Surlykke, A. New York: Springer Find this resource:. Echolocation signals of the Atlantic bottlenose dolphin Tursiops truncatus in open waters. Fish Eds. New York: Plenum Press. New York: Springer-Verlag. Ayrapetyants, A. Echolocation in nature. Belkovich, V. Sensory bases of cetacean orientation. International Journal of Comparative Psychology, 19 , 25— Busnel, R. Animal sonar systems: Biology and bionics Vols. Animal sonar systems , New York: Plenum Press.
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Sound detection thresholds in marine mammals. Tavolga Ed. New York: Pergamon Press. Kellogg, W. Echo ranging in the porpoise. Science , , — Kick, S. Journal of Neuroscience, 4 , — Kloepper, L. Support for the beam focusing hypothesis in the false killer whale. Active echolocation beam focusing in the false killer whale Pseudorca crassidens Journal of Experimental Biology, , — Kyhn, L. Journal of Experimental Biology , , — Biosonar performance of foraging beaked whales Mesoplodon densirostris. Nasal sound production in echolocating delphinids Tursiops truncatus and Pseudorca crassidens is dynamic, but unilateral: Clicking on the right side and whistling on the left side.
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Nagai Ed. Honolulu, HA: Tokai University. Animal sonar: Processes and performance. A false killer whale adjusts its hearing when it echolocates.
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Oxford Research Encyclopedia of Neuroscience. Publications Pages Publications Pages. Oxford Research Encyclopedias Neuroscience. Search within subject: Select Cognitive Neuroscience Computational Neuroscience Development. Disorders of the Nervous System Invertebrate Neuroscience. Molecular and Cellular Systems Motor Systems. Biosonar and Sound Localization in Dolphins.
Read More. Search within Show Summary Details View PDF Biosonar and Sound Localization in Dolphins Summary and Keywords Toothed whales and dolphins, odontocete cetaceans, produce very loud biosonar sounds in order to navigate and to locate and catch their prey of fish and squid. Performance Capabilities of Dolphin Biosonar Toothed whales, including dolphins, have been measured to make arguably the loudest sounds produced by any animal when they are producing their sonar, or echolocation, clicks.
Outgoing Clicks, Two-Way Travel Time, and Distance Localization Bottlenose dolphins searching for a target at a fixed distance when they are not moving produce the next outgoing click around 20 milliseconds after the return of the echo from the preceding click Au, Click Production Mechanisms How does an animal working with fast traveling sound produce loud echolocation signals that are very precisely timed and rapidly changed? Click to view larger Figure 1. Exploitation Route Biological meatmaterials will inspire the very active field of cloaking, metamaterials and transformation acoustics.
Paul E. Nachtigall
These have great promise for sonar and radar applcaitions as well as building acoustics. Sectors Aerospace, Defence and Marine,Construction. It is increasingly used in the life sciences, as software is becoming available and amenable to the complexity of biological systems. Also, a large portion of accessibility is due to the power of modern desktop computers. This aspect - that we call Physical Ecology - is expanding and is poised to touch many realms of life Sciences. For us the impact has been significant as the model predictions have allowed us to better understand the sensory ecology of the organisms we study, mostly insects, but also plants.
Collaborator Contribution Provide training, support and access to imaging infrastructure. Support with analysis and interpretation. Impact Data produced are currently analysised for future publication. Collaborator Contribution Logistical support, consulting, and access to their collection and research infrastructure. Impact Data collection so far Start Year No Geographic Reach International Primary Audience Other audiences Results and Impact Gave presentation at the biggest and most influential topical international research conference.
The title is BATtleships and it shows how we can use ultrasound to detect and localize objects in the absence of light. No Geographic Reach Local Primary Audience Study participants or study members Results and Impact Bristol Moth Group led by Ray Barnett from Bristol City Museum is a stakeholder in the project through providing logistical support in acquiring specimens and developing the research focus.
Members of the research team provided feedback at the annual meeting of the moth group. Year s Of Engagement Activity Marc Wilhelm Holderied Principal Investigator. Bruce Drinkwater Co-Investigator. Daniel Robert Co-Investigator. We found that butterflies have stronger echoes than moths, which means moths are less visible to bat biosonar compared to a butterfly of the same size flying at night.
