Human Echolocation

Echolocation was a key development in toothed whale evolution, favoring their ecological success and adaptive radiation across multiple habitats. Previous bioacoustic and morphological studies suggest that environmental pressures have influenced the evolution of echolocation in odontocetes. This hypothesis demands further investigation, especially regarding molecular mechanisms involved in odontocetes' adaptive radiation across multiple habitats. Here we show that the coding sequences of four hearing genes involved in echolocation (CDH23, SLC26A5, TMC1 and CLDN14) have different signatures of molecular evolution among riverine, coastal and oceanic dolphins, suggesting that the evolutionary constraints of these habitats have shaped the genetic diversity underlying toothed whale sonars. Our comparative analysis across 37 odontocete species has revealed patterns of accelerated evolution within coastal and riverine lineages, supporting the hypothesis that these habitats generate specific selective pressures to sonar propagation, which are not found in the ocean (e.g., clutter and reverberation). Specific branches with sites under diversifying selection include: three coastal/estuarine species which have recently diverged from closely-related lineages inhabiting freshwater (Cephalorhynchus commersonii, Sotalia guianensis and Orcaella heinsohni -CDH23), and three species that operate specialized Narrow Band High Frequency Sonars (Phocoena sinus -SLC26A5, Neophocaena phocaenoides and Cephalorhynchus commersonii -CDH23). All positively selected lineages are coastal or estuarine from shallow waters (< 100), corroborating current knowledge on these species' sonars. Among river dolphin branches, positive selection was found on specific sites of the genes CDH23 and SLC26A5, when compared to other cetaceans and Laurasiatherians. Finally, the detection of sites with different overall substitution rates (dN/dS) among river and marine dolphins, together with the finding of different amounts of positively selected sites in each environmental group, suggests distinct selective pressures acting in these groups in the molecular evolution of echolocation. 1 .

Vocalizations play a crucial role in the social systems of many animals and may inadvertently reveal behavioural characteristics of the sender. Bats, the second largest mammalian order, rely extensively on vocalizations owing to their nocturnal lifestyle and complex social systems, making them ideal for studying links between vocalizations and consistent behavioural traits. In this study, we developed a new testing regime to investigate whether consistent individual vocalization differences in nectarivorous bats are associated with specific behavioural types. We exposed 60 wild, male Glossophaga soricina handleyi bats to novel and risky stressors and assessed their behavioural and vocal responses. Proactive, exploratory and bold bats were more likely to produce social calls, and among the vocalizing bats, more agitated bats produced higher numbers of social calls. We thus show that bat vocalization behaviour can be indicative of a certain behavioural type, potentially allowing conspecifics to assess personalities from a distance, which in turn could impact subsequent social interactions, group dynamics and reproductive success. Our results, in combination with previous findings in birds, suggest that advertent or inadvertent longdistance broadcasting of personality may be widespread, thus opening up new exciting questions about the links between vocalizations and sociality.

• We investigate fractal scaling behavior in two aspects of dolphin echolocation. • We employ two widely used fractal analysis methods and compare their results. • Results indicate persistent fractal scaling in both echolocation measures. • Possible explanations for observed between-subject differences are discussed.

• We investigate fractal scaling behavior in two aspects of dolphin echolocation. • We employ two widely used fractal analysis methods and compare their results. • Results indicate persistent fractal scaling in both echolocation measures. • Possible explanations for observed between-subject differences are discussed.

Bat echolocation is an ability consisting of many subtasks such as navigation, prey detection and object recognition. Understanding the echolocation capabilities of bats comes down to isolating the minimal set of acoustic cues needed to complete each task. For some tasks, the minimal cues have already been identified. However, while a number of possible cues have been suggested, little is known about the minimal cues supporting obstacle avoidance in echolocating bats. In this paper, we propose that the Interaural Intensity Difference (IID) and travel time of the first millisecond of the echo train are sufficient cues for obstacle avoidance. We describe a simple control algorithm based on the use of these cues in combination with alternating ear positions modeled after the constant frequency bat Rhinolophus rouxii. Using spatial simulations (2D and 3D), we show that simple phonotaxis can steer a bat clear from obstacles without performing a reconstruction of the 3D layout of the scene. As such, this paper presents the first computationally explicit explanation for obstacle avoidance validated in complex simulated environments. Based on additional simulations modelling the FM bat Phyllostomus discolor, we conjecture that the proposed cues can be exploited by constant frequency (CF) bats and frequency modulated (FM) bats alike. We hypothesize that using a low level yet robust cue for obstacle avoidance allows bats to comply with the hard real-time constraints of this basic behaviour.

Aerial-hawking bats searching the sky for prey face the problem that flight and echolocation exert independent and possibly conflicting influences on call intervals. These bats can only exploit their full echolocation range unambiguously if they emit their next call when all echoes from the preceding call would have arrived. However, not every call interval is equally available. The need to reduce the high energetic costs of echolocation forces aerial-hawking bats to couple call emission to their wingbeat. We compared the wingbeat periods of 11 aerial-hawking bat species with the delays of the last-expected echoes. Acoustic flight-path tracking was employed to measure the source levels (SLs) of echolocation calls in the field. SLs were very high, extending the known range to 133 dB peak equivalent sound pressure level. We calculated the maximum detection distances for insects, larger flying objects and background targets. Wingbeat periods were derived from call intervals. Small and medium-sized bats in fact matched their maximum detection range for insects and larger flying targets to their wingbeat period. The tendency to skip calls correlated with the species' detection range for background targets. We argue that a species' call frequency is at such a pitch that the resulting detection range matches their wingbeat period.

