Convergent acoustic field of view in echolocating bats

Jakobsen, Lasse; Ratcliffe, John M.; Surlykke, Annemarie

doi:10.1038/nature11664

Cited by 108 publications

(144 citation statements)

References 22 publications

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“…We examined which parameter set had a high probability of consecutively capturing two prey items. The sonar beam of the bat was modeled as a circular piston oscillating in an infinite baffle (23,24) (Fig. S1).…”

Section: Methodsmentioning

confidence: 99%

Echolocating bats use future-target information for optimal foraging

Fujioka

Aihara

Sumiya

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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When seeing or listening to an object, we aim our attention toward it. While capturing prey, many animal species focus their visual or acoustic attention toward the prey. However, for multiple prey items, the direction and timing of attention for effective foraging remain unknown. In this study, we adopted both experimental and mathematical methodology with microphone-array measurements and mathematical modeling analysis to quantify the attention of echolocating bats that were repeatedly capturing airborne insects in the field. Here we show that bats select rational flight paths to consecutively capture multiple prey items. Microphone-array measurements showed that bats direct their sonar attention not only to the immediate prey but also to the next prey. In addition, we found that a bat's attention in terms of its flight also aims toward the next prey even when approaching the immediate prey. Numerical simulations revealed a possibility that bats shift their flight attention to control suitable flight paths for consecutive capture. When a bat only aims its flight attention toward its immediate prey, it rarely succeeds in capturing the next prey. These findings indicate that bats gain increased benefit by distributing their attention among multiple targets and planning the future flight path based on additional information of the next prey. These experimental and mathematical studies allowed us to observe the process of decision making by bats during their natural flight dynamics.bat sonar | aerial capture | microphone array | mathematical modeling | flight dynamics S electively focusing attention on a particular target allows us to effectively extract information (1-4). Animals spatially focus their attention toward prey for suitable foraging (5, 6). During prey pursuit, most animals direct their visual attention toward it [e.g., tiger beetle (7), dragonfly (8), and falcon (9)]. Specifically, for example, dragonflies maintain a prey item at a constant retinal position during approaching it so that they steer an interception flight path (interception strategy) (10). However, for multiple prey items, the direction and timing of attention for effective foraging remain unknown.Echolocating bats actively emit sonar signals to obtain surrounding information and adaptively change the characteristics of the emissions depending on the situation (11). Therefore, their attention in terms of the sonar (sonar attention) is characterized as the direction to which bats emit their sonar beams (12-14). When echolocating bats approach an airborne insect, the sonar attention directs toward the prey (12, 13). During natural foraging, the sonar attention of bats alternately shifts from their flying direction to the side (15). Additionally the wild bats are capable of capturing two prey items within the short interval of 1 s (16).We predicted that bats localize multiple prey items by distributing their attention between them and then select an efficient flight path to successively capture the multiple prey. To test this prediction, ...

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Section: Methodsmentioning

confidence: 99%

Echolocating bats use future-target information for optimal foraging

Fujioka

Aihara

Sumiya

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…From these data, call intensity was estimated as described in Jakobsen and Surlykke (Jakobsen and Surlykke, 2010). Call intensity is flexible in vespertilionids and varies based on habitat and task (Jakobsen and Surlykke, 2010;Jakobsen et al, 2013). Pulse interval (time elapsed from onset of call to onset of next call) and call duration were measured from the oscillogram of the channel recording the highest intensity signals (Fig.…”

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confidence: 99%

Niche-specific cognitive strategies: object memory interferes with spatial memory in the predatory bat, Myotis nattereri

Hulgard

Ratcliffe

2014

Journal of Experimental Biology

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Related species with different diets are predicted to rely on different cognitive strategies: those best suited for locating available and appropriate foods. Here we tested two predictions of the nichespecific cognitive strategies hypothesis in bats, which suggests that predatory species should rely more on object memory than on spatial memory for finding food and that the opposite is true of frugivorous and nectivorous species. Specifically, we predicted that: (1) predatory bats would readily learn to associate shapes with palatable prey and (2) once bats had made such associations, these would interfere with their subsequent learning of a spatial memory task. We trained freeflying Myotis nattereri to approach palatable and unpalatable insect prey suspended below polystyrene objects. Experimentally naïve bats learned to associate different objects with palatable and unpalatable prey but performed no better than chance in a subsequent spatial memory experiment. Because experimental sequence was predicted to be of consequence, we introduced a second group of bats first to the spatial memory experiment. These bats learned to associate prey position with palatability. Control trials indicated that bats made their decisions based on information acquired through echolocation. Previous studies have shown that bat species that eat mainly nectar and fruit rely heavily on spatial memory, reflecting the relative consistency of distribution of fruit and nectar compared with insects. Our results support the niche-specific cognitive strategies hypothesis and suggest that for gleaning and clutter-resistant aerial hawking bats, learning to associate shape with food interferes with subsequent spatial memory learning.

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“…Dynamic changes to the acoustic field of view (Jakobsen et al, 2013;Wisniewska et al, 2012) may help echolocating animals inspect their surroundings or lock on to specific targets, shaping the perception of their surroundings via changes in the acoustic gaze (Moss, 2010;Moss et al, 2011). Here, we show that wild Atlantic spotted dolphins seem to increase their vertical biosonar beam width by 50% over a fourfold decrease in range.…”

Section: Discussionmentioning

confidence: 75%

Single-click beam patterns suggest dynamic changes to the field of view of echolocating Atlantic spotted dolphins (Stenella frontalis) in the wild

Jensen

Wahlberg

Beedholm

et al. 2015

Journal of Experimental Biology

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Echolocating animals exercise an extensive control over the spectral and temporal properties of their biosonar signals to facilitate perception of their actively generated auditory scene when homing in on prey. The intensity and directionality of the biosonar beam defines the field of view of echolocating animals by affecting the acoustic detection range and angular coverage. However, the spatial relationship between an echolocating predator and its prey changes rapidly, resulting in different biosonar requirements throughout prey pursuit and capture. Here, we measured single-click beam patterns using a parametric fit procedure to test whether free-ranging Atlantic spotted dolphins (Stenella frontalis) modify their biosonar beam width. We recorded echolocation clicks using a linear array of receivers and estimated the beam width of individual clicks using a parametric spectral fit, cross-validated with well-established composite beam pattern estimates. The dolphins apparently increased the biosonar beam width, to a large degree without changing the signal frequency, when they approached the recording array. This is comparable to bats that also expand their field of view during prey capture, but achieve this by decreasing biosonar frequency. This behaviour may serve to decrease the risk that rapid escape movements of prey take them outside the biosonar beam of the predator. It is likely that shared sensory requirements have resulted in bats and toothed whales expanding their acoustic field of view at close range to increase the likelihood of successfully acquiring prey using echolocation, representing a case of convergent evolution of echolocation behaviour between these two taxa.

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Convergent acoustic field of view in echolocating bats

Cited by 108 publications

References 22 publications

Echolocating bats use future-target information for optimal foraging

Echolocating bats use future-target information for optimal foraging

Niche-specific cognitive strategies: object memory interferes with spatial memory in the predatory bat, Myotis nattereri

Single-click beam patterns suggest dynamic changes to the field of view of echolocating Atlantic spotted dolphins (Stenella frontalis) in the wild

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