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      A sensorimotor model shows why a spectral jamming avoidance response does not help bats deal with jamming

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          Abstract

          For decades, researchers have speculated how echolocating bats deal with masking by conspecific calls when flying in aggregations. To date, only a few attempts have been made to mathematically quantify the probability of jamming, or its effects. We developed a comprehensive sensorimotor predator-prey simulation, modeling numerous bats foraging in proximity. We used this model to examine the effectiveness of a spectral Jamming Avoidance Response (JAR) as a solution for the masking problem. We found that foraging performance deteriorates when bats forage near conspecifics, however, applying a JAR does not improve insect sensing or capture. Because bats constantly adjust their echolocation to the performed task (even when flying alone), further shifting the signals' frequencies does not mitigate jamming. Our simulations explain how bats can hunt successfully in a group despite competition and despite potential masking. This research demonstrates the advantages of a modeling approach when examining a complex biological system.

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          Most cited references74

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          Acoustic masking in marine ecosystems: intuitions, analysis, and implication

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            Echolocation behavior of big brown bats, Eptesicus fuscus, in the field and the laboratory.

            Echolocation signals were recorded from big brown bats, Eptesicus fuscus, flying in the field and the laboratory. In open field areas the interpulse intervals (IPI) of search signals were either around 134 ms or twice that value, 270 ms. At long IPI's the signals were of long duration (14 to 18-20 ms), narrow bandwidth, and low frequency, sweeping down to a minimum frequency (Fmin) of 22-25 kHz. At short IPI's the signals were shorter (6-13 ms), of higher frequency, and broader bandwidth. In wooded areas only short (6-11 ms) relatively broadband search signals were emitted at a higher rate (avg. IPI= 122 ms) with higher Fmin (27-30 kHz). In the laboratory the IPI was even shorter (88 ms), the duration was 3-5 ms, and the Fmin 30- 35 kHz, resembling approach phase signals of field recordings. Excluding terminal phase signals, all signals from all areas showed a negative correlation between signal duration and Fmin, i.e., the shorter the signal, the higher was Fmin. This correlation was reversed in the terminal phase of insect capture sequences, where Fmin decreased with decreasing signal duration. Overall, the signals recorded in the field were longer, with longer IPI's and greater variability in bandwidth than signals recorded in the laboratory.
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              Bats aggregate to improve prey search but might be impaired when their density becomes too high.

              Social foraging is a very common yet extremely complex behavior. Numerous studies attempted to model it with little supporting evidence. Studying it in the wild is difficult because it requires monitoring the animal's movement, its foraging success, and its interactions with conspecifics. We present a novel system that enables full night ultrasonic recording of freely foraging bats, in addition to GPS tracking. As they rely on echolocation, audio recordings of bats allow tapping into their sensory acquisition of the world. Rapid changes in echolocation allowed us to reveal the bats' dynamic reactions in response to prey or conspecifics—two key behaviors that are extremely difficult to assess in most animals. We found that bats actively aggregate and forage as a group. However, we also found that when the group became too dense, bats were forced to devote sensory attention to conspecifics that frequently entered their biosonar "field of view," impairing the bats' prey detection performance. Why then did bats fly in such high densities? By emitting echolocation calls, bats constantly provide public information about their detection of prey. Bats could therefore benefit from intentionally flying at a distance that enables eavesdropping on conspecifics. Group foraging, therefore, probably allowed bats to effectively operate as an array of sensors, increasing their searching efficiency. We suggest that two opposing forces are at play in determining the efficient foraging density: on the one hand, higher densities improve prey detection, but on the other hand, they increase conspecific interference.
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                Author and article information

                Contributors
                Role: Senior Editor
                Role: Reviewing Editor
                Journal
                eLife
                Elife
                eLife
                eLife
                eLife Sciences Publications, Ltd
                2050-084X
                28 July 2020
                2020
                : 9
                : e55539
                Affiliations
                [1 ]Sagol School of Neuroscience, Tel Aviv University Tel AvivIsrael
                [2 ]Department of Zoology, Tel Aviv University Tel AvivIsrael
                University of Oxford United Kingdom
                University of Oxford United Kingdom
                University of Oxford United Kingdom
                Author information
                https://orcid.org/0000-0001-9763-4621
                Article
                55539
                10.7554/eLife.55539
                7406351
                32718437
                67f4e8af-e926-4514-ad8e-4937f2bde515
                © 2020, Mazar and Yovel

                This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

                History
                : 28 January 2020
                : 21 July 2020
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100007297, Office of Naval Research Global;
                Award ID: N62909-16-1-2133-P00003
                Award Recipient :
                The funders had no role in study design, data collection, and interpretation, or the decision to submit the work for publication.
                Categories
                Research Article
                Computational and Systems Biology
                Neuroscience
                Custom metadata
                An elaborated bat-predator model shows that even in high bat-densities, bats can successfully catch flying insects and that changing their signals’ frequency is not necessary for dealing with sensory interference.

                Life sciences
                p. kuhli,echolocation,bats,sensory,jamming,jamming avoidance response,modeling,simulation,other
                Life sciences
                p. kuhli, echolocation, bats, sensory, jamming, jamming avoidance response, modeling, simulation, other

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