Size,shape and hue modulate attraction and landing responses of the braconid parasitoid <Emphasis Type="Italic">Fopius arisanus</Emphasis> to fruit odour-baited visual targets

Female parasitoids are guided by multisensory information, including chemical and physical cues during host location. In the present study, we investigated the behavioural responses of naïve Fopius arisanus (Sonan) females to visual targets baited with guava odour. In non-choice wind tunnel tests, the attraction and landing responses of parasitoids to spheres painted with different colours, and targets of different shapes and sizes were evaluated. Females were more frequently attracted and landed more often on dark yellow targets than on targets with other colours. There was no correlation between the brightness of each colour and the attraction or landing responses. In contrast, both responses were correlated with relative reflectance (hue) of the coloured targets. A positive correlation was observed between attraction and hue, and a negative correlation between landing and hue. F. arisanus was attracted to and landed more often on spheres than on other shape models. The attraction response of this parasitoid was affected by the size of the targets, with spheres of 10 and 12 cm diameter being more attractive than spheres of 8, 6 and 4 cm diameter. The fact that F. arisanus females were able to discriminate among visual targets that differ in colour, shape and size stresses the importance of vision during host location by this species.     

Red oilseed rape? The potential for manipulation of petal colour in control strategies for the pollen beetle (Meligethes aeneus)

The pollen beetle (Meligethes aeneus) is a major pest of oilseed rape (Brassica napus) at the inflorescence stage and is well known to prefer colours called yellow by human observers over many other colours. While commercial cultivars of oilseed rape have yellow flowers, little is known about the potential to manipulate host plant location and reduce subsequent infestation by this pest through variation in flower colour. We investigated the responses of pollen beetles to flowers of a white-petalled oilseed rape variety that had been dyed different colours in semi-field arena and field experiments. Flowers dyed blue or red were less heavily infested than those dyed yellow or the white flowers, indicating that blue and red flowers were less attractive than yellow and white ones. This response was most likely due to differences in petal colour because olfactometer studies showed that beetle responses to the odours of the coloured treatments did not differ. The comparatively high infestation of untreated white flowers is interpreted as a consequence of their high UV reflectance; the presence of a UV receptor in M. aeneus is suggested, and its role in visually guided insect–plant interactions in this species described. The potential for manipulation of petal colour in control strategies for the pollen beetle is discussed.     

Plant scents modify innate colour preference in foraging swallowtail butterflies

Flower-visiting insects exhibit innate preferences for particular colours. A previous study demonstrated that naive Papilio xuthus females prefer yellow and red, whereas males are more attracted to blue. Here, we demonstrate that the innate colour preference can be modified by olfactory stimuli in a sexually dimorphic manner. Naive P. xuthus were presented with four coloured discs: blue, green, yellow and red. The innate colour preference (i.e. the colour first landed on) of the majority of individuals was blue. When scent from essential oils of either orange flower or lily was introduced to the room, females’ tendency to select the red disc increased. Scents of lavender and flowering potted Hibiscus rosa-sinensis, however, were less effective. Interestingly, the odour of the non-flowering larval host plant, Citrus unshiu, shifted the preference to green in females. In males, however, all plant scents were less effective than in females, such that blue was always the most favoured colour. These observations indicate that interactions between visual and olfactory cues play a more prominent role in females.     

Plasticity of Escape Responses: Prior Predator Experience Enhances Escape Performance in a Coral Reef Fish

Teleost and amphibian prey undertake fast-start escape responses during a predatory attack in an attempt to avoid being captured. Although previously viewed as a reflex reaction controlled by the autonomic nervous system, the escape responses of individuals when repeatedly startled are highly variable in their characteristics, suggesting some behavioural mediation of the response. Previous studies have shown that fishes are able to learn from past experiences, but few studies have assessed how past experience with predators affect the fast-start response. Here we determined whether prior experience with the smell or sight of a predator (the Dottyback, Pseudochromis fuscus) affected the escape response of juveniles of the Spiny Chromis (Acanthochromis polyacanthus). Results show that individuals exposed to any of the predator cues prior to being startled exhibited a stronger escape response (i.e., reduced latency, increased escape distance, mean response speed, maximum response speed and maximum acceleration) when compared with controls. This study demonstrates the plasticity of escape responses and highlights the potential for naïve reef fish to take into account both visual and olfactory threat cues simultaneously to optimise the amplitude of their kinematic responses to perceived risk.     

