Jamming Avoidance Response Research Articles

Hearing your voice in the crowd: How do bats echolocate in dense swarms?

In order to navigate their environment and find food, bats rely on comparing returning echoes to their broadcast signal. Through decades of research, we have a good understanding of how single bats accomplish this task, but we still don’t know how bats in dense groups can echolocate without interference from others. A spectral Jamming Avoidance Response (JAR) has long been proposed as one strategy, in which bats flying together shift frequencies to avoid interference. Recent work, however, questions this strategy, and suggests bats may not use any JAR for sensing in groups. Bats have long served as bioinspiration for active sensing devices, so understanding strategies for collective sensing in bats has implications for applications of synthetic sonar. In this talk, I will review the “hot topic” of bat biosonar in swarms and show new data from our research that suggests spectro-temporal variation may play a role for sensing in even the largest, densest bat swarms.

Echolocating Daubenton's bats call louder, but show no spectral jamming avoidance in response to bands of masking noise during a landing task.

Echolocating bats listen for weak echoes to navigate and hunt, which makes them prone to masking from background noise and jamming from other bats and prey. As for electrical fish that display clear spectral jamming avoidance responses (JAR), bats have been reported to mitigate the effects of jamming by shifting the spectral contents of their calls, thereby reducing acoustic interference to improve echo-to-noise ratio (ENR). Here, we tested the hypothesis that frequency-modulating bats (FM bats) employ a spectral JAR in response to six masking noise bands ranging from 15 to 90 kHz, by measuring the -3 dB endpoints and peak frequency of echolocation calls from five male Daubenton's bats (Myotis daubentonii) during a landing task. The bats were trained to land on a noise-generating spherical transducer surrounded by a star-shaped microphone array, allowing for acoustic localization and source parameter quantification of on-axis calls. We show that the bats did not employ spectral JAR as the peak frequency during jamming remained unaltered compared with that of silent controls (all P>0.05, 60.73±0.96 kHz, mean±s.e.m.), and -3 dB endpoints decreased in noise irrespective of treatment type. Instead, Daubenton's bats responded to acoustic jamming by increasing call amplitude via a Lombard response that was bandwidth dependent, ranging from a mean of 0.05dB/dB (95% confidence interval 0.04-0.06dB/dB) noise for the most narrowband noise (15-30 kHz) to 0.17dB/dB (0.16-0.18dB/dB) noise for the most broadband noise (30-90 kHz). We conclude that Daubenton's bats, despite having the vocal flexibility to do so, do not employ a spectral JAR, but defend ENRs via a bandwidth-dependent Lombard response.

Spooky Interaction at a Distance in Cave and Surface Dwelling Electric Fishes.

Glass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. Their electric organ discharges (EODs) are energetically costly adaptations used in social communication and for localizing conspecifics and other objects including prey at night and in turbid water. Interestingly, a troglobitic population of blind cavefish Eigenmannia vicentespelea survives in complete darkness in a cave system in central Brazil. We examined the effects of troglobitic conditions, which includes a complete loss of visual cues and potentially reduced food sources, by comparing the behavior and movement of freely behaving cavefish to a nearby epigean (surface) population (Eigenmannia trilineata). We found that the strengths of electric discharges in cavefish were greater than in surface fish, which may result from increased reliance on electrosensory perception, larger size, and sufficient food resources. Surface fish were recorded while feeding at night and did not show evidence of territoriality, whereas cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in EOD frequencies that were below 10 Hz despite being within close proximity of about 50 cm. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in EOD frequencies should have triggered the “jamming avoidance response,” a behavior in which fish change their EOD frequencies to increase the difference between individuals. Pairs of fish also showed significant interactions between EOD frequencies and relative movements at large distances, over 1.5 m, and at high differences in frequencies, often >50 Hz. These interactions are likely “envelope” responses in which fish alter their EOD frequency in relation to higher order features, specifically changes in the depth of modulation, of electrosocial signals.

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

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.