Modern advances in acoustic technology have made possible new and broad ranges of research in bioacoustics, particularly with regard to echolocating bats. In the present study we present an acoustic guide to the calls of 15 species of bats in the Arava (rift valley), Israel, with a focus on their bioacoustics, habitat use and explaining differences between similar species. We also describe a potential case of frequency separation where four bat species using six call types appear to separate the frequencies of their calls to minimise overlap. The studied community of bat species is also found in other Middle Eastern deserts including the deserts of Jordan, Syria and Saudi Arabia and we hope that data gathered will benefit other bat researchers in the region.

Nectar-feeding glossophagine bats searching for flowers are guided by their echolocation system as well as olfactory cues in detecting and recognizing nectar sources. Therefore, chiropterophilous plants, which depend on these bats as pollinators, may be expected to have evolved acoustically conspicuous flowers that facilitate detection. As it is poorly understood how bats manage to find and recognize flowers acoustically, we investigated the echoes of some of the flowers pollinated by bats. Echoes of bell-shaped bat-pollinated flowers have characteristic features with respect to the echoes they reflect to a calling bat and differ from the echoes of leaves or other objects in their surroundings: the echoes are comparatively long and of complex spectral composition. Owing to the specific shape of the flowers, characteristic 'spectral directional patterns' result when the spectra of the echoes are plotted against the angle of sound incidence. We suggest that bats are able to recognize such flowers -and probably other objects as well -not only by a characteristic spectral composition of the echo but also by comparing sequential echoes, at the same time taking into account their exact calling position relative to the object.

Many animals use social cues to find refuges. Bats can find roosts using the echolocation and social calls of conspecifics, but they might also use scent cues, a possibility which is less studied. The entrances of bat roosts are often marked by guano and urine, providing possible scent cues. We conducted eight experiments to test whether bats use the scent of guano and urine to find potential roosts. In field experiments, we tested ifMolossus molossus(velvety free-tailed bats) in Panama andEptesicus fuscus(big brown bats) in Ohio would investigate artificial roost boxes that were scented with guano and urine more often than a paired unscented control. We did not detect any difference in flights near the scented versus unscented roosts, and we detected only one entrance into any artificial roost (scented). In six captive experiments, we tested for the attraction ofDesmodus rotundus(common vampire bats) andMolossus molossusto areas scented with guano and urine, under several condition...

In a false killer whale Pseudorca crassidens, echo perception thresholds were measured using a go/no-go psychophysical paradigm and one-up-one-down staircase procedure. Electronically synthesized echoes were triggered by whale-emitted echolocation pulses, and the echo amplitudes were presented proportional to the triggering biosonar pulse amplitudes, thus imitating the basic feature of real target echoes. Echo thresholds were measured in terms of attenuation relative to the source level of the biosonar pulses. The echo threshold dependence on echo delay was investigated. With increasing echo delay, the threshold echo attenuation decreased from -49.3 dB at 2 ms to -79.5 dB at 16 ms, with a regression slope of -31.5 dB per delay decade. At delays longer than 16 ms, the threshold remained nearly constant around -80.4 dB. This echo threshold dependence on delay is interpreted as a release from forward masking by the preceding emitted pulse. This release may well compensate for the echo level decrease with distance which is from 20 to 40 dB per distance decade, depending on target properties.

For forty years, there has been growing uncertainty about whether Hill&#39;s horseshoe bat (Rhinolophus hilli) still persists in Nyungwe National Park, Rwanda. Only known from one small area within the National Park, R. hilli is listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN) based on its extremely small geographic range and presumed low number of mature individuals. Here, we present and describe bat species occurrence data contributed to the Global Biodiversity Information Facility (GBIF) that we collected as part of a long-term collaborative project to rediscover this lost species. This data paper describes the conservation relevance, survey methods, and findings resulting from cave roost surveys, capture surveys, and acoustic sampling of bat echolocation activity in Nyungwe National Park and surrounding areas in southwestern Rwanda from 2013-2020. We report the discovery of an extant population of Hill&#39;s horseshoe bat (Rhinolop...

Wind turbines (WTs) frequently kill bats worldwide. During environmental impact assessments, consultant ecologists often use automated ultrasonic detectors (AUDs) to estimate the activity and identity of bats in the zone of highest mortality risk at WTs in order to formulate mitigation schemes, such as increased curtailment speeds to prevent casualties. While acknowledging the potential of acoustic monitoring, we evaluate the limitations of AUDs for monitoring bats at WTs and highlight directions for future research. We show that geometric attenuation and atmospheric attenuation of ultrasonic echolocation calls, in conjunction with limited sensitivity of ultrasonic microphones, severely constrain detection distances of bats at WTs. Taking into account the acoustic shadow produced by the nacelle, AUDs cover only approximately 23% of the risk zone for a bat calling at 20 kHz and 4% for a bat calling at 40 kHz, assuming a 60 m blade length. This percentage will further decrease with increasing blade lengths in modern WTs. Additionally, the directionality of echolocation calls and the dynamic flight behaviour of bats constrain the detectability of bats. If a call can be detected, the low interspecific and high intraspecific variation of echolocation call characteristics may impair species identification, limiting the power to predict population-level effects of fatalities. We conclude that technical, physical, and biological factors severely constrain acoustic monitoring in its current form. We suggest the use of several AUDs, installed at complementary sites at WTs, and the testing of other techniques, such as radar, cameras, and thermal imaging, to inform stakeholders on the mortality risk of bats at WTs.

