Warning coloration in sawflyAthalia rosae larva and concealing coloration in butterflyPieris rapae larva feeding on similar plants evolved through individual selection

Green larvae of the butterfly Pieris rapae and black larvae of the sawfly Athalia rosae feed on green leaves of the same cruciferous plants. To demonstrate that P. rapae has concealing coloration and that A. rosae has warning coloration, the larvae of the two species were supplied to naive chicks Gallus gallus on white, green or black backgrounds. P. rapae larvae were palatable and their green body color acted as a concealing coloration. On the other hand, A. rosae larvae were unpalatable and their black body color acted as a warning coloration. There is a general consensus that warning coloration is an altruistic character which needs victims, and thus can evolve through kin selection or green beard selection. However, black A. rosae larvae were seldom injured by chicks' attack, in particular, on the green background. Therefore, the warning coloration of A. rosae larvae can be a selfish character and hence can evolve through individual selection as well as concealing coloration of P. rapae.     

Local adaptation and divergence in colour signal conspicuousness between monomorphic and polymorphic lineages in a lizard

Population differences in visual environment can lead to divergence in multiple components of animal coloration including signalling traits and colour patterns important for camouflage. Divergence may reflect selection imposed by different receivers (conspecifics, predators), which depends in turn on the location of the colour patch. We tested for local adaptation of two genetically and phenotypically divergent lineages of a rock‐inhabiting lizard, Ctenophorus decresii, by comparing the visual contrast of colour patches to different receivers in native and non‐native environments. The lineages differ most notably in male throat coloration, which is polymorphic in the northern lineage and monomorphic in the southern lineage, but also differ in dorsal and lateral coloration, which is visible to both conspecifics and potential predators. Using models of animal colour vision, we assessed whether lineage‐specific throat, dorsal and lateral coloration enhanced conspicuousness to conspecifics, increased crypsis to birds or both, respectively, when viewed against the predominant backgrounds from each lineage. Throat colours were no more conspicuous against native than non‐native rock but contrasted more strongly with native lichen, which occurs patchily on rocks inhabited by C. decresii. Conversely, neck coloration (lateral) more closely matched native lichen. Furthermore, although dorsal coloration of southern males was consistently more conspicuous to birds than that of northern males, both lineages had similar absolute conspicuousness against their native backgrounds. Combined, our results are consistent with local adaptation of multiple colour traits in relation to multiple receivers, suggesting that geographic variation in background colour has influenced the evolution of lineage‐specific coloration in C. decresii.     

Teasing apart crypsis and aposematism – evidence that disruptive coloration reduces predation on a noxious toad

Both cryptic and aposematic colour patterns can reduce predation risk to prey. These distinct strategies may not be mutually exclusive, because the impact of prey coloration depends on a predator's sensory system and cognition and on the environmental background. Determining whether prey signals are cryptic or aposematic is a prerequisite for understanding the ecological and evolutionary implications of predator–prey interactions. This study investigates whether coloration and pattern in an exceptionally polymorphic toad, Rhinella alata, from Barro Colorado Island, Panama reduces predation via background matching, disruptive coloration, and/or aposematic signaling. When clay model replicas of R. alata were placed on leaf litter, the model's dorsal pattern – but not its colour – affected attack rates by birds. When models were placed on white paper, patterned and un‐patterned replicas had similar attack rates by birds. These results indicate that dorsal patterns in R. alata are functionally cryptic and emphasize the potential effectiveness of disruptive coloration in a vertebrate taxon.     

A fish‐eye view of cuttlefish camouflage using in situ spectrometry

Cuttlefish are colour blind yet they appear to produce colour‐coordinated patterns for camouflage. Under natural in situ lighting conditions in southern Australia, we took point‐by‐point spectrometry measurements of camouflaged cuttlefish, Sepia apama, and various natural objects in the immediate visual surrounds to quantify the degree of chromatic resemblance between cuttlefish and backgrounds to potential fish predators. Luminance contrast was also calculated to determine the effectiveness of cuttlefish camouflage to this information channel both for animals with or without colour vision. Uniform body patterns on a homogeneous background of algae showed close resemblance in colour and luminance; a Uniform pattern on a partially heterogeneous background showed mixed levels of resemblance to certain background features. A Mottle pattern with some disruptive components on a heterogeneous background showed general background resemblance to some benthic objects nearest the cuttlefish. A noteworthy observation for a Disruptive body pattern on a heterogeneous background was the wide range in spectral contrasts compared to Uniform and Mottle patterns. This suggests a shift in camouflage tactic from background resemblance (which hinders detection by the predator) to more specific object resemblance and disruptive camouflage (which retards recognition). © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 535–551.     

