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1
Pike, Thomas W. "Interference coloration as an anti-predator defence." Biology Letters 11, no. 4 (April 2015): 20150159. http://dx.doi.org/10.1098/rsbl.2015.0159.
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Interference coloration, in which the perceived colour varies predictably with the angle of illumination or observation, is extremely widespread across animal groups. However, despite considerable advances in our understanding of the mechanistic basis of interference coloration in animals, we still have a poor understanding of its function. Here, I show, using avian predators hunting dynamic virtual prey, that the presence of interference coloration can significantly reduce a predator's attack success. Predators required more pecks to successfully catch interference-coloured prey compared with otherwise identical prey items that lacked interference coloration, and attacks against prey with interference colours were less accurate, suggesting that changes in colour or brightness caused by prey movement hindered a predator's ability to pinpoint their exact location. The pronounced anti-predator benefits of interference coloration may explain why it has evolved independently so many times.
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Lakhani, Leena. "PROTECTIVE COLORATION IN ANIMALS." International Journal of Research -GRANTHAALAYAH 2, no. 3SE (December 31, 2014): 1–5. http://dx.doi.org/10.29121/granthaalayah.v2.i3se.2014.3515.
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Animals have range of defensive markings which helps to the risk of predator detection (camouflage), warn predators of the prey’s unpalatability (aposematism) or fool a predator into mimicry, masquerade. Animals also use colors in advertising, signalling services such as cleaning to animals of other species, to signal sexual status to other members of the same species. Some animals use color to divert attacks by startle (dalmatic behaviour), surprising a predator e.g. witheyespots or other flashes of color or possibly by motion dazzle, confusing a predator attack by moving a bold pattern like zebra stripes. Some animals are colored for physical protection, such as having pigments in the skin to protect against sunburn; some animals can lighten or darken their skin for temperature regulation. This adaptive mechanism is known as protective coloration. After several years of evolution, most animals now achieved the color pattern most suited for their natural habitat and role in the food chains. Animals in the world rely on their coloration for either protection from predators, concealment from prey or sexual selection. In general the purpose of protective coloration is to decrease an organism’s visibility or to alter its appearance to other organisms. Sometimes several forms of protective coloration are superimposed on one animal.
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Nielsen, Matthew E., and Johanna Mappes. "Out in the open: behavior’s effect on predation risk and thermoregulation by aposematic caterpillars." Behavioral Ecology 31, no. 4 (May 20, 2020): 1031–39. http://dx.doi.org/10.1093/beheco/araa048.
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Abstract Warning coloration should be under strong stabilizing selection but often displays considerable intraspecific variation. Opposing selection on color by predators and temperature is one potential explanation for this seeming paradox. Despite the importance of behavior for both predator avoidance and thermoregulation, its role in mediating selection by predators and temperature on warning coloration has received little attention. Wood tiger moth caterpillars, Arctia plantaginis, have aposematic coloration, an orange patch on the black body. The size of the orange patch varies considerably: individuals with larger patches are safer from predators, but having a small patch is beneficial in cool environments. We investigated microhabitat preference by these caterpillars and how it interacted with their coloration. We expected caterpillar behavior to reflect a balance between spending time exposed to maximize basking and spending time concealed to avoid detection by predators. Instead, we found that caterpillars preferred exposed locations regardless of their coloration. Whether caterpillars were exposed or concealed had a strong effect on both temperature and predation risk, but caterpillars in exposed locations were both much warmer and less likely to be attacked by a bird predator (great tits, Parus major). This shared optimum may explain why we observed so little variation in caterpillar behavior and demonstrates the important effects of behavior on multiple functions of coloration.
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Stevens, Martin, Annette C. Broderick, Brendan J. Godley, Alice E. Lown, Jolyon Troscianko, Nicola Weber, and Sam B. Weber. "Phenotype–environment matching in sand fleas." Biology Letters 11, no. 8 (August 2015): 20150494. http://dx.doi.org/10.1098/rsbl.2015.0494.
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Camouflage is perhaps the most widespread anti-predator strategy in nature, found in numerous animal groups. A long-standing prediction is that individuals should have camouflage tuned to the visual backgrounds where they live. However, while several studies have demonstrated phenotype–environment associations, few have directly shown that this confers an improvement in camouflage, particularly with respect to predator vision. Here, we show that an intertidal crustacean, the sand flea ( Hippa testudinaria ), has coloration tuned to the different substrates on which it occurs when viewed by potential avian predators. Individual sand fleas from a small, oceanic island (Ascension) matched the colour and luminance of their own beaches more closely than neighbouring beaches to a model of avian vision. Based on past work, this phenotype–environment matching is likely to be driven through ontogenetic changes rather than genetic adaptation. Our work provides some of the first direct evidence that animal coloration is tuned to provide camouflage to prospective predators against a range of visual backgrounds, in a population of animals occurring over a small geographical range.
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Stevens, Martin, Johanna Mappes, and Siiri-Lii Sandre. "The effect of predator appetite, prey warning coloration and luminance on predator foraging decisions." Behaviour 147, no. 9 (2010): 1121–43. http://dx.doi.org/10.1163/000579510x507001.
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AbstractAposematic prey advertise their defence to visually hunting predators using conspicuous warning colouration. Established theory predicts that aposematic signals should evolve towards increased conspicuousness and similarity to enhance predator education. Contrary to theoretical expectations, there is often considerable within- and between-species variation in aposematic signals of animals sharing the same ecological niche, phylogeny and predators. This may be explained by varying responses of predators that weaken the selection pressure for a consistent signal. By presenting painted mealworm larvae as prey to great tits as predators we tested if different aposematic colour patterns have different values as a means of initial protection and learnt avoidance from predators, and how widely birds generalise their learnt avoidance to other colour patterns. We also investigated how the colour and luminance of the pattern elements affect predator attack decisions. Finally, we studied if hunger affects the predators' reaction to differently coloured prey. We found that similarity in colour was not crucial to the survival of aposematic prey, since learnt avoidance was not influenced by colour, and predators remembered and generalised widely in their learnt avoidance to other colours. We found that initial avoidance was, however, apparently influenced by luminance contrast. Interestingly, the predators' level of hunger was more important than the colour of the aposematic signal in determining birds' decisions to attack chemically-defended insect larvae. We discuss the implications of visual properties of prey colour pattern and predator appetite for the evolution of insect defences and warning signals. In addition we propose a methodological approach to effectively control for predator appetite in laboratory experiments.
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Miller, C. W., and S. D. Hollander. "Predation on heliconia bugs, Leptoscelis tricolor: examining the influences of crypsis and predator color preferences." Canadian Journal of Zoology 88, no. 1 (January 2010): 122–28. http://dx.doi.org/10.1139/z09-128.
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Individuals in natural populations commonly vary in color, and such color variation can be important for survival under predation pressure. Potential prey may be more likely to survive when they are cryptic against their backgrounds. Alternatively, individual coloration, regardless of background, may itself best predict predation events. Few studies have simultaneously tested the importance of crypsis and predator color preferences in explaining predation events. In this study we used objective measures of coloration to examine whether heliconia bugs, Leptoscelis tricolor Westwood, 1842 (Hemiptera: Coreidae), resembling their background were less likely to be eaten by avian predators (crypsis hypothesis). Next, we evaluated whether insect color, irrespective of background, best explains predation events (color preference hypothesis). We found the strongest evidence for the crypsis hypothesis; predators chose prey that differed most from their background in color saturation. Some evidence was also found for the color preference hypothesis; predators avoided brightly colored prey. These results suggest that crypsis can be effective in detouring predation. However, when potential prey are detected, predator color preferences may best explain predation events.
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Stevens, Martin, and Graeme D. Ruxton. "Linking the evolution and form of warning coloration in nature." Proceedings of the Royal Society B: Biological Sciences 279, no. 1728 (November 23, 2011): 417–26. http://dx.doi.org/10.1098/rspb.2011.1932.
