Jolyon Troscianko

University of Exeter | UoE · Centre for Ecology and Conservation

Quantitative measurements of colour, pattern and morphology are vital to a growing range of disciplines. Digital cameras are readily available and already widely used for making these measurements, having numerous advantages over other techniques, such as spectrometry. However, off‐the‐shelf consumer cameras are designed to produce images for human...

Evading detection by predators is crucial for survival. Camouflage is therefore a widespread adaptation, but despite substantial research effort our understanding of different camouflage strategies has relied predominantly on artificial systems and on experiments disregarding how camouflage is perceived by predators. Here we show for the first time...

Understanding the adaptive function of conspicuous coloration has been a major focus of evolutionary biology for much of the last century. Although considerable progress has been made in explaining how conspicuous coloration can be used in functions as diverse as sexual and social signaling, startling predators, and advertising toxicity [1], there...

To understand the function of colour signals in nature, we require robust quantitative analytical frameworks to enable us to estimate how animal and plant colour patterns appear against their natural background as viewed by ecologically relevant species. Due to the quantitative limitations of existing methods, colour and pattern are rarely analysed...

Ornaments used in courtship often vary wildly among species, reflecting the evolutionary interplay between mate preference functions and the constraints imposed by natural selection. Consequently, understanding the evolutionary dynamics responsible for ornament diversification has been a longstanding challenge in evolutionary biology. However, comp...

Camouflage is a widespread and well-studied anti-predator strategy, yet identifying which patterns provide optimal protection in any given scenario remains challenging. Besides the virtually limitless combinations of colours and patterns available to prey, selection for camouflage strategies will depend on complex interactions between prey appearan...

Shadows that are produced across the surface of an object (self-shadows) are potentially an important source of information for visual systems. Animal patterns may exploit this principle for camouflage, using pictorial cues to produce false depth information that manipulates the viewer’s detection/recognition processes. However, pictorial cues coul...

The nests of ground‐nesting birds rely heavily on camouflage for their survival, and predation risk, often linked to ecological changes from human activity, is a major source of mortality. Numerous ground‐nesting bird populations are in decline, so understanding the effects of camouflage on their nesting behavior is relevant to their conservation c...

The nests of ground-nesting birds rely heavily on camouflage for their survival, and predation pressures, often linked to human activity, are a major source of mortality. Numerous ground-nesting bird populations are in decline, so understanding the effects of camouflage on their nesting behaviour is of relevance to their conservation concern. Habit...

Spectroradiometery is a vital tool in a wide range of biological, physical, astronomical and medical fields, yet its cost and accessibility are frequent barriers to use. Research into the effects of artificial light at night (ALAN) further compounds these difficulties with requirements for sensitivity to extremely low light levels across the ultrav...

An object's colour, brightness and pattern are all influenced by its surroundings, and a number of visual phenomena and "illusions" have been discovered that highlight these often dramatic effects. Explanations for these phenomena range from low-level neural mechanisms to high-level processes that incorporate contextual information or prior knowled...

Encroachment of artificial light at night (ALAN) into natural habitats is increasingly recognized as a major source of anthropogenic disturbance. Research focussed on variation in the intensity and spectrum of ALAN emissions has established physiological, behavioural and population-level effects across plants and animals. However, little attention...

The persistence of imperfect mimicry in nature presents a challenge to mimicry theory. Some hypotheses for the existence of imperfect mimicry make differing predictions depending on how mimetic fidelity is measured. Here, we measure mimetic fidelity in a brood parasite-host system using both trait-based and response-based measures of mimetic fideli...

Fear influences almost all aspects of a prey species’ behaviour, such as its foraging and movement, and has the potential to cause trophic cascades. The superior low-light vision of many predators means that perceived predation risk in prey is likely to be affected by light levels. The widespread and increasing intensity of artificial light at nigh...

Spectroradiometery is a vital tool in a wide range of biological, physical, astronomical and medical fields, yet its cost and accessibility are frequent barriers to use. Research into the effects of artificial light at night (ALAN) further compounds these difficulties with requirements for sensitivity to extremely low light levels across the ultrav...

Camouflage is one of the most apparent examples of evolution by natural selection. We are interested in using artificial evolution to better understand the evolution and function of camouflage patterns and strategies. To facilitate this research, we have designed CamoEvo, an open access toolbox for camouflage research experiments.