Disruptive contrast in animal camouflage

Camouflage typically involves colour patterns that match the background. However, it has been argued that concealment may be achieved by strategic use of apparently conspicuous markings. Recent evidence supports the theory that the presence of contrasting patterns placed peripherally on an animal's body (disruptive coloration) provides survival advantages. However, no study has tested a key prediction from the early literature that disruptive coloration is effective even when some colour patches do not match the background and have a high contrast with both the background and adjacent pattern elements (disruptive contrast). We test this counter-intuitive idea that conspicuous patterns might aid concealment, using artificial moth-like targets with pattern elements designed to match or mismatch the average luminance (lightness) of the trees on which they were placed. Disruptive coloration was less effective when some pattern elements did not match the background luminance. However, even non-background-matching disruptive patterns reduced predation relative to equivalent non-disruptive patterns or to unpatterned controls. Therefore, concealment may still be achieved even when an animal possesses markings not found in the background. Disruptive coloration may allow animals to exploit backgrounds on which they are not perfectly matched, and to possess conspicuous markings while still retaining a degree of camouflage.     

Disruptive coloration, crypsis and edge detection in early visual processing

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.     

Crypsis through disruptive coloration in an isopod

The white-spotted colour morph of the marine isopod Idotea baltica appears cryptic on the brown alga Fucus vesiculosus with its white-coloured epizoites Electra crustulenta and Balanus improvisus. This study shows that the crypsis of this coloration is achieved through disruptive coloration rather than through background matching. Crypsis through background matching requires that the sizes and the shapes of the pattern elements should closely resemble those of the visual background. Comparisons between the white spots of the isopods and those of their natural background contradicted this prediction. Disruptive coloration, which aims to obscure the true form of the animal by partly blending with the background and distracting the attention of the viewer from the contour of the animal to unessential patterns, presupposes more marginal elements than expected by the pattern element distribution in the background, and also highly variable and complex elements. Comparison between the observed spot distribution and simulated individuals with randomly distributed spots showed that the spots in these isopods do indeed touch the body outline more often than expected. Furthermore, the spots were highly variable and complex.     

Warning coloration can be disruptive: aposematic marginal wing patterning in the wood tiger moth

Warning (aposematic) and cryptic colorations appear to be mutually incompatible because the primary function of the former is to increase detectability, whereas the function of the latter is to decrease it. Disruptive coloration is a type of crypsis in which the color pattern breaks up the outline of the prey, thus hindering its detection. This delusion can work even when the prey's pattern elements are highly contrasting; thus, it is possible for an animal's coloration to combine both warning and disruptive functions. The coloration of the wood tiger moth (Parasemia plantaginis) is such that the moth is conspicuous when it rests on vegetation, but when it feigns death and drops to the grass‐ and litter‐covered ground, it is hard to detect. This death‐feigning behavior therefore immediately switches the function of its coloration from signaling to camouflage. We experimentally tested whether the forewing patterning of wood tiger moths could function as disruptive coloration against certain backgrounds. Using actual forewing patterns of wood tiger moths, we crafted artificial paper moths and placed them on a background image resembling a natural litter and grass background. We manipulated the disruptiveness of the wing pattern so that all (marginal pattern) or none (nonmarginal pattern) of the markings extended to the edge of the wing. Paper moths, each with a hidden palatable food item, were offered to great tits (Parus major) in a large aviary where the birds could search for and attack the “moths” according to their detectability. The results showed that prey items with the disruptive marginal pattern were attacked less often than prey without it. However, the disruptive function was apparent only when the prey was brighter than the background. These results suggest that warning coloration and disruptive coloration can work in concert and that the moth, by feigning death, can switch the function of its coloration from warning to disruptive.     

Contrast versus colour in aposematic signals

Conspicuousness is an important feature of warning coloration. One hypothesis for its function is that it increases signal efficacy by facilitating avoidance learning. An alternative, based on the handicap hypothesis, suggests that the degree of conspicuousness holds information directly about the quality of the prey, and that predators associate and learn about the conspicuousness of the coloration, and not the actual colour pattern. We studied the relative importance of signal contrast and the colours of signals for predator attention during discrimination. We used young chicks, Gallus gallus domesticus, as predators and small blue or red paper cones on either matching or contrasting paper backgrounds as stimuli associated with palatable or unpalatable chick crumbs. In four treatment groups, birds could use either cone and/or background colour, cone colour only, background colour only or cone-to-background contrast as cues for discrimination. Only birds in the contrast treatment failed to learn their discrimination task. Birds that had a choice between cone and background colour as cues used the cone colour and they learned the task faster than did birds that had to use background colour as a cue. The results suggest that birds primarily attend to the colours of signals and disregard contrast in discrimination tasks; they thus fail to support a handicap function of conspicuous aposematic coloration. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Coincident disruptive coloration

