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  • 1
    Language: English
    In: Methods in ecology and evolution, 2015-11, Vol.6 (11), p.1320-1331
    Description: Summary 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 viewing, meaning that their uncalibrated photographs cannot be used for making reliable, quantitative measurements. Many studies still fail to appreciate this, and of those scientists who are aware of such issues, many are hindered by a lack of usable tools for making objective measurements from photographs. We have developed an image processing toolbox that generates images that are linear with respect to radiance from the RAW files of numerous camera brands and can combine image channels from multispectral cameras, including additional ultraviolet photographs. Images are then normalised using one or more grey standards to control for lighting conditions. This enables objective measures of reflectance and colour using a wide range of consumer cameras. Furthermore, if the camera's spectral sensitivities are known, the software can convert images to correspond to the visual system (cone‐catch values) of a wide range of animals, enabling human and non‐human visual systems to be modelled. The toolbox also provides image analysis tools that can extract luminance (lightness), colour and pattern information. Furthermore, all processing is performed on 32‐bit floating point images rather than commonly used 8‐bit images. This increases precision and reduces the likelihood of data loss through rounding error or saturation of pixels, while also facilitating the measurement of objects with shiny or fluorescent properties. All cameras tested using this software were found to demonstrate a linear response within each image and across a range of exposure times. Cone‐catch mapping functions were highly robust, converting images to several animal visual systems and yielding data that agreed closely with spectrometer‐based estimates. Our imaging toolbox is freely available as an addition to the open source ImageJ software. We believe that it will considerably enhance the appropriate use of digital cameras across multiple areas of biology, in particular researchers aiming to quantify animal and plant visual signals.
    Subject(s): image processing ; pattern analysis ; colour measurement ; cone‐catch quanta ; animal coloration ; camera calibration ; spectrometer ; communication ; signalling ; colour vision ; Standard Paper ; Morphometrics
    ISSN: 2041-210X
    E-ISSN: 2041-210X
    Source: Wiley Online Library All Journals
    Source: Alma/SFX Local Collection
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  • 2
    Language: English
    In: Scientific reports, 2016-01-29, Vol.6 (1), p.19966-19966
    Description: 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 in a natural system, that survival probability of wild animals is directly related to their level of camouflage as perceived by the visual systems of their main predators. Ground-nesting plovers and coursers flee as threats approach, and their clutches were more likely to survive when their egg contrast matched their surrounds. In nightjars - which remain motionless as threats approach - clutch survival depended on plumage pattern matching between the incubating bird and its surrounds. Our findings highlight the importance of pattern and luminance based camouflage properties, and the effectiveness of modern techniques in capturing the adaptive properties of visual phenotypes.
    Subject(s): Adaptation, Physiological ; Predatory Behavior ; Animals ; Color ; Birds ; Visual Perception ; Biological Mimicry ; Plumage ; Predators ; Camouflage ; Survival ; Visual perception ; Index Medicus
    ISSN: 2045-2322
    E-ISSN: 2045-2322
    Source: Nature Open Access
    Source: Academic Search Ultimate
    Source: PubMed Central
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  • 3
    Language: English
    In: BMC evolutionary biology, 2017-01-06, Vol.17 (1), p.7-7
    Description: Quantifying the conspicuousness of objects against particular backgrounds is key to understanding the evolution and adaptive value of animal coloration, and in designing effective camouflage. Quantifying detectability can reveal how colour patterns affect survival, how animals' appearances influence habitat preferences, and how receiver visual systems work. Advances in calibrated digital imaging are enabling the capture of objective visual information, but it remains unclear which methods are best for measuring detectability. Numerous descriptions and models of appearance have been used to infer the detectability of animals, but these models are rarely empirically validated or directly compared to one another. We compared the performance of human 'predators' to a bank of contemporary methods for quantifying the appearance of camouflaged prey. Background matching was assessed using several established methods, including sophisticated feature-based pattern analysis, granularity approaches and a range of luminance and contrast difference measures. Disruptive coloration is a further camouflage strategy where high contrast patterns disrupt they prey's tell-tale outline, making it more difficult to detect. Disruptive camouflage has been studied intensely over the past decade, yet defining and measuring it have proven far more problematic. We assessed how well existing disruptive coloration measures predicted capture times. Additionally, we developed a new method for measuring edge disruption based on an understanding of sensory processing and the way in which false edges are thought to interfere with animal outlines. Our novel measure of disruptive coloration was the best predictor of capture times overall, highlighting the importance of false edges in concealment over and above pattern or luminance matching. The efficacy of our new method for measuring disruptive camouflage together with its biological plausibility and computational efficiency represents a substantial advance in our understanding of the measurement, mechanism and definition of disruptive camouflage. Our study also provides the first test of the efficacy of many established methods for quantifying how conspicuous animals are against particular backgrounds. The validation of these methods opens up new lines of investigation surrounding the form and function of different types of camouflage, and may apply more broadly to the evolution of any visual signal.