A Review: Neural-Inspired Photonic Functional Systems for Dynamic RF Signal Processing

Drawing inspiration from our nature, photonic systems that use light to imitate neural algorithms and behaviors of nature could be effective to solve complex problems in human's civilized society that have been challenging for conventional electronic to tackle. Since neural algorithms are natural designs that have undergone hundreds of million years of evolution and govern the survival of the organism, therefore, those neural algorithms are highly effective for the designated tasks. The goal of this article is to review the recent demonstrations of the photonic implementations of small scale functional neural algorithms for dynamic RF signal processing applications. In this article, two small-scale neural algorithms are reviewed - (i) spike timing dependent plasticity, an algorithm that governs how neural network are connecting together and how learning/adaptation can be achieved in animals, and (ii) jamming avoidance response in Eigenmannia, an algorithm in a gene of electric fish that mitigates frequency jamming between neighboring electric fish. The photonic circuits that are inspired by the two neural algorithms are also presented and the real-life applications of the neural algorithms in human society will be discussed.

A JAR of Chirps: The Gymnotiform Chirp Can Function as Both a Communication Signal and a Jamming Avoidance Response.

The weakly electric gymnotiform fish produce a rhythmic electric organ discharge (EOD) used for communication and active electrolocation. The EOD frequency is entrained to a medullary pacemaker nucleus. During communication and exploration, this rate can be modulated by a pre-pacemaker network, resulting in specific patterns of rate modulation, including stereotyped communication signals and dynamic interactions with conspecifics known as a Jamming Avoidance Response (JAR). One well-known stereotyped signal is the chirp, a brief upward frequency sweep usually lasting less than 500 ms. The abrupt change in frequency has dramatic effects on phase precession between two signalers. We report here on chirping in Brachyhypopmus cf. sullivani, Microsternarchus cf. bilineatus Lineage C, and Steatogenys cf. elegans during conspecific playback experiments. Microsternarchus also exhibits two behaviors that include chirp-like extreme frequency modulations, EOD interruptions with hushing silence and tumultuous rises, and these are described in terms of receiver impact. These behaviors all have substantial impact on interference caused by conspecifics and may be a component of the JAR in some species. Chirps are widely used in electronic communications systems, sonar, and other man-made active sensing systems. The brevity of the chirp, and the phase disruption it causes, makes chirps effective as attention-grabbing or readiness signals. This conforms to the varied assigned functions across gymnotiforms, including pre-combat aggressive or submissive signals or during courtship and mating. The specific behavioral contexts of chirp expression vary across species, but the physical structure of the chirp makes it extremely salient to conspecifics. Chirps may be expected in a wide range of behavioral contexts where their function depends on being noticeable and salient. Further, in pulse gymnotiforms, the chirp is well structured to comprise a robust jamming signal to a conspecific receiver if specifically timed to the receiver’s EOD cycle. Microsternarchus and Steatogenys exploit this feature and include chirps in dynamic jamming avoidance behaviors. This may be an evolutionary re-use of a circuitry for a specific signal in another context.

Jamming Avoidance Response Inspired by Wave-type Weakly Electric Fish

Weakly electric fish use the electric field to detect objects in the neighborhood or communicate with conspecifics. They generate electric field with their electric organ and the electroreceptors sense the distortion of electric field caused by nearby objects. They use a modulated frequency signal of the Electric Organ Discharge (EOD), and it can be disturbed by similar frequency signals that neighboring weakly electric fish emit. They have a particular behavior response to change their EOD frequencies to avoid signal jamming. It is called jamming avoidance response. Inspired by the behavior of wave-type weakly electric fish, we propose an engineering perspective of jamming avoidance response model with the amplitude-phase modulation graph. The time course of the amplitude-phase graph of the EOD signal provides a cue to detect the jamming signal. We argue that the temporal integration can determine the shift direction of the EOD as well as the amount of the frequency shift to be moved frequency for the jamming avoidance response. Alternatively, as a fast adapting measure, the cross product of point vectors in the amplitude-phase graph allows early decision for jamming avoidance. We demonstrate the methods with simulations and the real experiments in the underwater environment.

Biomimetic photonics: jamming avoidance system in Eigenmannia.

Biomimetic photonics extract the good design of nature and mimic it with photonics. The weakly electric fish genus, Eigenmannia, has a unique neural algorithm - jamming avoidance response, to facilitate their survival in the deep dark ocean, by automatically adjusts the local transmitter carrier frequency to move away from the jamming frequency when it is within the jamming spectral range. Examining our own wireless microwave systems, the situation of inadvertent jamming is very similar as that in Eigenmannia. In this article, a biomimetic photonic approach inspired by the jamming avoidance response in a weakly electric fish genus, Eigenmannia, is naturally adopted to experimentally tackle signal jamming in wireless systems. Mimicking the system with photonics enables the proposed scheme to work for frequencies from hundreds of MHz to tens of GHz.

