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In animal communication, receivers benefit from signals providing reliable information on signallers’ traits of interest. Individuals involved in conflicts, such as competition between rivals, should pay particular attention to cues that are ‘unfakeable’ by the senders due to the intrinsic properties of the production process. In bioacoustics, the best-known example of such ‘index signals’ is the relationship between a sender’s body size and the dominant frequency of their vocalizations. Dominant frequency may however not only depend on an animal’s morphology but also on the interaction between the sound production system and its immediate environment. Here, we experimentally altered the environment surrounding calling frogs and assessed its impact on the signal produced. More specifically, we altered water level, which forced frogs to float on the surface and tested how this manipulation affected the shuttling of air between the lungs and the vocal sac, and how this in turn impacted the calls’ dominant frequency. Our results show that frogs that are floating are able to fully inflate their lungs and vocal sacs, and that the associated change in airflow or air pressure is correlated with a decrease of call dominant frequency.

Multimodal signaling systems are shaped not only by a signaler’s physical abilities but also by external factors such as the position of signal receivers and the properties of the medium through which the signals are transmitted. To fully understand the evolution and function of multimodal communication, it is essential to investigate the behavior in the wild. Here, I present evidence that socially monogamous songbirds perform complex courtship displays that can produce multimodal and multicomponent signals in wild conditions. Cordon-bleus (Uraeginthus spp.) are socially monogamous songbirds from East Africa. Both sexes of cordon-bleus perform multimodal courtship displays by holding a piece of nest material, bobbing up and down, and singing. My previous laboratory study using high-speed video cameras revealed that courtship bobbing includes multiple rapid steps similar to human tap-dancing, which presumably contributes to producing non-vocal sounds and/or vibrations in addition to visual signals. As a result of field observation and behavioral analysis, I found that wild cordon-bleus perform tap-dance like displays just as captive cordon-bleus. I also observed that wild cordon-bleus produced non-vocal sounds and shook branches during courtship, which can contribute to multimodal signal production (i.e., visual, acoustic, and vibrational signals). My findings imply that the courtship displays of cordon-bleus are an ideal candidate for investigating the role and function of multimodal communication in animals, and demonstrate the importance of further quantitative studies in both laboratory and field. Electronic supplementary material The online version of this article (10.1007/s00114-020-01686-x) contains supplementary material, which is available to authorized users.

Individuals produce advertisement signals with intended purposes and targets. However, these signals can be received by “eavesdroppers,” who may extract information from them and alter their behavior according to the extracted information. In anuran systems, males congregate at breeding sites to produce advertisement calls to attract receptive females and fend off rival males. Both sexes directly assess these calls in dyadic encounters and make decisions based on the call’s characteristics, e.g., frequency. What is unknown is whether bystander males eavesdrop on these same calls to inform their future competitive decisions. Here, we examined whether male green tree frogs (Hyla cinerea) eavesdrop on competing males, assess their competitor’s call frequency, and respond accordingly. We exposed males to playbacks of two competing males that varied in call frequency—high, average, low—and quantified latency to call, time spent calling, and number of calling bouts. We found that males had reduced latency to call and called more when eavesdropping low-frequency competition, but not average or high-frequency competition. Focal male size also influenced how they responded, with larger males being more responsive than smaller males. Our results indicate that male green tree frogs are capable of eavesdropping on nearby male calls and produce behavioral responses accordingly. Further, it appears males are able to alternate between assessment strategies dependent upon the frequency of the eavesdropped competition. These findings indicate that males not only directly assess an opponent’s call in dyadic encounters, but also indirectly through eavesdropping. Animals produce signals with intended purposes and targets, but which can be received by nearby eavesdroppers. Eavesdropped signals can elicit complex phenotypic changes in the eavesdropper, and lead to significant fitness consequences for the signal producer and eavesdropper. Thus, examining whether and to what extent individuals eavesdrop is an important step in understanding the evolution of signal production and response. Here, we examined whether male green tree frogs, H. cinerea, eavesdrop on nearby competing males and base their own calling behaviors on eavesdropped male’s calling characteristics. Calling behavior was mediated by focal male body size and eavesdropped male’s call frequency. Larger males reduced response latency and called more to nearby low-frequency males, while smaller males reduced response latency to nearby calls of average frequency. These results indicate that males will extract information from their competitive environment through eavesdropping and produce behavioral responses according to the eavesdropped information.

