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Kofiau’s terrestrial mammal fauna shares many taxa with oceanic islands lying close to New Guinea. Its fauna is distinctive in possessing a mixture of Moluccan near-endemics, such as Pteropus chrysoproctus, along with Melanesian species, like Dobsonia beauforti, that reach their westernmost limit on Kofiau. Very little has been published on the terrestrial vertebrate fauna on Kofiau compared to the adjacent islands. This paper presents two surveys of the terrestrial mammal fauna of Kofiau Island, undertaken in 2011 and 2019, increasing the number of species recorded from the island from 1 to 20: one rodent, two marsupials and 17 bats. Wiantoro, Sigit, Tim F. Flannery, Dan Brown, Kyle N. Armstrong, and Kristofer M. Helgen. 2023. The mammal fauna of Kofiau Island, off western New Guinea. In Contributions to Mammalogy and Zooarchaeology of Wallacea, ed. K. M. Helgen and R. K. Jones. Records of the Australian Museum 75(5): 653–662.

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. [ABSTRACT FROM AUTHOR]

Ecological interactions, including competition, predation, and environmental conditions, may significantly impact acoustic signalling behaviour. Here we characterise nocturnal signalling patterns in the bladder grasshopper Bullacris unicolor and relate this to biotic and abiotic factors, thus providing insights into ecological drivers of acoustic signalling behaviour. Passive acoustic recorders monitored nocturnal calling activity of the focal species, competitors, and predatory bats across the distribution of B. unicolor. Results indicate that B. unicolor calls preferentially at certain times of the night, but that peak activity period varies across the geographic range. There was a strong relationship between B. unicolor activity and bat activity. Bullacris unicolor populations further north showed an overall avoidance of bat echolocation call period, whereas further south an overlapping of call periods between B. unicolor and bat echolocation was observed. Bats at northern sites showed a distinct activity period early in the night and B. unicolor may thus reduce predation risk by shifting signalling activity to later in the night. In contrast, bats were active throughout the night at southern sites and B. unicolor did not delay calling activity in this region of its distribution, although the species did shift signalling slightly to reduce peak overlap with co-existing pneumorid species. [ABSTRACT FROM AUTHOR]

Albert S.-H. Feng was an outstanding family man and brilliant scientist, with a creative mind, a gift for dealing with people of all types, and a warm, personable demeanor. He was blessed with many talents, making him a sought-after colleague and collaborator. His love for people and travel took him to many destinations around the world where he studied the neuroethology of frog and bat communication both in the field and in the lab. He has made many fundamental contributions to our understanding of the vertebrate auditory system. These include characterizing the "delay-tuned" neurons in the bat midbrain underlying target detection, and in discovering several terrestrial amphibians in which the upper limit of hearing extends well into the ultrasonic range, forever changing our long-held perception of frogs as "low-frequency animals". [ABSTRACT FROM AUTHOR]

Background: Various mammalian species emit ultrasonic vocalizations (USVs), which reflect their emotional state and mediate social interactions. USVs are usually analyzed by manual or semi-automated methodologies that categorize discrete USVs according to their structure in the frequency-time domains. This laborious analysis hinders the effective use of USVs as a readout for high-throughput analysis of behavioral changes in animals. Results: Here we present a novel automated open-source tool that utilizes a different approach towards USV analysis, termed TrackUSF. To validate TrackUSF, we analyzed calls from different animal species, namely mice, rats, and bats, recorded in various settings and compared the results with a manual analysis by a trained observer. We found that TrackUSF detected the majority of USVs, with less than 1% of false-positive detections. We then employed TrackUSF to analyze social vocalizations in Shank3-deficient rats, a rat model of autism, and revealed that these vocalizations exhibit a spectrum of deviations from appetitive calls towards aversive calls. Conclusions: TrackUSF is a simple and easy-to-use system that may be used for a high-throughput comparison of ultrasonic vocalizations between groups of animals of any kind in any setting, with no prior assumptions. [ABSTRACT FROM AUTHOR]