Eyes convey important information about the external and internal worlds of animals. Individuals can follow the gaze of others to learn about the location of salient objects as well as assess eye qualities to evaluate the health, age or other internal states of conspecifics. Because of the increasing prevalence of artificial lighting at night (ALAN...

Egg rejection is a crucial defence strategy against brood parasitism that requires the host to correctly recognise the foreign egg. Rejection behaviour has, thus, evolved in many hosts, facilitated by the visual differences between the parasitic and host eggs, and driving hosts to rely on colour and pattern cues. On the other hand, the need to reco...

Chimpanzee (Pan troglodytes) sclera appear much darker than the white sclera of human eyes, to such a degree that the direction of chimpanzee gaze may be concealed from conspecifics. Recent debate surrounding this topic has produced mixed results, with some evidence suggesting that (1) primate gaze is indeed concealed from their conspecifics, and (...

Eye gaze is an important source of information for animals, implicated in communication, cooperation, hunting and antipredator behaviour. Gaze perception and its cognitive underpinnings are much studied in primates, but the specific features that are used to estimate gaze can be difficult to isolate behaviourally. We photographed 13 laboratory-hous...

Camouflage research has long shaped our understanding of evolution by natural selection, and elucidating the mechanisms by which camouflage operates remains a key question in visual ecology. However, the vast diversity of colour patterns found in animals and their backgrounds, combined with the scope for complex interactions with receiver vision pr...

An object's colour, brightness and pattern are all influenced by its surroundings, and a number of visual phenomena and "illusions" have been discovered that highlight these often dramatic effects. Explanations for these phenomena range from low-level neural mechanisms to high-level processes that incorporate contextual information or prior knowled...

The sun is the most reliable celestial cue for orientation available to daytime migrants. It is widely assumed that diurnal migratory insects use a ‘time-compensated sun compass’ to adjust for the changing position of the sun throughout the day, as demonstrated in some butterfly species. The mechanisms used by other groups of diurnal insect migrant...

Individual identification is crucial for studying animal ecology and evolution. In birds this is often achieved by capturing and tagging. However, these methods are insufficient for identifying individuals/species that are secretive or difficult to catch. Here, we employ an automatic analytical approach to predict the identity of bird females based...

The nighttime environment is being altered rapidly over large areas worldwide through introduction of artificial lighting, from streetlights and other sources. This is predicted to impact the visual ecology of many organisms, affecting both their intra- and interspecific interactions. Here, we show the effects of different artificial light sources...

Parallel evolution, in which independent populations evolve along similar phenotypic trajectories, offers insights into the repeatability of adaptive evolution. Here, we revisit a classic example of parallelism, that of repeated evolution of brighter males in the Trinidadian guppy (Poecilia reticulata). In guppies, colonisation of low predation hab...

Understanding what maintains the broad spectrum of variation in animal phenotypes and how this influences survival is a key question in biology. Frequency dependent selection – where predators temporarily focus on one morph at the expense of others by forming a “search image” – can help explain this phenomenon. However, past work has never tested r...

The motion dazzle hypothesis posits that high contrast geometric patterns can cause difficulties in tracking a moving target and has been argued to explain the patterning of animals such as zebras. Research to date has only tested a small number of patterns, offering equivocal support for the hypothesis. Here, we take a genetic programming approach...

Identification of individuals greatly contributes to understanding animal ecology and evolution, and in many cases can only be achieved using expensive and invasive techniques. Advances in computing technology offer alternative cost-effective techniques which are less invasive and can discriminate between individuals based on visual and/or acoustic...

Parallel evolution, in which independent populations evolve along similar phenotypic trajectories, offers insights into the repeatability of adaptive evolution. Here, we revisit a classic example of parallelism, that of repeated evolution of brighter males in the Trinidadian guppy. In guppies, colonisation of low predation habitats is associated wi...

The grass finches (family Estrildidae) are the host family to the brood-parasitic indigobirds and whydahs (genus Vidua). They are unusual among birds in having highly ornamentedand diverse nestlings. On pages 2526–2538, Jamie et al. provide quantitative evidence that many of these colours and patterns are by nestling Vidua parasites. First and seco...