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Many animals are toxic or unpalatable and signal this to predators with warning signals (aposematism). Aposematic appearance has long been a classical system to study predator–prey interactions, communication and signalling, and animal behaviour and learning. The area has received considerable empirical and theoretical investigation. However, most research has centred on understanding the initial evolution of aposematism, despite the fact that these studies often tell us little about the form and diversity of real warning signals in nature. In contrast, less attention has been given to the mechanistic basis of aposematic markings; that is, ‘what makes an effective warning signal?’, and the efficacy of warning signals has been neglected. Furthermore, unlike other areas of adaptive coloration research (such as camouflage and mate choice), studies of warning coloration have often been slow to address predator vision and psychology. Here, we review the current understanding of warning signal form, with an aim to comprehend the diversity of warning signals in nature. We present hypotheses and suggestions for future work regarding our current understanding of several inter-related questions covering the form of warning signals and their relationship with predator vision, learning, and links to broader issues in evolutionary ecology such as mate choice and speciation.
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Brandley, Nicholas, Matthew Johnson, and Sönke Johnsen. "Aposematic signals in North American black widows are more conspicuous to predators than to prey." Behavioral Ecology 27, no. 4 (January 1, 2016): 1104–12. http://dx.doi.org/10.1093/beheco/arw014.
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Abstract The iconic red hourglass of the black widow spiders (genus Latrodectus) is traditionally considered an aposematic signal, yet experimental evidence is lacking. Here, we present data that suggest that black widow coloration may have evolved to be an aposematic signal that is more conspicuous to their vertebrate predators than to their insect prey. In choice experiments with wild birds, we found that the red-and-black coloration deters potential predators: Wild birds were ~3 times less likely to attack a black widow model with an hourglass than one without. Using visual-system appropriate models, we also found that a black widow’s red-and-black color combo is more apparent to a typical bird than a typical insect. Additionally, an ancestral reconstruction reveals that red dorsal coloration is ancestral in black widows and that at some point some North American widows lost their red dorsal coloration. Behaviorally, differences in red dorsal coloration between 2 North American species are accompanied by differences in microhabitat that affects how often a bird will view a black widow’s dorsal region. All observations are consistent with a cost–benefit trade-off of being more conspicuous to predators than to prey. We suggest that limiting detection by prey may help explain why red and black aposematic signals occur frequently in nature.
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Sherratt, Thomas N., and Casey A. Peet-Paré. "The perfection of mimicry: an information approach." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1724 (May 22, 2017): 20160340. http://dx.doi.org/10.1098/rstb.2016.0340.
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We consider why imperfect deceptive mimics can persist when it appears to be in the predator's interest to discriminate finely between mimics and their models. One theory is that a receiver will accept being duped if the model and mimic overlap in appearance and the relative costs of attacking the model are high. However, a more fundamental explanation for the difficulty of discrimination is not based on perceptual uncertainty, but simply based on a lack of information. In particular, predators in the process of learning may cease sampling imperfect mimics entirely because the immediate pay-off and future value of information is low, allowing such mimics to persist. This outcome will be particularly likely when the model is relatively costly to attack and/or the discriminative rules the predator has to learn are complex. Information limitations neatly explain why predators tend to adopt discriminative rules based on single traits (such as stripe colour), rather than on combinations of traits (such as stripe order). They also explain why predators utilize certain salient discriminative traits while ignoring equally informative ones (a phenomenon known as overshadowing), and why imperfect mimics may be more common in phenotypically diverse prey communities. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
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Cezário, Rodrigo Roucourt, Vinicius Marques Lopez, Stanislav Gorb, and Rhainer Guillermo-Ferreira. "Dynamic iridescent signals of male copperwing damselflies coupled with wing-clapping displays: the perspective of different receivers." Biological Journal of the Linnean Society 134, no. 1 (June 2, 2021): 229–39. http://dx.doi.org/10.1093/biolinnean/blab068.
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Abstract Dynamic signals are a widespread phenomenon in several taxa, usually associated with intraspecific communication. In contrast, dynamic iridescent signals are detectable only at specific angles of illumination; hence, the animal can hide the signal to avoid detection when necessary. This structural coloration is mostly dependent on the illumination, the contrast against the background and the vision of the receiver. Complex behavioural displays can be coupled with structural coloration to create dynamic visual signals that enhance these functions. Here, we address whether iridescence of the males of a damselfly that inhabits dark rainforests, Chalcopteryx scintillans, can be considered a dynamic visual signal. We analyse whether coloration is perceived by conspecifics, while reducing detectability to eavesdroppers against three types of backgrounds. Our results suggest that the visual background affects the detectability of male hindwings by different receivers, mostly predators and prey. We discuss whether these results and the angle dependence of colour could indicate a mechanism to avoid unwanted intraspecific interactions or even to lure both predators and prey. We conclude that the main functions of the dynamic iridescent signal are to communicate with conspecifics while hindering the signal for prey, adding evidence of the multifunctionality of structural coloration coupled with behavioural displays in animals.
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Duchateau, Marie José, Joseph Macedonia, and Melissa Plasman. "Anti-predation behaviour of Dickerson's collared lizard, Crotaphytus dickersonae." Animal Biology 57, no. 2 (2007): 231–46. http://dx.doi.org/10.1163/157075607780377956.
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AbstractMales of Dickerson's collared lizard (Crotaphytus dickersonae) are conspicuously bright blue in colour and can be detected at great distances. In contrast, females are brown and much less conspicuous. Given the visibility of males to predators, the question arises how they avoid predation and whether the sexes differ in anti-predator behaviour. Using a slowly approaching human as a simulated predator, approach and flight distances were recorded, as were the presence of other anti-predation responses such as pursuit deterrence signalling, distraction behaviour and aggressive threat. The lizards were captured and physical data such as cloacal temperatures, weight and snout-vent length were obtained. To assess further the effect of coloration on predation pressure, test subjects were painted to make them inconspicuous (brown) or conspicuous (blue) and recaptured after a week. After shedding their painted skin, subjects were approached one final time. Few direct relationships were found between anti-predation displays and body weight, size or temperature. Exhibition of pursuit deterrence signalling or distraction behaviour was rare, and no subject displayed aggressive behaviour (except when caught). Interestingly, males fled sooner, and tended to use more refuge than females, which probably indicates stronger predation pressure on males. However, an overall low use of refuge, the observer's ability to approach most subjects closely before they fled, and few sightings of potential predators, suggest that weak local predation pressure helps to explain why sexually selected conspicuous male coloration has been able to evolve in C. dickersonae.
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Garcia, T. S., D. J. Paoletti, and A. R. Blaustein. "Correlated trait response: comparing amphibian defense strategies across a stress gradient." Canadian Journal of Zoology 87, no. 1 (January 2009): 41–49. http://dx.doi.org/10.1139/z08-130.
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Animals inhabiting complex environments often contend with multiple stressors that can select for conflicting responses. Individuals can mediate these conflicts by utilizing correlated responses across multiple traits. In aquatic habitats, larval amphibians often face conflicting, simultaneous pressures, such as ultraviolet-B (UV-B) radiation and predators. UV-B radiation and predation risk influence behavior and body color in many amphibian species, altering activity rates, refuge use, and coloration. When both UV-B and predators are present, individuals can avoid conflicts by coupling behavior with body color to form a correlated response. UV-B exposure rates vary along an elevation gradient, thus trait combinations may also vary. We quantified changes in activity rates and body color in two anuran species, the red-legged frog ( Rana aurora Baird and Girard, 1852) (low elevations) and the cascades frog ( Rana cascadae Slater, 1939) (high elevations), during exposure to predator chemical cues (rough-skinned newt, Taricha granulosa (Skilton, 1849)) and UV-B radiation. Rana aurora decreased activity in response to UV-B and became more cryptic over time, while R. cascadae coupled decreased activity rates in response to predators with dark body coloration to screen out UV-B. Both species responded with a correlated trait response, yet employed opposite strategies. This observed species difference may be reflective of differences in stress across habitats and availability of alternative defenses.