The rapid control of a sonar-guided vehicle to pursue a goal while avoiding obstacles has been a persistent research topic for decades. Taking into account the limited field-of-view of practical sonar systems and vehicle kinematics, we propose a neural model for obstacle avoidance that maps the 2-D sensory space into a 1-D motor space and evaluates motor actions while combining obstacles and goal information. A two-stage winner-take-all (WTA) mechanism is used to select the final steering action. To avoid excessive scanning of the environment, an attentional system is proposed to control the directions of sonar pings for efficient, task-driven, sensory data collection. A mobile robot was used to test the proposed model navigating through a cluttered environment using a narrow field-of-view sonar system. We further propose a spiking neural model using spike-timing representations, a spike-latency memory, and a "race-to-first-spike" WTA circuit. [ABSTRACT FROM AUTHOR]

The rapid control of a sonar-guided vehicle to pursue a goal while avoiding obstacles has been a persistent research topic for decades. Taking into account the limited field-of-view of practical sonar systems and vehicle kinematics, we propose a neural model for obstacle avoidance that maps the 2-D sensory space into a 1-D motor space and evaluates motor actions while combining obstacles and goal information. A two-stage winner-take-all (WTA) mechanism is used to select the final steering action. To avoid excessive scanning of the environment, an attentional system is proposed to control the directions of sonar pings for efficient, task-driven, sensory data collection. A mobile robot was used to test the proposed model navigating through a cluttered environment using a narrow field-of-view sonar system. We further propose a spiking neural model using spike-timing representations, a spike-latency memory, and a “race-to-first-spike” WTA circuit.

Acoustic recording is rarely applied in studying Philippine bats, which is reflected by the scarcity of related publications in the country. As a result, the echolocation calls of many local bat species are still unknown, and a reliable bat call library does not exist. Here, we described the echolocation call of some insectivorous bats in Polillo Island and used the call characteristics to define each species. We captured and recorded the echolocation calls of cave-dwelling bats in Puting Bato Cave 5 in October and November 2019. Using Bat Sound, we measured the spectral and temporal call characteristics and determined the call structure and duty cycle of all recorded individuals. Then, we applied multivariate discriminant function analysis (DFA) to classify the calls into species and identify the call parameter with the highest discriminating power. In total, we recorded 104 individual bats from five species belonging to four families. All species from families Miniopteridae and Vespertilionidae produced steep frequency-modulated (FM) sweeps, while the species belonging to families Hipposideridae and Rhinolophidae emitted calls with constant frequency and FM components. Among the recorded species, Hipposideros coronatus had the highest peak frequency record (> 150 kHz), while Myotis macrotarsus had the lowest (< 40 kHz). Meanwhile, the longest call duration was recorded from Rhinolophus arcuatus (> 40 ms), while Miniopterus paululus produced the shortest call (< 3 ms). The DFA perfectly classified the calls into the correct species and peak frequency was the most important predictor among the call parameters measured. Our results provide strong evidence that insectivorous bats in Puting Bato Cave 5 produce species-specific echolocation calls, and acoustic recording can be a reliable method to enhance research on these cave-dwelling bats. [ABSTRACT FROM AUTHOR]

The ability of "target tracking," such as keeping a target object in sight, is crucial for various activities. However, most sensing systems experience a certain degree of delay due to information processing, which challenges accurate target tracking. The long history of studies on animal behavior has revealed several tactics for it, although a systematic understanding of how individual tactics are combined into a strategy has not been reached. This study demonstrates a multifaceted tracking strategy in animals, which mitigates the adverse delay effects with small implementation costs. Using an active-sensing bat to measure their sensing state while chasing natural prey, we found that bats use a tracking strategy by combining multiple echolocation and flight tactics. The three echolocation tactics, namely the predictive control of sensing direction accompanied by adjusting the sensing rate and angular range, produce a direct compensation effect. Simultaneously, the flight tactic, the counter maneuver, assists echolocation by stabilizing the target direction. Our simulation results demonstrate that these combined tactics improve tracking accuracy over a wide range of delay constraints. In addition, a concise rule based on the angular velocity between bats and targets explains how bats control these tactics, suggesting that bats successfully reduce the burden of multitasking management. Our findings reveal the sophisticated strategy in animals' tracking systems and provide insights into understanding and developing efficiently integrated strategies in target tracking across various disciplines. [Display omitted] • Bats concurrently deploy three echolocation tactics and a flight tactic for tracking • These echolocation and flight tactics were combined to improve tracking accuracy • A single kinematic parameter possibly explains the control of these four tactics • We proposed a framework for how bats integrate these tactics Target tracking is an essential ability for various behavioral contexts. Nishiumi et al. reveal that bats use a combination of several echolocation and flight tactics to effectively track agilely fleeing targets under information delay constraints. They also identify the specific roles of each tactic and propose a control scheme for these tactics. [ABSTRACT FROM AUTHOR]

