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(A) Predictions of models of colour discrimination (solid lines) fitted to honeybee spectral sensitivity data (filled circles ; von Helversen, 1972). Geometrical interpretations of the models are illustrated in Figs 3 and 4. In each case, curves are least-squared best-fits for the model in question. (i ) Discrimination by an achromatic mechanism (Fig. 3A). (ii ) Discrimination limited by receptor noise without interactions between receptors (Fig. 3B). (iii ) Discrimination limited by the most sensitive receptor mechanism, without interactions between receptors (Fig. 3C). (iv) Discrimination by two chromatic mechanisms (ellipse in Fig. 4C), and also dominance and city block models (parallelogram in Fig. 4C), which are indistinguishable for these data (see Section VI.3). Modified from Brandt & Vorobyev 1997. Only curve iv accurately describes the honeybee's colour thresholds. (B) Spectral sensitivities of three vertebrates as predicted by the receptor-noise-limited colour opponent model (as curve iv above ; see Appendix B) : a dichromat, the tree shrew (Tupaia belangeri ; Jacobs & Neitz, 1986) ; a trichromat, human (Sperling & Harwerth, 1971) ; and a tetrachromat, Pekin robin, (Leiothrix lutea ; Maier, 1992). Each study had two subjects, indicated by separate symbols (o, j). Curves are displaced on the vertical axis for clarity. Modified from Vorobyev & Osorio (1998).
Source publication
Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detec...
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... trained to prefer a coloured target over a dark one, or a dark target over a coloured one (Neumeyer, 1991). More fundamentally, for light-adapted eyes behavioural spectral sensitivities often are mediated by chromatic, not achromatic mechanisms. Adjusting intensities according to these sensitivities does not then exclude achromatic signals (see Fig. 5 ; Section VI.3). Finally, where two or more receptor types contribute to the achromatic mechanism, and are randomly arranged (as in primates) spectral differences can locally lead to an achromatic signal even if the intensities are properly adjusted for the average. Given the difficulties of excluding achromatic signals, a more ...
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... (A) One achromatic mechanism is used for colour discrimination, where the distance in colour space ∆S is given by ∆S # l (k S ∆q S jk M ∆q M jk L ∆q L )# . The three positive coefficients (i.e. k S , k M , k L ) denote the weights of the inputs of receptors to a mechanism, that might be deduced by fitting the model to experimental data (see Fig. 5). The dotted line indicates the axis in the colour space corresponding to this mechanism. The two planes orthogonal to the mechanism's axis give contours of equal discriminability. (B) Discrimination is limited by noise in the three receptor mechanisms, with stage 2 mechanisms (see Fig. 1) absent or not adding noise. This is a ...
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... ∆X i (with i l 1, 2) denotes the difference in the chromaticity co-ordinates, and g ik (with i, k l 1, 2) the components of a metric tensor that can be fitted to experimental data (see Fig. 5). The parallelogram describes the contours of equal discriminability predicted by dominance and city-block metrics. The dominance metric predicts a parallelogram with its sides (and axes, dashed lines) parallel to the axes of the mechanisms mediating discrimination (e.g. receptor or colour opponent signals). Alternatively, the city ...
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... the vertical axis for clarity. Modified from Vorobyev & Osorio (1998). the stage in the visual pathway that limits performance. In practice, however, different modelsthat might implicate quite different physiological mechanisms -often make similar predictions, so that very accurate behavioural measurements are needed to distinguish between them (Fig. 5). Sufficiently accurate measurements are hard to obtain from most ...
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... fitted a dominance metric model to monkey and human spectral sensitivities. Later Nuboer & Moed (1983) used a similar approach to make inferences about post-receptoral mechanisms from spectral sensitivity in the rabbit (Oryctolagus cuniculus). Backhaus (1991) fitted a city block metric model to honeybee colour discrimination (Section V.2c ; Fig. ...
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... models of colour thresholds have more parameters than ellipsoid models. Therefore, before invoking a polygonal model, it is desirable to show that thresholds are significantly less well fitted by an ellipsoid (Figs 3B, 4C). In reality, given the scatter of experimental data, it is difficult to distinguish between ellipsoidal and polygonal models (Fig. 5). For example, ellipsoidal models fit the thresholds for both humans (Poirson & Wandell, 1990) and bees (Brandt & Vorobyev, 1997) almost as well as polygonal models (Fig. 5). Brandt & Vorobyev (1997) tested a number of models on von Helversen's (1972) measurements of honeybee spectral sensitivity (Fig. 5). Models that assume that ...