Studies of sexual communication typically focus on the design and information content of a signal of interest, but the timing of signal production relative to nearby competitors can be crucial. Male fiddler crabs, Uca mjoebergi, court females with a stereotyped claw-waving display, and males are often observed waving in synchrony with nearby claw-waving males. Using female mate preference experiments with robots that imitate male claw waves, we found evidence that females are more attracted to males whose waves immediately precede a synchronous group of waves (leaders); females also favoured males that waved in opposite phase to a synchronous group (alternators). By contrast, males whose waves lagged behind a group of synchronous wavers (laggards) were no more attractive. We discuss a simple sensory process that could explain how this female preference arises. Our results agree with past findings suggesting that synchrony in fiddler crabs occurs as an epiphenomenon of adaptive male responses to female preferences.

Animals communicate using a vast array of different signals in different modalities. For chimpanzees, vocalizations, gestures and facial expressions are all important forms of communication, yet these signals have rarely been studied together holistically. The current study aimed to provide the first comprehensive repertoire of flexibly combined (‘free’) multimodal (MM) signals, and assess individual and contextual factors influencing production of, and responses to, unimodal (UM) and MM signals in wild chimpanzees. In total, 48 different free MM signals were produced. MM signals were produced at a significantly lower rate than UM signals, but 22 of 26 focal animals were observed to produce free MM signals. The relative production rates of different types of UM and MM signals differed significantly between the behavioural contexts investigated, showing flexible use of signals across contexts. In contrast, individual factors such as age, sex or rank of signaller did not appear to influence the type of signal produced or the likelihood of eliciting a response. Finally, we compared recipient responses to free MM grunt-gesture signals and matched UM component signals and found that these MM signals were more likely to elicit a response than a grunt alone, but were as likely to elicit a response as the gesture alone. The overall findings point to a widespread capacity for wild chimpanzees to flexibly combine signals from different modalities and highlight the importance of adopting a multimodal approach to studying communication.

We know that microbes contribute to the production of odors that some animals use to communicate, but how common is this phenomenon? Recent studies capitalizing on new molecular technologies are uncovering fascinating associations between microbes and odors of wild animals, but causality is difficult to ascertain. Fundamental questions about the nature of these unique host-microbe interactions also remain unanswered. For instance, do microbes benefit from signaling associations with hosts? How does microbial community structure influence signal production? How do hosts regulate microbes in order to generate appropriate signals? Here, we review the current state of knowledge on microbially produced signals in animals and discuss key research foci that can advance our understanding of microbial-based signaling in the animal world.

Several hypotheses could explain the evolution of multimodal signals. One possibility is that such signals allow for communication even when one signalling modality is temporarily unavailable. However, little is known about the consequences of the permanent evolutionary loss of a signal modality. We used the field cricket Teleogryllus oceanicus to test the hypothesis that the loss of one mode of signalling can be accommodated by flexibly switching to another pre-existing modality. Field crickets use cues that carry social information in the form of both long-range acoustic signals and short-range cuticular hydrocarbons (CHCs), but males in some T. oceanicus populations have permanently lost the ability to sing because of a morphological mutation erasing sound-producing structures on their wings. In assays testing responsiveness to substrate-borne CHCs, T. oceanicus females responded to the presence of male, but not female, CHCs, which is consistent with known sexual dimorphism in field cricket chemical cues. However, we found no evidence for signal compensation in male crickets that have experienced an evolutionary loss of acoustic signals: females did not differentially respond to the CHCs of constitutively silent males compared to those of normal males. The ability of organisms to shift adaptively from one signalling modality to another following the evolutionary loss of a signal is likely to be constrained by both the degree to which signal production and receiving is flexible and the existence of suitably preadapted alternative modalities.

SummaryIt is now well established that bacterial populations utilize cell-to-cell signaling (quorum-sensing, QS) to control the production of public goods and other co-operative behaviours. Evolutionary theory predicts that both the cost of signal production and the response to signals should incur fitness costs for producing cells. Although costs imposed by the downstream consequences of QS have been shown, it has not been demonstrated that the production of QS signal molecules (QSSMs) results in a decrease in fitness. We measured the fitness cost to cells of synthesising QSSMs by quantifying metabolite levels in the presence of QSSM synthases. We found that: (i) bacteria making QSSMs have a growth defect that exerts an evolutionary cost, (ii) production of QSSMs correlates with reduced intracellular concentrations of QSSM precursors, (iii) the production of heterologous QSSMs negatively impacts the production of a native QSSM that shares common substrates, and (iv) supplementation with exogenously added metabolites partially rescued growth defects imposed by QSSM synthesis. These data provide the first direct experimental evidence that the production of QS signals carries fitness costs to producer cells.Originality-Significance StatementBacterial cells within populations communicate with each other to control social behaviors by producing diffusible quorum sensing (QS) signal molecules. Evolutionary theory predicts that both the cost of signal production and the response to signals should incur fitness costs for producing cells. Here we provide the first empirical evidence that the production of QS signals incurs fitness costs to producing cells. Since QS plays a major role in bacterial pathogenicity, this finding will underpin novel antimicrobial strategies that are urgently needed to replace currently available antimicrobials that are becoming obsolete through the ever-rising incidence of resistance.

