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A good location of song or call posts and visual display sites of males is crucial for territory defence and mate attraction. These sites are typically located at prominent positions to ensure an efficient, long-distance sexual advertisement. If the purpose of display sites is to maximize visibility, a suitable strategy would be to use multiple display sites rather than just one site. We investigated this in the ground-displaying houbara bustard by using two recent technological advances that enabled us collecting high precision data, GSM/GPRS loggers provided with accelerometer and very high-resolution digital elevation models of the terrain. We found that 12 out of 20 marked males used two or three display sites instead of just one as previously assumed in this species. The most used display site had the largest viewshed and use of both alternative sites decreased in proportion to their decreasing viewsheds. The number of display sites was apparently determined by two factors. First, it was correlated with display intensity, suggesting that using multiple display sites may be a mechanism to increase sexual signal transmission in males that are dominant or in better condition. Second, supplementary display sites were not used when the principal display site already provided an excellent view of the surroundings, e.g. when it was located on a hilltop. These results confirmed that the function of secondary display sites is to supplement the viewshed provided by the principal display site, and so maximize sexual signal transmission.Significance statementPerforming sexual display from just a single place is often not enough to reach all possible mates or competitors, so using multiple posts may be crucial for an effective sexual signal transmission. This is particularly important when the display is visual, and topographical barriers or vegetation may block the male’s line of view. Using last generation GSM/GPRS loggers equipped with accelerometers and very high-resolution digital elevation models of the terrain, we show how houbara bustard males, who perform a costly running display on the ground, have developed a complex display pattern that involves the use of various nearby display sites. These display sites are used in proportion to their visibilities, which shows that this multiple display site system has evolved to maximize the aggregated visual field of males and so increase their visibility to females and neighbour males.

During the last decade, many studies have focused on the detrimental effects of noise pollution on acoustic communication. Surprisingly, although it is known that noise exposure strongly influences health in humans, studies on wildlife remain scarce. In order to gain insight into the consequences of traffic noise exposure, we experimentally manipulated traffic noise exposure as well as the endocrine status of animals to investigate physiological and phenotypic consequences of noise pollution in an anuran species. We showed that noise exposure increased stress hormone level and induced an immunosuppressive effect. In addition, both traffic noise exposure and stress hormone application negatively impacted H. arborea vocal sac coloration. Moreover, our results suggest profound changes in sexual selection processes because the best quality males with initial attractive vocal sac coloration were the most impacted by noise. Hence, our study suggests that the recent increases in anthropogenic noise worldwide might affect a broader range of animal species than previously thought, because of alteration of visual signals and immunity. Generalizing these results to other taxa is crucial for the conservation of biodiversity in an increasingly noisy world. Durante la última década, muchos estudios se han enfocado en los efectos nocivos de la contaminación sonora sobre la comunicación acústica. Sorprendentemente, aunque se sabe que la exposición al sonido influye considerablemente sobre la salud humana, los estudios sobre la vida silvestre todavía son escasos. Para poder entender las consecuencias de la exposición al ruido del tráfico, manipulamos de manera experimental la exposición al ruido del tráfico así como el estado endocrino de algunos animales para investigar las consecuencias fisiológicas y fenotípicas de la contaminación sonora en una especie de anuro. Demostramos que la exposición al ruido incrementó el nivel de la hormona del estrés e indujo un efecto inmunorepresor. Además, tanto la exposición al ruido del tráfico y la aplicación de la hormona del estrés impactaron negativamente a la coloración del saco vocal de H. arbórea. Sumado a esto, nuestros resultados sugieren cambios profundos en los procesos de selección sexual porque los machos de mejor calidad con la coloración inicial más atractiva del saco vocal fueron los más impactados por el ruido. Por lo tanto, nuestro estudio sugiere que los incrementos recientes en el ruido antropogénico a nivel mundial pueden afectar a una gama más extensa de especies animales de lo que se pensaba previamente debido a la alteración de las señales visuales y la inmunidad. Generalizar estos resultados para otros taxones es crucial para la conservación de la biodiversidad en un mundo cada vez más ruidoso.

This study, based on the AISAS model, explores the impact of the interaction effect between visual and auditory signals on consumer purchase behavior. Using experimental methods, 120 participants were randomly assigned to four different visual and auditory signal combinations, and their purchase intentions and actual purchase behavior were measured. The results show that the interaction effect between visual and auditory signals has a significant impact on both purchase intentions and actual purchase behavior, and there is a significant positive relationship. Specifically, when visual and auditory signals are mutually consistent, consumers have the highest purchase intentions and actual purchase behavior; when both visual and auditory signals are absent, consumers have the lowest purchase intentions and actual purchase behavior; when either the visual or auditory signal is missing, consumers’ purchase intentions and actual purchase behavior are between the two extremes. This study provides a new perspective for understanding consumers’ decision-making processes in multi-sensory environments and offers valuable insights for the development of marketing strategies.