A history of the study of Lepidoptera in caves in Serbia is given. On this basis, a comparative analysis with Lepidoptera species in neighboring countries -Croatia, Romania and Bulgaria, was carried out. The presence of cavernicolous habitats and ecological niches suitable for Lepidoptera was investigated. There is a need to investigate these groups of organisms in Serbia and it is suggested that caves in Serbia be a priority in this research.

Caves present a crucial habitat for most bat species in Iran, but data on cave-dwelling bats are relatively scarce. Tadovan Cave in Fars Province is the richest cave in terms of bat species observed, with ten species recorded to date. Data from published sources are listed here, alongside data from the present study, which included three expeditions to the cave in March 2008, December 2013 and October 2015. An overview is presented of the cave chambers used by ten bat species from four different families: Rhinolophus hipposideros, R. blasii, R. euryale, R. mehelyi and R. ferrumequinum (Rhinolophidae); Rhinopoma microphyllum and R. muscatellum (Rhinopomatidae); Myotis blythii and M. capaccinii (Vespertilionidae) and Miniopterus pallidus (Miniopteridae). Microclimatic data of the cave chambers are provided, as well as body measurements of individual bats from the cave. A general decline in numbers of bat individuals is noted for all species, compared to visual counts reported from 1980 and 2012. Conservation issues are discussed and urgent needs are raised both for systematic studies and for development of a detailed conservation plan for this cave.

Human echolocation describes how people use reflected sounds to obtain information about their ambient world. We investigated, by using auditory models, how three perceptual parameters, loudness, pitch and sharpness, determine echolocation. We used acoustic recordings from two previous studies, both from stationary situations, and their resulting perceptual data as input to our analysis. An initial analysis was on the room acoustics of the recordings. The parameters of interest were sound pressure level, autocorrelation and spectral centroid. The auditory models were used to analyze echolocation resulting from the perceptual variables, i.e. loudness, pitch and sharpness. Relevant auditory models were chosen to simulate each variable. Based on these results, we calculated psychophysical thresholds for detecting a reflecting object with constant physical size. A non-parametric method was used to determine thresholds for distance, loudness, pitch and sharpness. Difference thresholds were calculated for the psychophysical variables, since a 2-Alternative-Forced-Choice Paradigm had originally been used. We found that (1) blind persons could detect objects at lower loudness values, lower pitch strength, different sharpness values and at further distances than sighted persons, (2) detection thresholds based on repetition pitch, loudness and sharpness varied and depended on room acoustics and type of sound stimuli, (3) repetition pitch was useful for detection at shorter distances and was determined from the peaks in the temporal profile of the autocorrelation function, (4) loudness at shorter distances provides echolocation information, (5) at longer distances, timbre aspects, such as sharpness, might be used to detect objects. We also discuss binaural information, movements and the auditory model approach. Autocorrelation was assumed as a proper measure for pitch, but the question is raised whether a mechanism based on strobe integration is a viable possibility.

Human echolocation describes how people, often blind, use reflected sounds to obtain information about their ambient world. Using auditory models for three perceptual variables, loudness, pitch and one aspect of timbre, namely sharpness, we determined how these variables can make people detect objects by echolocation. We used acoustic recordings and the resulting perceptual data from a previous study with stationary situations, as input to our analysis. One part of the analysis was on the physical room acoustics of the sounds, i.e. sound pressure level, autocorrelation and spectral centroid. In a second part we used auditory models to analyze echolocation resulting from the perceptual variables loudness, pitch and sharpness. Based on these results, a third part was the calculation of psychophysical thresholds with a non-parametric method for detecting a reflecting object with constant physical size for distance, loudness, pitch and sharpness. Difference thresholds were calculated for the psychophysical variables, since a 2-Alternative-Forced-Choice Paradigm had originally been used. We determined (1) detection thresholds based on repetition pitch, loudness and sharpness varied and their dependency on room acoustics and type of sound stimuli. We found (2) that repetition pitch was useful for detection at shorter distances and was determined from the peaks in the temporal profile of the autocorrelation function, (3) loudness at shorter distances provides echolocation information, (4) at longer distances, timbre aspects, such as sharpness, might be used to detect objects. (5) It is suggested that blind persons may detect objects at lower values for loudness, pitch strength and sharpness and at further distances than sighted persons. We also discuss the auditory model approach. Autocorrelation was assumed as a proper measure for pitch, but we ask whether a mechanism based on strobe integration is a viable possibility.

Blind people use auditory information to locate sound sources and sound-reflecting objects (echolocation). Sound source localization benefits from the hearing system&#39;s ability to suppress distracting sound reflections, whereas echolocation would benefit from &quot;unsuppressing&quot; these reflections. To clarify how these potentially conflicting aspects of spatial hearing interact in blind versus sighted listeners, we measured discrimination thresholds for two binaural location cues: inter-aural level differences (ILDs) and inter-aural time differences (ITDs). The ILDs or ITDs were present in single clicks, in the leading component of click pairs, or in the lagging component of click pairs, exploiting processes related to both sound source localization and echolocation. We tested 23 blind (mean age = 54 y), 23 sighted-age-matched (mean age = 54 y), and 42 sighted-young (mean age = 26 y) listeners. The results suggested greater ILD sensitivity for blind than for sighted listener...