Flexibility is considered a defining feature of great ape gestural communication. Previous research has suggested that there is a ‘means–ends’ dissociation between gesture type and context, whereby one signal may be used across contexts and several signals used within the same context. Such flexibility in signal production demands contextual comprehension, whereby recipients may perceive the context-free message of a given manual gesture, but also decide how to respond by inferring the signaller's goals from the accompanying context. We conducted naturalistic observations of wild East African chimpanzee, Pan troglodytes schweinfurthii, manual gestures, focusing on recipient perspective- during communicative interactions. Our results indicate that chimpanzees recognize the context-free meanings of gestures and they are also able to respond flexibly by inferring the meaning from the combination of gesture and context, including relative rank. When analysed at the level of gesture type, some gestures were tightly associated with dominant responses and outcomes. Chimpanzee manual gestures are primarily used for directing a recipient's movement or attention but the motivation underlying these gestural requests is inferred by the recipient from the context.

Blind cavefish use a form of active sensing in which burst-coast swimming motions generate flow signals detected by the lateral line. To determine if blind cavefish have evolved behavioral specializations for active flow-sensing, including the ability to regulate flow signal production through lateral line feedback, the swimming kinematics of blind and sighted morphs of Astyanax were compared before and after 24 h of familiarization with a novel, dark environment and with and without lateral line functionality. Although both morphs showed little difference in the vast majority of kinematic parameters measured, blind morphs differed significantly from sighted morphs in having a much higher incidence of swim cycle sequences devoid of sharp turns. Both lateral line deprivation and familiarization with the arena led to significant declines in this number for blind, but not sighted morphs. These findings suggest that swimming kinematics are largely conserved, but that blind morphs have nevertheless evolved enhanced abilities to use lateral line feedback when linking swim cycles into continuous, straight trajectories for exploratory purposes. This behavioral specialization can best be understood in terms of the intermittent and short-range limitations of active flow-sensing and the challenges they pose for spatial orientation and navigation.

The majority of anuran amphibians (frogs and toads) use acoustic communication to mediate sexual behavior and reproduction. Generally, females find and select their mates using acoustic cues provided by males in the form of conspicuous advertisement calls. In these species, vocal signal production and reception are intimately tied to successful reproduction. Research with anurans has demonstrated that acoustic communication is modulated by reproductive hormones, including gonadal steroids and peptide neuromodulators. Most of these studies have focused on the ways in which hormonal systems influence vocal signal production; however, here we will concentrate on a growing body of literature that examines hormonal modulation of call reception. This literature suggests that reproductive hormones contribute to the coordination of reproductive behaviors between signaler and receiver by modulating sensitivity and spectral filtering of the anuran auditory system. It has become evident that the hormonal systems that influence reproductive behaviors are highly conserved among vertebrate taxa. Thus, studying the endocrine and neuromodulatory bases of acoustic communication in frogs and toads can lead to insights of broader applicability to hormonal modulation of vertebrate sensory physiology and behavior.

We examined intra-patriline behavioral plasticity in communication behavior by generating lifetime behavioral profiles for the performance of the vibration signal and waggle dance in workers which were the progeny of three unrelated queens, each inseminated with the semen of a single, different drone. We found pronounced variability within each patriline for the tendency to produce each signal, the ontogeny of signal performance, and the persistence with which individual workers performed the signals throughout their lifetimes. Within each patriline, the number of workers that performed each signal and the distribution of onset ages for each signal were significantly different. In each patriline, workers of all ages could perform vibration signals; vibration signal production began 3–5 d before waggle dancing; and some workers began performing waggle dances at ages typically associated with precocious foraging. Most workers vibrated and waggled only 1–2 d during their lifetimes, although each patriline contained some workers that performed the signal persistently for up to 8 or 9 d. We also found marked variability in signal performance among the three worker lineages

Much is known about the way bats adjust their echolocation behaviour in response to environmental structure or to locate insect prey. By contrast, little is known about how echolocation calls are modulated in response to familiarity of the environment and objects within it. Here we show that the echolocating Megachiropteran bat Rousettus aegyptiacus produces echolocation signals at the same rate whether an obstacle is predictable or unpredictable in location, but that it has a reduced rate of echolocation signal production in a familiar environment with no obstacle present. This suggests that signal production is reduced in a familiar environment absent of 'clutter' but that probing the environment for maximum information is more important for this species than minimizing any cost of probing the environment in a cluttered space.