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... less well fitted by an ellipsoid (Figs 3B, 4C). In reality, given the scatter of experimental data, it is difficult to distinguish between ellipsoidal and polygonal models (Fig. 5). For example, ellipsoidal models fit the thresholds for both humans (Poirson & Wandell, 1990) and bees (Brandt & Vorobyev, 1997) almost as well as polygonal models (Fig. 5). Brandt & Vorobyev (1997) tested a number of models on von Helversen's (1972) measurements of honeybee spectral sensitivity (Fig. 5). Models that assume that receptor signals do not interact (Fig. 1B) fail to explain the data. This implies that receptor signals are integrated by some neural mechanism (Fig. 1, stage 2) before responses ...
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... between ellipsoidal and polygonal models (Fig. 5). For example, ellipsoidal models fit the thresholds for both humans (Poirson & Wandell, 1990) and bees (Brandt & Vorobyev, 1997) almost as well as polygonal models (Fig. 5). Brandt & Vorobyev (1997) tested a number of models on von Helversen's (1972) measurements of honeybee spectral sensitivity (Fig. 5). Models that assume that receptor signals do not interact (Fig. 1B) fail to explain the data. This implies that receptor signals are integrated by some neural mechanism (Fig. 1, stage 2) before responses to different stimuli are compared (stage 3). Likewise, single-mechanism models -such as those described in Section V.2.cdo not fit ...
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... new model of colour discrimination thresholds (Fig. 5A) suggesting a minor modification of the noise-limited models discussed so far (Vorobyev & Osorio, 1998 ; Appendix B) fits experimental data well. It takes account of the ' ecological ' consideration that chromatic signals are more reliable than achromatic. We have mentioned that both bees and birds use chromatic signals for colour ...
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... traditional use of threshold models is to test hypotheses about physiological mechanisms, although as we have seen (Fig. 5) different mechanisms can give quite similar predictions. A second use is to investigate the ecology, evolution and design of colour vision. For example, it is now easy to measure spectra of natural objects such as food plants or bird plumage. Given an accurate model of performance, one can compare the suitability of different types of ...
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The visual systems of most species contain photoreceptors with distinct spectral sensitivities that allow animals to distinguish lights by their spectral composition. In Drosophila, photoreceptors R1-R6 have the same spectral sensitivity throughout the eye and are responsible for motion detection. In contrast, photoreceptors R7 and R8 exhibit heter...
Citations
... A combination of physiological or genetic and computational methods is typically employed to determine what colors are discriminable to animal eyes (Kelber et al. 2003). Physiological methods include microspectrophotometry and electrophysiology, both of which involve stimulating photoreceptors with different colors of light to determine the wavelengths of their peak sensitivities. ...
... Physiological methods include microspectrophotometry and electrophysiology, both of which involve stimulating photoreceptors with different colors of light to determine the wavelengths of their peak sensitivities. Genetic methods can provide the same information, but require knowledge of the gene sequences and spectral sensitivities of opsins of related taxa, as well as the spectral properties of any optical filters within the eye (Kelber et al. 2003). Computational methods can then be used to calculate chromatic contrasts between different colors (Gawryszewski 2018). ...
Physiological or genetic assays and computational modeling are valuable tools for understanding animals’ visual discrimination capabilities. Yet sometimes, the results generated by these methods appear not to jive with other aspects of an animal’s appearance or natural history, and behavioral confirmatory tests are warranted. Here we examine the peculiar case of a male jumping spider that displays red, black, white, and UV color patches during courtship despite the fact that, according to microspectrophotometry and color vision modeling, they are unlikely able to discriminate red from black. To test whether some optical or neurological component could have been missed using these methods, we conduct mate choice experiments. Some females are presented with a choice between males with their red leg coloration painted over with either red or black paint, while other females are presented with a choice between males with the same coloration painted over by either red or white paint. This latter pairing of red and white males should have been easily distinguishable to the spiders and served as a control to ensure our experimental setup was conducive to natural mating behavior. Red males were more likely to mate than white males (P = 0.035), whereas red and black males had identical mating success (P = 1.0). This suggests that previous physiological and computational work on these spiders was correct in concluding that they are unable to discriminate between red and black. Any functional significance of displaying both colors, rather than only black, remains unresolved.
... I then averaged the colour distance (ΔS) for each comparison and compared the resulting values to a standard colour discriminability threshold of ΔS = 1. This threshold represents when two colours become just distinct enough to tell apart by the modelled viewer, also known as a 'just-noticeable-difference' (JND; Kelber et al., 2003;Vorobyev et al., 2001). I did not test for statistical differences in the mean ΔS values of artificial versus live prey, as differences in values greater than one are difficult to interpret without further behavioural data from the relevant receiver(s) (Santiago et al., 2020). ...