Body Colouration Related to the Deposition of Pteridines in the Epidermis and Other Organs of Dysdercus Species (Insecta; Heteroptera: Pyrrhocoridae)

In epidermal cells of Dysdercus species, two types of pigment granules were detected using both light and electron microscopic methods; the granules differed in colour, size, distribution and osmiophily. Red (D. intermedius) and yellow (D. nigrofasciatus) epidermal cells contained both types of granules, but in white cells only one type was present. Chromatographic analyses showed that the larger granules were more transparent to electrons, and contained uric acid, while the smaller ones contained erythropterin, became coloured later, and were osmiophilic. In accordance with these findings, in the testes of D. intermedius both granule types were present, but in the testes of D. nigrofasciatus only those containing erythropterin. The number of granules per cell varied with the species and developmental stage. Epidermal cells of D. intermedius contained more erythropterin granules than those of D. nigrofasciatus, the reverse occurring in the testes. This pattern corresponded to the visible colouration of the insects. As the development progressed, a decrease of the red and an increase of the white granules took place in the coloured epidermal cells. The main amount of pteridines, except isoxanthopterin, was accumulated in the integument of the insects studied. Chemical and histological data showed the influence of pterins on insect colouration. Orange, yellow and red colours were caused by different amounts of erythropterin containing special granules in the epidermal cells, and the white colour only by uric acid containing granules. A partial melanization of the cuticle resulted in dark spots below which pteridines were deposited additionally in the epidermal cells. Considering erythropterin, the quantitative chemical data are in accordance with the histological ones and also with the colouration externally visible. Intensively red coloured stages had a higher concentration of erythropterin and more corresponding granules than the light-red coloured ones; the lowest amount was found in yellow coloured insects. Therefore, the pigmentation effect of erythropterin, which reached from yellow to orange and red, depended on its concentration and played the most important role in the colouration of the Dysdercus species studied, uric acid was responsible for the colouration of the white parts of the integument.     

Quantifying Variability of Avian Colours: Are Signalling Traits More Variable?

Background

Increased variability in sexually selected ornaments, a key assumption of evolutionary theory, is thought to be maintained through condition-dependence. Condition-dependent handicap models of sexual selection predict that (a) sexually selected traits show amplified variability compared to equivalent non-sexually selected traits, and since males are usually the sexually selected sex, that (b) males are more variable than females, and (c) sexually dimorphic traits more variable than monomorphic ones. So far these predictions have only been tested for metric traits. Surprisingly, they have not been examined for bright coloration, one of the most prominent sexual traits. This omission stems from computational difficulties: different types of colours are quantified on different scales precluding the use of coefficients of variation.

Methodology/Principal Findings

Based on physiological models of avian colour vision we develop an index to quantify the degree of discriminable colour variation as it can be perceived by conspecifics. A comparison of variability in ornamental and non-ornamental colours in six bird species confirmed (a) that those coloured patches that are sexually selected or act as indicators of quality show increased chromatic variability. However, we found no support for (b) that males generally show higher levels of variability than females, or (c) that sexual dichromatism per se is associated with increased variability.

Conclusions/Significance

We show that it is currently possible to realistically estimate variability of animal colours as perceived by them, something difficult to achieve with other traits. Increased variability of known sexually-selected/quality-indicating colours in the studied species, provides support to the predictions borne from sexual selection theory but the lack of increased overall variability in males or dimorphic colours in general indicates that sexual differences might not always be shaped by similar selective forces.     

Characteristics of the high frequency escape reactions of Oithona SP.

The cyclopoid copepod Oithona was found to exhibit multiple escape reactions when entrained within quantified flow fields. The distance of the escape from the flow‐producing predator mimic (a siphon) decreased with a concurrent decrease in escape distance and speed. Although individuals became behaviorally more sensitive to fluid motion with each successive escape reaction, the lower thresholds were not manifested as more distant escape reactions. Overall, the escape distance and speed decreased significantly with decreased signal strength. The decrease may result from the high cost of the escape reaction, which was calculated to account for 36% of the normal metabolic rate and 500 times the cost of normal swimming.     