Blind people may detect objects from the information in reflected sounds, echolocation. Detection as a function of the number of clicks compared to a continuous noise was tested by presenting clicks of 5 ms with rates from 1 to 64 clicks during a 500 ms period and a 500-ms continuous white noise. The sounds were recorded in an ordinary room through an artificial binaural head. The reflecting object was an aluminum disk, diameter 0.5 m, at distances of 1 and 1.5 m. These sounds were later presented to 3 blind and 16 sighted participants in a laboratory using a 2AFC methodology. The task was to detect which of the two sounds that contained a reflecting object. Feedback was provided. The blind participants had a higher detection than the sighted, but there were also differences among the blind. These results are put in relation to physical features such as the autocorrelation function and spectral variations.

Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average -3 dB beam width of 5.0˚makes the narwhal click the most directional biosonar signal reported for any species to date. The beam shows a dorsal-ventral asymmetry with a narrower beam above the beam axis. This may be an evolutionary advantage for toothed whales to reduce echoes from the water surface or sea ice surface. Source level measurements show narwhal click intensities of up to 222 dB pp re 1 μPa, with a mean apparent source level of 215 dB pp re 1 μPa. During ascents and descents the narwhals perform scanning in the vertical plane with their sonar beam. This study provides valuable information for reference sonar parameters of narwhals and for the use of acoustic monitoring in the Arctic.

Belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) are highly social Arctic toothed whales with large vocal repertoires and similar acoustic profiles. Passive Acoustic Monitoring (PAM) that uses multiple hydrophones over large spatiotemporal scales has been a primary method to study their populations, particularly in response to rapid climate change and increasing underwater noise. This study marks the first acoustic comparison between wild belugas and narwhals from the same location and reveals that they can be acoustically differentiated and classified solely by echolocation clicks. Acoustic recordings were made in the pack ice of Baffin Bay, West Greenland, during 2013. Multivariate analyses and Random Forests classification models were applied to eighty-one singlespecies acoustic events comprised of numerous echolocation clicks. Results demonstrate a significant difference between species' acoustic parameters where beluga echolocation was distinguished by higher frequency content, evidenced by higher peak frequencies, center frequencies, and frequency minimums and maximums. Spectral peaks, troughs, and center frequencies for beluga clicks were generally > 60 kHz and narwhal clicks < 60 kHz with overlap between 40-60 kHz. Classification model predictive performance was strong with an overall correct classification rate of 97.5% for the best model. The most important predictors for species assignment were defined by peaks and notches in frequency spectra. Our results provide strong support for the use of echolocation in PAM efforts to differentiate belugas and narwhals acoustically. Only three species of cetaceans occupy the Arctic year-round: the beluga (Delphinapterus leucas), narwhal (Monodon monoceros), and bowhead whale (Balaena mysticetus). As toothed whales (odontocetes), the beluga and narwhal are closely related and are the only two members of the Monodontidae family. They use echolocation to identify objects and locate prey, unlike the bowhead whale, a baleen whale, that has not evolved this sense 1,2 . Belugas are circumpolar in their distribution with approximately 22 subpopulations, or stocks, some of which are highly migratory and others resident in both Arctic and sub-Arctic waters . Most populations migrate from wintering regions among the pack ice and return to the same estuarine summering areas to feed, molt, and give birth . In contrast, narwhals occur in approximately 12 stocks and have a more restricted distribution occupying waters of the Canadian Arctic, West and East Greenland, and western Russia within the Atlantic Arctic . Narwhals in the Canadian Arctic and West Greenland undergo extensive annual migrations with high site fidelity from their summer ranges in fjords of Greenland and Baffin Island to their wintering grounds in Baffin Bay and northern Davis Strait . Across their respective distributions, belugas and most of the world's narwhals overlap for much of the year in the waters of the Canadian Arctic and Baffin Bay, West Greenland, during their annual migrations (Fig. ).

Rhythm is an essential component of human speech and music but very little is known about its evolutionary origin and its distribution in animal vocalizations. We found a regular rhythm in three multisyllabic vocalization types (echolocation call sequences, male territorial songs and pup isolation calls) of the neotropical bat Saccopteryx bilineata. The intervals between element onsets were used to fit the rhythm for each individual. For echolocation call sequences, we expected rhythm frequencies around 6-24 Hz, corresponding to the wingbeat in S. bilineata which is strongly coupled to echolocation calls during flight. Surprisingly, we found rhythm frequencies between 6 and 24 Hz not only for echolocation sequences but also for social vocalizations, e.g. male territorial songs and pup isolation calls, which were emitted while bats were stationary. Fourier analysis of element onsets confirmed an isochronous rhythm across individuals and vocalization types. We speculate that attentional tuning to the rhythms of echolocation calls on the receivers' side might make the production of equally steady rhythmic social vocalizations beneficial.

