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Newman BA, Dyal JR, Miller KV, Cherry MJ, D'Angelo GJ. Influence of visual perception on movement decisions by an ungulate prey species. Biol Open 2023; 12:bio059932. [PMID: 37843403 PMCID: PMC10602006 DOI: 10.1242/bio.059932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 09/01/2023] [Indexed: 10/17/2023] Open
Abstract
Visual perception is dynamic and depends on physiological properties of a species' visual system and physical characteristics of the environment. White-tailed deer (Odocoileus virginianus) are most sensitive to short- and mid-wavelength light (e.g. blue and green). Wavelength enrichment varies spatially and temporally across the landscape. We assessed how the visual perception of deer influences their movement decisions. From August to September 2019, we recorded 10-min locations from 15 GPS-collared adult male deer in Central Florida. We used Hidden-Markov models to identify periods of movement by deer and subset these data into three time periods based on temporal changes in light environments. We modeled resource selection during movement using path-selection functions and simulated 10 available paths for every path used. We developed five a priori models and used 10-fold cross validation to assess our top model's performance for each time period. During the day, deer selected to move through woodland shade, avoided forest shade, and neither selected nor avoided small gaps. At twilight, deer avoided wetlands as cloud cover increased but neither selected nor avoided other cover types. Visual cues and signals are likely more conspicuous to deer in short-wavelength-enriched woodland shade during the day, while at twilight in long-wavelength-enriched wetlands during cloud cover, visual cues are likely less conspicuous. The nocturnal light environment did not influence resource selection and likely has little effect on deer movements because it's relatively homogenous. Our findings suggest visual perception relative to light environments is likely an underappreciated driver of behaviors and decision-making by an ungulate prey species.
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Affiliation(s)
- Blaise A. Newman
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602, USA
| | - Jordan R. Dyal
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602, USA
| | - Karl V. Miller
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602, USA
| | - Michael J. Cherry
- Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, 700 University Blvd., Kingsville, TX 78363, USA
| | - Gino J. D'Angelo
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green Street, Athens, GA 30602, USA
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2
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Thomas DHN, Kjernsmo K, Scott-Samuel NE, Whitney HM, Cuthill IC. Interactions between color and gloss in iridescent camouflage. Behav Ecol 2023; 34:751-758. [PMID: 37744171 PMCID: PMC10516679 DOI: 10.1093/beheco/arad050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 05/10/2023] [Accepted: 05/25/2023] [Indexed: 09/26/2023] Open
Abstract
Iridescence is a taxonomically widespread form of structural coloration that produces often intense hues that change with the angle of viewing. Its role as a signal has been investigated in multiple species, but recently, and counter-intuitively, it has been shown that it can function as camouflage. However, the property of iridescence that reduces detectability is, as yet, unclear. As viewing angle changes, iridescent objects change not only in hue but also in intensity, and many iridescent animals are also shiny or glossy; these "specular reflections," both from the target and background, have been implicated in crypsis. Here, we present a field experiment with natural avian predators that separate the relative contributions of color and gloss to the "survival" of iridescent and non-iridescent beetle-like targets. Consistent with previous research, we found that iridescent coloration, and high gloss of the leaves on which targets were placed, enhance survival. However, glossy targets survived less well than matt. We interpret the results in terms of signal-to-noise ratio: specular reflections from the background reduce detectability by increasing visual noise. While a specular reflection from the target attracts attention, a changeable color reduces the signal because, we suggest, normally, the color of an object is a stable feature for detection and identification.