Colour learning in two behavioural contexts: how much can a butterfly keep in mind?

Here we examine the ability of butterflies to learn colour cues in two different behavioural contexts, nectar foraging and oviposition, more or less simultaneously. We first trained female Battus philenor (Papilionidae) butterflies to associate a given colour with the presence of host plant leaf extract and assayed their colour preference; we then trained a subset of these butterflies to associate a second colour with the presence of sucrose solution and assayed colour preference once more. When offered an array of four unscented and unrewarding coloured models, ‘single-trained’ butterflies consistently alighted most frequently on their oviposition training colour. Green-trained butterflies landed on nontrained colours only about 4% of the time, while butterflies trained to red, yellow or blue made about 23% of their landings on nontrained colours; of those nontrained landings, most were on green. The majority of ‘dual-trained’ butterflies made the greatest number of visits to both training colours in the appropriate behavioural context; that is, they probed the models of their sucrose-associated colour and alighted on the models of their oviposition-associated colour. Landings or probes on nontrained colours in one context were consistently biased towards what was learned in the alternative context, suggesting an information-processing constraint in the butterflies. This paper provides a clear demonstration that butterflies can learn in two behavioural contexts within a short span of time. A capacity for such dual conditioning presumably permits female butterflies to forage effectively for egg-laying sites and nectar resources even when those activities are intermingled in time. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.       

Colour preferences and colour vision in poultry chicks

The dramatic colours of biological communication signals raise questions about how animals perceive suprathreshold colour differences, and there are long-standing questions about colour preferences and colour categorization by non-human species. This study investigates preferences of foraging poultry chicks (Gallus gallus) as they peck at coloured objects. Work on colour recognition often deals with responses to monochromatic lights and how animals divide the spectrum. We used complementary colours, where the intermediate is grey, and related the chicks' choices to three models of the factors that may affect the attractiveness. Two models assume that attractiveness is determined by a metric based on the colour discrimination threshold either (i) by chromatic contrast against the background or (ii) relative to an internal standard. An alternative third model is that categorization is important. We tested newly hatched and 9-day-old chicks with four pairs of (avian) complementary colours, which were orange, blue, red and green for humans. Chromatic contrast was more relevant to newly hatched chicks than to 9-day-old birds, but in neither case could contrast alone account for preferences; especially for orange over blue. For older chicks, there is evidence for categorization of complementary colours, with a boundary at grey.     

Colour choice behaviour in the pollen beetle Meligethes aeneus (Coleoptera: Nitidulidae)

The pollen beetle Meligethes aeneus Fabricius (Coleoptera, Nitidulidae), a pest of oilseed rape (Brassica napus), is known to respond to coloured stimuli; however, current understanding of the underlying mechanisms of colour choice in this species is limited. In the present study, physiological and behavioural experiments are conducted to determine the response of the pollen beetle to colours in the field. Spectral sensitivity is measured in 10 animals using the electroretinogram technique. Light flashes (100 ms) at varied wavelengths (340–650 nm, 10‐nm steps) and at different light intensities are applied to the eye after dark adaptation. In behavioural experiments in the field, 100 water traps of varying colours (from yellow to green to blue with varying amounts of white and black added, and with known spectral reflectance) are set out on a bare soil field in May 2008. The mean spectral sensitivity curve of M. aeneus peaks at 520 nm; however, a model template fitted to the long wavelength tail of the observed curve reveals a peak at approximately 540 nm (green). A secondary sensitivity peak is observed in the ultraviolet (UV) range (370 nm). A total of 2482 pollen beetles are captured in the coloured traps. The results show that the pollen beetles' preference for yellow over other colours can be modelled as a colour opponent mechanism (green versus blue); however, further experiments are needed to specify responses to colours with higher UV reflectance. These findings may be used to optimize trap colours for monitoring to help develop integrated pest management strategies for pollen beetle control.     