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Stevens, Martin, Isabel S. Winney, Abi Cantor, and Julia Graham. "Outline and surface disruption in animal camouflage." Proceedings of the Royal Society B: Biological Sciences 276, no. 1657 (November 18, 2008): 781–86. http://dx.doi.org/10.1098/rspb.2008.1450.
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Camouflage is an important strategy in animals to prevent predation. This includes disruptive coloration, where high-contrast markings placed at an animal's edge break up the true body shape. Successful disruption may also involve non-marginal markings found away from the body outline that create ‘false edges’ more salient than the true body form (‘surface disruption’). However, previous work has focused on breaking up the true body outline, not on surface disruption. Furthermore, while high contrast may enhance disruption, it is untested where on the body different contrasts should be placed for maximum effect. We used artificial prey presented to wild avian predators in the field, to determine the effectiveness of surface disruption, and of different luminance contrast placed in different prey locations. Disruptive coloration was no more effective when comprising high luminance contrast per se , but its effectiveness was dramatically increased with high-contrast markings placed away from the body outline, creating effective surface disruption. A model of avian visual edge processing showed that surface disruption does not make object detection more difficult simply by creating false edges away from the true body outline, but its effect may also be based on a different visual mechanism. Our study has implications for whether animals can combine disruptive coloration with other ‘conspicuous’ signalling strategies.
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Ximenes, Nathalia G., Vinicius De Souza Moraes, Jean C. G. Ortega, and Felipe M. Gawryszewski. "Color lures in orb-weaving spiders: a meta-analysis." Behavioral Ecology 31, no. 2 (January 21, 2020): 568–76. http://dx.doi.org/10.1093/beheco/arz210.
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Abstract Lures are deceptive strategies that exploit sensory biases in prey, usually mimicking a prey’s mate or food item. Several predators exploit plant–pollinator systems, where visual signals are an essential part of interspecific interactions. Many diurnal, and even nocturnal, orb-web spiders present conspicuous body coloration or bright color patches. These bright colors are regarded as color-based lures that exploit biases present in insect visual systems, possibly mimicking flower colors. The prey attraction hypothesis was proposed more than 20 years ago to explain orb-web spider coloration. Although most data gathered so far has corroborated the predictions of the prey attraction hypothesis, there are several studies that refute these predictions. We conducted a multilevel phylogenetic meta-analysis to assess the magnitude of the effect of conspicuous orb-web spider body coloration on prey attraction. We found a positive effect in favor of the prey attraction hypothesis; however, there was substantial heterogeneity between studies. Experimental designs comparing conspicuous spiders to painted spiders or empty webs did not explain between-studies heterogeneity. The lack of theoretical explanation behind the prey attraction hypothesis makes it challenging to address which components influence prey attraction. Future studies could evaluate whether color is part of a multicomponent signal and test alternative hypotheses for the evolution of spider colors, such as predator avoidance and thermoregulation.
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Titcomb, Georgia C., David W. Kikuchi, and David W. Pfennig. "More than mimicry? Evaluating scope for flicker-fusion as a defensive strategy in coral snake mimics." Current Zoology 60, no. 1 (February 1, 2014): 123–30. http://dx.doi.org/10.1093/czoolo/60.1.123.
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Abstract Coral snakes and their mimics often have brightly colored banded patterns, generally associated with warning coloration or mimicry. However, such color patterns have also been hypothesized to aid snakes in escaping predators through a “flicker-fusion” effect. According to this hypothesis, banded color patterns confuse potential predators when a snake transitions from resting to moving because its bands blur together to form a different color. To produce this motion blur, a moving snake’s bands must transition faster than the critical flicker-fusion rate at which a predator’s photoreceptors can refresh. It is unknown if coral snakes or their mimics meet this requirement. We tested this hypothesis by measuring the movement speed and color patterns of two coral snake mimics, Lampropeltis triangulum campbelli and L. elapsoides, and comparing the frequency of color transitions to the photoreceptor activity of the avian eye. We found that snakes often produced a motion blur, but moving snakes created a blurring effect more often in darker conditions, such as sunrise, sunset, and nighttime when these snakes are often active. Thus, at least two species of coral snake mimics are capable of achieving flicker-fiision, indicating that their color patterns may confer an additional defense aside from mimicry.
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Vitt, Laurie J., and William E. Cooper Jr. "Tail loss, tail color, and predator escape in Eumeces (Lacertilia: Scincidae): age-specific differences in costs and benefits." Canadian Journal of Zoology 64, no. 3 (March 1, 1986): 583–92. http://dx.doi.org/10.1139/z86-086.
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The tail loss adaptation in Eumeces of the southeastern United States is complex. Juveniles possess tails that are colored differently from those of adults and apparently distract the attention of potential predators from the body to the tail. Adult tails are cryptically colored. Frequency of tail loss is high across size groups. Experiments on growth of tailed and tailless juveniles suggest no effect of tail loss on growth and, thus, there may be little cost of tail loss to juveniles other than the temporary loss of the autotomy adaptation. Lipids in adult tails constitute nearly 50% of total standing lipids and are reduced during reproduction similar to other lipid reserves. This suggests that tail loss in adults is expensive, particularly prior to or during the breeding season. We suggest that the high costs of tail loss in Eumeces are offset by the increased probability of predator escape via tail loss. Tail loss data are minimal estimates of escape via distraction of a predator's attack to the tail as indicated by predation experiments. The presence, coloration, and behaviors of the tail may result in a high proportion of predation attempts being redirected to the tail followed by total misses.
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Stoddard, Mary Caswell, and Mark E. Hauber. "Colour, vision and coevolution in avian brood parasitism." Philosophical Transactions of the Royal Society B: Biological Sciences 372, no. 1724 (May 22, 2017): 20160339. http://dx.doi.org/10.1098/rstb.2016.0339.
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The coevolutionary interactions between avian brood parasites and their hosts provide a powerful system for investigating the diversity of animal coloration. Specifically, reciprocal selection pressure applied by hosts and brood parasites can give rise to novel forms and functions of animal coloration, which largely differ from those that arise when selection is imposed by predators or mates. In the study of animal colours, avian brood parasite–host dynamics therefore invite special consideration. Rapid advances across disciplines have paved the way for an integrative study of colour and vision in brood parasite–host systems. We now know that visually driven host defences and host life history have selected for a suite of phenotypic adaptations in parasites, including mimicry, crypsis and supernormal stimuli. This sometimes leads to vision-based host counter-adaptations and increased parasite trickery. Here, we review vision-based adaptations that arise in parasite–host interactions, emphasizing that these adaptations can be visual/sensory, cognitive or phenotypic in nature. We highlight recent breakthroughs in chemistry, genomics, neuroscience and computer vision, and we conclude by identifying important future directions. Moving forward, it will be essential to identify the genetic and neural bases of adaptation and to compare vision-based adaptations to those arising in other sensory modalities. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
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Umeton, Diana, Jenny C. A. Read, and Candy Rowe. "Unravelling the illusion of flicker fusion." Biology Letters 13, no. 2 (February 2017): 20160831. http://dx.doi.org/10.1098/rsbl.2016.0831.
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For over 150 years, researchers have investigated the anti-predator function of animal patterns. However, this work has mainly focused on when prey remain still, and has only recently started to incorporate motion into the study of defensive coloration. As motion breaks camouflage, a new challenge is to understand how prey avoid predators while moving around their environment, and if a moving prey can ever be camouflaged. We propose that there is a solution to this, in that a ‘flicker fusion effect’ can change the appearance of the prey in the eyes of their predators to reduce the chances of initial detection. This effect occurs when a high contrast pattern blurs at speed, changing the appearance of the prey, which may help them better match their background. Despite being widely discussed in the literature, the flicker fusion effect is poorly described, there is no clear theoretical framework for testing how it might reduce predation, and the terminology describing it is, at best, rather confusing. Our review addresses these three key issues to enable researchers to formulate precise predictions about when the flicker fusion effect occurs, and to test how it can reduce predation.