Modern technology has taken great strides to restore motion to amputees with prostheses. A key limitation in many cases is lack of a reliable controlling interface to the prosthetic devices. To address this issue, our lab has developed the Regenerative Peripheral Nerve Interface (RPNI). RPNIs transduce signals between residual peripheral nerves, muscle grafts, and prosthetic devices. Prior to this study, RPNI's signal production was primarily evaluated during single evoked maximal action potential. The purpose of this study was to characterize RPNI function during and after repeated submaximal use. RPNIs (n=5) were constructed in a rat model by transferring the EDL muscle from the lower hind limb to the hip region and implanting the transected peroneal nerve into the muscle. Control EDL muscles (n=8) were left in the native location. The muscles were evaluated at least five months postoperatively in terms of maximum evoked compound muscle action potentials, force production, force production during repeated use, and post-fatigue force production. There was a strong correlation between maximum compound muscle action potential amplitude and maximum contractile force (r=0.83 p < 0.01); thus, force was an indication of signaling. RPNI and Control muscles both fatigued as exponential regressions. Percent post fatigue force production did not differ significantly between the groups, with Controls recovering to 85% of initial maximum force and RPNIs recovering to 60%. RPNIs produce and recover signals in the same relative manner as Controls indicating RPNIs are prime candidates as controlling interfaces for myoelectric prosthetic devices.

The vibration signal of the honeybee functions as ‘modulatory communication’ because it elicits a general increase in activity that may help integrate the behaviour of workers that perform different, interrelated task sets. Workers that produce vibration signals contact numerous other bees, some of which receive the signal while others are ‘bypassed’ (antennated but not vibrated). Vibrating bees may therefore select among potential recipients. We monitored vibration signal behaviour in six observation colonies to investigate the possible selection of recipients by vibrating bees and the factors that might influence these choices. Vibrating bees roamed throughout the nest and bypassed more than half of all workers contacted. Vibration signals were not directed towards specific worker age groups. There were no differences in the mean age of vibrated versus bypassed workers or the proportion of recipients that were of preforaging versus foraging age. The likelihood of receiving vibration signals was influenced by recipient activity level. Significantly more workers were vibrated if they were inactive versus active when contacted by a signalling bee. Signal production was not consistently influenced by relatedness. Vibrating bees from only a single patriline in one of our study colonies were more likely to perform signals on supersisters than on half-sisters. In all other colonies no kin preferences were observed during signal performance. Thus, vibrating bees may choose among potential recipients and direct their signals towards inactive workers of all ages and levels of relatedness. This, in combination with their movement throughout the colony, could help to activate simultaneously multiple worker groups that perform interdependent tasks, but which may be spatially segregated in the nest.

Animal displays are often perceived by intended and unintended receivers in more than one sensory system. In addition, cues that are an incidental consequence of signal production can also be perceived by different receivers, even when the receivers use different sensory systems to perceive them. Here we show that the vocal responses of male túngara frogs ( Physalaemus pustulosus ) increase twofold when call-induced water ripples are added to the acoustic component of a rival’s call. Hunting bats ( Trachops cirrhosus ) can echolocate this signal by-product and prefer to attack model frogs when ripples are added to the acoustic component of the call. This study illustrates how the perception of a signal by-product by intended and unintended receivers through different sensory systems generates both costs and benefits for the signaler.

The spread of antibiotic resistance, together with the lack of antibiotics based on novel molecular scaffolds, marks the so-called 'post-antibiotic era'. Interference with bacterial virulence has emerged as an attractive approach among the current potential strategies for developing new anti-infective drugs. Furthermore, the discovery that virulence gene expression is mostly regulated by quorum sensing (QS) has raised a lot of interest and prompted a lot of research aimed at finding inhibitors of this mechanism.This paper deals with the most recent strategies aimed at discovering new inhibitors able to disrupt the different steps of the QS system, targeting signal production, signal molecules and signal receptors. The authors provide an overview of the literature, including research papers, mostly dealing with inhibitors of the Staphylococcus aureus and Pseudomonas aeruginosa QS systems, and reviews dealing with the application of the newest technologies in the field. They also highlight the field's latest prospects and emerging concerns regarding their possible clinical applications.QS inhibition is a promising strategy against infections. However, despite the discovery of a huge number of QS inhibitors, with about 40 patents, the potential of QS inhibition is still to be fully assessed. The current validation methods of QS inhibitors must be optimized, and the discovery that QS disruption may favor or select more virulent strains must be investigated in depth. Given the current market-dependent situation, it should be possible to develop hits into licensed drugs through joint ventures between private companies, academia and public institutions.

The gold standard for rate modulation is the sinus node. To improve the rate modulation provided by artificial sensors, new sensors have to be developed or 2 different sensor systems can be combined within a single device. Association combination of a sensor with a rapid-response fast-rate increase sensor (activity) and a progressive, more specific sensor (QT ventilation) is generally used. Sensor combinations require adequate sensor blending for signal production and prioritization during rate modulation. However, in the new devices, some other aspects of rate modulation could be taken into consideration, particularly circadian rate variations to obtain lower rates at nighttime than during daytime, and automatic adaptation of the slope of rate increase during exercise, according to the patient’s fitness, heart function, age, etc. Despite the need for automaticity, manual programming could continue to be useful to adapt rate modulation with data from sensor trending memories.