Biological meatmaterials will inspire the very active field of cloaking, metamaterials and transformation acoustics. Aerospace, Defence and Marine,Construction. This method is standard within the engineering and physics community. The method has impacted on our capacity to model the complex interaction of organisms with their physical environment. Our results suggest that lingual echolocation based on tongue clicks is in fact much more sophisticated than previously believed.
They also reveal a new parameter under active control in animal sonar—the angle between consecutive beams. Our findings suggest that acoustic scanning of space by mammals is highly flexible and modulated much more selectively than previously recognized. Most sensory systems have an active component, i. For example, eye movements are important for visual perception, sniffs are crucial for olfactory percepts, and finger movements for touch percepts. A classic example of an active-sensing system is bat echolocation, or biosonar.
Echolocating bats actively emit the energy with which they probe their surroundings, and they can control many aspects of sensory acquisition, such as the temporal or spectral resolution of their signals. A key open question in bat echolocation concerns bats' ability to actively change the area scanned by their emitted beam. Here, we used a large microphone array to study the echolocation behavior of Egyptian fruit bats.
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We found that these bats apply a new strategy to alter the area scanned by their beam; specifically, bats changed their acoustic field-of-view by changing the direction of consecutively emitted beams. Importantly, they did so in an environment-dependent manner, increasing the scanned area more when there were more objects in their surroundings. They also increased their field-of-view when approaching a target. These findings provide the first example for active changes in sensing volume, which occur in response to changes in environmental complexity and target-distance, and they suggest that active sensing of space is more flexible than previously thought.
PLoS Biol 9 9 : e This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Dooling, PI provided travel support for YY.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Echolocating bats emit ultrasonic signals and analyze the returning echoes to perceive their surroundings. Bat echolocation, an active sensory system, enables an acoustic representation of the environment through precise control of outgoing sonar signals. Laryngeal bats control many aspects of their sensory acquisition: they determine the timing of acquisition and the information flow  —  , they control the intensity of the emission as well as its direction  —  , and they control the spectral and temporal resolution of the acquired data  — .
Another acoustic parameter potentially under active control by echolocating bats is the pattern of the sonar beam. It has been debated whether bats can actively adjust the width of the sonar beam in response to task conditions, but empirical studies have not yet adequately addressed this question.
It seems likely that bats would benefit greatly from the ability to control the beam pattern. They could for instance narrow the beam in order to concentrate energy onto a certain object, or they could widen the beam to increase the size of the sector that is being scanned.
Studying the bat's active control over the shape and directionality of sonar emissions is technically difficult because reconstruction of the beam pattern requires a large circumferential ultrasonic microphone array in a setting where a free-flying bat engages in sonar tasks. A recent study suggests that laryngeal echolocating bats can change the space covered by their beam through adjustments in their call spectrum . Here, we aimed to examine a very different mechanism by which echolocating bats might control the effective space they scan, namely adjustments in the angle between sequentially emitted sonar clicks.
We studied this question in lingual echolocating bats. Lingual echolocation is exhibited by one family of fruit bats, Rousettus , and has been historically considered to be more rudimentary than laryngeal echolocation . The primary reason behind this notion was that these bats were believed to have very little control over their sonar emissions.
In contrast, we recently demonstrated that the lingual echolocator Rousettus aegyptiacus Egyptian fruit bat uses a sophisticated strategy for beam-steering: This bat emits sonar clicks in pairs, and it directs the maximum slope of each sonar beam towards the target, rather than directing the center of the beam, thereby optimizing stimulus localization in the horizontal plane .
Here, we further tested Egyptian fruit bats' active control over their echolocation-based sensory acquisition. To this end, we tracked the flight trajectories of Egyptian fruit bats in a large room, and recorded their echolocation behavior when performing a landing task under different levels of environmental complexity. We found that lingual echolocation allows much more selective control over sonar signal parameters than previously believed. We discovered that Egyptian fruit bats alter the intensity of their emissions as they approach and lock the sonar beam onto a target, and that emission intensity changes with environmental complexity.
Such a strategy has never been observed before in any bat species, and therefore comprises a new dimension of active control in lingual bat echolocation. The sphere was the only object in an empty flight room Figure 1A , and it was randomly moved between trials. Recordings were taken in complete darkness, forcing the bats to rely only on echolocation see Materials and Methods.