Elucidating the factors that influence the evolution of signal complexity is essential in understanding animal communication. Compared to vocal and color signals, movement-based visual signals only start to attract attention recently. In this study, we tested the social complexity (social structure promotes signal complexity) and background noise hypotheses (background noise promotes signal complexity) on the evolution of movement-based visual signal complexity. We collected display signals from twelve populations across the distribution range of the Asian agamid lizard, Phrynocephalus przewalskii. Their various components (tail coil, tail lash, body turning, and limb flapping) were quantified. Furthermore, we measured the population density and sexual size dimorphism (SSD), as estimates of social complexity, and estimate background noise using presence of plant and wind speed. We tested associations between measurements of variability in individual signal components and the overall display with estimates of social complexity and background noise using linear mixed models. We found evidence to suggest that both SSD and the noise environment impact the delivery of multiple display components, particularly the duration and maximum speed of display components. Importantly, our findings suggest that social and environmental factors do not impact males and females equally. Our data are consistent with both social complexity and background noise hypotheses, and our research provides direct evidence on the links among display complexity, social complexity, and background noise.Significance statementThe evolution of animal signal complexity has fascinated biologists for generations. We know much about vocal and color signals; nevertheless, movement-based visual signals only start to attract attention recently. Here we tested the factors influencing the evolution of display complexity using P. przewalskii as a study system, particularly around the social complexity (social structure promotes signal complexity) and background noise hypotheses (background noise promotes signal complexity). Our data are consistent with both social complexity and background noise hypotheses and provide direct evidence on the links among movement-based visual signal complexity, social complexity, and background noise.

Animal colour patterns remain a lively focus of evolutionary and behavioural ecology, despite the considerable conceptual and technical developments over the last four decades. Nevertheless, our current understanding of the function and efficacy of animal colour patterns remains largely shaped by a focus on stationary animals, typically in a static background. Yet, this rarely reflects the natural world: most animals are mobile in their search for food and mates, and their surrounding environment is usually dynamic. Thus, visual signalling involves not only animal colour patterns, but also the patterns of animal motion and behaviour, often in the context of a potentially dynamic background. While motion can reveal information about the signaller by attracting attention or revealing signaller attributes, motion can also be a means of concealing cues, by reducing the likelihood of detection (motion camouflage, motion masquerade and flicker-fusion effect) or the likelihood of capture following detection (motion dazzle and confusion effect). The interaction between the colour patterns of the animal and its local environment is further affected by the behaviour of the individual. Our review details how motion is intricately linked to signalling and suggests some avenues for future research. This Review has an associated Future Leader to Watch interview with the first author.

Background Among potential hosts, the rejection of foreign eggs, which is a common and effective strategy to counter brood parasitism, depends on egg recognition. Multimodal and multicomponent recognition cues of brood parasitic eggs, which include both tactile (size, shape, and texture) and visual (size, shape, color, and maculation) cues, are potentially involved in the perception and discrimination of foreign eggs by hosts. An egg rejection experiment on the host with different types of model eggs can help to accurately assess the relative contribution of different components on egg recognition and constraints to rejection, in which videos can help identify the method of host rejection. Methods Here, we assessed egg recognition and rejection responses by Oriental reed warblers (Acrocephalus orientalis), one of the most common hosts of common cuckoos (Cuculus canorus) which breed in eastern China. We designed six groups of model eggs for rejection experiments in which sensory cues included three grades of size and two categories of visual mimicry. Results Our experiments confirmed that the multimodal traits, which included variation in size, were significant predictors of egg rejection: We detected significantly higher rejection rates of mimetic spotted model eggs than of nonmimetic blue eggs. However, large model eggs did not yield higher rejection rates and, instead, these were less likely to be rejected and more likely to be deserted compared with smaller eggs. Further video‐recording data showed that there was no significant effect of egg size on the egg recognition rate (percentage of nests with evidence of egg pecking). No evidence that the egg appearance had an effect on the method of egg rejection (ejection or nest desertion) was found. Conclusions Only visual signals, such as color and maculation, contributed to the recognition of foreign eggs by Oriental reed warblers as recognizable clues, but not the egg size. The egg size had an impact on the type of egg rejection. It was less feasible for the warblers to eject large eggs and that is why they opted more often for desertion as the mean of model egg rejection. The significantly lower egg rejection rate of large eggs suggested that although some of them were recognized as foreign eggs, hosts failed to reject these eggs and finally the eggs were assumed to being accepted by the commonly used nest‐checking methods. The relative contribution of egg size and appearance (color and maculation) on egg recognition and rejection of Oriental reed warblers were studied. We detected significantly higher rejection rates of mimetic spotted model eggs than of nonmimetic blue eggs. Large model eggs did not yield higher rejection rates, and instead, these were less likely to be rejected and more likely to be deserted compared with smaller eggs.

