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Calls to "break up" radical echo chambers by injecting them with alternative viewpoints are common. Yet, thus far there is little evidence about the impact of such counter-messaging. To what extent and how do individuals who inhabit a radical echo chamber engage with messages that challenge their core beliefs? Drawing on data from the radical right forum Stormfront we address this question with a large-scale content and longitudinal analysis of users' posting behavior, which analyses more than 35,000 English language contributions to the forum spanning 2011 through 2013. Our findings show that engaging with oppositional views is actually a core practice among Stromfront users which invites active participation and encourages engagement. Indeed, many "echoes" in the echo chamber we studied were not core beliefs being restated, but the sound of opposing viewpoints being undermined and marginalized. These findings underscore the limited potential for counter-messages to undermine radical echo chambers. [ABSTRACT FROM AUTHOR]

As development of wind energy facilities continues, questions of why fatalities of migrating insectivorous bats occur at turbines still remain. Numerous hypotheses have been proposed, including a feeding-attraction hypothesis that suggests bats may be attracted to insects congregating near turbine nacelles. To test this hypothesis, we analyzed echolocation calls of hoary (Lasiurus cinereus) and silver-haired (Lasionycteris noctivagans) bats recorded over 72 nights at a wind energy facility in Southern Alberta, Canada. We recorded calls at 3 heights: 67 m at turbine nacelles, 30 m at meteorological towers, and ground level at turbines and meteorological towers. We used feeding buzzes as indicators of foraging behavior. We compared the occurrence of feeding buzzes across heights, and between turbines and meteorological towers to test the prediction that if bats are attracted to turbines for foraging, there will be a greater proportion of feeding buzzes at turbines, and in particular, at nacelle height. We found no significant evidence that foraging rates were higher at nacelle height compared to 30 m or ground level, or between turbines and meteorological towers for either species. For silver-haired bats, foraging activity was greater at meteorological towers, and in particular, at 30 m height. These results do not support the feeding-attraction hypothesis for silver-haired or hoary bats, and suggest that while some bats forage in the vicinity of wind turbines, they are not specifically attracted to turbines to feed. [ABSTRACT FROM AUTHOR]

Several taxonomically distinct mammalian groups—certain microbats and cetaceans (e.g., dolphins)—share both morphological adaptations related to echolocation behavior and strong signatures of convergent evolution at the amino acid level across seven genes related to auditory processing. Aye-ayes (Daubentonia madagascariensis) are nocturnal lemurs with a specialized auditory processing system. Aye-ayes tap rapidly along the surfaces of trees, listening to reverberations to identify the mines of wood-boring insect larvae; this behavior has been hypothesized to functionally mimic echolocation. Here we investigated whether there are signals of convergence in auditory processing genes between aye-ayes and known mammalian echolocators. We developed a computational pipeline (Basic Exon Assembly Tool) that produces consensus sequences for regions of interest from shotgun genomic sequencing data for nonmodel organisms without requiring de novo genome assembly. We reconstructed complete coding region sequences for the seven convergent echolocating bat–dolphin genes for aye-ayes and another lemur. We compared sequences from these two lemurs in a phylogenetic framework with those of bat and dolphin echolocators and appropriate nonecholocating outgroups. Our analysis reaffirms the existence of amino acid convergence at these loci among echolocating bats and dolphins; some methods also detected signals of convergence between echolocating bats and both mice and elephants. However, we observed no significant signal of amino acid convergence between aye-ayes and echolocating bats and dolphins, suggesting that aye-aye tap-foraging auditory adaptations represent distinct evolutionary innovations. These results are also consistent with a developing consensus that convergent behavioral ecology does not reliably predict convergent molecular evolution. [ABSTRACT FROM AUTHOR]