When approaching the target, bats significantly increased the inter-click angle by 6. This increase in inter-click angle occurred abruptly, coinciding with the time when the bats locked on the landing target, i. Population analysis of trials Figure 1D confirmed that the increase of the inter-click angle was abrupt; in fact, it could occur within 2 click-pairs, i. A Schematic of single trial showing flight trajectory and direction of echolocation clicks in an Egyptian fruit bat black lines. Dots at circumference, microphones; arrow, point of locking onto target.
B Illustration of the inter-click angle. Black lines, direction of beam's peak; gray ellipse, polar representation of the sonar beam. D Population average inter-click angle along the bats' approach to a single object. The angle was normalized separately for each bat to its average un-locked angle see Materials and Methods. This abrupt increase in inter-click angle may result from the bat's need to increase the field-of-view; or it may represent the animal's attempt to position the maximum slope of its sonar beam onto the target .
To further elucidate the possible roles of this abrupt change in inter-click angle, we conducted additional experiments that aimed to challenge the bat's scanning behavior. To this end, we manipulated the spatial complexity number of objects that the bat encountered within its field-of-view as it flew towards the landing sphere. In the next set of experiments, we manipulated the complexity of the environment, and examined how this influenced the Egyptian fruit bat's echolocation behavior. We hypothesized that when introducing a set of objects obstacles in the vicinity of the landing-point, which increases the environmental complexity, the bats would alter their scanning behavior to inspect several objects—thus increasing their field-of-view.
To test this hypothesis, we studied the bats' behavior in two new setups Figure 2A : i Open room condition: In 56 trials 8—12 trials per bat we removed the sphere where the bats were trained to land. These trials were randomly introduced in between one-object trials; hence the bats reacted by vigorously searching for the target while flying around the room. The width of the corridor, its angle relative to the walls of the room, and the position of the landing sphere within the corridor were all randomly varied between trials. This setup mimics natural situations, in which a bat has to negotiate fruitless branches the nets , before landing on a branch with a fruit the target.
In all illustrations, bat's trajectory is depicted by a gray line and the direction of the beam's peak by a black line. A Top, schematic of the three experimental setups. Bottom, inter-click angle in the different experimental conditions. U, unlocked; L, locked; E-L, instances of early-locking prior to the final locking.
Biosonar and Sound Localization in Dolphins
Note increase in inter-click angle with environmental complexity. B—C Increase in inter-click angle along the approach, during multiple-object experiments. B In these experiments, the inter-click angle along the approach had a higher value higher than in the one-object setup and exhibited a gradual increase after the final locking onto the landing target. C When using the bat's entrance between the nets as an alternative locking criterion, it became evident that most of the increase in inter-click angle has occurred between 1 and 0.
Note different x -axis in B and C. Egyptian fruit bats increased the angle between sequential clicks when environmental complexity increased Figure 2A , bottom. This behavioral pattern was consistent across all the individual bats that we tested Figure S2. In the multiple-object setup, the bats increased the inter-click angle significantly beyond the point of maximum slope i. This suggests that, at least in this case, the inter-click angle plays another role in addition to placing the maximum slope on target for optimizing localization. We propose that widening the angle between the beam axes of sonar click pairs serves to modulate the bat's field-of-view.
During the last time-bin before landing Figure 2B , right-most point , the inter-click angle has increased on average by When doing so, the point in the beam that was pointed to the center of the target was 2. In the multiple-object experiment Figure 2B , unlike in the one-object setup Figure 1D , it seemed that the bats did not increase the inter-click angle abruptly when we used the same locking criterion , but instead began the approach to the landing sphere with a large inter-click angle, and gradually increased even further after the final locking onto the landing target Figure 2B.
We therefore tested an alternative sonar locking criterion for the multiple-object experiments, defining locking as the moment when the bats entered a corridor between the nets. This criterion revealed a clearer picture of the inter-click angle dynamics in the multiple-object situation Figure 2C : Well before passing between the nets, the bats used an intermediate inter-click angle 5. When the bats approached closer to the net corridor, they rapidly increased the inter-click angle to nearly its final value; subsequently, after the bats entered the net corridor, another slight increase was observed, which brought the inter-click angle to an average value that was Maintaining such a high inter-click angle could possibly allow the bat to track both the target and the off-axis objects distal poles as the animal approaches landing—providing a potential strategy for target landing while avoiding collisions.