Vibration is an important part of the sensory world in spiders, and many species have adapted vibration as a major part of their conspecific communication. While nearly all male wolf spiders produce vibrations during courtship, the “purring” wolf spider, Gladicosa gulosa, also produces an acoustic signal in conjunction with its vibratory display. However, with limited previous research on this species, the evolutionary significance of this component remains unknown. Given that spiders are not known to possess sensory structures for directly perceiving airborne sound, this raises a number of questions about the production, reception, and possible role of the signal. We measured male signal production and male/female responses to isolated acoustic signals on both vibrating (paper) and non-vibrating (granite) substrates. We found that male signals, both vibratory and acoustic, are only present in vibrating substrates. We also found significant differences in phonotaxis based on sex of the focal individual, stimulus type, and substrate type. These results suggest that the substrate plays an important role in both production and reception of the acoustic signal, and that under certain conditions, acoustic signaling may have a role in the communication network in this species.

Humans have a capacity to perceive and synchronize with rhythms. This is unusual in that only a minority of other species exhibit similar behavior. Study of synchronizing species (particularly anurans and insects) suggests that simultaneous signal production by different individuals may play a critical role in the development of regular temporal signaling. Accordingly, we investigated the link between simultaneous signal production and temporal regularity in our own species. Specifically, we asked whether inter-individual synchronization of a behavior that is typically irregular in time, speech, could lead to evenly-paced or "isochronous" temporal patterns. Participants read nonsense phrases aloud with and without partners, and we found that synchronous reading resulted in greater regularity of durational intervals between words. Comparison of same-gender pairings showed that males and females were able to synchronize their temporal speech patterns with equal skill. These results demonstrate that the shared goal of synchronization can lead to the development of temporal regularity in vocalizations, suggesting that the origins of musical rhythm may lie in cooperative social interaction rather than in sexual selection.

Preconjugal ciliates learn classical repetition error-correction codes to safeguard mating messages and replies from corruption by rivals and local ambient noise. Because individual cells behave as memory channels with Szilárd engine attributes, these coding schemes also might be used to limit, diagnose, and correct mating-signal errors due to noisy intracellular information processing. The present study, therefore, assessed whether heterotrich ciliates effect fault-tolerant signal planning and execution by modifying engine performance, and consequently entropy content of codes, during mock cell-cell communication. Socially meaningful serial vibrations emitted from an ambiguous artificial source initiated ciliate behavioral signaling performances known to advertise mating fitness with varying courtship strategies. Microbes, employing calcium-dependent Hebbian-like decision making, learned to diagnose then correct error syndromes by recursively matching Boltzmann entropies between signal planning and execution stages via power or refrigeration cycles. All eight serial contraction and reversal strategies incurred errors in entropy magnitude by the execution stage of processing. Absolute errors, however, subtended expected threshold values for single bit-flip errors in three-bit replies, indicating coding schemes protected information content throughout signal production. Ciliate preparedness for vibrations selectively and significantly affected the magnitude and valence of Szilárd engine performance during modal and nonmodal strategy corrective cycles. But entropy fidelity for all replies mainly improved across learning trials as refinements in engine efficiency. Fidelity neared maximum levels for only modal signals coded in resilient three-bit repetition error-correction sequences. Together, these findings demonstrate microbes can elevate survival/reproductive success by learning to implement classical fault-tolerant information processing in social contexts.

International audience; Vibrations and sounds, collectively called vibroacoustics, play significant roles in intracolony communication in termites, social wasps, ants, and social bees. Modalities of vibroacoustic signal production include stridulation, gross body movements, wing movements, high-frequency muscle contractions without wing movements, and scraping mandibles or tapping body parts on resonant substrates. Vibroacoustic signals are perceived primarily via Johnston's organs in the antennae and subgenual organs in the legs. Substrate vibrations predominate as vibroacoustic modalities, with only honey bees having been shown to be able to hear airborne sound. Vibroacoustic messages include alarm, recruitment, colony activation, larval provisioning cues, and food resource assessment. This review describes the modalities and their behavioral contexts rather than electrophysiological aspects, therefore placing emphasis on the adaptive roles of vibroacoustic communication. Although much vibroacoustics research has been done, numerous opportunities exist for continuations and new directions in vibroacoustics research.

