Identification of sympatric bat species by the echolocation calls

One hundred and thirty-eight echolocation calls of 63 free-flying individuals of five bat species (Rhinolophus ferrumequinum,Myotis formosus,Myotis ikonnikovi,Myotis daubentoni and Murina leucogaster)were recorded (by ultrasonic bat detector (D980)) in Zhi'an village of Jilin Province,China.According to the frequency-time spectra,these calls were categorized into two types:FM/CF (constant frequency) / FM (R.ferrumequinum) and FM (frequency modulated)(M.formosus,M.ikonnikovi,M.daubentoni and M.leucogaster).Sonograms of the calls of R.ferrumequinum could easily be distinguished from those of the other four species.For the calls of the remaining four species,six echolocation call parameters,including starting frequency,ending frequency,peak frequency duration,longest inter-pulse interval and shortest inter-pulse interval,were examined by stepwise discriminant analysis.The results show that 84.1% of calls were correctly classified,which indicates that these parameters of echolocation calls play an important role in identifying bat species.These parameters can be used to test the accuracy of general predictions based on bats' morphology in the same forest and can provide essential information for assessing patterns of bat habitat use.     

Identification of sympatric bat species by the echolocation calls

One hundred and thirty-eight echolocation calls of 63 free-flying individuals of five bat species (Rhinolophus ferrumequinum, Myotis formosus, Myotis ikonnikovi, Myotis daubentoni and Murina leucogaster) were recorded (by ultrasonic bat detector (D980)) in Zhi’an village of Jilin Province, China. According to the frequency-time spectra, these calls were categorized into two types: FM/CF (constant frequency) / FM (R. ferrumequinum) and FM (frequency modulated) (M. formosus, M. ikonnikovi, M. daubentoni and M. leucogaster). Sonograms of the calls of R. ferrumequinum could easily be distinguished from those of the other four species. For the calls of the remaining four species, six echolocation call parameters, including starting frequency, ending frequency, peak frequency duration, longest inter-pulse interval and shortest inter-pulse interval, were examined by stepwise discriminant analysis. The results show that 84.1% of calls were correctly classified, which indicates that these parameters of echolocation calls play an important role in identifying bat species. These parameters can be used to test the accuracy of general predictions based on bats’ morphology in the same forest and can provide essential information for assessing patterns of bat habitat use. __________ Translated from Journal of Northeast Normal University (Natural Science Edition), 2006, 38 (3): 109–114 [译自: 东北师范大学学报(自然科学版)]     

Variations in the echolocation calls of the European free-tailed bat

The echolocation calls of Tadarida teniotis were studied in an outdoor flight enclosure (captive individuals) and in the wild using single microphones or an array of four microphones. Calls were characterized by measures of 10 call variables. Comparison of individual calls recorded on four microphones arrayed in a tetrahedron with 1 m between each microphone revealed that all calls were not equally detectable by all microphones but that there were no significant differences in call features obtained from calls recorded on all four microphones. A comparison of 47 calls recorded by all four microphones showed no significant differences in the features of the four recordings of each call. Analysis of calls of five individuals flying individually in an outdoor flight cage revealed significant individual differences in call features. In the field, T. teniotis used long, narrowband search-phase calls, usually without harmonics. Analysis of 1876 search-phase echolocation calls of T. teniotis recorded in the field in Israel and Greece in 2002, 2005 and 2006 showed significant year-to-year and site-to-site differences in some call features. When flying in the presence of conspecifics, T. teniotis changed their echolocation calls. We found a range of different buzzes in the wild, and based on their structure we attempted to classify them as feeding and social buzzes. The features of individual calls comprising buzzes differed significantly among buzzes, and yet there were no consistent differences between what we classified as feeding and social buzzes.     

On population encoding and decoding of auditory information for bat echolocation

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.     

Moth wing scales slightly increase the absorbance of bat echolocation calls

Coevolutionary arms races between predators and prey can lead to a diverse range of foraging and defense strategies, such as countermeasures between nocturnal insects and echolocating bats. Here, we show how the fine structure of wing scales may help moths by slightly increasing sound absorbance at frequencies typically used in bat echolocation. Using four widespread species of moths and butterflies, we found that moth scales are composed of honeycomb-like hollows similar to sound-absorbing material, but these were absent from butterfly scales. Micro-reverberation chamber experiments revealed that moth wings were more absorbent at the frequencies emitted by many echolocating bats (40-60 kHz) than butterfly wings. Furthermore, moth wings lost absorbance at these frequencies when scales were removed, which suggests that some moths have evolved stealth tactics to reduce their conspicuousness to echolocating bats. Although the benefits to moths are relatively small in terms of reducing their target strengths, scales may nonetheless confer survival advantages by reducing the detection distances of moths by bats by 5-6%.     