Differences in auditory perception between species are influenced by phylogenetic origin and the perceptual challenges imposed by the natural environment, such as detecting prey-or predator-generated sounds and communication signals. Bats are well suited for comparative studies on auditory perception since they predominantly rely on echolocation to perceive the world, while their social calls and most environmental sounds have low frequencies. We tested if hearing sensitivity and stimulus level coding in bats differ between high and low-frequency ranges by measuring auditory brainstem responses (ABRs) of 86 bats belonging to 11 species. In most species, auditory sensitivity was equally good at both high-and low-frequency ranges, while amplitude was more finely coded for higher frequency ranges. Additionally, we conducted a phylogenetic comparative analysis by combining our ABR data with published data on 27 species. Species-specific peaks in hearing sensitivity correlated with peak frequencies of echolocation calls and pup isolation calls, suggesting that changes in hearing sensitivity evolved in response to frequency changes of echolocation and social calls. Overall, our study provides the most comprehensive comparative assessment of bat hearing capacities to date and highlights the evolutionary pressures acting on their sensory perception.

Bats employ a variety of social calls for communication purposes. However, for most species, social calls are far less studied than echolocation calls and their specific function often remains unclear. We investigated the function of in-flight social calls during autumn swarming in front of a large hibernaculum in Northern Germany, whose main inhabitants are two species of Myotis bats, Natterer's bats (Myotis nattereri) and Daubenton's bats (Myotis daubentonii). We recorded social calls in nights of high swarming activity and grouped the calls based on their spectro-temporal structure into ten types and verified our visual classification by a discriminant function analysis. Whenever possible, we subsequently assigned social calls to either M. daubentonii or M. nattereri by analyzing the echolocation calls surrounding them. As many bats echolocate at the same time during swarming, we did not analyze single echolocation calls but the "soundscape" surrounding each social call instead, encompassing not only spectral parameters but also the timbre (vocal "color") of echolocation calls. Both species employ comparatively similar social call types in a swarming context, even though there are subtle differences in call parameters between species. To additionally gain information about the general function of social calls produced in a swarming context, we performed playback experiments with free-flying bats in the vicinity of the roost, using three different call types from both species, respectively. In three out of six treatments, bat activity (approximated as echolocation call rate) increased during and after stimulus presentation, indicating that bats inspected or approached the playback site. Using a camera trap, we Frontiers in Ecology and Evolution 01 frontiersin.org Bergmann et al. 10.3389/fevo.2022.950951 were sometimes able to identify the species of approaching bats. Based on the photos taken during playbacks, we assume one call type to support interspecific communication while another call type works for intraspecific group cohesion.

Bats are highly gregarious animals, displaying a large spectrum of social systems with different organizational structures. One important factor shaping sociality is group stability. To maintain group cohesion and stability, bats often rely on vocal communication. The Honduran white bat, Ectophylla alba, exhibits an unusual social structure compared to other tentroosting species. This small white-furred bat lives in perennial stable mixed-sex groups. Tent construction requires several individuals and, as the only tent roosting species so far, involves both sexes. The bats´social system and ecology render this species an interesting candidate to study social behaviour and vocal communication. In our study, we investigated the social behaviour and vocalizations of E. alba in the tent by observing two stable groups, including pups, in the wild. We documented 16 different behaviours, among others play and fur chewing, a behaviour presumably used for scent-marking. Moreover, we found 10 distinct social call types in addition to echolocation calls, and for seven call types we were able to identify the corresponding broad behavioural context. Most of the social call types were affiliative, including two types of contact calls, maternal directive calls, pup isolation calls and a call type related to the fur-chewing behaviour. In sum, this study entails an ethogram and describes the social vocalizations of a tent-roosting phyllostomid bat, providing the basis for further in-depth studies about the sociality and vocal communication in E. alba.

Rhythm is an essential component of human speech and music but very little is known about its evolutionary origin and its distribution in animal vocalizations. We found a regular rhythm in three multisyllabic vocalization types (echolocation call sequences, male territorial songs and pup isolation calls) of the neotropical batSaccopteryx bilineata. The intervals between element onsets were used to fit the rhythm for each individual. For echolocation call sequences, we expected rhythm frequencies around 6–24 Hz, corresponding to the wingbeat inS. bilineatawhich is strongly coupled to echolocation calls during flight. Surprisingly, we found rhythm frequencies between 6 and 24 Hz not only for echolocation sequences but also for social vocalizations, e.g. male territorial songs and pup isolation calls, which were emitted while bats were stationary. Fourier analysis of element onsets confirmed an isochronous rhythm across individuals and vocalization types. We speculate that attentional ...

Bat pups produce isolation calls to solicit maternal care. During maturation, pup isolation calls may gradually develop into echolocation calls or exist in parallel to them, depending on the species involved. We studied the ontogeny of isolation calls in nectivorous bats, Glossophaga soricina. Isolation calls of G. soricina pups were frequency modulated calls uttered in bouts of varying length. Newborn pups already produced both isolation calls and echolocation call precursors (which developed into ‘normal’ echolocation calls), indicating that isolation calls of G. soricina pups occur independently and exist in parallel to echolocation calls during ontogeny. We found strong statistical evidence for an individual signature encoded in isolation calls. Moreover, we provide evidence for considerable changes in isolation call parameters over a short ontogenetic time span. Throughout ontogeny, the call interval decreased significantly whereas most frequency parameters increased significan...