Moths evolved tympanal hearing organs to detect the echolocation calls of predatory bats. Moths' auditory responses have been examined mainly for their sensitivity to the frequencies of bat cries: tympanate moths are basically tuned to the call frequencies of sympatric bats. Here, we add the finding that hearing sensitivity to 'pulse duration' in crambid moths is also affected by predation pressure from echolocating bats. Analysis of interspecific variation showed that minimum auditory thresholds had a significantly negative relationship with the forewing surface area, that is, acoustic conspicuousness to bat sonar, but no relationship with head width, which was assumed to correlate with tympanal organ size. Auditory thresholds increased as pulses shortened in the 1-10 ms duration range, and conspicuous moths with larger wing areas had lower thresholds than smaller moths. By contrast, 'intraspecific' variation, within a single population of the lurcerne moth, revealed no relationship between forewing area and any auditory characteristics. Moth hearing adapts to the echolocation pulse duration of sympatric bat communities, suggesting that evolutionary modification of hearing sensitivity is related to acoustic conspicuousness based on moth wing area. [ABSTRACT FROM AUTHOR]

Trophic guilds are useful concepts for advancing our knowledge of trophic structure of communities, dynamics of species interactions, redundancy in ecosystem services, resilience to disturbances, response to climate change, conservation strategies, etc. For insectivorous bats, current literature suggests 8 trophic-related guilds. These include 3 guilds based on the openness of foraging areas, 3 based on the style of feeding, and 2 recently proposed subguilds among gleaners. Some gleaners are "passive," using densely cluttered vegetation in which echolocation is ineffective, and others are "actively" gleaning, using echolocation to procure prey. None of these guilds is based on the actual diets of bats. We analyzed 33 reports of diet composition representing 51 species of arthropod-feeding bats inhabiting North and Central America. We wanted to determine if the classical guild structure was concordant with the actual diets of bats and to compare guild structure in the Nearctic with that in the Neotropics. Discriminant function and principle component analyses generated 5 groups of genera based on the proportion of various arthropod taxa (mainly orders) in their diets. These groups were very different from classical guilds and showed almost no overlap among bat genera between the 2 continental regions. A similar analysis based on prey flying ability and hardness of their exoskeletons suggested 4 guilds that were more consistent with classical guild concepts, had higher rates of unambiguous guild assignment, and also showed major continental differences. Our results suggest a new arrangement of 4 guilds for arthropod-feeding bats in North and Central America that are based primarily on 2 features of their prey. New molecular techniques should allow us to build on this arrangement by significantly improving the taxonomic level of prey identification. [ABSTRACT FROM AUTHOR]

The skulls of animals have to perform many functions. Optimization for one function may mean another function is less optimized, resulting in evolutionary trade-offs. Here, we investigate whether a trade-off exists between the masticatory and sensory functions of animal skulls using echolocating bats as model species. Several species of rhinolophid bats deviate from the allometric relationship between body size and echolocation frequency. Such deviation may be the result of selection for increased bite force, resulting in a decrease in snout length which could in turn lead to higher echolocation frequencies. If so, there should be a positive relationship between bite force and echolocation frequency. We investigated this relationship in several species of southern African rhinolophids using phylogenetically informed analyses of the allometry of their bite force and echolocation frequency and of the three-dimensional shape of their skulls. As predicted, echolocation frequency was positively correlated with bite force, suggesting that its evolution is influenced by a trade-off between the masticatory and sensory functions of the skull. In support of this, variation in skull shape was explained by both echolocation frequency (80%) and bite force (20%). Furthermore, it appears that selection has acted on the nasal capsules, which have a frequency-specific impedance matching function during vocalization. There was a negative correlation between echolocation frequency and capsule volume across species. Optimization of the masticatory function of the skull may have been achieved through changes in the shape of the mandible and associated musculature, elements not considered in this study. [ABSTRACT FROM AUTHOR]

Skulls of many living and extinct beaked whales ( Ziphiidae) contain various bizarre bone and tooth structures. Many of them show sexual dimorphism in their skull anatomy: males have bizarre skull structures, whereas females do not. Opinions differ as to what the function of these structures might be. Some believe that these are weapons; others, that they are sound transmitters. This article argues that these structures are the means of visual display. Many of the bizarre bone structures of beaked whales are not exposed like 'visuals' of terrestrial tetrapods, but are located deep in soft tissues. Nevertheless, toothed whales recognize objects (including three-dimensional bodies), using echolocation. So, along with visual means, they can 'see' and 'show' their internal bone structures with echoic imaging and use them as informational sources in social interactions and in individual or species recognition. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 510-515. [ABSTRACT FROM AUTHOR]