Directional sensitivity of echolocation in the horseshoe bat,Rhinolophus ferrumequinum

Summary The directionality of sound emission by a horseshoe bat (Rhinolophus ferrumequinum) has been determined for the constant frequency component of its orientation sounds. The bat was fixed in the center of an acoustic perimeter and the SPL of the orientation sounds measured with a scanning microphone at different angles compared with the SPL measured by another microphone located in the direction perpendicular to the plane of the horseshoe-like structure of the nose-leaf. The maximum SPL was always found in this direction which also corresponds to the flight direction of a bat in horizontal flight. Above and lateral to this direction the SPL decreases steadily with -6 dB-points at 24 above and 23 lateral. Below the flight direction we found a prominent side lobe with a -6 dB-point at 64 .When the present data are combined with measurements of the behavioral directionality of hearing at the same frequency (Grinnell and Schnitzler, 1977), the directionality diagram of the entire echolocation system is very narrow and points in the flight direction. The prominent downward side lobe of emission does not conspicuously increase echolocation effectiveness in the direction of the ground, since hearing sensitivity is falling off so steeply in that direction. However, without this downward beam of emission, signals from below the bat would be that much less effective.Interference with the structure of the nose-leaf by covering the upper part with vaseline or plugging the left nostril destroyed the smoothness of the normal sound field and demonstrated that this complex organ is a highly functional structure optimized in the course of evolution.With differences in mood or attention, the emitted pulses varied by as much as 20 dB (80–100 dB). The emission directionality pattern also varied. In most cases, as orientation sounds increased in SPL, the acoustic beam became smaller.Supported by Deutsche Forschungsgemeinschaft, grant No. Schn 138/1-6, Stiftung Volkswagenwerk, grant No. 111 858, and the Alexander von Humboldt StiftungWe thank W. Hollerbach and C. Nitsche for technical assistance.     

Mechanical adaptations for echolocation in the cochlea of the bat Hipposideros lankadiva

The cochlear mechanics of bats with long constant-frequency components in their echolocation calls are sharply tuned to the dominant second harmonic constant frequency. Hipposiderid bats employ a shorter constant-frequency call component whose frequency is less stable than in long-constant-frequency bats. To investigate to what degree cochlear mechanics in hipposiderid bats are already specialized for the processing of constant frequencies, we recorded distortion-product otoacoustic emissions in Hipposideros lankadiva. Iso-distortion threshold curves for the 2f1-f2 distortion-product otoacoustic emission reveal a threshold maximum close to the second harmonic constant frequency, between 65.0 and 70.0 kHz, and a second insensitivity close to the first harmonic constant frequency. The group delay of the 2f1-f2 distortion is prolonged for both frequency ranges, indicating that a specialized cochlear resonance may act to absorb the constant-frequency call components. Compared to long-constant-frequency bats, the threshold maximum at the second harmonic constant frequency is less pronounced and the optimum cochlear frequency separation is larger. Distortion-product otoacoustic emission suppression tuning curves and neuronal tuning curves recorded from neurons in the cochlear nucleus display an increase of tuning sharpness close to the second harmonic constant-frequency range which is smaller than that reported for long-constant-frequency bats. Our data suggest that the cochlea of hipposiderid bats represents an intermediate state between that of non-specialized bats and long-constant-frequency bats.     

Recognition of spatial parameters by echolocation in the vampire bat,Desmodus rotundus

Summary Three vampire bats (Desmodus rotundus) were trained in a two-choice apparatus (Fig. 1) to select the one of two passages that contained a vertical stick or narrow metal strip at a distance of 45 cm. To single sticks in isolation they responded at a width of 1.1 mm or more. Large surfaces in the vicinity of the target impaired the locating ability; the animals correctly choose a 20-mm-wide strip 2.5 cm in front of a strongly reflecting plate (Fig. 2) or 6 cm away on one side of it (Fig. 3).In a flight tunnel the response to single vertical obstacles of various size was studied. The sudden increase in echolocation-sound repetition rate as the obstacle was approached marked the response distance. This distance was 50–80 cm for thread obstacles 0.5 mm thick; the threshold diameter was 0.23 mm (Fig. 6). When the obstacles were mounted in a 30-cm-wide constriction of the tunnel the response occurred later; even a 10-mm-wide strip did not elicit a change in the sound pattern until the bats had approached to a distance of 60 cm (Fig. 6). The response distance increased significantly when the obstacles were moved in front of or beyond the constriction (Fig. 8).     

A comparison of supervised learning techniques in the classification of bat echolocation calls

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.     