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In addition to the increase in inter-click angle, we found that Egyptian fruit bats decrease their emission intensity along the approach to landing Figure 3A—C. We always refer here to peak intensity see Materials and Methods , but since the duration of the sonar clicks is very constant, this is also highly correlated to the click's total energy. Because the bats in this experiment were free to choose the trajectory of landing, it was not always relevant to analyze the bat's distance to the target: for instance when a bat circles the target, it could be very close to it in terms of distance but very far in terms of time-to-landing and may in fact be echolocating in a different direction.
We therefore examined the intensity versus time-to-locking Figure 3A—B , as well as intensity versus distance-to-target in trials in which the distance decreased nearly monotonically as the bat approached the landing sphere Figure 3C. Figure 3C shows six examples in which the bat flew directly to the target, exhibiting a salient reduction in intensity, with a 4—6 dB decrease with halving of the distance-to-target during the final approach Figure 3C , gray line, close to target. These results are consistent with reports in other bat species  , .
Interestingly, this decrease in intensity began only 80— cm before landing—similar to what was observed in laryngeal echolocators . Thus, the intensity dynamics along the approach seem to be shared by clicking and laryngeal bats. A Examples of six trials, showing that emission intensity gradually decreases with time along the approach. Average is depicted by thick gray line. B Population average intensity plotted as function of time relative to locking, for the one-object and multiple-object setups.
The two curves were shifted by 30 ms relative to each other, for display purposes only. C Examples of the same six trials as in A , with intensity plotted as function of distance to target. Note decrease in intensity that began 80— cm before landing. D Click intensity increased with the environmental complexity. Intensity was not lower when the bats were locked on the target before the final locking dark gray bar marked E-L. In addition to increasing the inter-click angle, bats also increased the intensity of their clicks with environmental complexity.
The intensity increased by 6. These modulations of intensity could be used by the bat to maintain fixed signal energy directed towards the region of interest, compensating for changes in signal-to-noise ratio due to a widening field-of-view see Figure 4 , and next section. Since we used a planar rather than a 3-D microphone array, and could not calculate the absolute emitted intensity, we performed explicit tests to control for the effects of bats' height, the distance from the microphones, and flight pitch see Materials and Methods.
The increase in intensity, together with the increase in inter-click angle, both contribute to an increase in the effective area that is sampled by the bats via a single click-pair see next section and Discussion. A Multiple-object experiment. B One-object experiment. C No-object experiment. Dashed gray lines depict the effective increase in field-of-view due to the combined increases in inter-click angle and click intensity; here we assumed a constant hearing threshold at normalized intensity of 1.
Our two main findings—that Egyptian fruit bats increase their inter-click angle and also increase the click intensity with increased environmental complexity—suggest that the field-of-view scanned by the bat is under active control and adapted to the environment. These adaptive sonar signal changes served to increase the bat's field-of-view when the environment became more complex i. To examine this notion further, we quantified the field-of-view scanned by the bat, assuming a constant ensonification-intensity level and calculating the change in the angle of the sector covered by the bat's beam.
When we used the intensity at the crossing point of the two beams in the one-object setup as reference Figure 4 dashed lines, normalized intensity 1, see Materials and Methods , we found that the angle of the sector scanned by the bat with a single click-pair increased by a factor of 2. Interestingly, the same intensity corresponding to a normalized intensity of 1 in Figure 4 is directed towards the crossing point of the two beams where the object of interest is positioned in both the multiple- and one-object setups, and it is the peak intensity directed forwards in the no-object setup.
These modulations might thus reflect the bat's attempt to maintain a fixed energy impinging on the region of interest, compensating for the changes in signal-to-noise ratio due to the changes in field-of-view. The maximum distance range scanned by the bats also increased with environmental complexity, because detection range increases as the fourth root of the increase in intensity . We further examined several additional echolocation parameters in this set of experiments, and the results are summarized here.
However, spectral changes seem physiologically unlikely, considering the tongue-production mechanism of the brief lingual clicks. Thus, the most salient changes that we observed were changes in inter-click angle, and changes in click intensity. These two parameters changed in opposite directions along the approach path to an object inter-click angle increased while click intensity decreased during the approach , and both of these parameters increased substantially with environmental complexity.
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