... unnaturally saturated paint leading to greater detectability; Stoddard et al., 2018), or the fake caterpillars' inability to actively respond to predators (Paluh et al., 2014). Via spectral analysis, I found that avian predators would be able to easily distinguish both live and fake caterpillars from host plant foliage (Kelber et al., 2003;Vorobyev et al., 2001;Vorobyev & Osorio, 1998). Compared to host plant leaves, both caterpillar types were above the JND threshold of ΔS = 1 (Figure 3). ...
Animal colour patterns are often accompanied by specific, synergistic behaviours to most effectively defend prey against visual predators. Given the inherent context‐dependence of colour perception, understanding how these colour‐behaviour synergies function in a species' natural environment is crucial.
For example, refuge‐building species create a unique visual environment where most (or all) of the body is obscured unless closely inspected. How these built environments affect the perception of defensive colour patterns by predators is not well understood.
Using artificial caterpillars that resemble a refuge‐building species with conspicuous markings (Papilio troilus; Lepidoptera: Papilionidae), I tested the hypothesis that leaf rolls amplify the antipredator effect of this species' eyespots. I compared wild avian predation rates on 659 artificial swallowtail‐like caterpillars from four treatment groups: eyespotted and non‐eyespotted, and presented in leaf rolls or on open leaves of live host plants.
In support of my hypothesis, eyespots only reduced predation for larvae in leaf rolls. On open leaves, eyespots had no antipredator effect. I also found that leaf rolls reduced predation in general for both eyespotted and non‐eyespotted prey.
These results highlight the importance of considering relevant behaviours in studies of animal coloration whenever possible, including behaviours that influence colour perception indirectly (e.g. through habitat use or modification).
... Naturalists have long pondered the evolution and function of the many signals and cues animals use to communicate (Endler, 1992;Endler, 1993;Andersson, 1994;Johnstone, 1996;Martin Schaefer et al., 2004;Johansson and Jones, 2007;Hill, 2009;Jones and Ratterman, 2009;Rose et al., 2022). Visual signals, such as vibrant colours and contrasting patterns, have attracted more interest from researchers than other signals, likely because our species is visually oriented (Endler, 1992;Kelber et al., 2003;Endler et al., 2005). Eyespot patterns, characterised by concentric rings of different colours with a light outer ring and a dark centre (Stevens, 2005), are well-known patterns believed to reduce predation. ...
Eyespot patterns have evolved in many prey species. These patterns were traditionally explained by the eye mimicry hypothesis, which proposes that eyespots resembling vertebrate eyes function as predator avoidance. However, it is possible that eyespots do not mimic eyes: according to the conspicuousness hypothesis, eyespots are just one form of vivid signals where only conspicuousness matters. They might work simply through neophobia or unfamiliarity, without necessarily implying aposematism or the unprofitability to potential predators. To test these hypotheses and explore factors influencing predators’ responses, we conducted a meta-analysis with 33 empirical papers that focused on bird responses to both real lepidopterans and artificial targets with conspicuous patterns (i.e. eyespots and non-eyespots). Supporting the latter hypothesis, the results showed no clear difference in predator avoidance efficacy between eyespots and non-eyespots. When comparing geometric pattern characteristics, bigger pattern sizes and smaller numbers of patterns were more effective in preventing avian predation. This finding indicates that single concentric patterns have stronger deterring effects than paired ones. Taken together, our study supports the conspicuousness hypothesis more than the eye mimicry hypothesis. Due to the number and species coverage of published studies so far, the generalisability of our conclusion may be limited. The findings highlight that pattern conspicuousness is key to eliciting avian avoidance responses, shedding a different light on this classic example of signal evolution.
... There are differences among different species' photoreceptors as well. As an example, cockroach Periplaneta Americana's photoreceptor can only sense UV and green light, and butterfly Papilio Xuthus can sense UV, blue, violet, green, and red light (Kelber et al., 2003). ...
... For flies, however, green flowers would be likely to benefit from the addition of yellow pigmentation to enhance their visual attraction. Although the perceived chromatic contrast between a flower and its surroundings plays an important role in flower detection and recognition by pollinators (Giurfa et al., 1996;Kelber et al., 2003;Dyer and Chittka, 2004;van der Kooi et al., 2019), it is important to note that chromatic contrast is only one of several factors that influence pollinator preferences. Attributes such as floral colour, flower size, scent, rewards and pollinator learning also play significant roles, because colour represents only one component of the multisensory cues that guide pollinator foraging. ...
