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PubMed1999

Echolocation behaviour and prey-capture success in foraging bats: laboratory and field experiments on Myotis daubentonii.

During prey-capture attempts, many echolocating bats emit a 'terminal buzz', when pulse repetition rate is increased and pulse duration and interpulse interval are shortened. The buzz is followed by a silent interval (the post-buzz pause). We investigated whether variation in the structure of the terminal buzz, and the calls and silent periods following it, may provide information about whether the capture attempt was successful and about the size of prey detected - detail that is valuable in studies of habitat use and energetics. We studied the trawling bat Myotis daubentonii. The time between the first call of the approach phase and the end of the terminal phase was not related to prey size in the laboratory. The last portion of the terminal buzz (buzz II) was shortened or omitted during aborted capture attempts. Both in the laboratory and in the field, the mean interpulse interval immediately after the terminal buzz (post-buzz interpulse interval) was longer in successful captures than in unsuccessful attempts. In the laboratory, the post-buzz pause was longer after successful captures than for unsuccessful attempts, and the minimum frequency of the first search-phase call emitted after the buzz (Fmin) was higher than that of the last such call prior to the buzz. These effects were not apparent in field data. Both in the laboratory (85%) and in the field (74%), significant discrimination between successful and unsuccessful capture attempts was possible when the duration of the post-buzz pause, post-buzz interpulse interval and Fmin were entered into a discriminant analysis. Thus, variation in the echolocation calls of bats during prey-capture attempts can reveal substantial information about capture success and prey size.

Animals↗
PubMed1999

Scaling of echolocation call parameters in bats.

I investigated the scaling of echolocation call parameters (frequency, duration and repetition rate) in bats in a functional context. Low-duty-cycle bats operate with search phase cycles of usually less than 20 %. They process echoes in the time domain and are therefore intolerant of pulse-echo overlap. High-duty-cycle (>30 %) species use Doppler shift compensation, and they separate pulse and echo in the frequency domain. Call frequency scales negatively with body mass in at least five bat families. Pulse duration scales positively with mass in low-duty-cycle quasi-constant-frequency (QCF) species because the large aerial-hawking species that emit these signals fly fast in open habitats. They therefore detect distant targets and experience pulse-echo overlap later than do smaller bats. Pulse duration also scales positively with mass in the Hipposideridae, which show at least partial Doppler shift compensation. Pulse repetition rate corresponds closely with wingbeat frequency in QCF bat species that fly relatively slowly. Larger, fast-flying species often skip pulses when detecting distant targets. There is probably a trade-off between call intensity and repetition rate because 'whispering' bats (and hipposiderids) produce several calls per predicted wingbeat and because batches of calls are emitted per wingbeat during terminal buzzes. Severe atmospheric attenuation at high frequencies limits the range of high-frequency calls. Low-duty-cycle bats that call at high frequencies must therefore use short pulses to avoid pulse-echo overlap. Rhinolophids escape this constraint by Doppler shift compensation and, importantly, can exploit advantages associated with the emission of both high-frequency and long-duration calls. Low frequencies are unsuited for the detection of small prey, and low repetition rates may limit prey detection rates. Echolocation parameters may therefore constrain maximum body size in aerial-hawking bats.

Animals↗
PubMed2006

Echolocating bats use a nearly time-optimal strategy to intercept prey.

Acquisition of food in many animal species depends on the pursuit and capture of moving prey. Among modern humans, the pursuit and interception of moving targets plays a central role in a variety of sports, such as tennis, football, Frisbee, and baseball. Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion--such as a ballistic baseball, or a piece of food sinking in water. Many animals, however, have to capture prey that may make evasive and unpredictable maneuvers. Is CB an optimum solution to pursuing erratically moving targets? Do animals faced with such erratic prey also use CB? In this paper, we address these questions by studying prey capture in an insectivorous echolocating bat. Echolocating bats rely on sonar to pursue and capture flying insects. The bat's prey may emerge from foliage for a brief time, fly in erratic three-dimensional paths before returning to cover. Bats typically take less than one second to detect, localize and capture such insects. We used high speed stereo infra-red videography to study the three dimensional flight paths of the big brown bat, Eptesicus fuscus, as it chased erratically moving insects in a dark laboratory flight room. We quantified the bat's complex pursuit trajectories using a simple delay differential equation. Our analysis of the pursuit trajectories suggests that bats use a constant absolute target direction strategy during pursuit. We show mathematically that, unlike CB, this approach minimizes the time it takes for a pursuer to intercept an unpredictably moving target. Interestingly, the bat's behavior is similar to the interception strategy implemented in some guided missiles. We suggest that the time-optimal strategy adopted by the bat is in response to the evolutionary pressures of having to capture erratic and fast moving insects.