Most insectivorous bat species in the Neotropical family Phyllostomidae glean insects from ground, water or vegetation surfaces. They use similar and stereotypical echolocation calls that are generally very short (less than 1–3 ms), multi-harmonic and frequency-modulated (FM). By contrast, the common sword-nosed bat, Lonchorhina aurita, which has the longest noseleaf in the entire phyllostomid family, produces distinctly different echolocation calls. They are composed of a constant frequency (CF) component with a peak frequency of 45 kHz, followed by a short FM down-sweep at the end. With a mean call duration of 6.6 ms (max. 8.7 ms) when flying in the open they have the longest echolocation calls reported from phyllostomid bats. In cluttered environments, the CF-component is very short. In open habitats, however, L. aurita can emit pure CF-calls without the terminal FM-component. We also recorded in the field a distinct terminal group that closely resembles the feeding buzzes of aerial hawking bat species from other bat families. This is the first time the echolocation call design of L. aurita is presented. In addition, we contrast the echolocation behaviour of individuals flying in open and confined situations. Our results suggest that the unique echolocation system of L. aurita represents an adaptation to aerial hawking, a very unusual hunting mode within the phyllostomid family.

To study sensorimotor behaviour in wild animals, it is necessary to synchronously record the sensory inputs available to the animal, and its movements. To do this, we have developed a biologging device that can record the primary sensory information and the associated movements during foraging and navigating in echolocating bats.This 2.6‐g tag records the sonar calls and echoes from an ultrasonic microphone, while simultaneously sampling fine‐scale movement in three dimensions from wideband accelerometers and magnetometers. In this study, we tested the tag on an European noctula Nyctalus noctula during target approaches and on four big brown bats Eptesicus fuscus during prey interception in a flight room.We show that the tag records both the outgoing calls and echoes returning from objects at biologically relevant distances. Inertial sensor data enables the detection of behavioural events such as flying, turning, and resting. In addition, individual wing‐beats can be tracked and synchronized to the bat's sound emissions to study the coordination of different motor events.By recording the primary acoustic flow of bats concomitant with associated behaviours on a very fine time‐scale, this type of biologging method will foster a deeper understanding of how sensory inputs guide feeding behaviours in the wild. [ABSTRACT FROM AUTHOR]

Highlights • The paper describes a computational model of prey pursuit in echolocating bats, the only mammals to hunt on the wing. • In contrast to earlier work, we model head movements observed in bats. • The responsiveness of the gaze direction allows bats to pursue and capture insects using reactive control. 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. [ABSTRACT FROM AUTHOR]

The acoustic arms race between insectivorous bats and their invertebrate prey has led to the convergent evolution of ultrasound hearing in seven orders of nocturnal insects. Upon hearing the echolocation calls of an approaching bat, such insects take defensive action. Here, we document a previously unknown sense of ultrasound hearing and phonotactic flight behaviour in the neuropteran family Myrmeleontidae (antlions). The antlion Myrmeleon hyalinus was presented with sound pulses at ultrasonic frequencies used by echolocating bats and its response thresholds in tethered flight determined. Behaviours included abdominal twitches, wing flicks, brief pauses in flight and flight cessation. Such behaviours create erratic evasive flight manoeuvres in other eared insects, particularly mantids and lacewings. Antlions responded best to ultrasound between 60 and 80 kHz (75 dB peSPL at 80 kHz), showing response thresholds similar to those of the related lacewings (Neuroptera, Chrysopidae). Yet, at lower ultrasonic frequencies (20-50 kHz), antlions were far less sensitive than lacewings. Based on calculated response distances, we conclude that antlions respond only after having been detected by bats rather than using early evasive flights. We argue that the high response threshold for lowfrequency ultrasound is adaptive for an insect that is mainly active close to and within vegetation, because a behavioural response to the lower ultrasonic frequencies used by high-flying bats would result in evasive action in the absence of actual predation risk. [ABSTRACT FROM AUTHOR]