Intraspecific variability in echolocation calls could be an important factor hampering the accurate acoustic identification of species in the field. We studied variations in the echolocation behavior of Lasiurus varius in relation to habitat structure. Echolocation calls of L. varius reflected the degree of clutter present in its foraging areas. Bats foraging in an uncluttered habitat emitted longer and lower-bandwidth calls, with the lowest frequency values, whereas bats foraging in a cluttered habitat broadcast shorter and broadband signals, showing an increase in frequency content of their calls. Discriminant function analysis gave an overall classification of 76% of the calls emitted in the different flight situations. Our results highlight the need for independent recordings at each study area or habitat type to circumvent potential echolocation call variations, particularly in fragmented landscapes. [ABSTRACT FROM AUTHOR]

In vertebrates, changes in cranial modularity can evolve rapidly in response to selection. However, mammals have apparently maintained their pattern of cranial integration throughout their evolutionary history and across tremendous morphological and ecological diversity. Here, we use phylogenetic, geometric morphometric and comparative analyses to test the hypothesis that the modularity of the mammalian skull has been remodelled in rhinolophid bats due to the novel and critical function of the nasal cavity in echolocation. We predicted that nasal echolocation has resulted in the evolution of a third cranial module, the 'nasal dome', in addition to the braincase and rostrum modules, which are conserved across mammals. We also test for similarities in the evolution of skull shape in relation to habitat across rhinolophids. We find that, despite broad variation in the shape of the nasal dome, the integration of the rhinolophid skull is highly consistent with conserved patterns of modularity found in other mammals. Across their broad geographical distribution, cranial shape in rhinolophids follows two major divisions that could reflect adaptations to dietary and environmental differences in African versus South Asian distributions. Our results highlight the potential of a relatively simple modular template to generate broad morphological and functional variation in mammals. [ABSTRACT FROM AUTHOR]

In this study we combine analyses of wing morphology, echolocation calls, and temporal and spatial activity patterns to explore mechanisms of ecological partitioning among 4 syntopic Antillean mormoopids (Pteronotus macleayii, P. parnellii, P. quadridens, and Mormoops blainvillei). We captured bats with mist nets and harp traps, and monitored bat activity using automated Anabat systems for 31 nights at Sierra del Rosario Biosphere Reserve in Cuba. The wing morphologies (very low wing-loading and average-aspect ratio) and echolocation calls (broadband steep frequency-modulated calls at high frequencies) of all 4 species suggest that Cuban mormoopids are adapted to slow maneuverable flight, adequate for hunting insects by slow aerial hawking in background-cluttered habitat. However, our data show that each species has a combination of wing and echolocation call characters, presumably reflecting differences in their foraging behavior and microhabitat use. All 4 species were present at the 3 sampling sites and a majority showed similar activity rates at each site. Thus, we did not find strong evidence of spatial segregation during foraging. However, overall activity levels were higher in the primary forest when compared with 2 secondary-growth forests. Most pair-wise comparisons of temporal activity patterns between species were significant, suggesting high levels of temporal segregation. Our data suggest that wing morphology, echolocation call structure, and temporal activity patterns are morphological and behavioral factors that could facilitate resource partitioning among the Cuban mormoopid bats. [ABSTRACT FROM AUTHOR]

Brazilian free-tailed bats (Tadarida brasiliensis) emerge from cave roosts in dense columns in which adjacent bats are separated by only small distances. We describe and quantify variation in the structure of echolocation calls produced by these emerging bats and determine if call structure changes in relation to the rate of emergence measured using thermal infrared imaging. We recorded emergence calls at 2 roosts, 1 housing approximately 200,000 bats and the other approximately 17,000 bats. We found that Brazilian free-tailed bats emit distinct frequency-modulated (FMstart) and constant frequency (CFstart) calls during emergence that are significantly different from echolocation calls they emit while foraging. We propose that these calls provide different information for orientation within the emergence column. CFstart calls are very similar to social calls used by Brazilian free-tailed bats, suggesting 2 potential functions for this call type. The structure of both the FMstart and CFstart calls were not related to the number of bats emerging from a roost, although significant structural differences existed between sites. The differences between sites could be associated with the spacing of bats during emergence, because bats appeared to form tighter columns at the larger roost colony compared to the smaller colony. [ABSTRACT FROM AUTHOR]