Animals↗
PubMed1984

Automatic gain control in the bat's sonar receiver and the neuroethology of echolocation.

The sensitivity of the echolocating bat, Eptesicus fuscus, to sonar echoes at different time delays after sonar emissions was measured in a two-choice echo detection experiment. Since echo delay is perceptually equivalent to target range, the experiment effectively measured sensitivity to targets at different ranges. The bat's threshold for detecting sonar echoes at a short delay of only 1.0 msec after emissions (corresponding to a range of 17 cm) was 36 dB SPL (peak to peak), but the threshold decreased to 8 dB SPL at a longer delay of 6.4 msec (a range of 1.1 m). Prior research has shown that, at even longer delays (corresponding to ranges of 3 to 5 m), the bat's threshold is in the region of 0 dB SPL. Contractions of the bat's middle ear muscles synchronized with the production of echolocation sounds cause a transient loss in hearing sensitivity which appears to account for the observed echo detection threshold shifts. The bat's echo detection thresholds increase by approximately 11 dB for each reduction in target range by a factor of 2 over the span from 17 cm to 1.1 m. As range shortens, the amplitude of echoes from small targets also increases, by 12 dB for each 2-fold reduction in range. Thus, when approaching a target, the bat compensates for changes in echo strength as target range shortens by changing its hearing threshold. Since this compensation appears to occur in the middle ear, the bat regulates echoes reaching the cochlea to a stable amplitude during its approach to a target such as a flying insect. In addition to this automatic gain control linked to target range, the bat aims its head to track a target's position during approach, thus stabilizing echo amplitude even if the target's direction changes. We hypothesize that the bat's directional emissions, directional hearing, middle ear muscle contractions, and head aim response collectively create a three-dimensional spatial tracking filter which the bat locks onto targets to stabilize echo amplitudes during interception of prey. We further hypothesize that this regulation, which cancels echo amplitude changes caused by the target's changing spatial position, leaves the bat free to observe echo amplitude changes caused by the target's own actions, such as insect wing beats. Elimination of spatially dependent echo amplitude changes removes the cause of potentially troublesome changes in neural response latency and keeps stimulation from echoes in the "tip" region of auditory nerve fiber tuning curves.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

Recognition of aspect-dependent three-dimensional objects by an echolocating Atlantic bottlenose dolphin.

We examined the ability of a bottlenose dolphin (Tursiops truncatus) to recognize aspect-dependent objects using echolocation. An aspect-dependent object such as a cube produces acoustically different echoes at different angles relative to the echolocation signal. The dolphin recognized the objects even though the objects were free to rotate and sway. A linear discriminant analysis and nearest centroid classifier could classify the objects using average amplitude, center frequency, and bandwidth of object echoes. The results show that dolphins can use varying acoustic properties to recognize constant objects and suggest that aspect-independent representations may be formed by combining information gleaned from multiple echoes.

Acoustics↗
PubMed1997

Spatially selective auditory responses in the superior colliculus of the echolocating bat.

When a bat approaches a target, it continuously modifies its echolocation sounds and relies on incoming echo information to shape the characteristics of its subsequent sonar cries. In addition, acoustic information about the azimuth and elevation of a sonar target elicits orienting movements of the head and pinnae toward the sound source. This requires a common sensorimotor interface, where echo information is used to guide motor behaviors. Using single-unit neurophysiological methods and free-field auditory stimulation, we present data on biologically relevant specializations in the superior colliculus (SC) of the bat for orientation by sonar. In the bat's SC, two classes of spatially tuned neurons are distinguished by their sensitivity to echoes. One population shows facilitated, delay-tuned responses to pairs of sounds, simulating sonar emissions and echoes. Delay tuning, related to encoding target range, may play a role in guiding motor responses in echolocation, because the bat adjusts its emissions with changes in target distance. The delay-facilitated response depends on the direction of stimulation and on the temporal relationship between the simulated emission and echo in the sound pair, suggesting that this class of neurons represents the location of a target in three dimensions. A second population encodes the target in two dimensions, azimuth and elevation, and does not show a facilitated response to echoes delivered from any locus. Encoding of azimuth and elevation may be important for directing head aim, and this class may function in transforming auditory spatial information into signals used to guide acoustic orientation.