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Vaughn, Ashlee A., Antedra A. Finger, Porshia E. Gibbs, and Michael H. Ferkin. "Coat color and its effect on preference for the scent marks of opposite-sex conspecifics in the meadow vole Microtus pennsylvanicus." Current Zoology 58, no. 2 (April 1, 2012): 221–27. http://dx.doi.org/10.1093/czoolo/58.2.221.
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Abstract Many mammal species can distinguish between opposite-sex conspecifics that differ in a certain trait. In that coat coloration is associated with differences in physiological and behavioral traits, coat color may affect the attractiveness of odor cues produced by conspecifics. Individuals may be able to respond preferentially to conspecifics with a particular coat color. In the present study, we test the hypothesis that scent marks of brown and blond voles differ in their attractiveness to male and female conspecifics. Male voles and brown females did not discriminate between blond- and brown-coated opposite-sex conspecifics suggesting that they are neither selecting potential mates dissociatively nor associatively. However, blond females behaved as if the scent marks of blond males were more attractive than were the scent marks of brown males. Our data suggest that blond females who are already conspicuous to predators, may select blond males as mates because they do not appreciably increase the risk of detection to predators, particularly avian predators. Moreover, because these conspicuous males have survived to mate they may have good genes that reflect their relatively higher quality [Current Zoology 58 (2): 221–227 , 2012].
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Davidson, Gabrielle L., Alex Thornton, and Nicola S. Clayton. "Evolution of iris colour in relation to cavity nesting and parental care in passerine birds." Biology Letters 13, no. 1 (January 2017): 20160783. http://dx.doi.org/10.1098/rsbl.2016.0783.
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Strong selection pressures are known to act on animal coloration. Although many animals vary in eye colour, virtually no research has investigated the functional significance of these colour traits. Passeriformes have a range of iris colours, making them an ideal system to investigate how and why iris colour has evolved. Using phylogenetic comparative methods, we tested the hypothesis that conspicuous iris colour in passerine birds evolved in response to (a) coordination of offspring care and (b) cavity nesting, two traits thought to be involved in intra-specific gaze sensitivity. We found that iris colour and cooperative offspring care by two or more individuals evolved independently, suggesting that bright eyes are not important for coordinating parental care through eye gaze. Furthermore, we found that evolution between iris colour and nesting behaviour did occur in a dependent manner, but contrary to predictions, transitions to coloured eyes were not more frequent in cavity nesters than non-cavity nesters. Instead, our results indicate that selection away from having bright eyes was much stronger in non-cavity nesters than cavity nesters, perhaps because conspicuous eye coloration in species not concealed within a cavity would be more visible to predators.
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Rowland, Hannah M., Innes C. Cuthill, Ian F. Harvey, Michael P. Speed, and Graeme D. Ruxton. "Can't tell the caterpillars from the trees: countershading enhances survival in a woodland." Proceedings of the Royal Society B: Biological Sciences 275, no. 1651 (August 12, 2008): 2539–45. http://dx.doi.org/10.1098/rspb.2008.0812.
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Perception of the body's outline and three-dimensional shape arises from visual cues such as shading, contour, perspective and texture. When a uniformly coloured prey animal is illuminated from above by sunlight, a shadow may be cast on the body, generating a brightness contrast between the dorsal and ventral surfaces. For animals such as caterpillars, which live among flat leaves, a difference in reflectance over the body surface may degrade the degree of background matching and provide cues to shape from shading. This may make otherwise cryptic prey more conspicuous to visually hunting predators. Cryptically coloured prey are expected to match their substrate in colour, pattern and texture (though disruptive patterning is an exception), but they may also abolish self-shadowing and therefore either reduce shape cues or maintain their degree of background matching through countershading: a gradation of pigment on the body of an animal so that the surface closest to illumination is darker. In this study, we report the results from a series of field experiments where artificial prey resembling lepidopteran larvae were presented on the upper surfaces of beech tree branches so that they could be viewed by free-living birds. We demonstrate that countershading is superior to uniform coloration in terms of reducing attack by free-living predators. This result persisted even when we fixed prey to the underside of branches, simulating the resting position of many tree-living caterpillars. Our experiments provide the first demonstration, in an ecologically valid visual context, that shadowing on bodies (such as lepidopteran larvae) provides cues that visually hunting predators use to detect potential prey species, and that countershading counterbalances shadowing to enhance cryptic protection.
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Rojas, Bibiana, Armando Luis-MartÍnez, and Johanna Mappes. "Frequency-dependent flight activity in the colour polymorphic wood tiger moth." Current Zoology 61, no. 4 (August 1, 2015): 765–72. http://dx.doi.org/10.1093/czoolo/61.4.765.
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Abstract Predators efficiently learn to avoid one type of warning signal rather than several, making colour polymorphisms unexpected. Aposematic wood tiger moth males Parasemia plantaginis have either white or yellow hindwing coloration across Europe. Previous studies indicate that yellow males are better defended from predators, while white males have a positively frequency-dependent mating advantage. However, the potential frequency-dependent behavioural differences in flight between the morphs, as well as the role of male-male interactions in inducing flying activity, have not been previously considered. We ran an outdoor cage experiment where proportions of both male morphs were manipulated to test whether flying activity was frequencydependent and differed between morphs. The white morph was significantly more active than the yellow one across all treatments, and sustained activity for longer. Overall activity for both morphs was considerably lower in the yellow-biased environment, suggesting that higher proportions of yellow males in a population may lead to overall reduced flying activity. The activity of the yellow morph also followed a steeper, narrower curve than that of the white morph during peak female calling activity. We suggest that white males, with their presumably less costly defences, have more resources to invest in flight for predator escape and finding mates. Yellow males, which are better protected but less sexually selected, may instead compensate their lower flight activity by ‘flying smart’ during the peak female-calling periods. Thus, both morphs may be able to behaviourally balance the trade-off between warning signal selection and sexual selection. Our results emphasize the greater need to investigate animal behaviour and colour polymorphisms in natural or semi-natural environments.
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Rubi, Tricia L., David L. Clark, Jonathan S. Keller, and George W. Uetz. "Courtship behavior and coloration influence conspicuousness of wolf spiders (Schizocosa ocreata (Hentz)) to avian predators." Behavioural Processes 162 (May 2019): 215–20. http://dx.doi.org/10.1016/j.beproc.2018.12.023.
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Kassarov, Luka. "Are Birds the Primary Selective Force Leading to Evolution of Mimicry and Aposematism in Butterflies? An Opposing Point of View." Behaviour 140, no. 4 (2003): 433–51. http://dx.doi.org/10.1163/156853903322127922.
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AbstractBirds are universally considered to be the primary selective force leading to the evolution of mimicry in butterflies and the evolution of aposematic coloration. This concept does not take into account the visual capabilities of birds. In this paper it is argued that the aerial hawker insectivorous birds, which are the primary predators of butterflies, are not able to differentiate the separate elements in the color patterns of flying butterflies. They cannot distinguish details in color of the markings or their shape, size, and distribution. As a consequence, birds cannot serve as a selective force for evolution of mimicry and aposematic coloration in these insects. Many aspects of vision, and especially vision in birds, on which my conclusions are based are discussed in detail. The different morphological and behavioral characteristics of butterflies, especially their flight characteristics, correlate with their profitability as a source of energy and nutrients. The flight pattern of the butterfly is the first stimulus that the bird sees, not the color pattern. It is this characteristic flight pattern, not the bright aposematic coloration pattern, that birds are able to recognize and then learn rapidly to associate visually with the profitability of the prey. The characteristic flight behavior signals to the bird whether the prey is energetically profitable or not, thus whether to attack or ignore a potential prey. The ability to distinguish prey types by flight pattern allows the bird to conserve energy and maximize its feeding efficiency.
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Passos, Luiza. "How does captivity affect skin colour reflectance of golden mantella frogs?" Herpetological Journal, Volume 30, Number 1 (January 1, 2020): 13–19. http://dx.doi.org/10.33256/hj30.1.1319.