五种蝙蝠形态与回声定位叫声的性别差异

为研究角菊头蝠(Rhinolophus cornutus)、三叶蹄蝠(Aselliscus uheeleri)、大蹄蝠(Hipposideros armiger)、大鼠耳蝠(Myotis myotis)和大足鼠耳蝠(M．riketti)的形态和回声定位叫声的性别差异性,明确同种蝙蝠雌雄个体对食物、栖息地等资源利用的细微差异,我们利用超声波探测仪、Batsound分析软件及SPSS11．0统计软件对5种95只蝙蝠进行了录音、声波分析和统计分析。5种蝙蝠形态性别差异性不显著,角菊头蝠、三叶蹄蝠、大蹄蝠和大足鼠耳蝠叫声频率性别差异性显著,大鼠耳蝠叫声频率性别差异性不显著。角菊头蝠雌性叫声的基频、分音、主频率高于雄性,声脉冲时间、间隔时间大于雄性,调频(FM)带宽小于雄性;三叶蹄蝠、大蹄蝠叫声的基频、主频率雄性高于雌性,调频带宽雌性小于雄性;大足鼠耳蝠叫声的主频率雄性高于雌性,FM带宽雌性大于雄性[动物学报49(6)：742～747,2003]。     

Acoustic imaging in bat sonar: Echolocation signals and the evolution of echolocation

Summary Echolocating bats behave as though they perceive the crosscorrelation functions between their sonar transmissions and echoes as images of targets, at least with respect to perception of target range, horizontal direction, and shape. These data imply that bats use a multi-dimensional acoustic imaging system for echolocation with broadband, usually frequencymodulated signals. The perceptual structure of the echolocation signals used by different species of bats was investigated using the crosscorrelation functions between emitted signals and returning echoes as indices of perceptual acuity.Thebandwidth andaverage period of echolocation signals are identified as the principal acoustic features of broadband sonar waveforms that determine the quality of target perceptions. The multiple-harmonic structure of echolocation sounds, which is characteristic of the broadband signals of the majority of species of bats, yields a lower average period (separation of peaks in the crosscorrelation function) than would be expected from the average frequency of the signal as a whole, sharpening target localization.The frequency-modulation of the harmonics in the sonar sounds of bats reduces the heights of side-peaks in the crosscorrelation functions of the signals, promoting sharp, unambiguous determination of target position, and leads to the well-known coupling of perception of range and velocity for moving targets. The shapes of the frequency sweeps and bandwidths of frequency modulation contribute to reducing this range-velocity coupling. Harmonic organization nearly eliminates range-velocity coupling.The use of multiple-harmonics and fairly broad frequency modulation in sonar signals yields especially sharp resolution of target position to reject clutter interference. Such signals are commonly used by bats in cluttered environments. Very broad frequency sweeps with fewer harmonics may accomplish the same effect, but the low signal periodicity contributed by harmonic structure is an important factor in banishing side-peaks in the crosscorrelation function from perception.Abbreviations ACR autocorrelation function - AMB ambiguity diagram - CF constant frequency - FM frequency modulated - LFM linear frequency sweep - LPM linear period sweep - XCR crosscorrelation function     

Evolutionary aspects of calmodulin

Calmodulin (CaM) is a major cellular sensor of calcium signaling, interacts with numerous proteins associated with cellular second messenger systems (e.g., cyclic AMP, nitric oxide), and is associated with neurosecretory activity. An identical CaM protein consisting of four helix-loop-helix regions that arose by gene duplication is encoded by three nonallelic mammalian genes that are some of the most highly conserved genes known. Differential tissue and cellular expression of each CaM suggest unique functions that promote strong selective preservation of these replicate, yet distinct, CaM genes in mammals. Each gene displays the same exon-intron arrangement but is characterized by distinct promoter elements and by unique 5'- and 3'-untranslated regions that are highly conserved among human, rat, and mouse. These distinct untranslated regions may permit regulation of CaM levels at discrete cellular sites during differentiation and in highly specialized cell types such as neurons.     

Spatial processing within the mustache bat echolocation system: possible mechanisms for optimization