The complexity of high-frequency electric fields degrades electrosensory inputs: implications for the jamming avoidance response in weakly electric fish.

Sensory systems encode environmental information that is necessary for adaptive behavioural choices, and thus greatly influence the evolution of animal behaviour and the underlying neural circuits. Here, we evaluate how the quality of sensory information impacts the jamming avoidance response (JAR) in weakly electric fish. To sense their environment, these fish generate an oscillating electric field: the electric organ discharge (EOD). Nearby fish with similar EOD frequencies perform the JAR to increase the difference between their EOD frequencies, i.e. their difference frequency (DF). The fish determines the sign of the DF: when it has a lower frequency (DF > 0), EOD frequency is decreased and vice versa. We study the sensory basis of the JAR in two species: Apteronotus leptorhynchus have a high frequency (ca 1000 Hz), spatio-temporally heterogeneous electric field, whereas Eigenmannia sp. have a low frequency (ca 300 Hz), spatially uniform field. We show that the increased complexity of the Apteronotus field decreases the reliability of sensory cues used to determine the DF. Interestingly, Apteronotus responds to all JAR stimuli by increasing EOD frequency, having lost the neural pathway that produces JAR-related decreases in EOD frequency. Our results suggest that electric field complexity may have influenced the evolution of the JAR by degrading the related sensory information.

Chirping and asymmetric jamming avoidance responses in the electric fish Distocyclus conirostris.

Electrosensory systems of weakly electric fish must accommodate competing demands of sensing the environment (electrolocation) and receiving social information (electrocommunication). The jamming avoidance response (JAR) is a behavioral strategy thought to reduce electrosensory interference from conspecific signals close in frequency. We used playback experiments to characterize electric organ discharge frequency (EODf), chirping behavior and the JAR of Distocyclus conirostris, a gregarious electric fish species. EODs of D. conirostris had low frequencies (∼80-200 Hz) that shifted in response to playback stimuli. Fish consistently lowered EODf in response to higher-frequency stimuli but inconsistently raised or lowered EODf in response to lower-frequency stimuli. This led to jamming avoidance or anti-jamming avoidance, respectively. We compare these behaviors with those of closely related electric fish (Eigenmannia and Sternopygus) and suggest that the JAR may have additional social functions and may not solely minimize the deleterious effects of jamming, as its name suggests.

Active acoustic interference elicits echolocation changes in heterospecific bats.

Echolocating bats often forage in the presence of both conspecific and heterospecific individuals, which have the potential to produce acoustic interference. Recent studies have shown that at least one bat species, the Brazilian free-tailed bat (Tadarida brasiliensis), produces specialized social signals that disrupt the sonar of conspecific competitors. We herein discuss the differences between passive and active jamming signals and test whether heterospecific jamming occurs in species overlapping spatiotemporally, as well as whether such interference elicits a jamming avoidance response. We compare the capture rates of tethered moths and the echolocation parameters of big brown bats (Eptesicus fuscus) challenged with the playback of the jamming signal normally produced by Brazilian free-tailed bats and playback of deconstructed versions of this signal. There were no differences in the capture rates of targets with and without the jamming signal, although significant changes in both spectral and temporal features of the bats' echolocation were observed. These changes are consistent with improvements of the signal-to-noise ratio in the presence of acoustic interference. Accordingly, we propose to expand the traditional definition of the jamming avoidance response, stating that echolocation changes in response to interference should decrease similarity between the two signals, to include any change that increases the ability to separate returning echoes from active jamming stimuli originating from conspecific and heterospecific organisms. Flexibility in echolocation is an important characteristic for overcoming various forms of acoustic interference and may serve a purpose in interspecific interactions as well as intraspecific ones.

Frequency shifting reduces but does not eliminate acoustic interference between echolocating bats: A theoretical analysis.