Twenty-five characters or suites of characters from bats are considered in light of changes in bat classification. The characters include some associated with flower-visiting (two), echolocation (12), roosting (six), reproduction (two) and three are of unknown adaptive function. In both the 1998 and 2006 classifications of bats into suborders (Megachiroptera and Microchiroptera versus Yinpterochiroptera and Yangochiroptera, respectively), some convergences between suborders are the same (e.g. foliage roosting, tent building), but others associated with echolocation differ substantially. In the 1998 phylogeny convergences associated with echolocation (high duty cycle echolocation, nasal emission of echolocation calls) occurred among the Microchiroptera. In the 2006 phylogeny, they occur between Yinpterochiroptera and Yangochiroptera. While some traits apparently arose independently in two suborders (e.g., foliage-roosting, tent building, low intensity echolocation calls, noseleafs, nasal emission of echolocation calls, high duty cycle echolocation behaviour), others appear to have been ancestral (roosting in narrow spaces, laryngeal echolocation, stylohyal-tympanic contact, oral emission of echolocation calls, and small litter size). A narrow profile through the chest is typical of bats reflecting the thoracic skeleton. This feature suggests that the ancestors of bats spent the day in small crevices. Features associated with laryngeal echolocation appear to be ancestral, suggesting that echolocation evolved early in bats but was subsequently lost in one yinpterochiropteran lineage [Current Zoology 56 (4): 454-468, 2010]. [ABSTRACT FROM AUTHOR]

Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena phocoena) around North Sea offshore gas installations. – ICES Journal of Marine Science, 66: 734–745. Echolocation clicks of harbour porpoises (Phocoena phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (<200 m) the platform, and there was a pronounced diel pattern in echolocation activity; the number of porpoise encounters (visits) was greater by night than by day. The number of click trains with a minimum inter-click interval of <10 ms also increased at night. This was confirmed by a comparison of the ratios of feeding buzzes to search-phase clicks (feeding buzz ratios) and an analysis of the changes in pulse-repetition frequencies within each train. A reasonable interpretation of this pattern was that porpoises were feeding below or around the platform at night. The evidence for changes in activity during the morning and evening was less clear, so these may be transitional phases. The pattern of porpoise-echolocation behaviour around this platform is related most probably to the diel activity of their prey. If porpoises cluster regularly around such installations within 500-m shipping exclusion zones, they may be omitted from population surveys. We conclude that offshore installations may play an important role as nocturnal porpoise-feeding stations in an overfished environment, but that further replicated and controlled studies are required. These findings should be taken into consideration during offshore-installation-decommissioning decisions in the North Sea. [ABSTRACT FROM PUBLISHER]

Bats are among the few predators that can exploit the large quantities of aerial insects active at night. They do this by using echolocation to detect, localize, and classify targets in the dark. Echolocation calls are shaped by natural selection to match ecological challenges. For example, bats flying in open habitats typically emit calls of long duration, with long pulse intervals, shallow frequency modulation, and containing low frequencies--all these are adaptations for long-range detection. As obstacles or prey are approached, call structure changes in predictable ways for several reasons: calls become 'shorter, thereby reducing overlap between pulse and echo, and calls change in shape in ways that minimize localization errors. At the same time, such changes are believed to support recognition of objects. Echolocation and flight are closely synchronized: we have monitored both features simultaneously by using stereo photogrammetry and videogrammetry, and by acoustic tracking of flight paths. These methods have allowed us to quantify the intensity of signals used by free-riving bats, and illustrate systematic changes in signal design in relation to obstacle proximity. We show how signals emitted by aerial feeding bats can be among the most intense airborne sounds in nature. Wideband ambiguity functions developed in the processing of signals produce two-dimensional functions showing trade-offs between resolution of time and velocity, and illustrate costs and benefits associated with Doppler sensitivity and range resolution in echolocation. Remarkably, bats that emit broadband calls can adjust signal design so that Doppler-related overestimation of range compensates for underestimation of range caused by the bat's movement in flight. We show the potential of our methods for understanding interactions between echolocating bats and those prey that have evolved ears that detect bat calls. [ABSTRACT FROM AUTHOR]