Two-dimensional Fourier analysis of the spongy medullary keratin of structurally coloured feather barbs

We conducted two-dimensional (2D) discrete Fourier analyses of the spatial variation in refractive index of the spongy medullary keratin from four different colours of structurally coloured feather barbs from three species of bird: the rose-faced lovebird, Agapornis roseicollis (Psittacidae), the budgerigar, Melopsittacus undulatus (Psittacidae), and the Gouldian finch, Poephila guttata (Estrildidae). These results indicate that the spongy medullary keratin is a nanostructured tissue that functions as an array of coherent scatterers. The nanostructure of the medullary keratin is nearly uniform in all directions. The largest Fourier components of spatial variation in refractive index in the tissue are of the appropriate size to produce the observed colours by constructive interference alone. The peaks of the predicted reflectance spectra calculated from the 2D Fourier power spectra are congruent with the reflectance spectra measured by using microspectrophotometry. The alternative physical models for the production of these colours, the Rayleigh and Mie theories, hypothesize that medullary keratin is an incoherent array and that scattered waves are independent in phase. This assumption is falsified by the ring-like Fourier power spectra of these feathers, and the spacing of the scattering air vacuoles in the medullary keratin. Structural colours of avian feather barbs are produced by constructive interference of coherently scattered light waves from the optically heterogeneous matrix of keratin and air in the spongy medullary layer.     

Spatial distance and reactivity traits alter the positive perception of brushing by ewes

Gentle handling seems to elicit positive states in sheep. The study investigated whether spatial distance alters sheep responses to brushing and whether spatial distance is influenced by reactivity. Twenty Romane ewes were assessed in three sessions: in Sessions 1 and 3, one grid separated the test animal from pen mates, with no distance between them, and in Session 2 two grids separated the test animal from pen mates by a distance of about 1.7 m. Ewes had been genetically selected for low (R−) or high (R+) behavioural reactivity to social isolation. Body postures, head orientation, ear postures, closed and half-closed eyes, tail wagging and feeding behaviour, in addition to heart rate (HR) and HR variability, as the root mean square of successive differences (RMSSD), standard deviation of all normal-to-normal (NN) intervals (SDNN), RMSSD/SDNN ratio and ratio between low-frequency (LF) and high-frequency (HF) powers (LF/HF) were assessed. Data were analysed using generalized linear models and linear mixed models. Session, genetic line and phase (pre-, brushing and post-brushing) were considered fixed effects. Increased distance in Session 2 might not have influenced ewes’ responses. Fewer changes in ear postures were noted in Session 3 than 1 (P<0.01), suggesting that ewes were more relaxed in Session 3. The RMSSD/SDNN ratio was higher mainly during brushing in Sessions 1 and 3 (P<0.05), indicating that ewes were more relaxed during brushing, and at no distance between pen mates. However, spatial distance influenced R− and R+ ewes’ responses; R+ ewes performed more asymmetric ear postures in Session 2 than 1 and 3 (P<0.01), and in Session 3 than 1 (P<0.01), indicating that spatial distance had a negative effect on R+ ewes. Low reactive ewes spent less time on horizontal ear postures in Session 2 than 1 and 3 (P<0.01), and R+ ewes spent more time on horizontal postures in Session 1 than 3 (P<0.01). Curiously, R− ewes spent more time eating and ruminating in Session 3 than 1 (P<0.01), and in Session 2 than 1 and 3 (P<0.01), whereas R+ ewes ate and ruminated more in Session 1 than 3 (P<0.05). Higher HR was found among R− ewes in Session 2 than 1 and 3, and in Session 3 than 1 (P<0.01). High reactive ewes showed higher HR in Session 1 than 3 (P<0.01). The findings suggest that the social context might influence sheep responses to gentle handling, and the effects depend on their reactivity traits.     

Individual selection, kin selection, and the shifting balance in the evolution of warning colours: the evidence from butterflies

It is difficult to imagine how warning colours evolve in unpalatable prey. Firstly, novel warningly coloured variants gain no protection from their colours, since predators have not previously encountered and learnt their colour patterns. This leads to a frequency-dependent disadvantage of a rare variant within a species. Secondly, novel warningly coloured variants may be more conspicuous than non-aposematic prey.
Nevertheless, it is obvious that many palatable butterflies have bright colours used in intraspecific communication and in duping predators. Other palatable butterflies are already warningly coloured. Should such butterflies evolve unpalatability, perhaps because of a host-plant shift, these bright colours would be preadapted to a warning role. Warning colours could then continue to evolve by enhancement of memorable characteristics of these patterns, or by mimicry.
Even within lineages of warningly coloured, unpalatable butterflies, colour patterns have continued to evolve rapidly. This diversity of warning colour patterns could have evolved in a number of ways, including individual and kin selection, and by the shifting balance. Evidence for these mechanisms is discussed, as are the similarities between the evolution of warning colours and more general evolutionary processes, including sexual selection and speciation.     