Bats have been observed to shift the frequency of their echolocation calls in the presence of other echolocating bats, ostensibly as a way to reduce acoustic interference. Few studies, however, have examined the theoretical efficacy of such jamming avoidance responses. The present study uses the wideband ambiguity function to analyze the effects of acoustic interference from conspecifics and congeneric heterospecifics on the target acquisition ability of Myotis californicus and Myotis yumanensis, specifically whether unilateral or bilateral frequency shifts reduce the effects of such interference. Model results suggest that in conspecific interactions, M. yumanensis recovers its target acquisition ability more completely and with less absolute frequency shift than does M. californicus, but that alternative methods of jamming avoidance may be easier to implement. The optimal strategy for reducing heterospecific interference is for M. californicus to downshift its call and M. yumanensis to upshift its call, which exaggerates a preexisting difference in mean frequency between the calls of the two species. Further empirical research would elucidate whether these species do in practice actively employ frequency shifting or other means for jamming avoidance, as well as illuminate the role of acoustic interference in niche partitioning.

Complex acoustic signaling in the toadfish, Opsanus tau

Male oyster toadfish, Opsanus tau, produce long duration (250 to 650 ms) sexual advertisement calls or “boatwhistles” during the breeding season. When males are in close proximity, they employ multiple vocalization strategies. They normally alternate the production of boatwhistles to avoid temporal overlap. When the fundamental frequencies of multiple callers vary by more than 10 Hz, the frequency is correlated strongly with water temperature. However, when conspecifics with similar frequencies vocalized, the individuals shifted their fundamental frequencies independent of water temperature in a jamming avoidance response. Males also emit a single, short duration pulse or “grunt” (~100 ms), which are emitted almost exclusively during the boatwhistle of a conspecific male which can jam the signal. The disruptive grunt specifically targeted the second stage or tonal portion of the boatwhistle, believed to be the primary acoustic attractant for females, and its brevity and precision may allow its emitter to remain undetectable. While the acoustic repertoire of teleost fishes may be less diverse compared with terrestrial species, the toadfish can detect conspecific signals and employ different strategies to avoid temporal and frequency overlap, thus displaying a capacity for complex acoustic interactions.

A Model for Assessing ATP Demands of Sustained High Frequency Firing

The continuous electric organ discharge (EOD) of the weakly electric fish, Eigenmannia, reflects action potentials (APs) fired by the EO's muscle-derived electrocytes. EODs enable electrosensing and communication. AP frequency is neurally controlled, with acetylcholine-gated channels (AChRs) mediating synaptic transmission. According to EOD-linked whole-fish O2 consumption (for fish with EODs between ∼300-500 Hz) ATP demand per AP grows exponentially with frequency. The unimodal task, continual firing, and simple homogeneous structure of the EO render it especially suitable for probing excitable system energetics in relation to molecular, cellular and tissue features. We develop a model, Epm, to depict currents at the electrocyte's energy-dissipating Excitable posterior membrane. In situ, 3Na/2K-ATPases (pumps) counteract the dissipation of electrocyte ENa (and EK). Using Epm we calculate AP frequency-dependent “Na+-entry budgets” for synaptic activation (pulsatile and/or steady-state, with/without noise). Comparison of Epm-calculated ATP consumption (inferred from total Na+-entry) against published EOD-linked whole-fish O2 consumption suggests that EOD-linked energy demands external to electrocytes (neuronal, circulatory etc) exceed, several-fold, those of electrocyte excitability per se. Well-understood conductance processes (as modeled by Epm) proved fully adequate for generating sustained APs (including during jamming avoidance responses) from 200-600 Hz. By contrast, although we computationally impose the equivalent of fast stimulatory variations in [ACh], even at the bottom of this frequency range the means by which synaptic transmission machinery so reliably achieves the requisite fast variations is a mystery. The simple Eigenmannia EO therefore continues to emerge as a fascinating model system for studying not only the energetics but the subcellular and broader-level dynamics of high frequency excitability.

What does it feel like to be an electroreceptive fish?

The weakly electric knifefish Eigenmannia emits an electric organ discharge (EOD) of constant frequency and sinusoidal waveform that varies with sex and age. Eigenmannia discriminates among these except when stimulated at the same frequency as its own EOD frequency. In that case, it needs to perform a Jamming Avoidance Response (frequency shift) which results in a beating mixed signal. By a sophisticated analysis of the amplitude and phase modulations of the beat signal, Eigenmannia derives the frequency difference, its sign, and the waveform of the stimulus, hence the signaller’s identity. The human ear is not capable of an equivalent waveform analysis of acoustic stimuli.

No evidence for spectral jamming avoidance in echolocation behavior of foraging pipistrelle bats.