Molossops temminckii is the only species of the Molossidae capable of exploring background-cluttered space. We tested the hypothesis that M. temminckii uses the clutter rejection strategy in cluttered environments and determined whether the echolocation calls of this species show large-scale geographic variation. We recorded echolocation calls of 10 individuals of M. temminckii using 4 treatments with different degrees of clutter. We compared individuals recorded in Venezuela with individuals recorded in Brazil to verify geographic variation in calls. In the cluttered environments, M. temminckii emitted short downward frequency-modulated calls with short pulse intervals. In the uncluttered environments, M. temminckii emitted long upward frequency-modulated calls with longer intervals and shorter bandwidth. The decreased pulse duration and interval in cluttered environments support the hypothesis that M. temminckii uses the clutter rejection strategy. Additionally, we found that in Brazil, M. temminckii emits shorter calls with higher minimum frequency compared with bats recorded in Venezuela, indicating large-scale geographic variation, probably because of environmental factors. Molossops temminckii é a única espécie de Molossidae com capacidade de explorar áreas com obstáculos de fundo. Nesse trabalho testamos a hipótese do uso da estratégia de rejeição de obstáculo em ambientes fechados, e determinamos se há variação geográfica de larga escala nos chamados de ecolocalização de M. temminckii. Gravamos 10 indivíduos, em 4 tratamentos, com diferentes graus de obstáculos. Comparamos os chamados de ecolocalização gravados na Venezuela e Brasil para verificar a variação geográfica. Em ambientes com obstáculos, M. temminckii emite chamados curtos, de frequência modulada descendente, com intervalos curtos entre os chamados. Nos ambientes abertos, emite chamados longos, de frequência modulada ascendente, com intervalos mais longos e menor largura de banda. A menor duração e o menor intervalo em ambientes fechados suportam a hipótese que M. temminckii utiliza a estratégia de rejeição de obstáculo. No Brasil, M. temminckii emite chamados mais curtos, com frequência mínima mais alta, em comparação com os morcegos gravados na Venezuela. Esse fato indica variação geográfica de larga escala e fatores ambientais provavelmente contribuem para essa variação. [ABSTRACT FROM AUTHOR]

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„.

Big brown bats ( Eptesicus fuscus) emit frequency-modulated (FM) biosonar sounds containing two or more harmonic sweeps. Echoes from frontally located targets arrive with first and second harmonics intact, leading to focused delay images. Echoes from offside or distant objects arrive with the second harmonic relatively weaker (lowpass-filtered), leading to defocused images, which prevents their clutter interference effects (Bates et al. J Exp Biol 214:394-401, ). Realistic targets contain several glints at slightly different distances and reflect several echoes at correspondingly different delays. The bat registers the delay of the nearest glint's echoes in the time domain. The delays of echoes from the farther glints are registered in the frequency domain, from interference nulls in the spectrum. Lowpass-filtering of echoes directly affects the image of the nearest glint by defocusing the delay image. However, lowpass-filtering also is superimposed on the interference spectrum used to register the farther glints, which distorts the pattern of interference nulls, defocusing the farther glints inversely, in the spectral domain, before they are perceived as delays. Differences in blurring between time-domain and frequency-domain parts of images identifies separate computational paths to perceptually reconstruct objects and prevent interference from off-side or distant clutter. [ABSTRACT FROM AUTHOR]