Choruses of acoustically signaling frogs and toads are among the most impressive acoustic spectacles known from the natural world. They are loud, raucous social environments that form for one purpose and one purpose only: sex. The loud sexual advertisement signals that males produce are often necessary and sufficient to elicit responses from reproductive females, and they also function in communicating with other males during interactions over calling sites and territories. Frogs listening in a chorus must detect, recognize, localize, and discriminate among competing signals amid high levels of biotic, and often abiotic, background noise. In essence, frogs must solve a biological analog of the human cocktail party problem. In this chapter, we describe the frog’s cocktail party problem in functional terms relevant to frog reproduction and communication. We then describe results from experimental studies, mostly of behavior, that elucidate how the frog auditory system goes about solving problems related to auditory masking and auditory scene analysis.

A feature of the GFIS ion source is that every aspect of its operation and behavior—from its imaging resolution, the energy range over which it operates, the efficiency of signal production, and the damage it does to the materials that it examines—is ultimately affected by the choice of imaging gas. Ideally, the same source could rapidly be reconfigured to select and generate any one of a number of different ion beams. Because each type of ion has its own strengths and weaknesses, this feature would add substantially to the utility of the ion microscope.

We present an automated software tool "SModelS" to systematically confront theories Beyond the Standard Model (BSM) with experimental data. The tool consists of a general procedure to decompose such BSM theories into their Simplified Models Spectra (SMS). In addition, SModelS features a database containing the majority of the published SMS results of CMS and ATLAS. These results consist of the 95% confidence level upper limits on signal production cross sections. The two components together allow us to quickly confront any BSM model with LHC results. As a show-case example we will briefly discuss an application of our procedure to a specific supersymmetric model. It is one of our ongoing efforts to extend the framework to include also efficiency maps produced either by the experimental collaborations, by efforts performed within the phenomenological groups, or possibly also by ourselves. While the current implementation can handle null results only, it is our ultimate goal to build the Next Standard Model in a bottom-up fashion from both negative and positive results of several experiments. The implementation is open source, written in python, and available from http://smodels.hephy.at.

The nature of the transferrable factor which goes from irradiated objects to bystander objects remains undefined. Most agree that a chemical entity is the likely 'factor' although some authors have produced in vitro evidence for the involvement of a physical component or a very potent volatile capable of traveling through air distances. In this paper we test the hypothesis that the communicated signal may be physical at least in part.The in vivo fish model was used to allow signal production and response to occur in organisms in vivo without any shared blood or central nervous system (CNS) connections. A reporter assay and calcium flux measurements were used to detect signal production when irradiated fish were separated from unirradiated fish by (a) a plastic container, and (b) a foil-wrapped plastic container.The unirradiated fish showed bystander effects in both cases. The use of foil excludes the possibility of a light signal and although a highly active volatile could travel from one tank to another, the arrangement of sham and irradiated tanks makes it highly unlikely that this could explain our result.We conclude that there must be a physical component in the mechanism such as a weak acoustic or electromagnetic signal.

Studies of avian vocal mechanisms provide new insights into an important form of animal communication that has both striking parallels with and important differences from various aspects of human speech production. Birdsong is produced in a distinctive vocal organ, the syrinx, which in some groups contains two independently controlled sound generators. This article summarizes the current understanding of the mechanisms by which birds regulate the temporal and spectral characteristics of their vocal signals, including the role of sensory feedback, lateralization of neural function, and modulation of song by vocal tract filter. Together, these data suggest production constraints have strongly influenced the motor strategies for achieving vocal diversity.

SUMMARY Brown ghost knifefish, Apteronotus leptorhynchus, are a species of weakly electric fish that produce a continuous electric organ discharge (EOD)that is used in navigation, prey capture and communication. Stereotyped modulations of EOD frequency and amplitude are common in social situations and are thought to serve as communication signals. Of these modulations, the most commonly studied is the chirp. This study presents a quantitative analysis of chirp production in pairs of free-swimming, physically interacting male and female A. leptorhynchus. Under these conditions, we found that in addition to chirps, the fish commonly produce a second signal type, a type of frequency rise called abrupt frequency rises, AFRs. By quantifying the behaviours associated with signal production, we find that Type 2 chirps tend to be produced when the fish are apart, following periods of low aggression,whereas AFRs tend to be produced when the fish are aggressively attacking one another in close proximity. This study is the first to our knowledge that quantitatively describes both electrocommunication signalling and behavioural correlates on a subsecond time-scale in a wave-type weakly electric fish.