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Coloration is an important trait for social communication in amphibians, being used in intra- and intersexual signalling to express information about individual body condition and health state, amongst other things. The striking colour pattern exhibited by some anuran species are also used in “aposematic” signals to advertise unpalatability to predators. The aim of this study was to investigate how the captive environment affects the colour of golden mantella frogs by comparing captive reared frogs with wild conspecifics. A USB-2000 portable diode-array spectrometer and a xenon strobe light source were used to perform spectrophotometric measurements on captive and wild populations. Hue, chroma and brightness of skin colour were analysed as well as body condition using the scaled mass index. Analyses showed variation among populations, but significant differences were only found between captive and wild populations. Generalised linear mixed models were used to evaluate the effects of body condition on colour variation and showed that animals with lower body condition from one captive population had significantly different coloration than their wild counterparts. Importantly, one captive population was not greatly different in coloration from their wild counterparts – demonstrating that this problem is not inevitable in captivity. These results can have important implications for reintroduction programmes.
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Neumeister, H., K. W. Whitaker, H. A. Hofmann, and T. Preuss. "Social and Ecological Regulation of a Decision-Making Circuit." Journal of Neurophysiology 104, no. 6 (December 2010): 3180–88. http://dx.doi.org/10.1152/jn.00574.2010.
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Ecological context, sensory inputs, and the internal physiological state are all factors that need to be integrated for an animal to make appropriate behavioral decisions. However, these factors have rarely been studied in the same system. In the African cichlid fish Astatotilapia burtoni, males alternate between two phenotypes based on position in a social hierarchy. When dominant (DOM), fish display bright body coloration and a wealth of aggressive and reproductive behavioral patterns that make them conspicuous to predators. Subordinate (SUB) males, on the other hand, decrease predation risk by adopting cryptic coloration and schooling behavior. We therefore hypothesized that DOMs would show enhanced startle-escape responsiveness to compensate for their increased predation risk. Indeed, behavioral responses to sound clicks of various intensities showed a significantly higher mean startle rate in DOMs compared with SUBs. Electrophysiological recordings from the Mauthner cells (M-cells), the neurons triggering startle, were performed in anesthetized animals and showed larger synaptic responses to sound clicks in DOMs, consistent with the behavioral results. In addition, the inhibitory drive mediated by interneurons (passive hyperpolarizing potential [PHP] cells) presynaptic to the M-cell was significantly reduced in DOMs. Taken together, the results suggest that the likelihood for an escape to occur for a given auditory stimulus is higher in DOMs because of a more excitable M-cell. More broadly, this study provides an integrative explanation of an ecological and social trade-off at the level of an identifiable decision-making neural circuit.
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Webster, Richard J. "Does disruptive camouflage conceal edges and features?" Current Zoology 61, no. 4 (August 1, 2015): 708–17. http://dx.doi.org/10.1093/czoolo/61.4.708.
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Abstract Camouflage is ubiquitous in the natural world and benefits both predators and prey. Amongst the range of concealment strategies, disruptive coloration is thought to visually fragment an animal’s’ outline, thereby reducing its rate of discovery. Here, I propose two non-mutually exclusive hypotheses for how disruptive camouflage functions, and describe the visual mechanisms that might underlie them. (1) The local edge disruption hypothesis states that camouflage is achieved by breaking up edge information. (2) The global feature disruption hypothesis states camouflage is achieved by breaking up the characteristic features of an animal (e.g., overall shape or facial features). Research clearly shows that putatively disruptive edge markings do increase concealment; however, few tests have been undertaken to determine whether this survival advantage is attributable to the distortion of features, so the global feature disruption hypothesis is under studied. In this review the evidence for global feature disruption is evaluated. Further, I address if object recognition processing provides a feasible mechanism for animals’ features to influence concealment. This review concludes that additional studies are needed to test if disruptive camouflage operates through the global feature disruption and proposes future research directions.
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Kikuchi, David W., and David W. Pfennig. "A Batesian mimic and its model share color production mechanisms." Current Zoology 58, no. 4 (August 1, 2012): 658–67. http://dx.doi.org/10.1093/czoolo/58.4.658.
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Abstract Batesian mimics are harmless prey species that resemble dangerous ones (models), and thus receive protection from predators. How such adaptive resemblances evolve is a classical problem in evolutionary biology. Mimicry is typically thought to be difficult to evolve, especially if the model and mimic produce the convergent phenotype through different proximate mechanisms. However, mimicry may evolve more readily if mimic and model share similar pathways for producing the convergent phenotype. In such cases, these pathways can be co-opted in ancestral mimic populations to produce high-fidelity mimicry without the need for major evolutionary innovations. Here, we show that a Batesian mimic, the scarlet kingsnake Lampropeltis elapsoides, produces its coloration using the same physiological mechanisms as does its model, the eastern coral snake Micrurus fulvius. Therefore, precise color mimicry may have been able to evolve easily in this system. Generally, we know relatively little about the proximate mechanisms underlying mimicry.
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Valkonen, Janne K., Ossi Nokelainen, Marianne JokimãKi, Elviira Kuusinen, Mirva Paloranta, Maiju Peura, and Johanna Mappes. "From deception to frankness: Benefits of ontogenetic shift in the anti-predator strategy of alder moth Acronicta alni larvae." Current Zoology 60, no. 1 (February 1, 2014): 114–22. http://dx.doi.org/10.1093/czoolo/60.1.114.
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Abstract Animals can avoid prédation by masquerading as objects that are not food to their predators. Alder moth Acronicta alni larvae go through an impressive ontogenetic change from masquerade to highly conspicuous appearance: early larval stages resemble bird droppings but in the last instar the larval coloration changes into striking yellow-and-black stripes. We hypothesized that such a change may be driven by differential prédation favoring dissimilar anti-predator strategies in different life stages. We show with a series of laboratory assays that larvae are distasteful to birds regardless of their developmental stage, suggesting that ontogenetic color change is not driven by the differential chemical defense. Birds showed higher variance in hesitation toward conspicuous prey; some individuals hesitated long time before attacking whereas all birds attacked instantly masqueraded prey. We also found that the activity level of the larvae increased with age, which fits to the fact that larvae need to move from foliage to pupation sites. In the field by using artificial larvae resembling the two life-history stages we found prédation risk to vary during the season: In early summer larger yellow-and-black larvae were attacked most, whereas later in the summer small ‘bird-dropping-larvae’ suffered the highest prédation. We conclude that the ontogenetic switch from masquerading to aposema-tism is adaptive most likely because actively moving prey cannot mimic immotile objects and thus, aposematism during the active and vulnerable period when larvae are searching for pupation sites becomes beneficial.
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Crofts, Stephanie B., and Theodore Stankowich. "Stabbing Spines: A review of the Biomechanics and Evolution of Defensive Spines." Integrative and Comparative Biology 61, no. 2 (June 28, 2021): 655–67. http://dx.doi.org/10.1093/icb/icab099.
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Synopsis Spines are ubiquitous in both plants and animals, and while most spines were likely originally used for defense, over time many have been modified in a variety of ways. Here we take an integrative approach to review the form, function, and evolution of spines as a defensive strategy in order to make new connections between physical mechanisms and functional behavior. While this review focuses on spines in mammals, we reference and draw ideas from the literature on spines in other taxa, including plants. We begin by exploring the biomechanics of defensive spines, their varied functions, and nondefensive modifications. We pay particular attention to the mechanics involved in passive puncture and the ways organisms have overcome limitations associated with the low energy input. We then focus on the ecological, physiological, and behavioral factors that promote the evolution of spiny defenses, including predator- and habitat-mediated hypotheses. While there is considerable evidence to support both, studies have generally found that (1) defensive spines are usually effective against one class of attacker (e.g., larger predators) but ineffective against or even facilitate predation by others and (2) species that are more visible or exposed to predators are under much stronger selection to evolve defensive spines or some other robust defense. What type of defensive morphology that evolves, however, is less predictable and probably strongly dependent on both the dominant source of predation and the habitat structure of the organism (e.g., arboreal, terrestrial, and fossorial). We then explore traits that often are correlated with defensive spines and armor, potentially forming armor syndromes, suites of traits that evolve together with body armor in a correlated fashion. In mammals, these include aposematic warning coloration, locomotion style, diet, metabolic rate, and relative brain size. Finally, we encourage integration of mechanistic, behavioral, and evolutionary studies of defensive spines and suggest future avenues of research in the biomechanics, evolution, and behavior of spines and spiny organisms.