The minimum distance for which two points still can be separated from each other defines the resolving power of a visual system. In an echo-acoustic context, the resolving power is usually measured as the smallest perceivable distance of two reflecting surfaces on the range axis and is found to be around half a millimeter for bats employing frequency modulated (FM) echolocation calls. Only few studies measured such thresholds with physical objects, most often bats were trained on virtual echoes i.e., echoes generated and played back by a computer; moreover, bats were sitting while they received the stimuli. In these studies differences in structure depth between 200 and 340 μm were found. However, these low thresholds were never verified for free-flying bats and real physical objects. Here, we show behavioral evidence that the echo-acoustic resolving power for surface structures in fact can be as low as measured for computer generated echoes and even lower, sometimes below 100 μm. We found this exceptional fine discrimination ability only when one of the targets showed spectral interferences in the frequency range of the bats echolocation call while the other target did not. This result indicates that surface structure is likely to be perceived as a spectral quality rather than being perceived strictly in the time domain. Further, it points out that sonar resolving power directly depends on the highest frequency/shortest wavelength of the signal employed.

Echolocating bats exhibit excellent control over their acoustic signals emitted and skillfully interpret the returning echoes, allowing orientation and foraging in complete darkness. Echolocation may be a preadaptation for sophisticated vocal communication with conspecifics and, ultimately, vocal learning processes. In humans, the importance of auditory input for correct speech acquisition is obvious, whereas vocal production learning is rare and patchily distributed among nonhuman mammals. Bats comprise one of the few mammalian taxa capable of vocal production learning, with current behavioral evidence for three species belonging to two families; more evidence will probably forthcoming. The taxon's speciose nature makes bats well suited for phylogenetically controlled, comparative studies on proximate and ultimate mechanisms of mammalian vocal production learning.

Bat echolocation is primarily used for orientation and foraging but also holds great potential for social communication. The communicative function of echolocation calls is still largely unstudied, especially in the wild. Eavesdropping on vocal signatures encoding social information in echolocation calls has not, to our knowledge, been studied in free-living bats so far. We analysed echolocation calls of the polygynous batSaccopteryx bilineataand found pronounced vocal signatures encoding sex and individual identity. We showed experimentally that free-living males discriminate approaching male and female conspecifics solely based on their echolocation calls. Males always produced aggressive vocalizations when hearing male echolocation calls and courtship vocalizations when hearing female echolocation calls; hence, they responded with complex social vocalizations in the appropriate social context. Our study demonstrates that social information encoded in bat echolocation calls plays ...

Adult animals of many taxa exhibit extended parental care by transferring food to inexperienced offspring, thus allocating nutritional and sometimes even informational benefits such as the acquisition of adult dietary preferences and foraging skills. In bats, postweaning food provisioning is severely understudied, despite the taxon's diverse and complex foraging strategies. The Neotropical common big-eared bat, Micronycteris microtis, preys on relatively large insects gleaned from vegetation, finding its silent and motionless prey by echolocation. The demands of this cognitively challenging hunting strategy make M. microtis a likely candidate for maternal postweaning food provisioning. We studied five free-living mother epup pairs in their night roost using infrared video recordings. Each mother exclusively fed her own pup and motherepup recognition was mutual. Provisioned pups were volant and had started their own hunting attempts. Weaned pups were provisioned for 5 subsequent months with a variety of insects, reflecting the adult diet. Mothers transferred over 50% of their prey to pups. Maternal prey transfers declined as pups matured, whereas the pups' own prey captures increased. During prey transfers, aggressive behaviour between mothers and pups was rare. We argue that postweaning maternal food provisioning might yield two informational benefits for M. microtis pups. First, learning how to handle large and well-defended prey is mandatory for inexperienced pups and could be practised with prey items provided by their mothers. Second, acoustically characteristic echo images of prey items could be gained during motherepup prey transfers, probably facilitating the successful acquisition of M. microtis's complex hunting strategy.

As climate change intensifies, understanding the impact of environmental factors on bat activity becomes essential for their conservation. This study, centered in central Chile, utilizes data from automatic bat detectors and climatological stations to explore the effects of air temperature and relative humidity on the timing of activity and abundance of five bat species. Temperature exerts influence over the timing of activity and relative abundance, revealing species-specific responses. Relative humidity emerges as a significant factor affecting abundance, with drier nights exhibiting higher bat pass rates. These findings suggest that global warming has the potential to reshape bat behaviors, impacting foraging patterns and activity levels. Further studies are essential to provide deeper insights that can guide effective conservation efforts in the context of climate change.

Cetaceans show high cognitive abilities and strong social bonds. Acoustics is their primary modality to communicate and sense the environment. Research on their echolocation and vocalizations with conspecifics and with humans typically uses visual and tactile systems adapted from research on primates or birds. Such research would benefit from a purely acoustic communication system in which signals flow in both directions simultaneously. We designed and implemented a full duplex system to acoustically interact with cetaceans in the wild, featuring digital echo-suppression. We pilot tested the system in Arctic Norway and achieved an echo suppression of 18 dB leaving room for technical improvements addressed in the discussion. Nevertheless, the system enabled vocal interaction with the underwater acoustic scene by allowing experimenters to listen while producing sounds. We describe our motivations, then present our pilot deployment and give examples of initial explorative attempts to v...

