator-prey interactions take place in complex environments, and research on the sensory ecology of predator-detection relies on understanding when, where, and how prey experience and respond to predator cues. Bats are significant nocturnal predators, and insects have evolved diverse strategies for avoiding predation by Bats. While it is well-known that insects exhibit anti-Bat strategies, from avoidance flight to reduced acoustic signaling, the specific conditions that elicit some of these behaviors are less well-known. To illuminate how insects respond to Bats in nature, we studied how calling behavior changed when katydids experienced Echolocation calls in a Neotropical forest. The diverse Neotropical Bat community includes species that eavesdrop on prey sounds, such as the songs produced by male katydids. Previous research has shown that some katydid species respond to Echolocation calls by reducing acoustic signaling. To capture the interactions of Bats and katydids, we placed acoustic monitors at 8, 16, and 24 meters in 10 locations in the forest on Barro Colorado Island, Panama and recorded continuously for 24 hours at each location. We randomly selected 250 recordings with Echolocation calls and compared the acoustic spectrum of the forest before a Bat arrived, when a Bat was present, and after the Bat was no longer detectable. We tested whether the response to Bat calls changes with height, the family of Bat producing the calls, the duration of the Echolocation sequence, call amplitude, and call peak frequency. Bats appeared on ~50% of nighttime recordings, but Echolocation calls that could have been produced by eavesdropping Bats were rare (<4% of calls). Insect response to Bats was nuanced and context-dependent. Despite the rarity of truly dangerous predator cues, Echolocation decreased insect sound at several frequencies and heights. Insect response was not uniform, and in many cases Echolocation calls had little effect on insect activity, perhaps reflecting the fact that Echolocation calls were an inconsistent cue for the presence of eavesdropping Bats. These nuanced responses raise interesting questions about predator detection in noise and provide valuable context for laboratory investigations on the sensory ecology of how individual prey species respond to predator cues.
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the influence of Bat Echolocation call duration and timing on auditory encoding of predator distance in noctuoid moths
The Journal of Experimental Biology, 2018Co-Authors: Shira D Gordon, Hannah M Ter HofstedeAbstract:ABSTRACT Animals co-occur with multiple predators, making sensory systems that can encode information about diverse predators advantageous. Moths in the families Noctuidae and Erebidae have ears with two auditory receptor cells (A1 and A2) used to detect the Echolocation calls of predatory Bats. Bat communities contain species that vary in Echolocation call duration, and the dynamic range of A1 is limited by the duration of sound, suggesting that A1 provides less information about Bats with shorter Echolocation calls. To test this hypothesis, we obtained intensity–response functions for both receptor cells across many moth species for sound pulse durations representing the range of Echolocation call durations produced by Bat species in northeastern North America. We found that the threshold and dynamic range of both cells varied with sound pulse duration. The number of A1 action potentials per sound pulse increases linearly with increasing amplitude for long-duration pulses, saturating near the A2 threshold. For short sound pulses, however, A1 saturates with only a few action potentials per pulse at amplitudes far lower than the A2 threshold for both single sound pulses and pulse sequences typical of searching or approaching Bats. Neural adaptation was only evident in response to approaching Bat sequences at high amplitudes, not search-phase sequences. These results show that, for short Echolocation calls, a large range of sound levels cannot be coded by moth auditory receptor activity, resulting in no information about the distance of a Bat, although differences in activity between ears might provide information about direction.
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an aerial hawking Bat uses stealth Echolocation to counter moth hearing
Current Biology, 2010Co-Authors: Holger R Goerlitz, Gareth Jones, Hannah M Ter Hofstede, Matt R K Zeale, Marc W HolderiedAbstract:Ears evolved in many nocturnal insects, including some moths, to detect Bat Echolocation calls and evade capture [1, 2]. Although there is evidence that some Bats emit Echolocation calls that are inconspicuous to eared moths, it is difficult to determine whether this was an adaptation to moth hearing or originally evolved for a different purpose [2, 3]. Aerial-hawking Bats generally emit high-amplitude Echolocation calls to maximize detection range [4, 5]. Here we present the first example of an Echolocation counterstrategy to overcome prey hearing at the cost of reduced detection distance. We combined comparative Bat flight-path tracking and moth neurophysiology with fecal DNA analysis to show that the barbastelle, Barbastella barbastellus, emits calls that are 10 to 100 times lower in amplitude than those of other aerial-hawking Bats, remains undetected by moths until close, and captures mainly eared moths. Model calculations demonstrate that only Bats emitting such low-amplitude calls hear moth echoes before their calls are conspicuous to moths. This stealth Echolocation allows the barbastelle to exploit food resources that are difficult to catch for other aerial-hawking Bats emitting calls of greater amplitude.
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auditory based defence against gleaning Bats in neotropical katydids orthoptera tettigoniidae
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2010Co-Authors: Hannah M Ter Hofstede, Elisabeth K V Kalko, James H FullardAbstract:Neotropical katydids (Orthoptera: Tettigoniidae) are preyed on by gleaning Bats, which are known to use male calling songs to locate them. At least one katydid species has been reported to stop singing in response to Bat Echolocation calls. To investigate the relationship between this behavioural defence and ecological and sensory factors, we surveyed calling song characteristics, song cessation in response to the Echolocation calls of a sympatric gleaning Bat (Trachops cirrhosus), and T-cell responses (an auditory interneuron sensitive to ultrasound) in five katydid species from Panama. The two katydid species that stopped singing in response to Bat calls (Balboa tibialis and Ischnomela gracilis, Pseudophyllinae) also had the highest T-cell spike number and rate in response to these stimuli. The third pseudophylline species (Docidocercus gigliotosi) did not reliably cease singing and had low T-cell spiking activity. Neoconocephalus affinis (Copiphorinae) produced continuous calling song, possibly preventing males from hearing the Bat during singing, and did not show a behavioural response despite high T-cell activity in response to Bat calls. Steirodon rufolineatum (Phaneropterinae) did not cease singing and differed in T-cell activity compared to the other species. T-cell function might not be conserved in katydids, and evidence for this idea is discussed.