The evolution of a visual signal will be affected by signaler and receiver behavior, and by the physical properties of the environment where the signal is displayed. Crab spiders are typical sit-and-wait predators found in diverse ambush sites, such as tree bark, foliage, and flowers. Some of the flower-dweller species present a UV⁺-white visual lure that makes them conspicuous and attractive to their prey. We hypothesized that UV⁺-white coloration was associated with the evolution of a flower-dwelling habit. In addition, following up on results from a previous study we tested whether the UV⁺-white coloration evolved predominantly in flower-dwelling species occurring in Australia. We measured the reflectance of 1149 specimens from 66 species collected in Australia and Europe, reconstructed a crab spider phylogeny, and applied phylogenetic comparative methods to test our hypotheses. We found that the flower-dwelling habit evolved independently multiple times, and that this trait was correlated with the evolution of the UV⁺-white coloration. However, outside Australia non-flower-dwelling crab spiders also express a UV⁺-white coloration. Therefore, UV⁺-white reflectance is probably a recurring adaptation of some flower dwellers for attracting pollinators, although it may have other functions in non-flower dwellers, such as camouflage.

To efficiently provide an animal with relevant information, the design of its visual system should reflect the distribution of natural signals and the animal's tasks. In many behavioural contexts, however, we know comparatively little about the moment-to-moment information-processing challenges animals face in their daily lives. In predator avoidance, for instance, we lack an accurate description of the natural signal stream and its value for risk assessment throughout the prey's defensive behaviour. We characterized the visual signals generated by real, potentially predatory events by video-recording bird approaches towards an Uca vomeris colony. Using four synchronized cameras allowed us to simultaneously monitor predator avoidance responses of crabs. We reconstructed the signals generated by dangerous and non-dangerous flying animals, identified the cues that triggered escape responses and compared them with those triggering responses to dummy predators. Fiddler crabs responded to a combination of multiple visual cues (including retinal speed, elevation and visual flicker) that reflect the visual signatures of distinct bird and insect behaviours. This allowed crabs to discriminate between dangerous and non-dangerous events. The results demonstrate the importance of measuring natural sensory signatures of biologically relevant events in order to understand biological information processing and its effects on behavioural organization.

The anatomy of the mammalian visual system, from the retina to the neocortex, is organized hierarchically 1 . However, direct observation of cellular-level functional interactions across this hierarchy is lacking due to the challenge of simultaneously recording activity across numerous regions. Here we describe a large, open dataset—part of the Allen Brain Observatory 2 —that surveys spiking from tens of thousands of units in six cortical and two thalamic regions in the brains of mice responding to a battery of visual stimuli. Using cross-correlation analysis, we reveal that the organization of inter-area functional connectivity during visual stimulation mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas 3 . We find that four classical hierarchical measures—response latency, receptive-field size, phase-locking to drifting gratings and response decay timescale—are all correlated with the hierarchy. Moreover, recordings obtained during a visual task reveal that the correlation between neural activity and behavioural choice also increases along the hierarchy. Our study provides a foundation for understanding coding and signal propagation across hierarchically organized cortical and thalamic visual areas. A large, open dataset containing parallel recordings from six visual cortical and two thalamic areas of the mouse brain is presented, from which the relative timing of activity in response to visual stimuli and behaviour is used to construct a hierarchy scheme that corresponds to anatomical connectivity data.

Perceptual quality assessment plays a vital role in the visual communication systems owing to the existence of quality degradations introduced in various stages of visual signal acquisition, compression, transmission and display. Quality assessment for visual signals can be performed subjectively and objectively, and objective quality assessment is usually preferred owing to its high efficiency and easy deployment. A large number of subjective and objective visual quality assessment studies have been conducted during recent years. In this survey, we give an up-to-date and comprehensive review of these studies. Specifically, the frequently used subjective image quality assessment databases are first reviewed, as they serve as the validation set for the objective measures. Second, the objective image quality assessment measures are classified and reviewed according to the applications and the methodologies utilized in the quality measures. Third, the performances of the state-of-the-art quality measures for visual signals are compared with an introduction of the evaluation protocols. This survey provides a general overview of classical algorithms and recent progresses in the field of perceptual image quality assessment.