Arid environments are characterized by resource fluctuations that lead to spatial and temporal variability in species abundance, resulting in low species diversity. This study aimed to determine the activity patterns and habitat use by bats in an arid environment in western Algeria (Bechar region). In 2016, six sites were studied using acoustic bat detection. A total of 10 species were reported: Asellia tridens, Rhinopoma cystops, R. microphyllum, Tadarida teniotis, Miniopterus schreibersii, Eptesicus isabellinus, Hypsugo savii, Otonycteris hemprichii, Pipistrellus kuhlii (including P. kuhlii kuhlii and P. kuhlii deserti) and Vansonia rueppellii. Activity varied considerably from month to month and from site to site. Bats were particularly active in the spring and autumn. The first activity peak coincides with pregnancy (late April), followed by relatively low activity in August, probably due to summer torpor induced by high temperatures. The second peak in October coincides with mating and storage reserves before winter. Water bodies, oasis and urban lights concentrate bat activity. These results confirm the previously reported major role of water bodies in arid environments for bats. Further surveys should be carried out in the region and conservation measures should be taken to protect known roosts.

We studied the seasonal activity pattern of the Kuhl's pipistrelle Pipistrellus kuhlii in eight sites of the Bou Hedma National Park, central Tunisia, from June 2010 to June 2011, using both mistnetting and acoustic bat detection. Pipistrelles were captured all year-round only at water bodies. Captures peaked in late spring and early autumn. Pregnant females were observed from March to June, lactating females only in June, and flying juveniles from June to August. Echolocation calls and buzzes were recorded in all sites throughout the year. However, activity varied significantly among months and sites. Activity peaked in June and September after a noteworthy decline in August; the minimum was recorded in December and January. Bats mainly foraged at water bodies and around streetlamps. This result supports the previously reported major role of water bodies for bats in arid environments. Bats also foraged in the open acacia forest in summer, during the flowering period of Acacia Acacia tortilis raddiana. The steppe was the least used habitat. Social calls were mainly recorded in autumn around streetlamps, suggesting a swarming behaviour. Despite being a common bat species in the area, P. kuhlii should deserve conservation efforts that would benefit other bat species.

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Increasing aridity usually results in decreasing bat abundance and species richness, and the Saharan desert is an example of such impoverishment. Moreover, the harsh climatic and field conditions in this area restrict the feasibility of surveys. Therefore, the bat fauna of the Tunisian Sahara was unstudied until an expedition was conducted in May 2021. A total of seven species were recorded using passive bat detectors set mainly at water bodies, which concentrate bat activity. Echolocation calls of these species did not depart from published records for the Mediterranean area. Our data failed to identify the two ecomorphotypes of Pipistrellus kuhlii but confirmed the adaptability of this species to local conditions. For the first time in Tunisia, we recorded echolocation calls of Taphozous nudiventris, a species that has been rarely reported in North Africa. The highest species richness was identified at the largest wetlands of Oued Daghsen (Oued Dkouk Nature Reserve) and at Bordj e...

We report initial results from a study on behavioral responses of beaked and other whales to sonar and other sounds. This research is designed to provide new science-based approaches for mitigating the risk of sonar to beaked and other whales. The study was conducted at the Atlantic Undersea Test and Evaluation Center (AUTEC) range near Andros Island in the Bahamas, where Blainville&#39;s beaked whales (Mesoplodon densirostris) can regularly be detected using passive acoustic monitoring of their echolocation clicks. Tags recorded sound at the whale and behavior of the whale. Data were collected from 10 tag deployments, 6 on Blainville&#39;s beaked whales and 4 on pilot whales. 109 hours of data were collected from tags, 74 hours from beaked whales and 34 hours from pilot whales. Playbacks of mid-frequency sonar and killer whale calls were performed on 3 of the tagged whales, 1 beaked whale and 2 pilot whales. The tagged beaked whale responded to both sonar and killer whale sounds by...

We used radio tracking and direct observation to determine the effect of roost closure on the roosting and foraging behaviour of big brown bats {Eptesicus fuscus) in maternity colonies near Ottawa. Individuals were site loyal, but after eviction they moved short distances to new roosts where they tended to produce fewer offspring. The time spent on the first foraging flight, the maximum distance travelled, and the use of feeding areas did not change with exclusion. The results suggest that bats roost to take advantage of site-specific factors that may increase reproductive success.

Advances in molecular methods and analyses, such as DNA sequencing and phylogenetic reconstructions, are being widely used to help clarify the taxonomic challenge posed by cryptic species. While almost morphologically indistinguishable, such species can also present other diagnostic features, including ecological and physiological characteristics. The main goal of this work was to investigate whether it is possible to distinguish two cryptic bat species in Iberia, Eptesicus serotinus and Eptesicus isabellinus, through their echolocation call characteristics. After molecular identification of species' colonies, echolocation calls were recorded during emergence from roosts for 52 individuals. A stepwise discriminant analysis was used to test if the variables measured in the recordings could significantly differentiate the two species. This analysis was able to extract one discriminant function, with the variables' peak frequency and duration of pulses identified as statistically significant. These provided a correct overall classification of approximately 78.8 %. We found that on average peak frequency is higher in the echolocation calls of E. isabellinus compared with that of E. serotinus, but overlap occurred between 23.4 and 28.8 kHz. Moreover, in our recording conditions, calls belonging to E. isabellinus tended to be shorter than those of E. serotinus. Possibly, some acoustic differences could be explained by local adaptations to different climate conditions and ecological niches experienced by each species.