    Subject(s): Biological Evolution ; Food Chain ; Predatory Behavior ; Animals ; Models, Biological ; Vision, Ocular ; Computer Simulation ; Biological Mimicry ; Pigmentation ; Evolution ; Models ; Camouflage (Biology) ; Comparative analysis ; Methods ; Index Medicus
    ISSN: 1471-2148
    E-ISSN: 1471-2148
    Source: BioMedCentral Open Access
    Source: Academic Search Ultimate
    Source: PubMed Central
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  • 4
    Language: English
    In: Scientific reports, 2019-05-24, Vol.9 (1), p.7840-7840
    Description: 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, which disguises body outlines, may be effective against complex backgrounds. These ideas have rarely been tested and previous work focuses on artificial systems. Here, we test the camouflage strategies of the shore crab (Carcinus maenas) in two habitats, being a species that is highly variable, capable of plastic changes in appearance, and lives in multiple environments. Using predator (bird and fish) vision modelling and image analysis, we quantified background matching and disruption in crabs from rock pools and mudflats, predicting that disruption would dominate in visually complex rock pools but background matching in more uniform mudflats. As expected, rock pool individuals had significantly higher edge disruption than mudflat crabs, whereas mudflat crabs more closely matched the substrate than rock pool crabs for colour, luminance, and pattern. Our study demonstrates facultative expression of camouflage strategies dependent on the visual environment, with implications for the evolution and interrelatedness of defensive strategies.
    Subject(s): Image processing ; Habitats ; Camouflage ; Plasticity ; Visual stimuli ; Mud flats ; Coloration ; Index Medicus
    ISSN: 2045-2322
    E-ISSN: 2045-2322
    Source: Nature Open Access
    Source: Academic Search Ultimate
    Source: PubMed Central
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  • 5
    Book
    Book
    2014
    ISBN: 1400858720  ISBN: 9780691609614  ISBN: 9781400858729  ISBN: 0691067147  ISBN: 9780691067148  ISBN: 0691609616 
    Language: English
    Description: Martin Stevens examines the four extant complete cycles of Middle English mystery plays in light of the most recent research on the manuscripts, sources, and records relating to the medieval drama. The first comprehensive treatment of all four of the cycles, the book emphasizes the study of the surviving manuscripts as texts distinct from their performance history. Originally published in 1987. ThePrinceton Legacy Libraryuses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
    Subject(s): Drama ; European ; English, Irish, Scottish, Welsh- 2AB ; English drama ; Language & Literature ; Mysteries and miracle-plays, English ; History and criticism ; To 1500 ; Bible in literature ; English, Irish, Scottish, Welsh ; DRAMA
    ISBN: 1400858720
    ISBN: 9780691609614
    ISBN: 9781400858729
    ISBN: 0691067147
    ISBN: 9780691067148
    ISBN: 0691609616
    Source: De Gruyter eBooks
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  • 6
    Language: English
    In: Nature communications, 2013, Vol.4 (1), p.2475-2475
    Description: Cuckoo eggs famously mimic those of their foster parents to evade rejection from discriminating hosts. Here we test whether parasites benefit by repeatedly parasitizing the same host nest. This should make accurate rejection decisions harder, regardless of the mechanism that hosts use to identify foreign eggs. Here we find strong support for this prediction in the African tawny-flanked prinia (Prinia subflava), the most common host of the cuckoo finch (Anomalospiza imberbis). We show experimentally that hosts reject eggs that differ from an internal template, but crucially, as the proportion of foreign eggs increases, hosts are less likely to reject them and require greater differences in appearance to do so. Repeated parasitism by the same cuckoo finch female is common in host nests and likely to be an adaptation to increase the probability of host acceptance. Thus, repeated parasitism interacts with egg mimicry to exploit cognitive and sensory limitations in host defences.
    Subject(s): Biological Evolution ; Nesting Behavior ; Animals ; Passeriformes - physiology ; Zygote ; Discrimination (Psychology) - physiology ; Adaptation, Biological ; Female ; Pattern Recognition, Visual - physiology ; Finches - physiology ; Index Medicus
    ISSN: 2041-1723
    E-ISSN: 2041-1723
    Source: Nature Open Access
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  • 7
    Language: English
    In: Science (American Association for the Advancement of Science), 2017-08-04, Vol.357 (6350), p.eaan0221
    Description: Coloration mediates the relationship between an organism and its environment in important ways, including social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion. Methodological breakthroughs are accelerating knowledge of the processes underlying both the production of animal coloration and its perception, experiments are advancing understanding of mechanism and function, and measurements of color collected noninvasively and at a global scale are opening windows to evolutionary dynamics more generally. Here we provide a roadmap of these advances and identify hitherto unrecognized challenges for this multi- and interdisciplinary field.