Forests are a mosaic of light spectra, and colour signal efficiency might change in different light environments. Local adaptation in Heliconius butterflies is linked to microhabitat use and the colourful wing colour patterns may be adapted for signalling in different light environments. These toxic butterflies exhibit conspicuous colours as a warn...

Sexually selected ornaments range from highly dynamic traits to those that are fixed during development and relatively static throughout sexual maturity. Ornaments along this continuum differ in the information they provide about the qualities of potential mates, such as their parasite resistance. Dynamic ornaments enable real-time assessment of th...

Brood parasites use the parental care of others to raise their young and sometimes employ mimicry to dupe their hosts. The brood‐parasitic finches of the genus Vidua are a textbook example of the role of imprinting in sympatric speciation. Sympatric speciation is thought to occur in Vidua because their mating traits and host preferences are strongl...

Vision is the dominant sense for many animals, and there is an enormous diversity in visual capabilities. Understanding the visual abilities of a given species can therefore be key for investigating its behaviour and evolution. However, many techniques for quantifying visual capability are expensive, require specialized equipment or are terminal fo...

In the animal kingdom, conspicuous colors are often used for inter- and intra-sexual communication. Even though primates are the most colorful mammalian taxon, many questions, including what potential information color signals communicate to social partners, are not fully understood. Vervet monkeys (Chlorocebus pygerythrus) are ideal to examine the...

The motion dazzle hypothesis posits that high contrast geometric patterns can cause difficulties in tracking a moving target, and has been argued to explain the patterning of animals such as zebras. Research to date has only tested a small number of patterns, offering equivocal support for the hypothesis. Here, we take a genetic programming approac...

One of the most effective defensive strategies of hosts against brood parasites is rejection, commonly achieved by ejection of the parasitic egg or desertion of the parasitized nest. Nest desertion should be a costlier strategy than egg ejection, because birds must thesn spend additional time and energy renesting, and therefore we still cannot expl...

The seemingly transparent wings of many insects have recently been found to display unexpected structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Furthermore, to date investigations of WIPs ha...

Camouflage is a key defence across taxa and frequently critical to survival. A common strategy is background matching, resembling the colour and pattern of the environment. This approach, however, may be ineffective in complex habitats where matching one patch may lead to increased visibility in other patches. In contrast, disruptive coloration, wh...

To understand the function of colour signals in nature, we require robust quantitative analytical frameworks to enable us to estimate how animal and plant colour patterns appear against their natural background as viewed by ecologically relevant species. Due to the quantitative limitations of existing methods, colour and pattern are rarely analysed...

The seemingly transparent wings of many insects have recently been found to display dramatic structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Additionally, existing research has been restric...

Species-specific courtship phenotype estimates. (XLS)

Species-specific behavioral richness estimates from different sliding-window sizes (10 s–60 s). (XLS)

Summary of specimens located at the American Museum of Natural History used to quantify color complexity in the birds-of-paradise. (DOCX)

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype diversity conducted only on species without imputed species level values. mPGLS, multiple phylogenetic generalized least squares. (DOCX)

ImageJ plugin (java) for hierarchical clustering using chromatic and achromatic JNDs. JND, Just Noticeable Distance. (JAVA)

Species-specific behavioral diversity estimates from different sliding-window sizes (10 s–60 s). (XLS)

Species-specific acoustic diversity estimates from different sliding-window sizes (5 s–50 s). (XLS)

Partial summary (PC1–PC3) of PCA of 5739 notes produced by 32 bird-of-paradise species. PC loadings for PC1–PC3 were used to plot notes in three-dimensional PCA space prior to agglomerative hierarchical clustering based on Euclidean distances to categorize notes. PC, principal component; PCA, principal component analysis. (DOCX)

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype richness conducted only on species without imputed species level values. mPGLS, multiple phylogenetic generalized least squares. (DOCX)

Accumulation of unique behaviors plateaus by time windows of approximately 50 s for most species. Note, these are unique behaviors per individual (not per clip). This distinction is important because some individuals were recorded in several clips, but in the longer clips they might not be doing much behaviorally (leading to the initially surprisin...

Pairwise comparisons of behavioral richness (number of unique behaviors) estimates for windows between 10 and 60 s in duration. Within plots, each point represents a species in the family Paradisaeidae, with species-specific values obtained from rphylopars reconstructions incorporating intra- and interspecific variation. Best-fit lines in lower plo...