Occupancy analysis and its ability to account for differential detection probabilities is important for studies in which detecting echolocation calls is used as a measure of bat occurrence and activity. We examined the feasibility of remotely acquiring bat encounter histories to estimate detection probability and occupancy. We used echolocation detectors coupled to digital recorders operating at a series of proximate sites on consecutive nights in 2 trial surveys for the Hawaiian hoary bat (Lasiurus cinereus semotus). Our results confirmed that the technique is readily amenable for use in occupancy analysis. We also conducted a simulation exercise to assess the effects of sampling effort on parameter estimation. The results indicated that the precision and bias of parameter estimation were often more influenced by the number of sites sampled than number of visits. Acceptable accuracy often was not attained until at least 15 sites or 15 visits were used to estimate detection probability and occupancy. The method has significant potential for use in monitoring trends in bat activity and in comparative studies of habitat use. [ABSTRACT FROM AUTHOR]

Most previous studies considering intraspecific differences in bat echolocation call frequency among geographic groups have related this to morphological features not directly involved in producing the characteristics of the emitted signal. We related a pattern of intraspecific call differences to the size of nasal chambers (estimated from radiographs of museum specimens), expecting chamber dimensions to be functionally coupled with the sound source. Such a relationship is potentially informative in the context of competing hypotheses that account tot call frequency differences. Allopatry has been a precursor to differences in echolocation call frequency between isolated populations of the Australian endemic orange leaf-nosed bat (Rhinonicteris aurantia (Gray, 1845); Pilbara isolate: 120.9 ± 1.91 kHz; compared with Kimberley region: 114.65 ± 1.98 kHz and Northern Territory: 114.62 ± 2.10 kHz). Correlations with morphological features not directly involved in signal production or modification were either moderate (nose-leaf width) or absent (forearm length). Overall nasal volume was shown to be relatively smaller in the Pilbara population, which had higher average call frequency. This relationship was expected given the suggested function of nasal chambers in impedance matching. The finding is significant because nasal chamber size was the only character observed to vary in a species that was otherwise conserved morphologically, suggesting adaptation and not a simple scaling relationship with body size that might be more indicative of drift. We consider that the combination of patterns from echolocation call frequency and associated morphological features, as well as neutral DNA markers, provide adequate support for recognition of the separate populations of R. aurantia for conservation, according to more recent concepts that consider ecological as well as genetic characters when allocating groups to evolutionarily significant units. [ABSTRACT FROM AUTHOR]

Echolocation calls emitted by the 4 species of Cuban mormoopid bats were compared to determine vocal signatures that enable identification of each species in the field during their evening exodus. Echolocation calls produced by Mormoops blainvilli are downward frequency-modulated (FM) signals in the range of 68.4-52.5 kHz. Echolocation calls emitted by Pteronotus macleayii and P. quadridens have a similar design consisting of a short constant-frequency (CF) segment followed by a downward FM segment. The CF segment was at 70.0 kHz in calls from P. macleayii, and at 83.3 kHz in calls from P. quadridens. Echolocation calls from P. parnellii consist of a long CF segment, which is preceded by a short initial upward sweep and followed by a downward FM terminal sweep. The CF value of the 2nd harmonic was a good parameter for species identification. The features of the echolocation calls of each of the species were used to identify them during the evening exodus from 2 Cuban caves. [ABSTRACT FROM AUTHOR]

In recent years many cryptic bat species have been unmasked by differences in their echolocation calls. The yellow house bat (Scotophilus dinganii) is 1 of 3 species of Scotophilus currently described in southern Africa and is distinguished from the other 2 species by its size and yellow venter. Here we use genetic, morphological, and echolocation call data to show the existence of a cryptic species. We found that S. dinganii consists of 2 forms, one that uses a peak echolocation frequency of 44 kHz and the other a peak frequency of 33 kHz. Both forms have yellow venters. The 44-kHz phonic type is up to 15% smaller than the 33-kHz phonic type and differed genetically by an average cytochrome-b (Cytb) sequence divergence of 3.3%. Furthermore, combined phylogenetic analyses of Cytb and control region sequences indicate that the 2 phonic types are reciprocally monophyletic, suggesting that they are sibling species. [ABSTRACT FROM AUTHOR]