Background and Aims
Flower colour is a key feature in plant-pollinator interactions that make the flowers visible amid the surrounding green vegetation. Green flowers are expected to be scarcely conspicuous to pollinators; however, many of them are visited by pollinators even in the absence of other traits that might attract pollinators (e.g., floral scents). In this study, we investigate how entomophilous species with green flowers are perceived by pollinators.
Methods
We obtained reflectance spectra data of 30 European species that display green or green-yellow flowers to the human eye. These data were used to perform spectral analyses, calculate both chromatic (colour contrast against the background) and achromatic (colour contrast that relies on the signals from the green-sensitive photoreceptors) cues, and model colour perception by hymenopterans (bees) and dipterans (flies).
Key Results
The visibility of green flowers to bees and flies (i.e., their chromatic contrast values) was lower compared to other floral colours commonly pollinated by these insects, whereas green-yellow flowers were as conspicuous as the other flower colours. Green flowers with low chromatic contrast values exhibited higher achromatic contrasts, which is used to detect distant flowers at narrow visual angles, than green-yellow flowers. Additionally, the marker points (i.e., sharp transition in floral reflectance that aid pollinators in locating them) of green and green-yellow flowers aligned to some degree with the colour discrimination abilities of bees and flies.
Conclusions
We found that many entomophilous green and green-yellow flowers are conspicuous to bees and flies through their chromatic or achromatic contrasts. While acquiring pigments like carotenoids, which impart a yellowish hue to flowers and enhances their visibility to pollinators, could increase their conspicuousness, the metabolic costs of pigment production, along with the use of alternative strategies to attract pollinators, may have constrained carotenoid emergence in certain lineages of green-flowered species.
... La plupart des vertébrés ont un système de cônes pour la vision photopique, colorée, et de batônnets pour la vision scotopique, achromatique. Il y a toutefois des animaux qui n'ont pas les photorécepteurs requis pour voir en couleur, par exemple des poissons d'eau profonde et des céphalopodes (Kelber et al., 2003). Sur le plan méthodologique, la physiologie ne suffit pas pour dire que les animaux voient en couleurs : encore faut-il montrer qu'ils sont capables de discriminer des couleurs différentes. ...
Notes de lecture: éclairage et biodiversité.
Lecture notes: lighting and biodiversity.
... Linnaeus), Hyles lineata (J.C. Fabricius), Hyles galii (Rottemburg), and Xylocopa tranquebarica (Fabricius), can discriminate color (Kelber et al. 2002, 2003, Somanathan et al. 2008. In addition to visual characteristics, floral scents act as important cues for Lepidopteran insects (Liu et al. 2022). ...
The fall armyworm Spodoptera frugiperda (J.E. Smith; Lepidoptera: Noctuidae) is a notorious invasive insect pest. It is very important to understand the foraging behavior of this pest to develop more effective lures to monitor the immigration of this pest. In this study, the use of visual and olfactory cues in the foraging behavior of S. frugiperda was investigated through an attraction experiment in which color (produced from 8 different colored artificial flowers), odor (produced from honey water), and odorous color (produced from artificial flowers supplemented with honey water) were used. When we used 8 different colors to elicit adult responses, S. frugiperda showed a significant color preference despite limited activity (i.e., the total number of visits to the attractant), with black being the most preferred color, followed by orange preferred by both sexes and blue and green preferred only by females. When honey water was used as an attractant, S. frugiperda had relatively greater odor activity than color activity. When we sprayed the artificial flowers with honey, S. frugiperda showed even greater activity in terms of odor color than in terms of color or odor. Compared with male S. frugiperda, female adult S. frugiperda presented greater activity in response to all types of attractants. These findings suggest that S. frugiperda adults rely primarily on olfaction for foraging, with vision as a secondary sense, and that the combined use of olfactory and visual cues increases foraging efficiency. These results provide reference data for designing trapping strategies to monitor and control S. frugiperda.
... Birds are used color for specific behaviors; they can discriminate and choose between different colors (Kelber et al., 2003). Ditto many birds have a preference to specific, or disinclination to, food with different colors (Duan et al., 2014), but preference to specific food color may vary according to the food type (Teichmann et al., 2020). ...