Acoustic Stimulation↗
PubMed2004

Echolocation clicks of two free-ranging, oceanic delphinids with different food preferences: false killer whales Pseudorca crassidens and Risso's dolphins Grampus griseus.

Toothed whales (Odontoceti, Cetacea) navigate and locate prey by means of active echolocation. Studies on captive animals have accumulated a large body of knowledge concerning the production, reception and processing of sound in odontocete biosonars, but there is little information about the properties and use of biosonar clicks of free-ranging animals in offshore habitats. This study presents the first source parameter estimates of biosonar clicks from two free-ranging oceanic delphinids, the opportunistically foraging Pseudorca crassidens and the cephalopod eating Grampus griseus. Pseudorca produces short duration (30 micro s), broadband (Q=2-3) signals with peak frequencies around 40 kHz, centroid frequencies of 30-70 kHz, and source levels between 201-225 dB re. 1 micro Pa (peak to peak, pp). Grampus also produces short (40 micro s), broadband (Q=2-3) signals with peak frequencies around 50 kHz, centroid frequencies of 60-90 kHz, and source levels between 202 and 222 dB re. 1 micro Pa (pp). On-axis clicks from both species had centroid frequencies in the frequency range of most sensitive hearing, and lower peak frequencies and higher source levels than reported from captive animals. It is demonstrated that sound production in these two free-ranging echolocators is dynamic, and that free-ranging animals may not always employ biosonar signals comparable to the extreme signal properties reported from captive animals in long-range detection tasks. Similarities in source parameters suggest that evolutionary factors other than prey type determine the properties of biosonar signals of the two species. Modelling shows that interspecific detection ranges of prey types differ from 80 to 300 m for Grampus and Pseudorca, respectively.

Animal Communication↗
PubMed1966

Discriminative echolocation in a porpoise.

Operant conditioning techniques were used to establish a discriminative echolocation performance in a porpoise. Pairs of spheres of disparate diameters were presented in an under-water display, and the positions of the spheres were switched according to a scrambled sequence while the blindfolded porpoise responded on a pair of submerged response levers. Responses which identified the momentary state of the display were food-reinforced, while those which did not (errors) produced time out. Errors were then studied in relation to decreased disparity between the spheres. As disparity was decreased, errors which terminated runs of correct responses occurred more frequently and were followed by longer strings of consecutive errors. Increased errors and disruption of a stable pattern of collateral behavior were associated. Since some sources of error other than decreased disparity were present, the porpoise's final performance did not fully reflect the acuity of its echolocation channel.

Animals↗
PubMedDate not supplied

[Experience with the use of echolocation in the diagnosis of extraorganic tumors of the neck].

Echolocation was used to diagnose extraorganic [correction of intraorgan] tumors of the neck in 18 patients. The results evidence that echo signals help locate the tumor and its relation to other tissues and organs of the neck, its structure and size, the presence of the capsule or aggressive growth, and locate tumorous nodes beyond the tumor. Echolocation of tumors of the neck is an informative and simple diagnostic method.

Female↗
PubMed2007

Parallel thalamocortical pathways for echolocation and passive sound localization in a gleaning bat, Antrozous pallidus.

We present evidence for parallel auditory thalamocortical pathways that serve two different behaviors. The pallid bat listens for prey-generated noise (5-35 kHz) to localize prey, while reserving echolocation [downward frequency-modulated (FM) sweeps, 60-30 kHz] for obstacle avoidance. Its auditory cortex contains a tonotopic map representing frequencies from 6 to 70 kHz. The high-frequency (BF > 30 kHz) representation is dominated by FM sweep-selective neurons, whereas most neurons tuned to lower frequencies prefer noise. Retrograde tracer injections into these physiologically distinct cortical regions revealed that the high-frequency region receives input from the suprageniculate (SG) nucleus, but not the ventral division of the medial geniculate body (MGBv), in all experiments (n = 9). In contrast, the low-frequency region receives tonotopically organized input from the MGBv in all experiments (n = 16). Labeling in the SG was observed in only two of these experiments. Both cortical regions also receive sparse inputs from medial (MGBm) and parts of the dorsal division (MGBd) outside the SG. These results show that the low- and high-frequency regions of a single tonotopic map receive dominant inputs from different thalamic divisions. Within the low-frequency region, most neurons are binaurally inhibited, and an orderly map of interaural intensity difference (IID) sensitivity is present. We show that the input to the IID map arises from topographically organized projections from the MGBv. As observed in other species, a frequency-dependent organization is observed in the lateromedial direction in the MGBv. These data demonstrate that MGBv-to-auditory cortex connections are organized with respect to both frequency and binaural selectivity.

