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Aposematic signaling has been documented in a wide variety of taxa. These include, but are not limited to, A) Dendrobatid frogs, B) Salamandrid salamanders, C) Micrurus coral snakes, D) Nudibranchs, E) Heliconius butterflies, and F) Hymenopterans. Among these, similar colors have evolved, which are commonly some variation of yellow, red, and/or white. Printed under a CC BY license, original copyright J.P. Lawrence 2017.
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A few colors, such as red and yellow, are commonly found in aposematic (warning) signaling across taxa, independent of evolutionary relationships. These colors have unique traits (i.e., hue, brightness) that aid in their differentiation, and perhaps, their effectiveness in promoting avoidance learning. This repeated use calls into question the infl...
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... To assess the potential costs of transporting tadpoles on the dorsum in poison frogs, we used domestic chicks Gallus gallus domesticus. Domestic chicks as a proxy of natural avian predators have been used in studies about the ecology and evolution of aposematism in diverse organisms (Schuler and Hesse 1985;Roper and Wistow 1986;Roper and Cook 1989;Schuler and Roper 1992;Tullberg 1999, 2001;Hauglund et al 2006;Lawrence and Noonan 2018). Moreover, avian vision is well documented at the physiological level (Osorio et al 1999;Matsushima et al 2003), and it is known that chicks can learn to discriminate and categorize different colors and patterns (Ham and Osorio 2007;Aronsson and Gamberale-Stille 2008). ...
Aposematism is an anti-predator strategy where predators learn to associate the warning signal on prey with an unpleasant experience, and consequently, avoid attacking similar prey in the future. Conspicuous coloration in poison frogs (Dendrobatidae) is considered a warning signal. During parental care, parents transport their tadpoles on the dorsum, which could alter the detectability and recognition of such warning coloration by visually oriented predators. We tested this hypothesis using domestic chicks trained to avoid and discriminate between printed frog models with and without conspicuous-warning coloration. We tested whether the chicks recognized the warning coloration on printed frog models that varied in the quantity of tadpoles on the dorsum. Chicks first attacked frog models without warning coloration, whether they had tadpoles on the dorsum or not. In contrast, frog models with warning coloration were attacked last by chicks. Moreover, the frog models with warning coloration and without tadpoles experienced a lower risk of attack by chicks than similar frog models with tadpoles. However, aposematic frog models maintained the warning function of conspicuous coloration if it was located on parts of the parent's body that are not covered by the tadpoles when transported. Our results suggest that tadpoles on the dorsum of parents might compromise the effectiveness of the warning signal display in poison frogs increasing the risk of attack by visually oriented predators.
... Illustrations by Daniela Perez Our analyses suggest that the chromatic component of the internal colour (i.e. hue, saturation) is more strongly linked to aposematic signalling than luminance, at least dorsally, which is consistent with broad observations in other clades (Lawrence & Noonan, 2018;Ruxton et al., 2004). Chromatic contrast can be more important than luminance contrast for object recognition in birds, especially when targets are large (Zylinski & Osorio, 2013). ...
Many organisms use conspicuous colour patterns to advertise their toxicity or unpalatability, a strategy known as aposematism. Despite the recognized benefits of this anti‐predator tactic, not all chemically defended species exhibit warning coloration. Here, we use a comparative approach to investigate which factors predict the evolution of conspicuousness in frogs, a group in which conspicuous coloration and toxicity have evolved multiple times. We extracted colour information from dorsal and ventral photos of 594 frog species for which chemical defence information was available. Our results show that chemically defended and diurnal species have higher internal chromatic contrast, both ventrally and dorsally, than chemically undefended and/or nocturnal species. Among species that are chemically defended, conspicuous coloration is more likely to occur if species are diurnal. Our results also suggest that the evolution of conspicuous colour is more likely to occur in chemically defended prey with smaller body size. We discuss potential explanations for this association and suggest that prey profitability (related to body size) could be an important force driving the macroevolution of warning signals. Many organisms use warning signals to advertise that they are unpalatable or toxic. This, however, does not always happen, and many chemically defended organisms do not advertise their toxicity. When are organisms more likely to advertise their defences? We used information on frog species and found that species that are chemically defended are more likely to be conspicuous (as expected). We also found that if species are already chemically defended, they are more likely to exhibit contrasting colourations if they are diurnal, and if they are relatively small. Our findings can help us understand under which conditions aposematism is more likely to evolve in nature.