Bird presence in the agricultural ecosystem is a critical for preserving ecological balance due to its various ecological impacts. The composition of bird species and their feeding guilds in agricultural land was investigated in El-Zahraa village, Zagazig district, Sharkia Governorate, Egypt. The point count method was used to survey bird species from April 2021 to March 2022. The survey identified a total of 21 bird species belonging to 17 families and 7 orders. The order Passeriformes was the most abundant; consist of 10 families: Alaudidae, Cisticolidae, Corvidae, Estrildidae, Hirundinidae, Motacillidae, Muscicapidae, Passeridae, Pycnonotidae, Sturnidae. The composition of bird guilds indicated that granivorous and insectivores birds were being more numerous than other guilds (omnivores, carnivores and piscivorous) while, the frugivorous birds was the least represented. The dominant bird species were represented with 5 species: house sparrow, hooded crow, rock pigeon, cattle egret and laughing dove. Food preference experiments conducted on the hooded crow revealed that birds tend to consume Tamia, liver, chicken intestine, and fish in that order. Interestingly, the crows did not consume any amount of crushed maize. Additionally, in terms of color preference, food placed on a blue plastic sheet was favored over food on a red plastic sheet. The abundance of bird species and the diversity of their feeding guilds reflect the richness of food resources in the agricultural area. Furthermore, understanding the food preferences of the hooded crow may assist in utilizing this preferred and cost-effective food (Tamia) as bait to attract and control these birds.
... Whereas discrimination learning is part of everyday life, researchers have also used formal discrimination training paradigms to ask animals various questions about their umwelt (e.g., Kelber et al. 2003). During a discrimination learning process, animals usually develop a response curve centered around the S D , generalizing their responses to comparable stimuli, including ambiguous stimuli that are more distant from the S D (Strang and Muth 2023). ...
Spatial judgement bias tests (JBTs) can involve teaching animals that a bowl provides a reward in one location but does not in another. The animal is then presented with the bowl placed between the rewarded and the unrewarded locations (i.e., ambiguous locations) and their latency to approach reflects expectation of reward or ‘optimism’. Some suggest that greater ‘optimism’ indicates better welfare. Performance in JBTs, however, may also indicate a learning history independently from welfare determinants. We hypothesized that dogs’ ‘optimism’ in a follow-up JBT may be impacted by a learning treatment involving additional trials of a different discrimination task. Once enrolled, companion dogs (n = 16) were required to complete three study phases: (1) a pre-treatment JBT, (2) a learning treatment, and (3) a post-treatment JBT. During the JBTs, dogs were presented with five locations: one rewarded, one unrewarded, and three ambiguous (all unrewarded). Dogs were randomly assigned to a trial-based learning task—a nose-touch to the palm of the hand. In the Experimental discrimination treatment phase (n = 8), dogs were presented with two hands in each trial and only rewarded for touching one specific hand. In the Control treatment phase (n = 8), dogs were presented with one hand per trial in alternating sequence and were yoked to dogs in the Experimental group to receive the same number of rewarded and unrewarded trials (to control for possible frustration). Using a repeated measures mixed model with JBT repeated within dog, we found no difference in the change in approach latency to the ambiguous locations between the dogs across treatments. ‘Optimism’ as measured in this JBT was not altered by the additional discrimination trials used in our study.
... Within each rod and cone outer segment, opsin proteins are involved in light sensation when bound to a vitamin A-derived chromophore (Bowmaker, 2008). The opsin protein and chromophore interaction determine the wavelength of maximum absorption sensitivity (λ max ) (Kelber et al., 2003;Yokoyama, 2000). Most coral reef fishes use a shorter-wavelength shifted A 1 -based chromophore (Toyama et al., 2008). ...
Coral reef ecosystems show fluctuations in their prevailing light environment in response to both regular (e.g. between seasons) and more prevalent stochastic events (e.g. human‐induced sediment runoff). In these shifting environments, phenotypic plasticity provides an essential mechanism for coral reef fishes to adjust their visual capability to meet changing sensory requirements.
Here, we evaluate the growing area of research that highlights the many genetic and ecological mechanisms that affect the plastic responses of coral reef fish vision to environmental cues.
With an increasing number of disturbances in the marine environment, it is critical to understand the extent and limits of visual plasticity under natural and disturbed conditions. With our current knowledge and drawing upon a large body of work in freshwater fishes, we speculate whether coral reef fishes can adapt to the changes to their visual environment and where the limitations could lie.
Whilst coral reef fishes have shown visual adaptations under different light environments, the degree of plasticity is inconsistent between species. Thus, plasticity may not only be functionally significant in maintaining the performance of visually guided behaviours for single species but, more broadly, is likely key to sustaining ecosystem function.
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