Action Potentials↗
PubMed1993

Cephalometric correlates of echolocation in the chiroptera.

This study suggests that the evolution of head posture in bats is constrained by the demands of vocalization during echolocation. Nasal-emitting microchiropteran taxa are easily identified by their characteristic rotation of the basicranium ventrally about the cervical axis, the depression of the rostrum below the basicranial axis, and by the rotation of the lateral semicircular canals so as to maintain their horizontal orientation during flight. The converse is true for oral-emitting Microchiroptera. The general form of the microchiropteran skull has been canalized along two distinct evolutionary paths, respectively, towards oral-emitting or nasal-emitting forms.

Animals↗
PubMed1996

Integration time for short broad band clicks in echolocating FM-bats (Eptesicus fuscus).

Vespertilionid FM-bats (four Eptesicus fuscus and one Vespertilio murinus) were trained in an electronic phantom target simulator to detect synthetic echoes consisting of either one or two clicks. The threshold sound pressure for single clicks was around 47 dB peSPL for all five bats corresponding to a threshold energy of -95 dB re 1 Pa2*s. By varying the interclick interval, delta T, for double clicks it was shown that the threshold intensity was around -3 dB relative to the threshold for single clicks at delta T up to 2.4 ms, indicating perfect power summation of both clicks. A threshold shift of -13.5 dB for a 1 ms train of 20 clicks (0.05 ms interclick interval) confirmed that the bats integrated the power of the stimuli. At delta T longer than around 2.5 ms the threshold for double clicks was the same as for single clicks. Thus, the bats performed like perfect energy detectors with an integration time of approximately 2.4 ms. This integration time is an order of magnitude shorter than that reported for bats listening passively for pure tones. In our setup the bats emitted sonar signals with durations of 2-3 ms. Hence, the results may indicate that while echolocating the bats integration time is adapted to the duration of the sonar emissions.

Animals↗
PubMed1990

Convergence of temporal and spectral information into acoustic images of complex sonar targets perceived by the echolocating bat, Eptesicus fuscus.

1. FM echolocating bats (Eptesicus fuscus) were trained to discriminate between a two-component complex target and a one-component simple target simulated by electronically-returned echoes in a series of experiments that explore the composition of the image of the two-component target. In Experiment I, echoes for each target were presented sequentially, and the bats had to compare a stored image of one target with that of the other. The bats made errors when the range of the simple target corresponded to the range of either glint in the complex target, indicating that some trace of the parts of one image interfered with perception of the other image. In Experiment II, echoes were presented simultaneously as well as sequentially, permitting direct masking of echoes from one target to the other. Changes in echo amplitude produced shifts in apparent range whose pattern depended upon the mode of echo presentation. 2. Eptesicus perceives images of complex sonar targets that explicitly represent the location and spacing of discrete glints located at different ranges. The bat perceives the target's structure in terms of its range profile along a psychological range axis using a combination of echo delay and echo spectral representations that together resemble a spectrogram of the FM echoes. The image itself is expressed entirely along a range scale that is defined with reference to echo delay. Spectral information contributes to the image by providing estimates of the range separation of glints, but it is transformed into these estimates. 3. Perceived absolute range is encoded by the timing of neural discharges and is vulnerable to shifts caused by neural amplitude-latency trading, which was estimated at 13 to 18 microseconds per dB from N1 and N4 auditory evoked potentials in Eptesicus. Spectral cues representing the separation of glints within the target are transformed into estimates of delay separations before being incorporated into the image. However, because they are encoded by neural frequency tuning rather than the time-of-occurrence of neural discharges, the perceived range separation of glints in images is not vulnerable to amplitude-latency shifts. 4. The bat perceives an image that is displayed in the domain of time or range. The image receives no evident spectral contribution beyond what is transformed into delay estimates. Although the initial auditory representation of FM echoes is spectrogram-like, the time, frequency, and amplitude dimensions of the spectrogram appear to be compressed into an image that has only time and amplitude dimensions.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1991

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat, Rhinolophus rouxi.