The biorobotic emulation of swimming and flying animals carrying out short-distance echolocation while maneuvering is considered. A simple and lightweight sonar for use on a small, maneuverable underwater vehicle for short-distance echolocation is explored. This sonar has four sensors and uses broadband, high-frequency signals to echolocate. The frequency-time characteristics of these signals are compared to those of bats and dolphins. The biosonar is paired with a biologically inspired, maneuverable, underwater vehicle, the combined use of sensors and maneuverability being analogous to animal behavior. Homing experiments have been carried out in an acoustic test facility where identification and localization of multiple targets is based on fusion of acoustic returns from multiple pings.

A pacific bottlenose dolphin was trained in a two-alternative cross-modal matching-to-sample paradigm. The animal was able to inspect complex PVC-pipe shapes through echolocation or vision but never through both senses simultaneously. Acoustic data was collected through a 3-channel high-frequency recording system while the dolphin performed one of the following tasks: (1) match a complex shape with its sonar only (pure echoic matching), (2) match from vision to echolocation and (3) match from echolocation to vision. Simultaneously, synchronized in-air and underwater video was recorded documenting the approach path of the dolphin to either the sample object or to the alternative objects. The collected data was analyzed for type of click signals used, the frequency range of the emitted clicks, number of clicks emitted before a successive match and variations of click type with different objects.

Rough-toothed dolphin's abundance and distribution is largely unknown worldwide and evaluation of its conservation status in the Mediterranean Sea is necessary. A rough-toothed dolphin was sighted offshore Eastern Sicily (Mediterranean Sea) in July 2017 and acoustic data were acquired in the same area of Watkins, Tyack, Moore, and Notarbartolo di Sciara [(1987). Mar. Mamm. Sci. 3, 78-82]. An automatic detection algorithm was developed to identify the echolocation clicks recorded within both datasets and a recurrent inter-click interval value was identified during the new encounter. Distinctive whistle classes were also identified with similar contour shapes within both datasets.

Computational models of animal biosonar seek to identify critical aspects of echo processing responsible for the superior, real-time performance of echolocating bats and dolphins in target tracking and clutter rejection. The Spectrogram Correlation and Transformation (SCAT) model replicates aspects of biosonar imaging in both species by processing wideband biosonar sounds and echoes with auditory mechanisms identified from experiments with bats. The model acquires broadband biosonar broadcasts and echoes, represents them as time-frequency spectrograms using parallel bandpass filters, translates the filtered signals into ten parallel amplitude threshold levels, and then operates on the resulting timeof-occurrence values at each frequency to estimate overall echo range delay. It uses the structure of the echo spectrum by depicting it as a series of local frequency nulls arranged regularly along the frequency axis of the spectrograms after dechirping them relative to the broadcast. Computations take place entirely on the timing of threshold-crossing events for each echo relative to threshold-events for the broadcast. Threshold-crossing times take into account amplitude-latency trading, a physiological feature absent from conventional digital signal processing. Amplitude-latency trading transposes the profile of amplitudes across frequencies into a profile of time-registrations across frequencies. Target shape is extracted from the spacing of the object's individual acoustic reflecting points, or glints, using the mutual interference pattern of peaks and nulls in the echo spectrum. These are merged with the overall range-delay estimate to produce a delay-based reconstruction of the object's distance as well as its glints. Clutter echoes indiscriminately activate multiple parts in the nulldetecting system, which then produces the equivalent glint-delay spacings in images, thus blurring the overall echo-delay estimates by adding spurious glint delays to the image. Blurring acts as an anticorrelation process that rejects clutter intrusion into perceptions.

Arrays of tidal turbines are being considered for tidally energetic coastal sites which can be important habitat for many species of marine mammal. Understanding risks to marine mammals from collisions with moving turbine blades must be overcome before regulators can issue licenses for many developments. To understand these risks, it is necessary to understand how animals move around operational turbines and to document the rate at which interactions occur. We report on the design, and performance, of a seabed mounted sensor platform for monitoring the fine scale movements of cetaceans and pinnipeds around operational tidal turbines. The system comprises two high-frequency multibeam active sonars, which can accurately track animals in the horizontal plane. By offsetting the vertical angle of the sonars, the relative intensity of targets on the two sonars can also be used to resolve a vertical component of the animal location. For regularly vocalizing species, i.e., small cetaceans, ...

Small echolocating bats are set apart from most other mammals by their relatively large cerebellum, a feature that has been associated to echolocation, as it is presumed to indicate a relatively enlarged number of neurons in the cerebellum in comparison to other brain structures. Here we quantify the neuronal composition of the cerebral cortex, cerebellum and remaining brain structures of seven species of large Pteropodid bats (formerly classified as megachiropterans), one of which echolocates, and six species of small bats (formerly classified as microchiropterans), all of which echolocate. This chiropteran data is compared to 60 mammalian species in our dataset to determine whether the relatively large cerebellum of the small echolocating bats, and possibly that of the echolocating Pteropodid, contains a relatively enlarged number of neurons. We find no evidence that the distribution of neurons differs between microchiropterans and megachiropterans, but our data indicate that micr...