Frequency shifts in signals of bats flying near conspecifics have been interpreted as a spectral jamming avoidance response (JAR). However, several prerequisites supporting a JAR hypothesis have not been controlled for in previous studies. We recorded flight and echolocation behavior of foraging Pipistrellus pipistrellus while flying alone and with a conspecific and tested whether frequency changes were due to a spectral JAR with an increased frequency difference, or whether changes could be explained by other reactions. P. pipistrellus reacted to conspecifics with a reduction of sound duration and often also pulse interval, accompanied by an increase in terminal frequency. This reaction is typical of behavioral situations where targets of interest have captured the bat’s attention and initiated a more detailed exploration. All observed frequency changes were predicted by the attention reaction alone, and do not support the JAR hypothesis of increased frequency separation. Reaction distances of 1–11 m suggest that the attention response may be elicited either by detection of the conspecific by short range active echolocation or by long range passive acoustic detection of echolocation calls.

전기물고기의 방해 회피 반응 모델링과 응용

In this paper, we suggest a phase difference algorithm inspired by weakly electric fish. Weakly electric fish is a fish which generates electric field though its electric organ in the tail. The weakly electric fish search for prey and detect an object by using electrolocation. The weakly electric fish have Jamming Avoidance Response (JAR) to avoid jamming signal. One of pulse-type weakly electric fish Gymnotus carapo also have JAR to reduce the probability of coincidence of pulses. We analyze this response signal and design the phase difference algorithm. We expect that simple algorithm inspired by weakly electric fish can be used in many engineering fields.

Influence of call structure on the jamming avoidance response of echolocating bats

AbstractBats rely heavily on echolocation for orientation and prey detection, hence acoustic signals that interfere with echo reception are problematic. When flying in the presence of other bats, some species adjust their echolocation to avoid frequency overlap with the calls of nearby conspecifics, known as a jamming avoidance response (JAR). One aspect of JAR that has not been thoroughly examined is how the spectral structure of the jamming signal impacts the jamming response. Our objective was to examine how the structural characteristics of an echolocation broadcast impact JAR in free-flying Brazilian free-tailed bats, Tadarida brasiliensis . We created 4 echolocation playbacks that differed only in call shape and frequency modulation. We examined the response of bats when flying in the presence of an unchanging broadcast (static stimulus) and when the playback signal was abruptly switched as the bat approached the speaker (dynamic stimulus). Results revealed that the bandwidth of the interfering signal impacted the strength of the observed JAR, while the presence and/or length of a terminal quasi-constant frequency section in the interfering signal did not. Our results agree with laboratory studies documenting JAR in the presence of white noise, as well as field studies demonstrating extensive variability in the echolocation calls of Brazilian free-tailed bats. We relate these results to previous findings on JAR, including a recent study documenting no JAR in a bat species and suggest further experiments to tease apart the physiological limitations of JAR. Overall, this study provides additional insight into the signal processing capabilities of bats and improves our understanding of how bats are able to orient using sound in a noisy world.

On-board recordings reveal no jamming avoidance in wild bats.

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.

Adaptive changes in echolocation sounds byPipistrellus abramusin response to artificial jamming sounds

The echolocation behavior of Pipistrellus abramus during exposure to artificial jamming sounds during flight was investigated. Echolocation pulses emitted by the bats were recorded using a telemetry microphone mounted on the bats' backs, and their adaptation based on acoustic characteristics of emitted pulses was assessed in terms of jamming-avoidance responses (JARs). In experiment 1, frequency-modulated jamming sounds (3 ms duration) mimicking echolocation pulses of P. abramus were prepared. All bats showed significant increases in the terminal frequency of the frequency-modulated pulse by an average of 2.1-4.5 kHz when the terminal frequency of the jamming sounds was lower than the bats' own pulses. This frequency shift was not observed using jamming frequencies that overlapped with or were higher than the bats' own pulses. These findings suggest that JARs in P. abramus are sensitive to the terminal frequency of jamming pulses and that the bats' response pattern was dependent on the slight difference in stimulus frequency. In experiment 2, when bats were repeatedly exposed to a band-limited noise of 70 ms duration, the bats in flight more frequently emitted pulses during silent periods between jamming sounds, suggesting that the bats could actively change the timing of pulse emissions, even during flight, to avoid temporal overlap with jamming sounds. Our findings demonstrate that bats could adjust their vocalized frequency and emission timing during flight in response to acoustic jamming stimuli.