1. The directionality of an echolocation system is determined by the acoustic properties of both the emitter and receiver, i.e., by the radiation pattern of the emitted pulse and the directionally of the external ears. We measured the directionality of the echolocation system of the greater mustache bat (Pteronotus parnellii) at the 30 kHz, 60 kHz and 90 kHz harmonics of its echolocation pulse by summing, at points throughout the frontal sound field, the echo attenuation due to the spread of pulse energy and the attenuation due to the spread of pulse energy and the attenuation due to the directionality of its external ears. The pulse radiation pattern at the 3 harmonics was measured by comparing the output of a microphone moved throughout the frontal sound field against a second reference microphone at the center of the field. External ear directionality at the 3. harmonics was measured by presenting free-field sounds throughout the frontal sound field, and recording the intensity thresholds of cochlear microphonic potentials, and the intensity thresholds of monaural neurons in the inferior colliculus tuned to one of the 3 harmonics. 2. When compared with ear directionality, the echolocation system was found to be more directional for the center of the sound field in several respects. At all harmonics, attenuation of sounds originating in the peripheral part of the field was increased by 10 to 13 dB. Areas of maximum sound intensity contracted toward the center of the field. Also, the isointensity contours of the echolocation system were more radially symmetrical about the center of the field. 3. At 60 kHz, sound intensity along the azimuth within the echolocation system was nearly constant 26 degrees to either side of the center of the field. This suggests that the radiation pattern of the echolocation pulse and the directionality of the external ears complement one another to produce an acoustic environment at the center of the sound field in which stimulus intensity is stabilized to allow more effective analysis of various aspects of the echolocation target. In particular, we suggest that this intensity stabilization may allow the bat to more effectively resolve the interaural intensity differences it uses to localize prey. 4. Predictions of the azimuthal spatial tuning of binaurally sensitive neurons in the inferior colliculus within the echolocation system were compared with their spatial tuning when only ear directionality is considered.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dietary composition and echolocation call design of three sympatric insectivorous bat species from China

Studying the diet of echolocating, insectivorous bats can provide important insights into their foraging behaviors and ecological constraints they are facing. By examining an extensive data set covering a period of 2 years, the present study identifies the dietary composition of three sympatric insectivorous bat species in rural areas of Beijing municipality. Each species clearly has different preferences for particular food items. Greater horseshoe bats, Rhinolophus ferrumequinum, preferred to catch nocturnal, actively flying insects, mostly moths (Lepidoptera), and to a lesser percentage flies (Diptera), beetles (Coleoptera), and flying ants and termites (Hymenoptera). Other nocturnal insects which do not exhibit any perceptible wing movements, such as true bugs (Homoptera), or strictly diurnal insects that hardly ever fly in the dark, such as grasshoppers (Orthoptera) and dragon- and damselflies (Odonata), were never found in droppings of horseshoe bats. Large mouse-eared bats, Myotis chinensis, preferentially glean relatively large terrestrial prey of the order Coleoptera (mostly carabid beetles) and Orthoptera, whereas greater tube-nosed bats, Murina leucogaster, consume predominantly smaller, diurnal Coleoptera (mostly soldier beetles, Cantharidae, and ladybugs, Coccinellidae). Our findings also indicate previously not described, significant spectro-temporal differences in the echolocation signals of M. chinensis and M. leucogaster. The results suggest that in our study area the dramatic differences in the dietary composition of these three bat species are mainly based upon differences in their foraging behaviors, including differences in their echolocation signal structure. The dietary data provide important background information for conservational efforts, such as habitat protection.     

大足鼠耳蝠的翼型和回声定位声波特征

大足鼠耳蝠(Myotis ricketti Thomas,1894)属翼手目(Chiroptera),蝙蝠科(Vespertilionidae),鼠耳蝠属(Myotis).     

Moth hearing in response to bat echolocation calls manipulated independently in time and frequency

We measured the auditory responses of the noctuid moth Noctua pronuba to bat echolocation calls which were manipulated independently in time and frequency. Such manipulations are important in understanding how insect hearing influences the evolution of echolocation call characteristics. We manipulated the calls of three bat species (Rhinolophus hipposideros, Myotis nattereri and Pipistrellus pipistrellus) that use different echolocation call features by doubling their duration or reducing their frequency, and measured the auditory thresholds from the A1 cells of the moths. Knowing the auditory responses of the moth we tested three predictions. (i) The ranking of the audibility of unmanipulated calls to the moths should be predictable from their temporal and/or frequency structure. This was supported. (ii) Doubling the duration of the calls should increase their audibility by ca. 3 dB for all species. Their audibility did indeed increase by 2.1-3.5 dB. (iii) Reducing the frequency of the calls would increase their audibility for all species. Reducing the frequency had small effects for the two bat species which used short duration (2.7-3.6 ms) calls. However, the relatively long-duration (50 ms), largely constant-frequency calls of R. hipposideros increased in audibility by 21.6 dB when their frequency was halved. Time and frequency changes influence the audibility of calls to tympanate moths in different ways according to call design. Large changes in frequency and time had relatively small changes on the audibility of calls for short, largely broadband calls. Channelling energy into the second harmonic of the call substantially decreased the audibility of calls for bats which use long-duration, constant-frequency components in echolocation calls. We discuss our findings in the contexts of the evolution of both bat echolocation call design and the potential responses of insects which hear ultrasound.