Even if an animal matches its surroundings perfectly in colour and texture, any mismatch between the spatial phase of its pattern and that of the background, or shadow created by its three-dimensional relief, is potentially revealing. Nevertheless, for camouflage to be fully broken, the shape must be recognizable. Disruptive coloration acts against object recognition by the use of high-contrast internal colour boundaries to break up shape and form. As well as the general outline, characteristic features such as eyes and limbs must also be concealed; this can be achieved by having the colour patterns on different, but adjacent, body parts aligned to match each other (i.e. in phase). Such 'coincident disruptive coloration' ensures that there is no phase disjunction where body parts meet, and causes different sections of the body to blend perceptually. We tested this theory using field experiments with predation by wild birds on artificial moth-like targets, whose wings and (edible pastry) bodies had colour patterns that were variously coincident or not. We also carried out an experiment with humans searching for analogous targets on a computer screen. Both experiments show that coincident disruptive coloration is an effective mechanism for concealing an otherwise revealing body form.     

Spectral reflectances of three tiger beetle subspecies (Neocicindela perhispida): Correlations with their habitat substrate

Abstract

The coloration and cuticular reflec-tivity of the three subspecies of the tiger beetle Neocicindela perhispida, that occur along coastal beaches of the North Island of New Zealand, were examined. The hardened forewings (elytra) of all three subspecies exhibited colour patterns that matched the sand of their respective beach habitats. The dark N. p. campbelli, which occurs on black ironsand beaches, absorbed significantly higher amounts of solar radiation than N. p. giveni whose white elytra blended well with the white quartz sands on which it occurred. The mottled N. p. perhispida, which inhabits yellowish-brown beaches, exhibited reflectivities generally intermediate to these two extremes.     

Crypsis in a heterogeneous environment: relationships between changeable polymorphic colour patterns and behaviour in a galaxiid fish

1. The ability to achieve optimal camouflage varies between microhabitats in heterogeneous environments, potentially restricting individuals to a single habitat or imposing a compromise on crypsis to match several habitats. However, animals may exhibit morphological and behavioural attributes that enhance crypsis in different habitats. 2. We used an undescribed fish species, Galaxias‘nebula’, to investigate two objectives. First, we examined two potential methods of enhancing crypsis: change in colour pattern and selection of a suitable background. Second, we characterised the colour pattern of this unstudied fish and assessed its capacity for crypsis. 3. No background selection was apparent but the area of dark pigment expressed varied between backgrounds, which may negate the requirement to be choosy about habitats. The capacity to change colour and selection of a background that maximises crypsis are most likely separate, non‐mutually exclusive strategies. 4. Galaxias‘nebula’ exhibits polymorphic, non‐interchangeable colour patterns that have elements of both background pattern matching and disruptive colouration. This, coupled with habitat characteristics, suggests a combination of generalist and specialist strategies of habitat use. The fish’s camouflage strategy and air‐breathing ability may be key to survival under increasing pressure from habitat degradation and invasive predators.     

Progressive background in moths, and a quantitative measure of crypsis

A method is presented for quantitative estimation of the degree of crypsis of species seen by visual predators against known backgrounds. It is based upon a comparison between transects taken across animal and background colour patterns. The method was applied to day-resting moths in deciduous forest in New Jersey. Each species is found for two to four weeks at characteristic dates, and there is a constant turnover of species. In both moths and backgrounds there is a regular change in the colour pattern parameters from winter through spring to early summer. Moths are on average more cryptic at their normal dates than they would be if present earlier or later in the year. Species with known resting sites are on average more cryptic on their resting sites than other background habitats. Species that rest on more than one background habitat are less cryptic on their preferred habitats than are specialists. Species that rest under leaves and are not visible from above are not very cryptic. Specific v. general resemblance, disruptive coloration, and factors affecting 'aspect diversity' are discussed. The new method of estimating crypsis is useful for studies of crypsis as well as in sexual selection. It is necessary to know much about the resting sites and behaviour of moths, as well as other functions of colour patterns, to understand colour pattern evolution.     