... Moreover, as strong UV reflectance does not appear to affect predation risk in artificial targets (Lyytinen et al., 2001) or heliconiian butterflies (Finkbeiner et al., 2017), it also seems improbable that the comparatively weak UV reflectance observed in poison frogs would be an important contribution to aposematic signals. Indeed, where UV reflectance has been reported in poison frogs pattern contrast remains high when UV is excluded, and other color pattern combinations that lack UV have both been found to result in greater visual contrast (Yeager & Barnett, 2020) and to be more likely to be avoided by avian predators (Lawrence & Noonan, 2018). ...
Warning signals are often characterized by highly contrasting, distinctive, and memorable colors. Greater chromatic (hue) and achromatic (brightness) contrast have both been found to contribute to greater signal efficacy, making longwave colored signals (e.g., red and yellow), that are perceived by both chromatic and achromatic visual pathways, particularly common. Conversely, shortwave colors (e.g., blue and ultraviolet) do not contribute to luminance perception yet are also commonly found in warning signals. Our understanding of the role of UV in aposematic signals is currently incomplete as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic heliconiian butterflies and poison frogs both of which reflect UV wavelengths, occupy similar habitats, and share similar classes of predators. Previous work on butterflies has found that UV reflectance does not affect predation risk but is involved in mate choice. As the butterflies, but not the frogs, have UV-sensitive vision, the function of UV reflectance in poison frogs is currently unknown. We found that despite showing up strongly in UV photographs, UV reflectance only appreciably affected visual contrast in the butterflies. As such, these results support the notion that although UV reflectance is associated with intraspecific communication in butterflies, it appears to be nonfunctional in frogs. Consequently, our data highlight that we should be careful when assigning a selection-based benefit to the presence of UV reflectance.
... However, yellow models were attacked by juvenile birds at significantly lower rates compared to red models. Some studies showed that, among aposematic colours, yellow was more effective for avoidance learning than red (Lawrence and Noonan 2018), while in other studies, birds learned to avoid the red moth models considerably faster than the yellow models (Rönkä et al. 2018). We suggest that in our study, this difference between attacks on yellow and red models may be explained by the innate nature of aversive responses to yellow prey, as indicated by some experiments (Lindström et al. 1999;Hauglund et al. 2006). ...
The direction and strength of selection for prey colouration by predators vary in space and time and depend on the composition of the predator community. We tested the hypothesis that bird selection pressure on prey colouration changes through the season due to changes in the proportion of naïve juvenile individuals in the bird community, because naïve and educated birds differ in their responses to prey colours. Bird predation on caterpillar-shaped plasticine models in two boreal forest sites increased sevenfold from early summer to mid-summer, and the time of this increase coincides with the fledging of juvenile birds. In early summer, cryptic (black and green) models were attacked at fivefold higher rates compared with conspicuous (red and yellow) models. By contrast, starting from fledging time, cryptic and conspicuous models were attacked at similar rates, hinting at a lower selectivity by naïve juvenile birds compared with educated adult birds. Cryptic models exposed in a group together with conspicuous models were attacked by birds at a threefold lower rate than cryptic models exposed singly, thus supporting the aposematic commensalism hypothesis. However, this effect was not observed in mid- and late summer, presumably due to the lack of avoidance of conspicuous prey by the juvenile birds. We conclude that selection pressure on prey colouration weakens considerably when naïve birds dominate in the community, because the survival advantages of aposematic colouration are temporarily lost for both the conspicuous and their neighbouring cryptic prey.
... Moreover, as strong UV reflectance does not appear to affect predation risk in artificial targets (Lyytinen et al. 2001) or heliconiian butterflies (Finkbeiner et al. 2017), it also seems improbable that the comparatively weak UV reflectance observed in poison frogs would be an important contribution to aposematic signals. Indeed, where UV reflectance has been reported in poison frogs other color pattern combinations that lack UV have actually been found to result in greater visual contrast (Yeager and Barnett 2020), and are more likely to be avoided by avian predators (Lawrence and Noonan 2018). ...
Warning signals are often characterized by highly contrasting, distinctive and memorable colors. Both chromatic (hue) and achromatic (brightness) contrast contribute to signal efficacy, making longwave colored signals (red and yellow) that generate both chromatic and achromatic contrast common. Shortwave colors (blue and ultraviolet) do not contribute to luminance perception, yet are also common in warning signals. The presence of UV aposematic signals is paradoxical as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic butterflies and frogs. We found that UV only appreciably affected visual contrast in the butterflies. As the butterflies, but not the frogs, have UV-sensitive vision these results support the notion that UV reflectance is associated with intraspecific communication, but appears to be non-functional in frogs. Consequently, we should be careful when assigning a selection-based benefit from UV reflectance.
