James B Barnett

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• PhD
• Professor (Assistant) at Trinity College Dublin

Aposematic species signal their unpalatability to potential predators with recognisable, and frequently conspicuous, colour patterns. These visual signals are often also associated with bold behaviour and a reduced propensity to escape from approaching predators. Bold behaviours may act as an aversive signal and allow defended prey to avoid the ene...

Animals use colour for a wide range of adaptive functions, ranging from cryptic colours that blend into their environments to bright, conspicuous signals that convey information, either to attract mates or to ward off predators and rivals. However, perhaps one of the most intriguing adaptations is how animals can make use of the absence of colour t...

Aposematic signals warn predators that prey should be avoided due to dangerous secondary defences. However, as warning signals do not always produce avoidance, warning colours may evolve as a trade-off balancing detectability against signal saliency. For Batesian mimics, which display salient signals but lack secondary defences, the costs of predat...

Transparency is an intuitive form of concealment and, in certain butterflies, transparent patches on the wings can contribute to several distinct forms of camouflage. However, perhaps paradoxically, the largely transparent wings of many clearwing butterflies (Ithomiini, Nymphalidae) also feature opaque, and often colorful, elements which may reduce...

Background matching camouflage enables animals to evade detection with colours and patterns that resemble and blend into the environment. Effective concealment can, however, be difficult to achieve as natural backgrounds are often heterogeneous and frequently made up of spatially distinct microhabitats that differ in their visual characteristics. M...

Many animals use colour to signal their quality and/or behavioural motivations. Colourful signals have been well studied in the contexts of competition and mate choice, however, the role of these signals in non-sexual, affiliative relationships is not as well understood. Here, we used wild social groups of the cichlid fish Neolamprologus pulcher to...

Colour is an important component of many different defensive strategies, but signal efficacy and detectability will also depend on the size of the coloured structures, and how pattern size interacts with the background. Consequently, size-dependent changes in colouration are common among many different species as juveniles and adults frequently use...

Variation in aposematic signals was once predicted to be rare, yet in recent years it has become increasingly well documented. Despite increases in the frequency with which polytypism and polymorphism have been suggested to occur, population-wide variance is rarely quantified. We comprehensively sampled a subpopulation of the poison frog Oophaga sy...

Warning signals are often characterized by highly contrasting, distinctive, and memorable colors. Greater chromatic (hue) and achromatic (brightness) contrast have both been found to contribute to greater signal efficacy, making longwave colored signals (e.g., red and yellow), that are perceived by both chromatic and achromatic visual pathways, par...

Optimal camouflage can, in principle, be relatively easily achieved in simple, homogeneous, environments where backgrounds always have the same color, brightness, and patterning. Natural environments are, however, rarely homogenous and species often find themselves viewed against varied backgrounds where the task of concealment is more challenging....

Warning signals are often characterized by highly contrasting, distinctive and memorable colors. Both chromatic (hue) and achromatic (brightness) contrast contribute to signal efficacy, making longwave colored signals (red and yellow) that generate both chromatic and achromatic contrast common. Shortwave colors (blue and ultraviolet) do not contrib...

Animals use color both to conceal and signal their presence, with patterns that match the background, disrupt shape recognition, or highlight features important for communication. The forms that these color patterns take are responses to the visual systems that observe them and the environments within which they are viewed. Increasingly, however, t...

Sensory and behavioural lateralization is thought to increase neural efficiency and facilitate coordinated behaviour across much of the animal kingdom. Complementary laterality, when tasks are lateralized to opposite sides, can increase the efficiency of multitasking, but predictable behaviour may increase predation risk. Laterality is, however, va...

Aposematic and sexual signals are often characterized by bright, highly contrasting colors. Many species can see colors beyond the human visible spectrum, and ultraviolet (UV) reflection has been found to play an important role in communication and sexual selection. However, the role of UV in aposematic signals is poorly explored. Poison frogs freq...

Colorful visual signals can provide receivers with valuable information about food, danger, and the quality of social partners. However, the value of the information that color provides varies depending on the situation, and color may even act as a sensory trap where signals that evolved under one context are exploited in another. Despite some eleg...

Camouflage patterns prevent detection and/or recognition by matching the background, disrupting edges, or mimicking particular background features. In variable habitats, however, a single pattern cannot match all available sites all of the time, and efficacy may therefore be reduced. Active color change provides an alternative where coloration can...

Group cohesion and collective decision-making are important for many social animals, like social insects, whose societies depend on the coordinated action of individuals to complete collective tasks. A useful model for understanding collective, consensus-driven decision-making is the fluid nest selection dynamics of ant colonies. Certain ant specie...

Significance Poison dart frogs are well known for their deadly toxins and bright colors; they are a classic example of warning coloration. However, conspicuousness is not the only consideration; defensive coloration must be effective against a diverse predator community with a variety of different visual systems, and variable knowledge of prey defe...

Defended prey often use distinctive, conspicuous, colours to advertise their unprofitability to potential predators (aposematism). These warning signals are frequently made up of salient, high contrast, stripes which have been hypothesized to increase the speed and accuracy of predator avoidance learning. Limitations in predator visual acuity, howe...

The effect of viewing distance on the perception of visual texture is well known: spatial frequencies higher than the resolution limit of an observer’s visual system will be summed and perceived as a single combined colour. In animal defensive colour patterns, distance-dependent pattern blending may allow aposematic patterns, salient at close range...

Striped patterns are common in nature and are used both as warning signals and camouflage. Their effectiveness in either role depends on their color and spatial frequency, and how these compare to the background. Although this general principle is well established, the specific detail of how visual texture influences defensive coloration remains un...

Aposematic signals are often characterized by high conspicuousness. Larger and brighter signals reinforce avoidance learning, distinguish defended from palatable prey and are more easily memorized by predators. Conspicuous signalling, however, has costs: encounter rates with naive, specialized or nutritionally stressed predators are likely to incre...

Camouflage and warning coloration are usually viewed as alternative defensive strategies at opposite ends of the conspicuousness continuum. However, camouflage is compromised by factors such as habitat heterogeneity and motion [1], and aposematism bears the cost of ineffectiveness against ignorant, hasty or nutritionally stressed predators [2]. To...

The spread of oil palm plantations across Southeast Asia has resulted in significant species loss and community change due to the simplification of what were once complex ecosystems. In this study we examined how the return of a former area of oil palm plantation in Selangor, Malaysia, to other uses may have affected the anuran assemblages present....