Come to the dark side: habitat selection of larval odonates depends on background visual patterns

1. Determining which environmental traits enable animals to inhabit and choose preferred habitats is key to understanding ecological processes. Habitat complexity and background colour patterns can act as selective pressures on animal behaviour, and ultimately affect habitat choice. 2. To investigate the role of environmental features on habitat selection, this study looked at whether dragonfly and damselfly larvae show a preference between dark/light or complex environments. Last‐instar larvae of Micrathyria didyma (Odonata: Libellulidae) and Acanthagrion lancea (Odonata: Coenagrionidae) were collected in the Neotropical savanna, and five experiments in laboratory conditions were subsequently carried out. The first experiment tested the preference of larvae for leaves in contrast to a white background. The second experiment compared a preference for white and black backgrounds. As both experiments showed a significant preference for darker backgrounds, a predator was included in the black background in the third experiment, and a macrophyte was included in the white background in the fourth experiment. In this way, favourable and unfavourable conditions were included in the habitat of choice. The fifth experiment tested the influence of environmental complexity on habitat choice. 3. The results of these experiments showed that larvae choose darker backgrounds independently of predation risk, and that macrophytes are as attractive as a dark background. They also suggest that the coenagrionid, but not the libellulid, prefer more complex environments. 4. Overall, these findings suggest that larvae exhibit behavioural preferences for background colour and complexity, which may ultimately drive habitat occupation.     

The detectability of the colour pattern in the aposematic firebug,Pyrrhocoris apterus: an image‐based experiment with human ‘predators’

Crypsis and aposematism are often regarded as two opposite protective strategies. However, there is large variation in prey appearance within both strategies. In this article, we investigated the conspicuousness of the aposematic red‐and‐black firebug, Pyrrhocoris apterus, by presenting images of natural and digitally manipulated phenotypes in their natural habitat on a computer screen to human ‘predators’, and comparing the detection times. We asked whether the natural colour pattern can be made more or less conspicuous by rearranging the spatial distribution of colour elements. Hence, we created a phenotype in which the black colour elements were moved to the body outline to test for a possible disruptive effect. In the ‘black’ and ‘red’ manipulations, we removed one of the two colours, creating two uniform colour variants. We found that some of our manipulations increased, but none reduced, the detection time significantly; this indicates that the naturally coloured firebug is highly conspicuous. The detection time varied among backgrounds and there was a significant relationship between detection time and chromatic similarity between the bug and the background for the natural and black phenotypes. Although background colour composition has an important effect on the signal, we argue that the coloration of P. apterus has evolved for high conspicuousness. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 806–816.     

Dorsal pattern polymorphism in female Iberian wall lizards: differences in morphology,dorsal coloration,immune response,and reproductive investment

Sex‐specific colour polymorphisms have been extensively documented in many different taxa. When polymorphism in colour pattern is restricted to females, the condition is known as female‐limited pattern polymorphism (FPP), which has been less commonly addressed in vertebrates. FPP is present in several lizard species, although most research on lizards has focused on carotenoid‐ and pteridine‐based coloration and not on melanin‐based polymorphisms. In the present study, we focus on Iberian wall lizards, Podarcis hispanicus, where two female melanin‐based dorsal patterns can be clearly distinguished: striped and reticulated‐blotched. We indirectly tested the hypothesis that selection acts differentially among P. hispanicus female morphs to create alternative morph‐specific phenotypic optima at different levels by investigating whether morphs differ in fitness proxies. We specifically examined whether the two female dorsal pattern morphs differed in adult morphology, dorsal coloration, immune response, reproductive investment, and growth. We did not find a relationship between melanin‐based coloration and hatchling growth and immune response, despite a correlation between these traits possibly being expected as a result of pleiotropy in the melanocortin system. However, our results show that female dorsal morphs in P. hispanicus differ in terms of adult morphology, dorsal coloration, and reproductive investment. Reticulated‐blotched P. hispanicus females had deeper heads and longer femora, less melanin, and more brownish coloration, and also had larger and heavier hatchlings than striped females.     

Evolution and assessment of colour patterns in stream-resident and anadromous male threespine stickleback Gasterosteus aculeatus from three regions

We compared the colour patterns of free swimming, reproductively active male threespine stickleback Gasterosteus aculeatus of the anadromous and stream ecotypes from three geographically distinct regions. Consistent with the hypothesis of environmentally mediated selection, our results indicate ecologically replicated differences in G. aculeatus coloration between anadromous and stream-resident populations, and that G. aculeatus probably have the visual acuity to discriminate colour pattern differences between anadromous and stream-resident fish.     

Effects of eyestalk ablation and limb amputation on the moult cycle of the shrimp Penaeus chinensis

The shrimp Penaeus chinensis at moult stage D_o were subjected to one of the three following treatments: bilateral eyestalk ablation, amputation of the fifth pair of pereiopods, and both of the above treatments. Two consecutive ecdyses after treatments were followed. Intact animals served as control. Precocious moulting was exhibited in all treated groups. Eyestalk ablation shortened the time to the first ecdysis more than does limb amputation. Additive effect was found in shrimps receiving both treatments. The duration between the first and second ecdyses in treated shrimps was shorter than that of intact animals, but the durations in the three treated groups were not significantly different from one another. Regenerates of limbs appeared after the second ecdysis following limb amputation. Further, change of body colour from black and green to red and white was observed in shrimps with eyestalk ablation.