Since the impressive reduction of transfusion-transmitted virus infections, bacterial infections by blood transfusion represent the most important infection risk. Platelet concentrates are the current focus of attention, as they are stored under temperature conditions which allow growth of contaminating bacteria up to 10(10) and more microbes per platelet bag. This paper does not consider the pathogen reduction methods but will assess suitable screening methods. Beside conventional microbiological approaches or surrogate markers, several efficient methods able to detect bacterial contamination in platelets are available on the market. They need to be divided into two different methodological principles: the cultivation methods and rapid methods. Cultivation or incubation methods require some time for signal production as they depend on growth of microbes. Thus, they have to be combined with early sampling, i.e., the sample to be examined has to be drawn from the blood component 1 day after donation. Their advantage is the relatively uncomplicated implementation into the logistics of blood banks. Because of the initially very low count of bacteria after donation, a certain small sampling error in application of that strategy remains. Rapid methods are able to produce the diagnosis within a short time. Therefore, they allow postponing of sample drawing, ideally up to the time immediately before transfusion. However, this procedure causes logistic complications. On the other hand, late sampling combined with a rapid method will prevent the transfusion of highly contaminated platelet concentrates leading to acute septic shock up to the death of the patient. Considering the sum of different aspects including the supply of patients, the potential improvement of microbial safety of platelet concentrates is comparable in both strategies.

SummarySexual signals are conspicuous and are typically assumed to be energetically costly, which keeps them honest. A recent study on fireflies has found that signal production is energetically cheap, but signalling remains expensive because of eavesdropping predators.

This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 283871. Human and nonhuman primate communication differs in various ways. In particular, humans base communicative efforts on mutual knowledge and conventions shared between interlocutors. In this study, we experimentally tested whether bonobos (Pan paniscus), a close relative to humans, are able to take into account the familiarity, i.e. the shared interaction history, when communicating with a human partner. In five experimental conditions we found that subjects took the recipients' attentional state and their own communicative effectiveness into account by adjusting signal production accordingly. More importantly, in case of communicative failure, subjects repeated previously successful signals more often with a familiar than unfamiliar recipient, with whom they had no previous interactions, and elaborated by switching to new signals more with the unfamiliar than the familiar one, similar to what has previously been found in two year-old children. We discuss these findings in relation to the human capacity to establish common ground between interlocutors, a crucial aspect of human cooperative communication. Publisher PDF

Research on the development of animal signals has been immensely influential on how we think about human speech and language development. Development of communication skills can be parsed into components of production, usage, and comprehension that may each have different developmental processes. Within a species different developmental processes may apply to different functional signals as well as to different components. In general, the greatest plasticity is found in development of comprehension and the least plasticity in signal production. More mobile species appear to have greater plasticity. Development of communication can be facilitated through subtle social cues or mere associational processes independent of more traditional rewards.

Recording of an ultrasonic vibration potential when a burst of ultrasound traverses a body containing a colloidal object can be used as the basis for an imaging method. The fundamentals of the theory of signal production and experimental demonstration of the imaging method are given. In a second imaging method, the use of ultrasound to modify x-ray phase contrast images where the ultrasound acts as a kind of "phase contrast" agent used to translate objects in space is demonstrated.

Introduction All communication occurs in a network environment with the exception of a subset of systems that unequivocally meet both of the following criteria: (a) a signal can never be received by more than one receiver; (b) a receiver can never receive more than one signal simultaneously. In other words, all communication networks have at least one of two defining properties: (a) signals can be, at least potentially, received by several receivers; and (b) receivers can, at least potentially, receive signals from several signallers at any one time. Consequently, in moving from a dyadic consideration of communication to a network view, signallers and receivers both take on a range of costs and benefits, which are the theme of this book. In this chapter, I will consider the implications of a particular type of receiving behaviour that becomes possible in a network, namely eavesdropping. I will begin by reviewing different definitions of eavesdropping that are found in the literature and the evidence for different types of eavesdropping, distinguishing between eavesdropping on signals and eavesdropping on signal interactions. I will then examine the costs, benefits and implications of eavesdropping on interactions, as recognition of this phenomenon emerged from considerations of qualitative differences between dyadic and network views of communication (McGregor, 1993; McGregor & Dabelsteen, 1996).

Studies of signal production and detection are complicated by the diverse modalities used by animals, constraints of human signal perception, and limitations of a controlled laboratory environment. These complications can be addressed by creative approaches to studying anatomical adaptations for signal production and detection, innovative technology, and careful studies of signal production and detection in the field. These solutions should overcome the perceptual limitations of researchers as they explore Umwelten in other species.

Conventional signals impose costs on senders through receiver retaliation rather than through investment in signal production. While several visual conventional signals have been described (mainly 'badges of status'), acoustic examples are rare; however, several aspects of repertoire use in songbirds are potential candidates. We performed interactive playback experiments to determine whether song-type matches (responding to a song with the same song type), repertoire matches (responding to a song with a different song type, but one in the repertoires of both singers) and unshared song types serve as conventional signals during male-male territorial interactions in banded wrens, Thryothorus pleurostictus. Our results demonstrate that these three signals incite varying levels of receiver aggression: song-type matches induce faster approach than do repertoire matches, and repertoire matches induce faster approach than do unshared song types. Production costs do not differ, while the receiver response does. Because territorial banded wrens approach opponents who signal aggressively, such opponents risk attack. This system will punish and prevent cheaters, as weak males signalling aggression will be subject to escalation by stronger or more-motivated opponents.