The big brown bat, Eptesicus fuscus, uses echolocation for orientation and foraging, and scans its surroundings by aiming its sonar beam at obstacles and prey. All call parameters are highly adaptable and determine the bat's acoustic field of view and hence its perception of the echo scene. The intensity (source level) and directionality of the emitted calls directly contribute to the bat's acoustic field of view; however, the source level and directionality of the big brown bat's sonar signals have not been measured in the field. In addition, for bats, navigation and prey capture require that they process several streams of acoustic information. By using stereotypic flight paths in known areas, bats may be able to reduce the sensory processing load for orientation and therefore allocate echo processing resources to prey. Herewe recorded the echolocation calls from foraging E. fuscus in the field with a microphone array and estimated call intensity and directionality, based on reconstructed flight trajectories. The source levels were intense with an average maximum source level of 138 dB (root mean square re. 20 µPa at 0.1 m). Furthermore, measurements taken from a subset of calls indicate that the echolocation signals in the fieldmay be more directional than estimated in the laboratory (halfamplitude angle 30 deg at 35 kHz). We also observed that E. fuscus appear to followstereotypic flight paths, and propose that this could be a strategy to optimize foraging efficiency by minimizing the sensory processing load. [ABSTRACT FROM AUTHOR]

In their natural environment, big brown bats forage for small insects in open spaces, as well as in vegetation and in the presence of acoustic clutter. While searching and hunting for prey, bats experience sonar interference, not only from densely cluttered environments, but also from calls of conspecifics foraging in close proximity. Previous work has shown that when two bats compete for a single prey item in a relatively open environment, one of the bats may go silent for extended periods of time, which can serve to minimize sonar interference between conspecifics. Additionally, pairs of big brown bats have been shown to adjust frequency characteristics of their vocalizations to avoid acoustic interference in echo processing. In this study, we extended previous work by examining how the presence of conspecifics and environmental clutter influence the bat's echolocation behavior. By recording multichannel audio and video data of bats engaged in insect capture in open and cluttered spaces, we quantified the bats' vocal and flight behaviors. Big brown bats flew individually and in pairs in an open and cluttered room, and the results of this study shed light on the different strategies that this species employs to negotiate a complex and dynamic environment. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We assessed the behavioral flexibility of the trawling long-legged bat, Macrophyllum macrophyllum (Phyllostomidae) in flight cage experiments by exposing it to prey suspended from nylon threads in the air and to food placed onto the water surface at varying distances to clutter-producing background (water plants). The bat revealed flexibility in foraging mode and caught prey in the air (aerial hawking) and from the water surface (trawling). M. macrophyllum was constrained in finding food very near to and within clutter. As echolocation was the prime sensory mode used by M. macrophyllum for detection and localization of food, the bat might have been unable to perceive sufficient information from prey near clutter as background echoes from the water plant increasingly overlapped with echoes from food. The importance of echolocation for foraging is reflected in a stereotypic call pattern of M. macrophyllum that resembles other aerial insectivorous and trawling bats with a pronounced terminal phase (buzz) prior to capture attempts. Our findings contrast studies of other phyllostomid bats that glean prey very near or from vegetation, often using additional sensory cues, such as prey-produced noise, to find food and that lack a terminal phase in echolocation behavior. In M. macrophyllum, acoustic characteristics of its foraging habitat have shaped its sonar system more than phylogeny.

One of the most efficient mechanisms to optimize signal-to-noise ratios is the Lombard effect - an involuntary rise in call amplitude due to ambient noise. It is often accompanied by changes in the spectro-temporal composition of calls. We examined the effects of broadband-filtered noise on the spectro-temporal composition of horseshoe bat echolocation calls, which consist of a constant-frequency component and initial and terminal frequency-modulated components. We found that the frequency-modulated components became larger for almost all noise conditions, whereas the bandwidth of the constant-frequency component increased only when broadband-filtered noise was centered on or above the calls' dominant or fundamental frequency. This indicates that ambient noise independently modifies the associated acoustic parameters of the Lombard effect, such as spectro-temporal features, and could significantly affect the bat's ability to detect and locate targets. Our findings may be of significance in evaluating the impact of environmental noise on echolocation behavior in bats. [ABSTRACT FROM AUTHOR]