What weta want: colour preferences of a frugivorous insect

Plants use colours as signals to attract mutualists and repel antagonists. Fleshy-fruits are often conspicuously coloured to signal different types of information including fruit maturity and spatial location. Previous work on fruit colour selection focus on large diurnal vertebrates, yet fruit colours are perceived differently by frugivores with different types of visual systems. Here, we tested whether a nocturnal, frugivorous, seed-dispersing insect selects fruits based on their pigmentation and whether different lighting conditions affect fruit colour selection. We captured 20 Wellington tree weta (Hemideina crassidens) from a forest reserve on the North Island of New Zealand and brought them into laboratory conditions to test their fruit colour preferences. The fruits of Coprosma acerosa, a native shrub species that naturally produces translucent, blue-streaked fruits, were dyed either red or blue. Fruits were then offered to weta in a binary (y-maze) choice test in two light conditions, either at night during a full moon or under artificial light conditions in the lab. Weta preferred unmanipulated, naturally blue-streaked fruits and artificially-blue coloured fruits over those dyed red. Furthermore, their colour preferences were unaffected by light environment. Our results therefore suggest that weta can discriminate between colours (using colour vision) in both light and dark light environments. Their consistent preferences for colours other than red indicate that weta might be responsible for the unusual colours of fleshy-fruits in New Zealand.     

The effects of the visual environment on responses to colour by domestic chicks

It is well known that development of vision is affected by experience, but there are few studies of environmental effects on colour vision. Natural scenes contain predominantly a restricted range of reflectance spectra, so such effects might be important, perhaps biasing visual mechanisms towards common colours. We investigated how the visual environment affects colour preferences of domestic chicks ( Gallus gallus), by training week-old birds to select small food containers distinguished from an achromatic alternative either by an orange or by a greenish-blue colour. Chicks that had been raised in control conditions, with long-wavelength-dominated reflectance spectra, responded more readily to orange than to blue. This was not due to avoidance of blue, as increasing saturation enhanced the chicks' preference for the same hue. The advantage of orange was, however, reduced or abolished for chicks raised in an environment dominated by blue objects. This indicates that responses to coloured food are affected by experience of non-food objects. If colours of ordinary objects in the environment do influence responses to specialised visual signals this might help explain why biological signals directed at birds are often coloured yellow, orange or red; long-wavelength-dominated spectra being more prevalent than short-wavelength-dominated spectra.     

The modelling of avian visual perception predicts behavioural rejection responses to foreign egg colours

How do birds tell the colours of their own and foreign eggs apart? We demonstrate that perceptual modelling of avian visual discrimination can predict behavioural rejection responses to foreign eggs in the nest of wild birds. We use a photoreceptor noise-limited colour opponent model of visual perception to evaluate its accuracy as a predictor of behavioural rates of experimental egg discrimination in the song thrush Turdus philomelos. The visual modelling of experimental and natural eggshell colours suggests that photon capture from the ultraviolet and short wavelength-sensitive cones elicits egg rejection decisions in song thrushes, while inter-clutch variation of egg coloration provides sufficient contrasts for detecting conspecific parasitism in this species. Biologically realistic sensory models provide an important tool for relating variability of behavioural responses to perceived phenotypic variation.     

The Polyarthra escape from response: Defense against interference from Daphnia

Direct observations show that almost all (97%) Polyarthra remata caught in the inhalant current of Daphnia pulex avoid inhalation by initiating escape responses. Microvideographic analysis shows that these responses are initiated, on average, 0.24 mm (about 2.5 body lengths) from the inhalant opening of the branchial chamber, when the Polyarthra are moving at a velocity of about 1.4 mm s^–1 (about 6 times their normal swimming speed — 0.24 mm s^–1). The stimulus for the escape response could be rapid acceleration or, more likely, shear. The average distance traveled during an escape response is at least 1.25 mm (about 12 body lengths).The Polyarthra escape response can provide a very effective defense against interference from Daphnia and may greatly increase the ability of Polyarthra spp. to coexist with Daphnia.     