Doppler shift compensation behaviour in horseshoe bats, Rhinolophus rouxi, was used to test the interference of pure tones and narrow band noise with compensation performance. The distortions in Doppler shift compensation to sinusoidally frequency shifted echoes (modulation frequency: 0.1 Hz, maximum frequency shift: 3 kHz) consisted of a reduced compensation amplitude and/or a shift of the emitted frequency to lower frequencies (Fig 2). Pure tones at frequencies between 200 and 900 Hz above the bat's resting frequency (RF) disturbed the Doppler shift compensation, with a maximum of interference between 400 and 550 Hz (Fig. 1). Minimum duration of pure tones for interference was 20 ms and durations above 40 ms were most effective (Fig. 3). Interfering pure tones arriving later than about 10 ms after the onset of the echolocation call showed markedly reduced interference (Fig. 4). Doppler shift compensation was affected by pure tones at the optimum interfering frequency with sound pressure levels down to -48 dB rel the intensity level of the emitted call (Fig. 5, 6). Narrow bandwidth noise (bandwidth from +/- 100 Hz to +/- 800 Hz) disturbed Doppler shift compensation at carrier frequencies between -250 Hz below and 800 Hz above RF with a maximum of interference between 250 and 500 Hz above resting frequency (Fig. 7). The duration and delay of the noise had similar influences on interference with Doppler shift compensation as did pure tones (Fig. 8, 9). Intensity dependence for noise interference was more variable than for pure tones (-32 dB to -45 dB rel emitted sound pressure level Fig. 10).(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

Electromotility of outer hair cells from the cochlea of the echolocating bat, Carollia perspicillata.

Isolated outer hair cells (OHCs) and explants ot the organ of Corti were obtained from the cochlea of the echolocating bat, Carollia perspicillata, whose hearing range extends up to about 100 kHz. The OHCs were about 10-30 microns long and produced resting potentials between -30 to -69 mV. During stimulation with a sinusoidal extracellular voltage field (voltage gradient of 2 mV/microns) cyclic length changes were observed in isolated OHCs. The displacements were most prominent at the level of the cell nucleus and the cuticular plate. In the organ of Corti explants, the extracellular electric field induced a radial movement of the cuticular plate which was observed using video subtraction and photodiode techniques. Maximum displacements of about 0.3-0.8 microns were elicited by stimulus frequencies below 100 Hz. The displacement amplitude decreased towards the noise level of about 10-30 nm for stimulus frequencies between 100-500 Hz, both in apical and basal explants. This compares well with data from the guinea pig, where OHC motility induced by extracellular electrical stimulation exhibits a low pass characteristic with a corner frequency below 1 kHz. The data indicate that fast OHC movements presumably are quite small at ultrasonic frequencies and it remains to be solved how they participate in amplifying and sharpening cochlear responses in vivo.

Animals↗
PubMed1996

Anatomical and physiological investigation of auditory input to the superior colliculus of the echolocating megachiropteran bat Rousettus aegyptiacus.