Bats echolocating in the natural environment face the formidable task of sorting signals from multiple auditory objects, echoes from obstacles, prey and the calls of conspecifics. Successful orientation in a complex environment depends on auditory information processing, along with adaptive vocal-motor behaviors and flight path control, which draw upon 3-D spatial perception, attention and memory. This article reviews field and laboratory studies that document adaptive sonar behaviors of echolocating bats, and point to the fundamental signal parameters they use to track and sort auditory objects in a dynamic environment. We suggest that adaptive sonar behavior provides a window to bats’ perception of complex auditory scenes.

Bats are among the few mammals that have acquired a sophisticated echolocation ability, attracting considerable attention for their uniqueness. Over the past 50 years, numerous research projects have been designed to study bat echolocation. The overall trend is complex and the dynamics of those publications are difficult to capture. In this study, we conducted quantitative bibliometric analyses of academic articles to identify global research trends in bat echolocation. Data were retrieved from the Web of Science , with 2914 articles sampled in our dataset from 1970 to 2021. We analyzed the global research trends in terms of annual publications, active journals, authors, institutions, and countries. We identified growth trends in the past 50 years, to which the United States was found to be the largest contributor. The University of Bristol, the University of Munich, and the Smithsonian Institute were the representative institutions of publication records. Meanwhile, Acta Chiropterologica, Journal of Experimental Biology , and Journal of the Acoustical Society of America were the top three active platforms for bat echolocation research. Co-occurrence analysis of keywords identified five clusters that correspond to five major research topics in bat echolocation: "habitat use and conservation," "evolution," "physiology and nervous system," "communication and social call," and "hunting and predation." The overlay visualization indicated that studies on the evolution of bat echolocation had become the latest research trend, which we summarized and reviewed. Lastly, based on the results obtained, we discussed the importance of future directions for integrative multi-omics studies to uncover the mechanisms and evolution of bat echolocation. • Bibliometric analyses of academic articles on bat echolocation were conducted. • Five research themes were identified by the co-occurrence of keywords. • Studies on the evolutionary aspects of bat echolocation are the latest trends. • We discuss the potential of integrative multi-omics studies in this field. [ABSTRACT FROM AUTHOR]

We assessed the behavioral flexibility of the trawling long-legged bat, Macrophyllum macrophyllum (Phyllostomidae) in flight cage experiments by exposing it to prey suspended from nylon threads in the air and to food placed onto the water surface at varying distances to clutter-producing background (water plants). The bat revealed flexibility in foraging mode and caught prey in the air (aerial hawking) and from the water surface (trawling). M. macrophyllum was constrained in finding food very near to and within clutter. As echolocation was the prime sensory mode used by M. macrophyllum for detection and localization of food, the bat might have been unable to perceive sufficient information from prey near clutter as background echoes from the water plant increasingly overlapped with echoes from food. The importance of echolocation for foraging is reflected in a stereotypic call pattern of M. macrophyllum that resembles other aerial insectivorous and trawling bats with a pronounced terminal phase (buzz) prior to capture attempts. Our findings contrast studies of other phyllostomid bats that glean prey very near or from vegetation, often using additional sensory cues, such as prey-produced noise, to find food and that lack a terminal phase in echolocation behavior. In M. macrophyllum, acoustic characteristics of its foraging habitat have shaped its sonar system more than phylogeny. [ABSTRACT FROM AUTHOR]