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Bertuzzi, Tatiane, David Santos de Freitas, Luiz Liberato Costa Corrêa, Alice Pozza Rodrigues, Mateus De Oliveira, Arthur Cardoso de Ávila, Gabriela Reis Ávila, and Alexandro Marques Tozetti. "DOES APOSEMATIC COLORATION REDUCE PREDATION RISK IN SNAKES? A SHORT PERIOD EXPERIMENT USING PLASTICINE SNAKE MODELS." Revista de Ciências Ambientais 14, no. 2 (August 24, 2020): 35. http://dx.doi.org/10.18316/rca.v14i2.6137.
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Aposematism in an anti-predation mechanism that occurs when animals exhibit conspicuous signals, which are often of a contrasting color patterns, to alert potential predators of their unpalatability or toxicity. This study aims to test (in a short period) the effectiveness of aposematic coloration by comparing the predatory attack upon snakes models with and without an alert coloration on the body. To simulate snakes, we made 80 greenish plasticine snake models. Half of the models had a red strip on the dorsal part of the body, imitating an aposematic coloration. The other half of the models had only a greenish tint. The models were exposed to predators for 12 hours in an area with countryside vegetation.. Among the 20 models showing signs of predation, 65% were purely greenish models and 35% were models with red coloration on the back. Attaks at extremities (head and tail) were meaningly more frequent on models with red coloration. Our results suggest the efficiency of red coloration as a warning sign and anti-predation mechanism, since the models with red coloration, imitating aposematic preys, were less preyed and were attacked preferentially at the extremities, which suggests caution by the predator.
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Jensen, Gregory C., and Michael S. Egnotovich. "A whiter shade of male: Color background matching as a function of size and sex in the yellow shore crab Hemigrapsus oregonensis (Dana, 1851)." Current Zoology 61, no. 4 (August 1, 2015): 729–38. http://dx.doi.org/10.1093/czoolo/61.4.729.
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Abstract Juveniles of the shore crab Hemigrapsus oregonensis are highly variable in color, ranging from the typical yellowishgreen of adults to pure white and myriad patterns of white mottling and other disruptive markings, but large individuals with white coloration appear to be very rare. Using image analysis to quantify the relative “whiteness” of beaches, we sampled crabs from nine locations in Washington State that varied widely in their amount of shell fragments and other light-colored material. The total proportion of white individuals in the different locations was strongly correlated to the proportion of white material on the beaches, but there was a striking difference between sexes. Although white specimens of both sexes declined significantly at sizes above 10 mm carapace width, white females generally persisted throughout the entire female size range on lighter-colored beaches while white males larger than 10 mm were virtually absent from all of the sampled populations. Pure white males held on dark backgrounds in captivity remained white, as they lack the dark chromatophores in their hypodermis needed to change color; off-white males became darker and in some cases lightened up again when transferred back to a white background. Behavioral differences between the sexes may result in differential mortality of white individuals by visual predators.
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FAÚNDEZ, EDUARDO I., and JAVIERA R. ROCCA. "A new species of Oncopeltus Stål, 1868 (Heteroptera: Lygaeidae) in the nominate subgenus from Ecuador." Zootaxa 4238, no. 2 (March 2, 2017): 249. http://dx.doi.org/10.11646/zootaxa.4238.2.4.
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Oncopeltus Stål is a lygaeine genus currently comprising 39 species classified in two subgenera (Slater & O’Donnell, 1995). Oncopeltus is distributed in both hemispheres in tropical and temperate areas. Species on this genus are commonly known as milkweed bugs, because of their trophic association with plants in the family Apocynaceae (Scudder & Duffey, 1971). From these plants, the bugs sequester cardenolides making them unpalatable for predators (Duffey & Scudder, 1972). These habits are also accompanied with their brightly reddish coloration, which has been interpreted as aposematism (Duffey & Scudder, 1972, O’Rourke, 1979; Faúndez et al., 2016). As these bugs attack several plants in the subfamily Asclepiadoideae; they have an economic impact on several ornamentally used species, and may sometimes be considered as garden pests (Faúndez & Rocca, 2016; Faúndez et al., 2016). Species of this group are also well known for generating some natural hybrids (O’Rourke, 1979); because of this, their systematic treatment at specific level has been confused, and the identity of several taxa remain unclear. The purpose of this contribution is to describe a new species in this genus from Ecuador.
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Kassarov, Luka. "ARE BIRDS ABLE TO TASTE AND REJECT BUTTERFLIES BASED ON 'BEAK MARK TASTING'? A DIFFERENT POINT OF VIEW." Behaviour 136, no. 8 (1999): 965–81. http://dx.doi.org/10.1163/156853999501676.
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AbstractIt is widely accepted that birds are able to taste toxic chemical substances in the wings of a butterfly by grabbing or pecking a small piece of the wing without disrupting the integrity of the integument ('beak mark tasting'). If found toxic, the bird will release the insect unharmed. This supposition has been used to explain some aspects of the interrelationship between birds as predators and butterflies as prey, especially the role of birds in the evolution of butterfly color patterns. It also is used to support the theory of aposematisc coloration, especially in butterflies. On the basis of the anatomy of the avian gustatory apparatus, the distribution of the taste buds in the beak cavity, and the physiology of taste, this author considers this supposition a misconception. The frequent beak marks seen on the wings of aposematic butterflies are not considered to be a proof of taste rejection by birds after contact with the chemical compound(s) supposed to provide the insect with a chemical defense, but a sign of active escape of the butterfly from its captor. Some aspects of the interrelationship between birds and butterflies, considered to be well explained on the basis of taste rejection of butterflies via 'beak mark tasting' by the birds, are critically discussed in this paper.
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Keith, Lloyd B., and Sara E. M. Bloomer. "Differential mortality of sympatric snowshoe hares and cottontail rabbits in central Wisconsin." Canadian Journal of Zoology 71, no. 8 (August 1, 1993): 1694–97. http://dx.doi.org/10.1139/z93-238.
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During 1990 and 1991 we livetrapped and radio-collared cottontail rabbits (Sylvilagus floridanus) and snowshoe hares (Lepus americanus) on five sites (three in lowland deciduous cover, two in conifer bogs) in central Wisconsin. The survival rates of these sympatric cottontails and snowshoes were equally high during snow-free periods from mid-March through October. With the onset of persistent snow cover (mean depth 20 cm) and low temperatures (mean daily minimum −14 °C) in November 1991, the 60-day survival rate of cottontails plummeted from 0.89 to 0.18 (P < 0.01) whereas snowshoe survival declined only moderately from 0.84 to 0.63 (P = 0.19). This interspecific difference reflected continued high survival of snowshoes (0.80), but not of cottontails (0.15), in the conifer bogs. Predation, primarily by coyotes, was the proximate cause of 37 of 39 rabbit and hare deaths, and was thus the overwhelming determinant of survival. We speculate that where persistent snow and low temperatures characterize winter, the cottontail's greater foot loading, brown coloration, and escape behavior markedly increase its vulnerability to predators. This probably explains the absence of cottontails from the forests of northern Wisconsin.
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Henze, Miriam J., Olle Lind, Bodo D. Wilts, and Almut Kelber. "Pterin-pigmented nanospheres create the colours of the polymorphic damselfly Ischnura elegans." Journal of The Royal Society Interface 16, no. 153 (April 17, 2019): 20180785. http://dx.doi.org/10.1098/rsif.2018.0785.