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Affiliation(s)
- Dylan H N Thomas
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Karin Kjernsmo
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Nicholas E Scott-Samuel
- School of Psychological Science, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK
| | - Heather M Whitney
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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3
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Hwang Y, Yoo S, Park C, Kang C. Comparative and experimental studies on the relationship between body size and countershading in caterpillars. J Evol Biol 2023; 36:1032-1039. [PMID: 36737844 DOI: 10.1111/jeb.14153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 10/04/2022] [Accepted: 12/14/2022] [Indexed: 02/05/2023]
Abstract
Countershading is a gradient of colouration in which the illuminated dorsal surfaces are darker than the unilluminated ventral surface. It is widespread in the animal kingdom and endows the body with a more uniform colour to decrease the chance of detection by predators. Although recent empirical studies support the theory of survival advantage conferred by countershading, this camouflage strategy has evolved only in some of the cryptic animals, and our understanding of the factors that affect the evolution of countershading is limited. This study examined the association between body size and countershading using lepidopteran larvae (caterpillars) as a model system. Specifically, we predicted that countershading may have selectively evolved in large-sized species among cryptic caterpillars if (1) large size constrains camouflage which facilitates the evolution of a trait reinforcing their crypsis and (2) the survival advantage of countershading is size-dependent. Phylogenetic analyses of four different lepidopteran families (Saturniidae, Sphingidae, Erebidae, and Geometridae) suggest equivocal results: countershading was more likely to be found in larger species in Saturniidae but not in the other families. The field predation experiment assuming avian predators did not support size-dependent predation in countershaded prey. Collectively, we found only weak evidence that body size is associated with countershading in caterpillars. Our results suggest that body size is not a universal factor that has shaped the interspecific variation in countershading observed in caterpillars.
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Affiliation(s)
- Yerin Hwang
- Department of Biosciences, Mokpo National University, Muan, South Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Sohee Yoo
- Department of Biosciences, Mokpo National University, Muan, South Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Chohee Park
- Department of Biosciences, Mokpo National University, Muan, South Korea
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
| | - Changku Kang
- Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
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4
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McLellan CF, Cuthill IC, Montgomery SH. Pattern variation is linked to anti-predator coloration in butterfly larvae. Proc Biol Sci 2023; 290:20230811. [PMID: 37357867 PMCID: PMC10291709 DOI: 10.1098/rspb.2023.0811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 06/07/2023] [Indexed: 06/27/2023] Open
Abstract
Prey animals typically try to avoid being detected and/or advertise to would-be predators that they should be avoided. Both anti-predator strategies primarily rely on colour to succeed, but the specific patterning used is also important. While the role of patterning in camouflage is relatively clear, the design features of aposematic patterns are less well understood. Here, we use a comparative approach to investigate how pattern use varies across a phylogeny of 268 species of cryptic and aposematic butterfly larvae, which also vary in social behaviour. We find that longitudinal stripes are used more frequently by cryptic larvae, and that patterns putatively linked to crypsis are more likely to be used by solitary larvae. By contrast, aposematic larvae are more likely to use horizontal bands and spots, but we find no differences in the use of individual pattern elements between solitary and gregarious aposematic species. However, solitary aposematic larvae are more likely to display multiple pattern elements, whereas those with no pattern are more likely to be gregarious. Our study advances our understanding of how pattern variation, coloration and social behaviour covary across lepidopteran larvae, and highlights new questions about how patterning affects larval detectability and predator responses to aposematic prey.
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Affiliation(s)
- Callum F. McLellan
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Innes C. Cuthill
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Stephen H. Montgomery
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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5
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Eaton MD, Benites P, Campillo L, Wilson RE, Sonsthagen SA. Gull Plumages are, and are Not, What They Appear to Human Vision. ANN ZOOL FENN 2022. [DOI: 10.5735/086.059.0116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- Muir D. Eaton
- Biology Department, 2500 University Ave, Drake University, Des Moines, Iowa 50310, USA
| | - Pilar Benites
- Museo de Zoología “Alfonso L. Herrera”, Facultad de Ciencias, Universidad Nacional Autónoma de México, Apartado Postal 70-399, Mexico City 04510, Mexico
| | - Luke Campillo
- School of Life Sciences, University of Hawai'i – Mānoa, 2538 McCarthy Mall, Honolulu, HI 96822, USA
| | - Robert E. Wilson
- National Museum of Natural History, Smithsonian Institution, 10th Street & Constitution Ave. NW, Washington, DC 20560, USA
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6
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Kelley JL, Kelley LA, Badcock DR. 3D animal camouflage. Trends Ecol Evol 2022; 37:628-631. [PMID: 35504749 DOI: 10.1016/j.tree.2022.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 04/03/2022] [Accepted: 04/04/2022] [Indexed: 11/28/2022]
Abstract
Camouflage is a fundamental way for animals to avoid detection and recognition. While depth information is critical for object detection and recognition, little is known about how camouflage patterns might interfere with the mechanisms of depth perception. We reveal how many common camouflage strategies could exploit 3D visual processing mechanisms.