... In many insects, including caterpillars, aposematism is an important antipredator strategy (Poulton, 1890;Cott, 1940). Yellow (Iniesta, Ratton, & Guerra, 2016;Lawrence & Noonan, 2018), red (Sill en-Tullberg, 1985;Sv adov a et al., 2009;Wennersten & Forsman, 2009), orange or different combinations of these colours (Exnerov a et al., 2006;Carroll & Sherratt, 2013) have been reported as aposematic. Recently, a worldwide study found evidence of lower attack rates on yellow caterpillar versus other colours in temperate and cold but not in tropical climates (Zvereva et al., 2019). ...
... Colour avoidance (i.e. due to aposematism) has been noticed in previous studies Iniesta et al., 2016;Lawrence & Noonan, 2018). However, most research has focused on antipredator responses of single bird species (e.g. ...
Prey detection and selection by birds can be influenced by prey coloration. Whereas certain colours can indicate to predators the unpalatability of prey (i.e. aposematism), other colours can render prey cryptic against the background. However, there are discrepancies in the response of birds to prey coloration reported in different studies. Such discrepancies can be the result of geographical or temporal (e.g. seasonal) differences between studies if birds in different regions respond differently to coloration or if responses vary seasonally due to changes in bird composition. Experimental studies aiming to understand bird responses to prey colour should consider the effect of geographical variation while accounting for seasonal as well as interannual variability. We investigated the effects of colour on attack rates by exposing plasticine caterpillars of different colours to bird communities in 13 Mediterranean forests in central Spain for a period from 17 weeks to 7 months. Overall, yellow and green dummy caterpillars suffered the lowest attack rates. We also observed a bimodal pattern of bird attack rates through time, with highest predation occurring in late winter and summer (June to September). Low attack rates on yellow dummies are probably a consequence of aposematism, while low attack rates on green dummies probably resulted from crypsis. Rapid decreases in attack rates over time are probably a result of avoidance learning, whereas the increase in attacks in summer could be explained by the increase in fledglings and migrant birds.
... In many insects, including caterpillars, aposematism is an important antipredator strategy (Poulton, 1890;Cott, 1940). Yellow (Iniesta, Ratton, & Guerra, 2016;Lawrence & Noonan, 2018), red (Sill en-Tullberg, 1985;Sv adov a et al., 2009;Wennersten & Forsman, 2009), orange or different combinations of these colours (Exnerov a et al., 2006;Carroll & Sherratt, 2013) have been reported as aposematic. Recently, a worldwide study found evidence of lower attack rates on yellow caterpillar versus other colours in temperate and cold but not in tropical climates (Zvereva et al., 2019). ...
... Colour avoidance (i.e. due to aposematism) has been noticed in previous studies Iniesta et al., 2016;Lawrence & Noonan, 2018). However, most research has focused on antipredator responses of single bird species (e.g. ...
... The function and evolution of this diversity have been the focus of much research, and poison frog color has been variously linked to aposematism, camouflage, and sexual signaling (Crothers & Cummings, 2015;Hegna et al., 2013;Maan & Cummings, 2008;Richards-Zawacki et al., 2012;Saporito et al., 2007;Summers et al., 1999;Tazzyman & Iwasa, 2010;Willink et al., 2013;Yang et al., 2019). Curiously, however, despite the characterization of aposematic color combinations ranging from red to green, yellow to blue, and black to white, UV reflectance has so far either not been described or not discussed in poison frogs (Barnett et al., 2018;Lawrence & Noonan, 2018;Saporito et al., 2007;Summers et al., 2003), whereas it has been found in aposematic Heliconius spp. butterflies that occur in similar habitats and are exposed to similar predators (Bybee et al., 2012;Dell'Aglio et al., 2018;Finkbeiner et al., 2017). ...
... While UV signals have not been formally described in poison frogs, they have been documented incidentally. Although UV components were not considered experimentally (or perhaps simply overlooked), it is interesting to note that in Dendrobates tinctorius a population displaying UV-reflective white color patterns performed poorest in predator learning experiments when compared against other conspicuous aposematic morphs (Lawrence & Noonan, 2018). ...
Aposematic and sexual signals are often characterized by bright, highly contrasting colors. Many species can see colors beyond the human visible spectrum, and ultraviolet (UV) reflection has been found to play an important role in communication and sexual selection. However, the role of UV in aposematic signals is poorly explored. Poison frogs frequently produce high‐contrast signals that have been linked to both aposematism and intraspecific communication. Yet despite considerable efforts studying interspecific and intraspecific diversity in color, poison frogs are not known to perceive UV, and UV reflection of the integument has not been described. We report UV‐reflective spots in a population of Oophaga sylvatica and quantify the effect of UV on visual contrast with models of avian vision. We found that the frogs are highly contrasting, but UV had a minimal effect on signal saliency. These data highlight the importance of considering UV reflectance within aposematic signals, but that UV should not necessarily be regarded as an independent signal.