    Subject(s): Biological Evolution ; Pigments, Biological - biosynthesis ; Reproduction ; Animals ; Pigmentation - genetics ; Color Vision - genetics ; Color Vision - physiology ; Pigmentation - physiology ; Color Perception - genetics ; Pigments, Biological - genetics ; Photoreceptor Cells - physiology ; Color Perception - physiology ; Index Medicus ; Biological Sciences ; Evolutionsbiologi ; Biologi ; Naturvetenskap ; Natural Sciences ; Evolutionary Biology
    ISSN: 0036-8075
    E-ISSN: 1095-9203
    Source: Single Journals
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 8
    Language: English
    In: Proceedings of the Royal Society. B, Biological sciences, 2007-06-22, Vol.274 (1617), p.1457-1464
    Description: Animals possess a range of defensive markings to reduce the risk of predation, including warning colours, camouflage, eyespots and mimicry. These different strategies are frequently considered independently, and with little regard towards predator vision, even though they may be linked in various ways and can be fully understood only in terms of predator perception. For example, camouflage and warning coloration need not be mutually exclusive, and may frequently exploit similar features of visual perception. This paper outlines how different forms of protective markings can be understood from predator perception and illustrates how this is fundamental in determining the mechanisms underlying, and the interrelation between, different strategies. Suggestions are made for future work, and potential mechanisms discussed in relation to various forms of defensive coloration, including disruptive coloration, eyespots, dazzle markings, motion camouflage, aposematism and mimicry.
    Subject(s): vision ; predation ; aposematism ; camouflage ; eyespots ; mimicry ; Animal camouflage ; Colors ; Predators ; Animals ; Color vision ; Military camouflage ; Evolution ; Review ; Snakes ; Visual perception ; Mimicry ; Predatory Behavior - physiology ; Movement - physiology ; Visual Perception - physiology ; Pigmentation - physiology ; Adaptation, Biological - physiology ; Index Medicus
    ISSN: 0962-8452
    E-ISSN: 1471-2954
    Source: PubMed Central
    Source: Alma/SFX Local Collection
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  • 9
    Language: English
    In: Nature communications, 2014-06-26, Vol.5 (1), p.4266-4266
    Description: Animal visual signals have the potential to act as an isolating barrier to prevent interbreeding of populations through a role in species recognition. Within communities of competing species, species recognition signals are predicted to undergo character displacement, becoming more visually distinctive from each other; however, this pattern has rarely been identified. Using computational face recognition algorithms to model primate face processing, we demonstrate that the face patterns of guenons (tribe: Cercopithecini) have evolved under selection to become more visually distinctive from those of other guenon species with whom they are sympatric. The relationship between the appearances of sympatric species suggests that distinguishing conspecifics from other guenon species has been a major driver of diversification in guenon face appearance. Visual signals that have undergone character displacement may have had an important role in the tribe's radiation, keeping populations that became geographically separated reproductively isolated on secondary contact.
    Subject(s): Biological Evolution ; Erythrocebus patas ; Animals ; Biometric Identification ; Cercopithecinae ; Species Specificity ; Cercopithecidae ; Computer Simulation ; Selection, Genetic ; Pattern Recognition, Visual ; Face ; Cercopithecus ; Index Medicus
    ISSN: 2041-1723
    E-ISSN: 2041-1723
    Source: Nature Open Access
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  • 10
    Language: English
    In: BMC evolutionary biology, 2014-09-13, Vol.14 (1), p.201-201
    Description: Stripes and other high contrast patterns found on animals have been hypothesised to cause "motion dazzle", a type of defensive coloration that operates when in motion, causing predators to misjudge the speed and direction of object movement. Several recent studies have found some support for this idea, but little is currently understood about the mechanisms underlying this effect. Using humans as model 'predators' in a touch screen experiment we investigated further the effectiveness of striped targets in preventing capture, and considered how stripes compare to other types of patterning in order to understand what aspects of target patterning are important in making a target difficult to capture. We find that striped targets are among the most difficult to capture, but that other patterning types are also highly effective at preventing capture in this task. Several target types, including background sampled targets and targets with a 'spot' on were significantly easier to capture than striped targets. We also show differences in capture attempt rates between different target types, but we find no differences in learning rates between target types. We conclude that striped targets are effective in preventing capture, but are not uniquely difficult to catch, with luminance matched grey targets also showing a similar capture rate. We show that key factors in making capture easier are a lack of average background luminance matching and having trackable 'features' on the target body. We also find that striped patterns are attempted relatively quickly, despite being difficult to catch. We discuss these findings in relation to the motion dazzle hypothesis and how capture rates may be affected more generally by pattern type.
    Subject(s): Learning ; Motion ; Predatory Behavior ; Animals ; Models, Biological ; Computer Simulation ; Humans ; Color ; Visual Perception ; Index Medicus
    ISSN: 1471-2148
    E-ISSN: 1471-2148
    Source: BioMedCentral Open Access
    Source: Academic Search Ultimate
    Source: PubMed Central
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