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Affiliation(s)
- Jennifer L Kelley
- School of Biological Sciences and UWA Oceans Institute, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Perth, Australia.
| | - Laura A Kelley
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - David R Badcock
- School of Psychological Sciences, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Perth, Australia
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7
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Kim SU, Lee YJ, Liu J, Kim DS, Wang H, Yang S. Broadband and pixelated camouflage in inflating chiral nematic liquid crystalline elastomers. NATURE MATERIALS 2022; 21:41-46. [PMID: 34489567 DOI: 10.1038/s41563-021-01075-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 07/07/2021] [Indexed: 05/24/2023]
Abstract
Living organisms such as fishes1, cephalopods2 and clams3 are cryptically coloured with a wide range of hues and patterns for camouflage, signalling or energy regulation. Despite extensive efforts to create colour-changing materials and devices4, it is challenging to achieve pixelated structural coloration with broadband spectral shifts in a compact space. Here, we describe pneumatically inflating thin membranes of main-chain chiral nematic liquid crystalline elastomers that have such properties. By taking advantage of the large elasticity anisotropy and Poisson's ratio (>0.5) of these materials, we geometrically program the size and the layout of the encapsulated air channels to achieve colour shifting from near-infrared to ultraviolet wavelengths with less than 20% equi-biaxial transverse strain. Each channel can be individually controlled as a colour 'pixel' to match with surroundings, whether periodically or irregularly patterned. These soft materials may find uses in distinct applications such as cryptography, adaptive optics and soft robotics.
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Affiliation(s)
- Se-Um Kim
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Young-Joo Lee
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Jiaqi Liu
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Dae Seok Kim
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
- Department of Polymer Engineering, Pukyong National University, Busan, South Korea
| | - Haihuan Wang
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Shu Yang
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
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8
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McLellan CF, Scott-Samuel NE, Cuthill IC. Birds learn to avoid aposematic prey by using the appearance of host plants. Curr Biol 2021; 31:5364-5369.e4. [PMID: 34624210 DOI: 10.1016/j.cub.2021.09.048] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/23/2021] [Accepted: 09/17/2021] [Indexed: 11/30/2022]
Abstract
The conspicuous warning signal of aposematic animals is learned by their predators, and the resulting avoidance benefits both parties.1-4 Given evidence that birds can distinguish the profitability of prey from the environmental context in which they appear,5 aposematic insects' host plants might also provide an important cue to foraging predators.6 The aposematic cinnabar moth (Tyria jacobaeae) larva is a specialist on its ragwort (Senecio spp.) host plant,7 presenting a consistent environment with which it could be reliably associated. Additionally, ragwort's defensive toxins prevent non-specialist, profitable insects from feeding on it.8 Thus, avian predators may recognize cues from ragwort, most likely its conspicuous yellow flowers,9,10 and use this information to avoid cinnabars. To test this hypothesis, we exposed artificial cinnabar and non-signaling "caterpillar" targets to wild avian predation by presenting them on ragwort and non-toxic host plants. We also manipulated the presence or absence of ragwort flowers on hosts. In doing so, we show that both targets are better protected on the cinnabar's natural ragwort host and that birds use ragwort's distinctive yellow flowers as the cue to avoidance. Additionally, we found that naive predators do not make prey host foraging distinctions, indicating that this avoidance behavior is learned through experience. Our findings are among the first to suggest that a host plant's features act as an extended phenotype that signals the toxicity of the prey that live on it. This prey-host relationship may facilitate the initial evolution of toxicity in non-signaling prey, but also inhibit the evolution of aposematic signals themselves. VIDEO ABSTRACT.