Dorsal view of raw (left side) and clustered (right side) images taken of a Wilson’s bird-of-paradise. Following clustering based on chromatic and achromatic thresholds (see Methods), every pixel in every image is assigned to a categorical color identity. The total number of colors in an image provides a measure of richness, and the numbers equival...

Bird-of-paradise behavioral scoring demonstration. In this video, a male western parotia Parotia sefilata performs a species-typical courtship dance for females perching above. This video demonstrates the concordance between a subsample of our scored behaviors and the actual performance of the bird in real-time. The behaviors represent BP1, BP2, SS...

Species-specific acoustic richness estimates from different sliding-window sizes (5 s–50 s). (XLS)

Species sampled for courtship behavior, including the number of individuals watched. (DOCX)

Species sampled for acoustic courtship complexity, including the number of individuals analyzed. (DOCX)

Pairwise comparisons of acoustic diversity (log transformed Shannon indices of acoustic complexity) estimates for windows between 5 and 50 s in duration. Within plots, each point represents a species in the family Paradisaeidae, with species-specific values obtained from rphylopars reconstructions incorporating intra- and interspecific variation. B...

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype diversity. Categorical comparisons of display site are made with respect to ground-displaying birds, and breeding system comparisons are made with respect to solitarily displaying birds. mPGLS, multiple phylogenetic generalized least squares. (DOCX)

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype richness. Categorical comparisons of display site are made with respect to ground-displaying birds, and breeding system comparisons are made with respect to solitarily displaying birds. mPGLS, multiple phylogenetic generalized least squares. (DOCX)

Ethogram describing behavioral subunits scored while observing courtship display behavior of birds-of-paradise. (DOCX)

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype diversity conducted using behavioral complexity metrics from a 10 s and a 60 s time window. For comparison, the analyses presented in the main text focus on behavioral complexity estimated from a 50 s time window. mPGLS, multiple phylogenetic generalized least...

mPGLS analyses of communication-relevant influences on three axes of courtship phenotype richness conducted using behavioral complexity metrics from 10 s and 60 s time windows. The analyses presented in the main text focus on behavioral complexity estimated from a 50 s time window. mPGLS, multiple phylogenetic generalized least squares. (DOCX)

There is no evidence for correlated evolution between color and behavioral diversity among birds-of-paradise. mPGLS regression reveals no significant relationship between behavioral and color diversity when controlling for acoustic diversity, display height, and display proximity. This plot is a phylo-signal-space plot in which species ornamentatio...

Pairwise comparisons of behavioral diversity (Shannon indices of behaviors) estimates for windows between 10 and 60 s in duration. Within plots, each point represents a species in the family Paradisaeidae, with species-specific values obtained from rphylopars reconstructions incorporating intra- and interspecific variation. Best-fit lines in lower...

Accumulation of unique notes plateaus at time windows of approximately 10 s for most species. (DOCX)

Pairwise comparisons of acoustic richness (number of unique note types) estimates for windows between 5 and 50 s in duration. Within plots, each point represents a species in the family Paradisaeidae, with species-specific values obtained from rphylopars reconstructions incorporating intra- and interspecific variation. Best-fit lines in lower plots...

Table S1. Biorepository ID for bird samples used archived in the Smithsonian Tropical Research Institute Cryological Collection in Panama and accession number for the SWS1 opsin gene at GenBank. Table S2. One‐way ANOVA (with individuals as random factors) results for chromatic JND comparisons between co‐mimics and conspecifics for Figure 1. Table...

Numerous animals rely on camouflage for defence. Substantial past work has identified the presence of multiple strategies for concealment, and tested the mechanisms underpinning how they work. These include background matching, D-RUP coloration to destroy target edges, and distractive markings that may divert attention from key target features. Des...

Adaptive coloration is under conflicting selection pressures: choosing potential mates and warning signalling against visually guided predators. Different elements of the colour signal may therefore be tuned by evolution for different functions. We investigated how mimicry in four pairs of Heliconius co‐mimics is potentially seen both from the pers...

The Common Cuckoo (hereafter Cuckoo) shows two adult plumage morphs—adult male plumage is grey and adult females are either grey or, less frequently, rufous. The situation is less clear in juveniles, as both sexes exhibit variable proportions of grey and rufous colour. We thus describe the patterns related to sex-specific plumage colour variation i...