Cone opsins and response of female chamois (Rupicapra rupicapra) to differently coloured raincoats

Alpine species are often exposed to intense levels of human recreational activities. Exactly how human disturbances influence the behaviour of these species is still open to much debate. For example, little is known regarding how the colourful clothing often worn by tourists influences the behaviour of animals. Tourists wearing colourful clothing may be more conspicuous to local wildlife and thus cause more disturbances. We therefore investigated this question in female chamois (Rupicapra rupicapra) in the Swiss Alps. We firstly investigated, via a morphological and an immunohistochemical approach, whether chamois are likely to have colour vision and would therefore be more likely to respond to different coloured clothing. We detected evidence of two cone types—short-wavelength-sensitive cones (S-cones, JH 455) and middle-wavelength-sensitive cones (M-cones, JH492) in the chamois retina—suggesting that chamois have dichromatic vision, similar to other ungulates. Secondly, via behavioural assays where a person wearing one of three coloured coats commonly worn by tourists (red, yellow and blue) approached a female chamois, we show that neither the alert and flight initiation distance nor the site of refuge were influenced by the raincoat colour. In addition, behavioural responses of the chamois were neither influenced by animal group size nor the presence of kids nor the time of the experiment. The results suggest that, although chamois possess colour vision, they do not react more strongly towards conspicuous colours worn by hikers. We discuss our results in light of what is already known about chamois biology and suggest implications for future studies.     

Nuptial Coloration and Mate Guarding Affect Escape Decisions of Male Lizards Psammodromus algirus

Males of many species show conspicuous breeding colours that are important for status signalling, but that may decrease crypsis and increase predation risk. However, prey may adjust their escape response, such that the optimal distance at which an animal starts to flee (approach distance) would be the point where the costs of staying exceed the cost of fleeing. We examined in the field the escape response of Psammodromus algirus lizards, to test the hypothesis that more conspicuous old males, showing orange nuptial coloration on most of the head, which presumably have a higher probability of being detected (i.e. increased costs of staying), have longer approach distances, independent of other environmental variables. As predicted, old brightly coloured males had significantly longer approach and flight distances than young dull males, and young males had longer ones than females. In contrast, neither the distance to the nearest refuge nor the air temperature when the lizards escaped were significantly different. In addition, although male and female lizards differed in their use of microhabitats, old and young males did not differ. We also found that old males guarding a female (i.e. increased costs of fleeing) had shorter approach distances than old males that were found alone.     

The responses of wild jacamars (Galbula ruficauda,Galbulidae) to aposematic,aposematic and cryptic,and cryptic butterflies in central Brazil

1. This article reports the responses of wild, adult jacamars to butterflies with distinct coloration types in central Brazil. Fully aposematic species, i.e. those exhibiting bright and/or contrasting colours on both wing surfaces (= A/A), were predominantly sight‐rejected by birds and, with one exception, the few butterflies attacked and captured were taste‐rejected afterwards. 2. Aposematic and cryptic butterflies, i.e. those exhibiting bright and/or contrasting colours on the upper and cryptic colours on the underwings (= A/C) were sight‐rejected while flying, when they show their conspicuous colours to predators. This suggests that birds associate butterfly colours with their difficulty of capture, as in the case of Morpho and several Coliadinae species. These butterflies, however, were heavily attacked at rest, when they are cryptic. 3, Fully cryptic butterflies, i.e. those exhibiting cryptic colours on both wing surfaces (= C/C) did not elicit sight rejections by birds. Comparisons involving the number of attacks and the capture success of flying and resting individuals showed no significant differences in species more frequently observed like some cracker butterflies (Hamadryas feronia and H. februa) and Taygetis laches. Compared with the A/C Coliadinae, these butterflies showed a lesser, although not significantly different, ability to escape while flying, but a greater and significantly different ability to escape while at rest. 4, A hunting tactic of jacamars, which consists of following flying A/C and C/C butterflies on sight, and waiting until they perch to locate and attack them, is described for the first time.