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Animal colours commonly act as signals for mates or predators. In many damselfly species, both sexes go through a developmental colour change as adults, and females often show colour polymorphism, which may have a function in mate choice, avoidance of mating harassment and camouflage. In the blue-tailed damselfly, Ischnura elegans , young males are bright green and turn blue as they reach maturity. Females are red ( rufescens ) or violet ( violacea ) as immatures and, when mature, either mimic the blue colour of the males ( androchrome ), or acquire an inconspicuous olive-green ( infuscans ) or olive-brown ( obsoleta ). The genetic basis of these differences is still unknown. Here, we quantify the colour development of all morphs of I. elegans and investigate colour formation by combining anatomical data and reflectance spectra with optical finite-difference time-domain simulations. While the coloration primarily arises from a disordered assembly of nanospheres in the epidermis, morph-dependent changes result from adjustments in the composition of pterin pigments within the nanospheres, and from associated shifts in optical density. Other pigments fine-tune hue and brilliance by absorbing stray light. These mechanisms produce an impressive palette of colours and offer guidance for genetic studies on the evolution of colour polymorphism and visual communication.
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Goulet, Denis, John M. Green, and Tim H. Shears. "Courtship, spawning, and parental care behavior of the lumpfish, Cyclopterus lumpus L., in Newfoundland." Canadian Journal of Zoology 64, no. 6 (June 1, 1986): 1320–25. http://dx.doi.org/10.1139/z86-196.
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The courtship, spawning, and paternal care behavior of lumpfish, Cyclopterus lumpus, in Broad Cove, Newfoundland, are described. Breeding lumpfish are sexually dimorphic and exhibit a distinct sexual dichromatism during reproduction. Spawning females are larger than males and pale blueish green in color. Male lumpfish nuptial coloration consists of a greyish black body and an orange–red ventral surface and fins. Spawning follows an extended courtship involving nest cleaning, fin brushing, and quivering. Females extrude pink eggs onto the surface of the nest which the male fertilizes. After fertilization, males mold the eggs into the nest, producing funnel-like depressions in the egg mass. Males remain with the eggs throughout the incubation period providing parental care. Pectoral fanning and puffing, the expelling of water from the mouth towards the surface of the egg mass, are the predominant parental care behaviors exhibited throughout the incubation period. Quantitative variation between males in the amount of time spent in parental care was independent of male size. Egg masses are maintained free of invertebrate predators by the male, but males are unable to defend eggs against predation by large groups of cunners, Tautogolabrus adspersus. Puffing behavior was more frequent towards the end of the incubation period than at the beginning. During hatching emergent larvae are swept from the nest site by male fanning and puffing behaviors.
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Alvarado, Sebastian G. "Molecular Plasticity in Animal Pigmentation: Emerging Processes Underlying Color Changes." Integrative and Comparative Biology 60, no. 6 (October 26, 2020): 1531–43. http://dx.doi.org/10.1093/icb/icaa142.
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Synopsis Animal coloration has been rigorously studied and has provided morphological implications for fitness with influences over social behavior, predator–prey interactions, and sexual selection. In vertebrates, its study has developed our understanding across diverse fields ranging from behavior to molecular biology. In the search for underlying molecular mechanisms, many have taken advantage of pedigree-based and genome-wide association screens to reveal the genetic architecture responsible for pattern variation that occurs in early development. However, genetic differences do not provide a full picture of the dynamic changes in coloration that are most prevalent across vertebrates at the molecular level. Changes in coloration that occur in adulthood via phenotypic plasticity rely on various social, visual, and dietary cues independent of genetic variation. Here, I will review the contributions of pigment cell biology to animal color changes and recent studies describing their molecular underpinnings and function. In this regard, conserved epigenetic processes such as DNA methylation play a role in lending plasticity to gene regulation as it relates to chromatophore function. Lastly, I will present African cichlids as emerging models for the study of pigmentation and molecular plasticity for animal color changes. I posit that these processes, in a dialog with environmental stimuli, are important regulators of variation and the selective advantages that accompany a change in coloration for vertebrate animals.
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Troscianko, Jolyon, John Skelhorn, and Martin Stevens. "Camouflage strategies interfere differently with observer search images." Proceedings of the Royal Society B: Biological Sciences 285, no. 1886 (September 5, 2018): 20181386. http://dx.doi.org/10.1098/rspb.2018.1386.
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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. Despite considerable progress, work has focused on how camouflage types prevent initial detection by naive observers. However, predators will often encounter multiple targets over time, providing the opportunity to learn or focus attention through search images. At present, we know almost nothing about how camouflage types facilitate or hinder predator performance over repeated encounters. Here, we use experiments with human subjects searching for targets on touch screens with different camouflage strategies, and control the experience that subjects have with target types. We show that different camouflage strategies affect how subjects improve in detecting targets with repeated encounters, and how performance in detection of one camouflage type depends on experience of other strategies. In particular, disruptive coloration is effective at preventing improvements in camouflage breaking during search image formation, and experience with one camouflage type (distraction) can decrease the ability of subjects to switch to and from search images for new camouflage types (disruption). Our study is, to our knowledge, the first to show how the success of camouflage strategies depends on how they prevent initial and successive detection, and on predator experience of other strategies. This has implications for the evolution of prey phenotypes, how we assess the efficacy of defences, and predator–prey dynamics.
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Rojas, Bibiana, Emily Burdfield-Steel, Hannu Pakkanen, Kaisa Suisto, Michael Maczka, Stefan Schulz, and Johanna Mappes. "How to fight multiple enemies: target-specific chemical defences in an aposematic moth." Proceedings of the Royal Society B: Biological Sciences 284, no. 1863 (September 27, 2017): 20171424. http://dx.doi.org/10.1098/rspb.2017.1424.
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Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth ( Arctia plantaginis ) displays conspicuous hindwing coloration and secretes distinct defensive fluids from its thoracic glands and abdomen. We presented the two defensive fluids from laboratory-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are target-specific: thoracic fluids, and particularly 2- sec -butyl-3-methoxypyrazine, which they contain, deterred birds, but caused no aversive response in ants. By contrast, abdominal fluids were particularly deterrent to ants, while birds did not find them repellent. Our study, to our knowledge, is the first to show evidence of a single species producing separate chemical defences targeted to different predator types, highlighting the importance of taking into account complex predator communities in studies on the evolution of prey defence diversity.
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Stevens, Martin. "Predator perception and the interrelation between different forms of protective coloration." Proceedings of the Royal Society B: Biological Sciences 274, no. 1617 (April 10, 2007): 1457–64. http://dx.doi.org/10.1098/rspb.2007.0220.
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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.
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Murali, Gopal, and Ullasa Kodandaramaiah. "Deceived by stripes: conspicuous patterning on vital anterior body parts can redirect predatory strikes to expendable posterior organs." Royal Society Open Science 3, no. 6 (June 2016): 160057. http://dx.doi.org/10.1098/rsos.160057.
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Conspicuous coloration, which presumably makes prey more visible to predators, has intrigued researchers for long. Contrastingly coloured, conspicuous striped patterns are common among lizards and other animals, but their function is not well known. We propose and test a novel hypothesis, the ‘redirection hypothesis’, wherein longitudinal striped patterns, such as those found on the anterior body parts of most lacertilians, redirect attacks away from themselves during motion towards less vulnerable posterior parts, for example, the autotomous tail. In experiments employing human ‘predators’ attacking virtual prey on a touchscreen, we show that longitudinal striped patterns on the anterior half of prey decreased attacks to the anterior and increased attacks to the posterior. The position of stripes mattered—they worked best when they were at the anterior. By employing an adaptive psychophysical procedure, we show that prey with striped patterning are perceived to move slower, offering a mechanistic explanation for the redirective effect. In summary, our results suggest that the presence of stripes on the body (i.e. head and trunk) of lizards in combination with caudal autotomy can work as an effective anti-predator strategy during motion.