A long recognized but little explored mode of intersexual communication in insects is use of low-frequency substrate-borne vibrational signals. Representatives of 10 insect orders are known to have adopted this mode; range of communication, informational content and receiver integration of signals and energy costs are discussed. Arctoperlarian stoneflies represent the epitome of evolution of vibrational communication. Their ancestral signals were monophasic volleys of evenly spaced drumbeats. Derived signals to achieve species-specificity and possibly to enable sexual.selection or some measure of reproductive fitness has involved modification of the ancestral form toward complex signals through: (1) changes in the rhythmic patterning of calls, (2) patterns of ♂-♀ duetting, and/or changes in the method of signal production such as rubbing or tremulation. Proposed paradigms for the evolution of vibrational communication and evolution of signal patterns are presented, with examples of the signals of several arctoperlarian species. The entire mating system of Arctoperlaria is discussed, and searching behavior in relation to vibrational communication is presented for Pteronarcella badia, Claassenia sabulosa, Perlinella drymo and Suwallia sp.

Landmines (and other UXO) gradually leak explosive chemicals into the soil at significant concentrations. Bacteria, which have adapted to scavenge low concentrations of nutrients, can detect these explosive chemicals. Uptake of these chemicals results in the triggering of specific bacterial genes. The authors have created genetically recombinant bioreporter bacteria that detect small concentrations of energetic chemicals. These bacteria are genetically engineered to produce a bioluminescent signal when they contact specific explosives. A gene for a brightly fluorescent compound can be substituted for increased sensitivity. By finding the fluorescent bacteria, you find the landmine. Detection might be accomplished using stand-off illumination of the minefield and GPS technology, which would result in greatly reduced risk to the deminers. Bioreporter technology has been proven at the laboratory scale, and will be tested under field conditions in the near future. They have created a bacterial strain that detects sub-micromolar concentrations of o- and p-nitrotoluene. Related bacterial strains were produced using standard laboratory protocols, and bioreporters of dinitrotoluene and trinitrotoluene were produced, screening for activity with the explosive compounds. Response time is dependent on the growth rate of the bacteria. Although frill signal production may require several hours, the bacteria can be applied over vast areas and scanned quickly, producing an equivalent detection speed that is very fast. This technology may be applicable to other needs, such as locating buried explosives at military and ordnance/explosive manufacturing facilities.

Colour image processing is usually performed on visual information which has been collected electronically. The principles and practice of this sort of information acquisition derive from techniques which were developed primarily for television applications. Whilst some aspects of television technology are inappropriate, or result in non-ideal images from the processing point of view, nevertheless the fundamental principles of scanning and baseband video signal production are sufficiently important to be included here.

Field studies of four sympatric parrot species in Costa Rica are revealing several possible functions for the well‐known ability of parrots to mimic new sounds throughout life. Despite earlier suggestions that this might facilitate exchanges of environmental information, all data so far suggest that vocal mimicry in the wild is associated with mediation of the fission/fusion of groups of parrots and/or of conflicts between mated pairs. Recent results using array recording and interactive playback will be summarized, and several technical problems created by the mechanisms of parrot vocal signal production discussed. [Research supported by NSF Grant IBN‐022927 and by continued encouragement and logistics provided by the staff of the Area Conservacion Guanacaste (Costa Rica).]

As a test of the automaticity of the food calling behaviour of cockerels, their sensitivity to the presence and nature of an audience was explored. Males were presented with either a highly preferred food or a non-food item in the presence of a familiar female, a strange female, a male, or with no audience at all. With food as a referent, there was significantly less food calling with no audience than in the presence of females, and even less with a male as a potential receiver. There was a significant amount of calling for the non-food item, especially in the presence of a strange female. Food calling to non-foods in certain social contexts is discussed as a case of deception. The modulation of signal production according to the nature of the receiver is considered in relation to the issue of intentionality in animal communication.

Animal signals evolve as adaptations to social as well as physical environments. Where the interests of signallers and responders differ, a coevolutionary "arms race" cycle of signal adoption, exaggeration, and devaluation may result. Stable, reliable signals evolve when costs of signalling constrain the evolution of bluff and exaggeration. Acoustic signals are especially costly, compared to other signal types, and are therefore especially likely to evolve as reliable signals in such "social competition" situations. Costs of acoustic signals include physiological costs of growth and signal production, probes by conspecific rivals and discriminating members of the other sex, and attacks by natural enemies such as predators and parasites.