... Learning is demonstrated is a relatively permanent change in behaviour that is brought about due to experience. Learning is a major component or type of avian cognition and is often assessed in research into the cognitive abilities of birds (for a contemporary example see, Lawrence and Noonan, 2018). Sub-types of learning in birds include social learning (e.g., Riebel, et al, 2012), song learning (Mennill, et al, 2018; Rivera-Cáceres and Templeton, 2017). ...
Human beings have for a long time been interested in and perhaps somewhat in awe of birds. In this first chapter, I present a selective account of how we have demonstrated our interest in the world’s avifauna. The accounts I present are both personal and of a more general nature and both historical and contemporary. I start by addressing the development of my interest in birds and how this interest has changed over the years. I then continue to consider time-based changes in bird watching and the different ways that bird behaviour may be understood through different approaches. I first present such variations in relation to the study of bird song and then move on to note how identification of birds uses different criteria when undertaken through binoculars versus when the bird is in the hand of someone who is ringing the bird. As the chapter is in essence an exposition of how humans have thought about and attempted to understand birds, I then present how birds have been classified through the development of taxonomic systems. I commence this consideration of taxonomy with that developed by Aristotle followed by Pliny the Elder, Linnaeus and more contemporary accounts. My aim in this chapter is to introduce the reader to the breadth of ways in which we interact with birds, and I close by stressing this notion and by presenting a novel way in which birds and their behaviour may be studied and understood. The new approach I am suggesting is that of the mapping sentence and the declarative mapping sentence couched within the facet theory approach to research, which are briefly considered prior to deeper evaluation in the next chapter.
... Learning is demonstrated is a relatively permanent change in behaviour that is brought about due to experience. Learning is a major component or type of avian cognition and is often assessed in research into the cognitive abilities of birds (for a contemporary example see, Lawrence and Noonan, 2018). Sub-types of learning in birds include social learning (e.g., Riebel, et al, 2012), song learning (Mennill, et al, 2018; Rivera-Cáceres and Templeton, 2017). ...
In this chapter I consider the assessment of avian cognitive behaviour in the wild. Research conducted into the avian cognitive abilities of birds has typically been undertaken within the setting of a laboratory, aviary or in another setting in which external variables may be controlled. In this book, much of what I have thus far been writing about has focussed upon research into bird behaviour that occurs and has been investigated in the wild, whereby wild I mean the location in which this behaviour usually occurs. The investigation of avian cognition in the places in which it can usually be seen is a relatively new area of research. It is perhaps extraordinary that the systematic and rigorous study of avian cognition with the aim of forming a battery of tests that can assess the cognitive skills of birds is only now being addressed by researchers. A scientist who has conducted seminal work in this area is Rachael Shaw (see, (Shaw et al., Anim Behav 109:101–111, 2015)). In their innovative research, Shaw and her colleagues Neeltje Boogert, Nicky Clayton and Kevin Burns (Anim Behav 81:1209–1216, 2011) developed a test battery in order to investigate avian intelligence. The research employed a sample of New Zealand robins (Petroica longipes), to whom the scientists presented their tests in an attempt to measure their cognition-related behaviours. The arising data that was collected from the bird’s performance of the tests was analysed using principal component analysis (PCA). The present chapter is the presentation and expatiation of a reanalysis of Shaw et al.’s (Anim Behav 109:101–111, 2015) data and I expand upon an article in which Shaw et al.’s (Anim Behav 109:101–111, 2015) data was analysed by myself and colleagues using the facet theory approach and published in the International Journal of Comparative Psychology (Hackett et al., Int J Comp Psychol, 32, 2019) (It should be noted that there is overlap between the contents of this chapter and this article). As this chapter unfolds, I present a facet theory analysis of avian cognitive performance in natural situations. I report the results from the statistical technique of smallest space analysis (SSA) which largely supported the PCA of Shaw et al. (Anim Behav 109:101–111, 2015) but proposed a structural reformation of the results. I also comment upon how partial order scalogram analysis with base coordinates (POSAC or POSA) which we used to analyse the performances of individual birds. In the POSA procedure profiles were assembled of each bird’s performance on all items in the tests in the battery, and profiles were analysed to enable comments to be made regarding the pertinence of the mapping sentence’s facets and elements produced using SSA.