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Wilson, Joseph S., Jeni Sage Sidwell, Matthew L. Forister, Kevin A. Williams, and James P. Pitts. "Thistledown velvet ants in the Desert Mimicry Ring and the evolution of white coloration: Müllerian mimicry, camouflage and thermal ecology." Biology Letters 16, no. 7 (July 2020): 20200242. http://dx.doi.org/10.1098/rsbl.2020.0242.
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Adaptive coloration among animals is one of the most recognizable outcomes of natural selection. Here, we investigate evolutionary drivers of white coloration in velvet ants (Hymenoptera: Mutillidae), which has previously been considered camouflage with the fruit of creosote bush ( Larrea tridentata ). Our analyses indicate instead that velvet ants evolved white coloration millions of years before creosote bush was widespread in North America's hot deserts. Furthermore, velvet ants and the creosote fruit exhibit different spectral reflectance patterns, which appear distinct to potential insectivorous predators. While the white coloration in velvet ants likely did not evolve as camouflage, we find that white-coloured species remain cooler than their red/orange relatives, and therefore we infer the white coloration likely evolved in response to Neogene desertification. This study shows the importance of cross-disciplinary investigation and of testing multiple hypotheses when investigating evolutionary drivers of adaptive coloration.
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Vinther, Jakob. "Reconstructing Vertebrate Paleocolor." Annual Review of Earth and Planetary Sciences 48, no. 1 (May 30, 2020): 345–75. http://dx.doi.org/10.1146/annurev-earth-073019-045641.
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Melanin and other pigments are now well known to be important in exceptional preservation of soft tissues in vertebrates and other animals. Because pigments confer coloration and even structural colors, they have opened a new field of paleocolor reconstruction. Since its inception about a decade ago, reconstruction of color patterns has been performed on several vertebrates, including feathered and scale-clad dinosaurs. Iridescence and other types of structural color can also be identified through melanosome shape and arrangement. How pigments and melanosomes fossilize and are altered has become an important research subject. Ancient color patterns that may range from crypsis to brilliant displays have revealed insights into the evolution and escalation of visual systems, the nature of ancient animal interactions, and how several unique characteristics of birds already arose among dinosaurs. ▪ Melanin and other pigments preserve in exceptional fossils; this opens paths for reconstructing coloration of extinct organisms, such as dinosaurs. ▪ The most abundant pigment is melanin, which can be identified chemically and through preserved melanosome microbodies. ▪ Melanosome shape reveals clues to original hue ranging from reddish brown and black to gray and structural coloration. ▪ Other pigments may preserve, such as porphyrin pigments in theropod dinosaur eggshells. ▪ Fossil color patterns contribute new insights into the evolution of visual systems, predator-prey interactions, and key innovations.
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Pegram, Kimberly V., Kaci Fankhauser, and Ronald L. Rutowski. "Variation in predator response to short-wavelength warning coloration." Behavioural Processes 187 (June 2021): 104377. http://dx.doi.org/10.1016/j.beproc.2021.104377.
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Stevens, Martin, and Innes C. Cuthill. "Disruptive coloration, crypsis and edge detection in early visual processing." Proceedings of the Royal Society B: Biological Sciences 273, no. 1598 (May 16, 2006): 2141–47. http://dx.doi.org/10.1098/rspb.2006.3556.
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Many animals use concealing markings to reduce the risk of predation. These include background pattern matching (crypsis), where the coloration matches a random sample of the background and disruptive patterns, whose effectiveness has been hypothesized to lie in breaking up the body into a series of apparently unrelated objects. We have previously established the effectiveness of disruptive coloration against avian predators, using artificial moth-like stimuli with colours designed to match natural backgrounds as perceived by birds. Here, we investigate the mechanism by which disruptive patterns reduce detectability, using a computational vision model of edge detection applied to photographs of our experimental stimuli, calibrated for bird colour vision. We show that, disruptive coloration is effective by exploiting edge detection algorithms that we use to model early visual processing. Thus, ‘false’ edges are detected within the body rather than at its periphery, so inhibiting successful detection of the animal's body outline.
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Tso, I.-Min, Shichang Zhang, Wei-Li Tan, Po Peng, and Sean J. Blamires. "Prey Luring Coloration of A Nocturnal Semi-Aquatic Predator." Ethology 122, no. 8 (June 14, 2016): 671–81. http://dx.doi.org/10.1111/eth.12512.
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Webster, Richard J., Christopher Hassall, Chris M. Herdman, Jean-Guy J. Godin, and Thomas N. Sherratt. "Disruptive camouflage impairs object recognition." Biology Letters 9, no. 6 (December 23, 2013): 20130501. http://dx.doi.org/10.1098/rsbl.2013.0501.
Full textAbstract:
Whether hiding from predators, or avoiding battlefield casualties, camouflage is widely employed to prevent detection. Disruptive coloration is a seemingly well-known camouflage mechanism proposed to function by breaking up an object's salient features (for example their characteristic outline), rendering objects more difficult to recognize. However, while a wide range of animals are thought to evade detection using disruptive patterns, there is no direct experimental evidence that disruptive coloration impairs recognition. Using humans searching for computer-generated moth targets, we demonstrate that the number of edge-intersecting patches on a target reduces the likelihood of it being detected, even at the expense of reduced background matching. Crucially, eye-tracking data show that targets with more edge-intersecting patches were looked at for longer periods prior to attack, and passed-over more frequently during search tasks. We therefore show directly that edge patches enhance survivorship by impairing recognition, confirming that disruptive coloration is a distinct camouflage strategy, not simply an artefact of background matching.
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Wainwright, J. Benito, Nicholas E. Scott-Samuel, and Innes C. Cuthill. "Overcoming the detectability costs of symmetrical coloration." Proceedings of the Royal Society B: Biological Sciences 287, no. 1918 (January 15, 2020): 20192664. http://dx.doi.org/10.1098/rspb.2019.2664.
Full textAbstract:
For camouflaged prey, enhanced conspicuousness due to bilaterally symmetrical coloration increases predation risk. The ubiquity of symmetrical body patterns in nature is therefore paradoxical, perhaps explicable through tight developmental constraints. Placing patterns that would be salient when symmetrical (e.g. high contrast markings) away from the axis of symmetry is one possible strategy to reduce the predation cost of symmetrical coloration. Artificial camouflaged prey with symmetrical patterns placed at different distances from the axis were used in both visual search tasks with humans and survival experiments with wild avian predators. Targets were less conspicuous when symmetrical patterning was placed outside a ‘critical zone’ near the midline. To assess whether real animals have evolved as predicted from these experiments, the saliency of features at different distances from the midline was measured in the cryptically coloured forewings of 36 lepidopteran species. Salience, both in absolute terms and relative to wing area, was greatest away from the axis of symmetry. Our work, therefore, demonstrates that prey morphologies may have evolved to exploit a loophole in the ability of mammalian and avian visual systems to spot symmetrical patterns.
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Fukuda, Shinpei, and Junji Konuma. "Using three-dimensional printed models to test for aposematism in a carabid beetle." Biological Journal of the Linnean Society 128, no. 3 (September 5, 2019): 735–41. http://dx.doi.org/10.1093/biolinnean/blz127.
Full textAbstract:
Abstract Many studies have demonstrated that bright colours sometimes evolve as warning coloration on the bodies of distasteful prey. However, few studies have demonstrated that the bright structural colours of beetles function as such aposematic signals for predators in the wild. To determine whether body colour might act as an aposematic signal in the carabid beetle Damaster blaptoides, we generated beetle models and conducted camera-trap and field experiments. Elaborate beetle models produced using a three-dimensional printer were used to determine which animals attack them in the wild. Red and black models were placed in forests to test which of the two types was attacked the least frequently. The camera-trap experiments indicated that mammals and birds were the potential predators of D. blaptoides. The field experiments revealed that predators attacked the red models significantly less frequently than the black models in each of three sites where red Damaster subspecies were distributed. In three sites where black Damaster subspecies were distributed, predators attacked both red and black models at similar rates. These results might imply that the predators learned more easily to avoid distasteful red beetles rather than black ones.