Most moths use ears solely to detect the echolocation calls of hunting, insectivorous bats and evoke evasive flight manoeuvres. This singularity of purpose predicts that this sensoribehavioural network will regress if the selective force that originally maintained it is removed. We tested this with noctuid moths from the islands of Tahiti and Moorea, sites where bats have never existed and where an earlier study demonstrated that the ears of endemic species resemble those of adventives although partially reduced in sensitivity. To determine if these moths still express the anti-bat defensive behaviour of acoustic startle response (ASR) we compared the nocturnal flight times of six endemic to six adventive species in the presence and absence of artificial bat echolocation sounds. Whereas all of the adventive species reduced their flight times when exposed to ultrasound, only one of the six endemic species did so. These differences were significant when tested using a phylogenetically based pairwise comparison and when comparing effect sizes. We conclude that the absence of bats in this habitat has caused the neural circuitry that normally controls the ASR behaviour in bat-exposed moths to become decoupled from the functionally vestigial ears of endemic Tahitian moths. [ABSTRACT FROM AUTHOR]

The structure of echolocation calls, and the distance over which bats perceive their environment, varies with the amount of structural clutter through which they are flying. Clutter and species had significant effects on the frequency-time characteristics of search-phase echolocation calls of northern long-eared (Myotis septentrionalis) and little brown bats (M. launchings). We tested an a priori derived model that predicted the pattern of differences in echolocation call variable values among clutter categories would provide insight into the relative maximum distances that bat species could perceive using echolocation. Specifically, the model predicted that species adapted to flying and foraging in cluttered habitats would have a shorter maximum perceptual distance than species adapted to flying and foraging in uncluttered habitats. The results supported this model and suggest the clutter-adapted M. septentrionalis had a shorter maximum perceptual distance than M. lucifugus, a species known to forage in a variety of habitats but mainly in uncluttered areas (i.e., over water). Using calls as the sampling unit, a neural network correctly classified >94% of the echolocation calls to species in high clutter. In medium and low clutter, >82% of the calls were correctly classified to species; however >90% correct classification was achieved by leaving >30% of calls unclassified. Researchers should develop clutter-specific call libraries to improve species classification accuracy for echolocation calls. [ABSTRACT FROM AUTHOR]

We have studied the effect of habitat and presence of conspecifics on echolocation characteristics of the emballonurid bat Balantiopteryx plicata. Calls during the search phase only showed differences between habitats in bandwidth, as has been found for other open-space bats. Characteristics of calls during the approach phase did change when bats entered open areas. Calls in the terminal phase showed no differences in the characters examined between habitats. Bats flying in groups shifted their peak frequency significantly, which maximized differences between individuals. These results are interpreted as an active mechanism of jamming avoidance. Bats flying in groups also tended to increase the mean of peak frequencies. [ABSTRACT FROM AUTHOR]

Echolocation calls were recorded from Pteronotus quadridens flying in the field and in an enclosed space. In the field, search calls contained 1 or 2 harmonics. Patterns of call design show a segment of quasi--constant frequency (QCF2nd-hamonic at 81-84 kHz), followed by a downward frequency-modulated (FM) component. The 2nd harmonic was always more intense than the 1st. Search, approach, and terminal phases of calls were described during hunting sequences of P. quadridens. The transition between call phases was characterized by monotonic variations in some acoustic parameters, including a decrease in call duration and an increase in repetition rate, bandwidth, and slope of the FM component. We also analyzed calls emitted by bats flying in confined spaces that consistently contained 3 harmonics, of which the 2nd harmonic contained the greatest energy. The values of call duration were shorter and bandwidth was higher than values characterizing calls emitted during the search phase in the field. [ABSTRACT FROM AUTHOR]

Presents a study which described designs of echolocation signals in aerial-hawking insectivorous bats from Malaysia. Materials and methods; Results; Discussion.

Describes field recordings of echolocation calls of the neotropical emballonurid sac winged bats Balantiopteryx (B.) plicata, B. io and B. infusca. Effects of body size on echolocation parameters; Interspecific variation in aspects of echolocation; Reason for the skewness in distribution of pulse interval.