The objective of this study was to investigate whether a representation of auditory space in the superior colliculus (SC) of the echolocating megachiropteran bat (Rousettus aegyptiacus) exists. Additionally the subcortical auditory connectivity of the SC was investigated. A total of 207 units were recorded in five awake animals while presenting acoustic stimuli (white noise, clicks, and pure tones) at different positions in space. Six units responded to acoustic stimulation. Three of these located within the superficial layers and one located in the intermediate layers were classified as omnidirectional units. Two units were located within the deep layers. One was classified as a hemifield unit, and the other as a frontal unit. All units responded phasically to acoustic stimulation with a latency of 4-150 ms. None of them could be activated by visual stimuli. We further examined the interaction of paired auditory and visual stimulation in 116 visually responsive units. Responses to visual stimulation were markedly altered by acoustic stimulation in 5 units. The influence of the acoustic stimuli was temporally and spatially restricted, and resulted either in a reduction or an elevation of unit responsiveness. Horseradish peroxidase was injected into the SC of eight animals to investigate the auditory subcortical connectivity of the SC. Retrograde labeling in auditory structures was rare compared with labeling found in nonauditory structures (e.g., retina, substantia nigra, parabigeminal nucleus). In auditory structures retrograde labeling was found mainly in the external nucleus of the inferior colliculus and in the nucleus of the brachium of the inferior colliculus. To a lesser extent it was found in the nucleus sagulum and in the area medial to the lemniscal nuclei. In one case the dorsal nucleus of the lateral lemniscus and the anterolateral periolivary nucleus were labeled. Our results reveal only a sparse auditory input into the SC of the flying fox, R. aegyptiacus. On the basis of single-unit recordings, we did not find an elaborate representation of auditory space as it is described for several other species. The existence of auditory and bimodal neurones, in combination with their response properties, nonetheless indicate that there might be a representation of auditory space in the SC of R. aegyptiacus.

Acoustic Stimulation↗
PubMed1990

Neural control of vocalization in bats: mapping of brainstem areas with electrical microstimulation eliciting species-specific echolocation calls in the rufous horseshoe bat.

1. The functional role of brainstem structures in the emission of echolocation calls was investigated in the rufous horseshoe bat. Rhinolophus rouxi, with electrical low-current microstimulation procedures. 2. Vocalizations without temporal and/or spectral distortions could be consistently elicited at low threshold currents (typically below 10 microA) within three clearly circumscribed brainstem areas, namely, the deep layers and ventral parts of the intermediate layers of the superior colliculus (SC), the deep mesencephalic nucleus (NMP) in the dorsal and lateral midbrain reticular formation and in a distinct area medial to the rostral parts of the dorsal nucleus of the lateral lemniscus. The mean latencies in the three vocal areas between the start of the electrical stimulus and the elicited vocalizations were 47 msec, 38 msec and 31 msec, respectively. 3. In pontine regions and the cuneiform nucleus adjacent to these three vocal areas, thresholds for eliciting vocalizations were also low, but the vocalizations showed temporal and/or spectral distortions and were often accompanied or followed by arousal of the animal. 4. Stimulus intensity systematically influenced vocalization parameters at only a few brain sites. In the caudo-ventral portions of the deep superior colliculus the sound pressure level of the vocalizations systematically increased with stimulus intensity. Bursts of multiple vocalizations were induced at locations ventral to the rostral parts of the cuneiform nucleus. No stimulus-intensity dependent frequency changes of the emitted vocalizations were observed. 5. The respiratory cycle was synchronized to the electrical stimuli in all regions where vocalizations could be elicited as well as in more ventrally and medially adjacent areas not yielding vocalizations on stimulation. 6. The possible functional involvement of the "vocal" structures in the audio-vocal feedback system of the Dopplercompensating horseshoe bat is discussed.

Animals↗
PubMed1987

The echolocation and hunting behavior of the bat, Pipistrellus kuhli.

The echolocation and hunting behavior of Pipistrellus kuhli was studied in the field using multi-exposure photography synchronized with high-speed tape recordings. During the search phase, the bats used 8-12 ms signals with sweeps (sweep width 3-6 kHz) and pulse intervals near 100 ms or less often near 200 ms. The bats seemed to have individual terminal frequencies that could lie between 35 and 40 kHz. The duty cycle of searching signals was about 8%. The flight speed of hunting bats was between 4.0 and 4.5 m/s. The bats reacted to insect prey at distances of about 70 to 120 cm. Given the flight speed, the detection distance was estimated to about 110 to 160 cm. Following detection the bat went into the approach phase where the FM sweep steepened (to about 60 kHz bandwidth) and the repetition rate increased (to about 30 Hz). The terminal phase or 'buzz', which indicates prey capture (or attempted capture), was composed of two sections. The first section contained signals similar to those in the approach phase except that the pulse duration decreased and the repetition rate increased. The second section was characterized by a sharp drop in the terminal frequency (to about 20 kHz) and by very short pulses (0.3 ms) at rates of up to 200 Hz. Near the beginning of the buzz the bat prepared for capturing the prey by extending the wings and forming a tail pouch. A pause of about 100 ms in sound emission after the buzz indicated a successful capture (Fig. 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