Dynamics of jamming avoidance in echolocating bats

Ulanovsky, Nachum; Fenton, M. Brock; Tsoar, Asaf; Korine, Carmi

doi:10.1098/rspb.2004.2750

Cited by 156 publications

(137 citation statements)

References 42 publications

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“…The ΔFs that we observed (3-6 kHz) are similar in size to frequency shifts that frequency-modulating echolocating bats make in other situations where interference is likely to occur: Conspecific bats flying in proximity shift their broadcast FM1 low frequencies away from each other, presumably to prevent interference with each other's sonar (21)(22)(23). In target-detection experiments, big brown bats avoid the frequency of continuous jamming tones in the range of 18-32 kHz by changing the low frequencies of FM1 in their broadcasts (24).…”

Section: Discussionsupporting

confidence: 63%

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

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

100

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Sonar broadcasts are followed by echoes at different delays from objects at different distances. When broadcasts are emitted rapidly in cluttered surroundings, echo streams from successive broadcasts overlap and cause ambiguity in matching echoes to corresponding broadcasts. To identify reactions to ambiguity in clutter, echolocating bats that emit multiple-harmonic FM sounds were trained to fly into a dense, extended array of obstacles (multiple rows of vertically hanging chains) while the sonar sounds the bat emitted were recorded with a miniature radio microphone carried by the bat. Flight paths were reconstructed from thermal-infrared video recordings. Successive rows of chains extended more than 6 m in depth, so each broadcast was followed by a series of echoes from multiple rows of chains that lasted up to 40 ms. Bats emitted sounds in pairs ("strobe groups") at short (20-40 ms) interpulse intervals (IPIs) alternating with longer IPIs (>50 ms). For many short IPIs, the stream of echoes from the first broadcast was still arriving when the second broadcast was emitted. This overlap caused ambiguity about matching echoes with broadcasts. Bats shifted frequencies of the first sound in each strobe group upward and the second sound downward by 3-6 kHz. When overlap and ambiguity ceased, frequency shifts ceased also. Frequency differences were small compared with the total broadcast band, which was 75-80 kHz wide, but the harmonic structure of echoes enhances the differences in spectrograms. Bats could use time-frequency comparisons of echoes with broadcasts to assign echoes to the corresponding broadcasts and thus avoid ambiguity.bat sonar | clutter interference | echo delay | FM sounds

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Section: Discussionsupporting

confidence: 63%

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

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

100

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“…Our results did not change even when reanalysing only the 30% most intense conspecifics calls emitted by extremely close conspecifics (less than ca 5 m; electronic supplementary material, figure S8a-b). Interestingly, the bats' response to conspecifics included an increase in frequency, which was also observed in some of the previous studies on jamming avoidance [10,11]. However, these studies did not control for signal duration and therefore might have interpreted this increase as a jamming avoidance response.…”

Section: Discussionmentioning

confidence: 58%

On-board recordings reveal no jamming avoidance in wild bats

et al. 2015

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Animals often deal with situations in which vast sensory input is received simultaneously. They therefore must possess sophisticated mechanisms to select important input and ignore the rest. In bat echolocation, this problem is at its extreme. Echolocating bats emit sound signals and analyse the returning echoes to sense their environment. Bats from the same species use signals with similar frequencies. Nearby bats therefore face the difficulty of distinguishing their own echoes from the signals of other bats, a problem often referred to as jamming. Because bats commonly fly in large groups, jamming might simultaneously occur from numerous directions and at many frequencies. Jamming is a special case of the general phenomenon of sensory segregation. Another well-known example is the human problem of following conversation within a crowd. In both situations, a flood of auditory incoming signals must be parsed into important versus irrelevant information. Here, we present a novel method, fitting wild bats with a miniature microphone, which allows studying jamming from the bat's ‘point of view’. Previous studies suggested that bats deal with jamming by shifting their echolocation frequency. On-board recordings suggest otherwise. Bats shifted their frequencies, but they did so because they were responding to the conspecifics as though they were nearby objects rather than avoiding being jammed by them. We show how bats could use alternative measures to deal with jamming instead of shifting their frequency. Despite its intuitive appeal, a spectral jamming avoidance response might not be the prime mechanism to avoid sensory interference from conspecifics.

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“…This kind of frequency shift has been described before in the context of Doppler compensation (Schnitzler 1973;Trappe & Schnitzler 1982) or jamming avoidance (e.g. Ulanovsky et al 2004) in bats, but this well known phenomenon has not typically been considered in discussions of vocal production learning. This may stem from the tendency of those interested in vocal production learning to focus on development of communication signals rather than shorter term accommodation of calls, especially those used for functions other than communication.…”

Section: Vocal Imitationmentioning

confidence: 89%

Convergence of calls as animals form social bonds, active compensation for noisy communication channels, and the evolution of vocal learning in mammals.

Tyack¹

2008

Journal of Comparative Psychology

135

146

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The classic evidence for vocal production learning involves imitation of novel, often anthropogenic sounds. Among mammals, this has been reported for African elephants, harbor seals, and dolphins. A broader taxonomic distribution has been reported for vocal convergence, where the acoustic properties of calls from different individuals converge when they are housed together in captivity or form social bonds in the wild. This kind of vocal convergence has been demonstrated for animals as diverse as songbirds, parakeets, bats, elephants, cetaceans, and primates. For most of these species, call convergence is thought to reflect a group-distinctive identifier, with shared calls reflecting and strengthening social bonds. Pooling data on vocal imitation and vocal convergence suggests a wider taxonomic distribution of vocal production learning among mammals than generally appreciated. The wide taxonomic distribution of this evidence for vocal production learning suggests that perhaps more of the neural underpinnings for vocal production learning are in place in mammals than is usually imagined. One ubiquitous function for vocal production learning that is starting to receive attention involves modifying signals to improve communication in a noisy channel.

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Dynamics of jamming avoidance in echolocating bats

Cited by 156 publications

References 42 publications

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

On-board recordings reveal no jamming avoidance in wild bats

Convergence of calls as animals form social bonds, active compensation for noisy communication channels, and the evolution of vocal learning in mammals.

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