The big brown bat, Eptesicus fuscus, uses echolocation for foraging and orientation. The limited operating range of biosonar implies that bats must rely upon spatial memory in familiar spaces with dimensions larger than a few meters. Prior experiments with bats flying in obstacle arrays have revealed differences In flight and acoustic emission patterns depending on the density and spatial extent of the obstacles. Using the same method, combined with acoustic microphone array tracking, we flew big brown bats in an obstacle array that varied in density and distribution in different locations in the flight room. In the initial experiment, six bats learned Individually stereotyped flight patterns as they became familiar with the space. After the first day, the repetition rate of sonar broadcasts dropped to a stable level, consistent with low-density clutter. In a second experiment, after acquiring their stable paths, each bat was released from each of two unfamiliar locations in the room. Each bat still followed the same flight path it learned originally. In a third experiment, performed 1 month after the first two experiments, three of the bats were re-flown in the same configuration of obstacles; these three resumed flying in their accustomed path. The other three bats were flown in a mirror-image reconfiguration of the obstacles; these bats quickly found stable flight paths that differed from their originally learned paths. Overall, the flight patterns indicate that the bats perceive the cluttered space as a single scene through which they develop globally organized flight paths. [ABSTRACT FROM AUTHOR]

The performance of a sonar system is closely related to the marine environment and the target characteristics. When dealing with the echoes of a traditional active sonar system, the sonar designers often do not take into account the influence of the environmental information and prior knowledge perceived by sonar receivers, making it difficult to obtain desired processing results. Based on the basic principle and key technology of sonar, this paper proposed a cognition-based intelligent sonar system in theory-cognitive sonar. Cognitive sonar is capable of jointly optimizing the transmission waveform and receiver according to the changes of environment so that its detection and identification performance can be significantly improved. [ABSTRACT FROM AUTHOR]

Abstract: Today''s acoustic monitoring devices are capable of recording and storing tremendous amounts of data. Until recently, the classification of animal vocalizations from field recordings has been relegated to qualitative approaches. For large-scale acoustic monitoring studies, qualitative approaches are very time-consuming and suffer from the bias of subjectivity. Recent developments in supervised learning techniques can provide rapid, accurate, species-level classification of bioacoustics data. We compared the classification performances of four supervised learning techniques (random forests, support vector machines, artificial neural networks, and discriminant function analysis) for five different classification tasks using bat echolocation calls recorded by a popular frequency-division bat detector. We found that all classifiers performed similarly in terms of overall accuracy with the exception of discriminant function analysis, which had the lowest average performance metrics. Random forests had the advantage of high sensitivities, specificities, and predictive powers across the majority of classification tasks, and also provided metrics for determining the relative importance of call features in distinguishing between groups. Overall classification accuracy for each task was slightly lower than reported accuracies using calls recorded by time-expansion detectors. Myotis spp. were particularly difficult to separate; classifiers performed best when members of this genus were combined in genus-level classification and analyzed separately at the level of species. Additionally, we identified and ranked the relative contributions of all predictor features to classifier accuracy and found measurements of frequency, total call duration, and characteristic slope to be the most important contributors to classification success. We provide recommendations to maximize accuracy and efficiency when analyzing acoustic data, and suggest an application of automated bioacoustics monitoring to contribute to wildlife monitoring efforts. [Copyright &y& Elsevier]

In this article, we study the neural encoding of acoustic information for FM-bats (such as Eptesicus fuscus) in simulation. In echolocation research, the frequency–time sound representation as expressed by the spectrogram is often considered as input. The rationale behind this is that a similar representation is present in the cochlea, i.e. the receptor potential of the inner hair cells (IHC) along the length of the cochlea, and hence similar acoustic information is relayed to the brain. In this article, we study to what extent the latter assumption is true. The receptor potential is converted into neural activity of the synapting auditory nerve cells (ANC), and information might be lost in this conversion process. Especially for FM-bats, this information transmission is not trivial: in contrast to other mammals, they detect short transient signals, and consequently neural activity can only be integrated over very limited time intervals. To quantify the amount of information transmitted we design a neural network-based algorithm to reconstruct the IHC receptor potentials from the spiking activity of the synapting auditory neurons. Both the receptor potential and the resulting neural activity are simulated using Meddis’ peripheral model. Comparing the reconstruction to the IHC receptor potential, we quantify the information transmission of the bat hearing system and investigate how this depends on the intensity of the incoming signal, the distribution of auditory neurons, and previous masking stimulation (adaptation). In addition, we show how this approach allows to inspect which spectral features survive neural encoding and hence can be relevant for echolocation. [ABSTRACT FROM AUTHOR]