Deals with a study that investigated the postnatal development of vocalizations and hearing in the phyllostomid bat. Information on the two types of isolation calls for young bats; Auditory range during postnatal development; Characterization of the echolocation calls of bats.

Presents a study which compared the measurable features of the echolocation calls of bats as recorded by two bat-detecting systems. Background information on the mammals; Materials and methods used; Findings and discussion.

Presents a study which examined levels of intraspecific variation in search-phase echolocation calls of bats. Materials and methods used; Findings and discussion.

Presents a study which identifies four distinct functional groups of bats and differences in signal structure that correlate with the typical echolocation tasks faced by each group. Perceptual problems for foraging bats; Signals adapted for specific tasks; Narrowband and broadband signals; Long CF signals with Doppler-shift compensation; Foraging habitats defined by clutter conditions; Sonar and search signals of insect-eating bats.

Features a study which explored the ability to discriminate between echolocation calls of adult and juvenile big brown bats (Eptesicus fuscus). Differences in the variation in the echolocation calls of bats; Materials and methods; Results.

Presents a study which examined the advantages and disadvantages of techniques that transform and analyze echolocation calls of bats. Materials and methods; Results and discussion; Conclusions.

This study describes variation patterns in the constant frequency (CF) segment of echolocation calls of the bat Hipposideros ruber within and among populations across the region of the Gulf of Guinea. Correlations of variation in CF with variation in body size, body condition, environmental humidity and presence of ecologically similar species are studied in an attempt to identify the forces driving the evolution of CF. We found that bats may adapt the frequency to humidity, and that CF may evolve under interspecific interactions, either of ecological or of social nature. The results support an adaptive value for the high values of CF, and challenge the ‘Allotonic Frequency Hypothesis’. We found correlation between frequency and a body condition index, which may trigger social selection processes in this species sexually dimorphic in CF. Combined social and environmental selection on CF could trigger diversification of bats along ecotones separating habitats with contrasting air humidity. [ABSTRACT FROM AUTHOR]

Presents a study on echolocation signals broadcast by free-flying naked-backed bats (Pteronotus davyi) from Panama. Materials and methods; Results; Discussion.

Presents a study on the echolocation behavior in the Cuban subspecies of Molossus molossus to investigate how search calls might be adapted to match the bat's hearing capabilities and optimize chance of detecting an insect. Materials and methods; Results; Discussion.

Contends the reliability of acoustic identification of species of bats using the qualitative approach. Points raised on the paper of Barclay (1999); Need for recognition of limitation in equipment and methods used; Suggestions forwarded.

Criticizes the qualitative approach of monitoring and acoustic identification of echolocation calls for identification of species of bats in the field. Intraspecific variation in bat echolocation calls; Limitations of equipment and methods; Guidelines for use of the method in field studies.

Focuses on a study on the identification of species of free-flying bats using the Titley Electronics Anabat II ultrasonic detector. Qualitative procedure and structural characteristics; Analysis of the echolocation calls of bats; Features of Anabat II.

Studies echolocation calls of bats over two streams in the Oregon Coast Range using Anabat II detectors. Correlation of the activity of bats with biomass of insects and minimum nightly temperature; Negative correlation of activity of bats with length of night; Implications of temporal variation in activity of bats on sampling.

Uses monitoring of echolocation calls to assess levels of activity of bats at altitudes less than or equal to 600 meters at a field site in Zimbabwe. Activity of echolocating bats at different altitudes shown as numbers of species encountered with the most energy in different bandwidths.

Presents the conservation implications of some recent findings about the ecology and behavior of bats, notably patterns of habitat use, foraging, and roosting. Utilization of echolocation method to capture the sounds that bats produce; Description of the patterns of bats' habitat use; Bats' food and feeding habits; Activities by humans and bats; Impact of perceptions of bats by humans.

Presents information on the history of study of the echolocation behavior of bats, or their use of sonar to avoid obstacles and catch flying insects and other prey. Importance of bats' ears for orientation when flying in the dark; Speculation by Hiram Maxim that bats might detect obstacles by emitting low-frequency sounds; Discovery that bats do not fly in total silence.