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Affiliation(s)
| | | | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, Bristol, UK
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9
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Mavrovouna V, Penacchio O, Allen WL. Orienting to the sun improves camouflage for bilaterally symmetrical prey. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blab130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Here, we investigate the camouflage consequences of animal orientation behaviour. Shadows can be a conspicuous cue to the presence of prey. For bilaterally symmetrical animals, light field modelling indicates that camouflage will be improved when an animal orients its longitudinal axis directly towards or away from the sun, because the appearance of shadows is minimized. We test this prediction with a field predation experiment, in which wild birds hunt for artificial camouflaged prey oriented with the longitudinal axis either parallel or perpendicular to the sun. We find that prey oriented parallel to the sun are 3.93 times more likely to survive than prey oriented perpendicular to the sun. This result demonstrates the strong orientation dependence of camouflage. Given the dramatic difference in survival of prey with different orientations, we suggest that camouflage should be investigated as an important determinant of the positional behaviour of animals.
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Affiliation(s)
- Veronica Mavrovouna
- Department of Biosciences, Swansea University, Singleton Campus, Swansea SA2 8PP, UK
| | - Olivier Penacchio
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews, Fife KY16 9JP, UK
| | - William L Allen
- Department of Biosciences, Swansea University, Singleton Campus, Swansea SA2 8PP, UK
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10
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Tan EJ, Elgar MA. Motion: enhancing signals and concealing cues. Biol Open 2021; 10:271863. [PMID: 34414408 PMCID: PMC8411570 DOI: 10.1242/bio.058762] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 07/02/2021] [Indexed: 01/15/2023] Open
Abstract
Animal colour patterns remain a lively focus of evolutionary and behavioural ecology, despite the considerable conceptual and technical developments over the last four decades. Nevertheless, our current understanding of the function and efficacy of animal colour patterns remains largely shaped by a focus on stationary animals, typically in a static background. Yet, this rarely reflects the natural world: most animals are mobile in their search for food and mates, and their surrounding environment is usually dynamic. Thus, visual signalling involves not only animal colour patterns, but also the patterns of animal motion and behaviour, often in the context of a potentially dynamic background. While motion can reveal information about the signaller by attracting attention or revealing signaller attributes, motion can also be a means of concealing cues, by reducing the likelihood of detection (motion camouflage, motion masquerade and flicker-fusion effect) or the likelihood of capture following detection (motion dazzle and confusion effect). The interaction between the colour patterns of the animal and its local environment is further affected by the behaviour of the individual. Our review details how motion is intricately linked to signalling and suggests some avenues for future research. This Review has an associated Future Leader to Watch interview with the first author. Summary: While motion can reveal information about the signaller, motion can also be a means of concealing cues by reducing the likelihood of detection or the likelihood of capture following detection.
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Affiliation(s)
- Eunice J Tan
- Division of Science, Yale-NUS College, Singapore 138527, Singapore
| | - Mark A Elgar
- School of BioSciences, University of Melbourne, Melbourne, Victoria 3010, Australia
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11
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Caro T, Brockelsby K, Ferrari A, Koneru M, Ono K, Touche E, Stankowich T. The evolution of primate coloration revisited. Behav Ecol 2021. [DOI: 10.1093/beheco/arab029] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Abstract
Primates are noted for their varied and complex pelage and bare skin coloration but the significance of this diverse coloration remains opaque. Using new updated information, novel scoring of coat and skin coloration, and controlling for shared ancestry, we reexamined and extended findings from previous studies across the whole order and the five major clades within it. Across primates, we found (i) direct and indirect evidence for pelage coloration being driven by protective coloration strategies including background matching, countershading, disruptive coloration, and aposematism, (ii) diurnal primates being more colorful, and (iii) the possibility that pelage color diversity is negatively associated with female trichromatic vision; while (iv) reaffirming avoidance of hybridization driving head coloration in males, (v) darker species living in warm, humid conditions (Gloger’s rule), and (vi) advertising to multiple mating partners favoring red genitalia in females. Nonetheless, the importance of these drivers varies greatly across clades. In strepsirrhines and cercopithecoids, countershading is important; greater color diversity may be important for conspecific signaling in more diurnal and social strepsirrhines; lack of female color vision may be associated with colorful strepsirrhines and platyrrhines; whereas cercopithecoids obey Gloger’s rule. Haplorrhines show background matching, aposematism, character displacement, and red female genitalia where several mating partners are available. Our findings emphasize several evolutionary drivers of coloration in this extraordinarily colorful order. Throughout, we used coarse but rigorous measures of coloration, and our ability to replicate findings from earlier studies opens up opportunities for classifying coloration of large numbers of species at a macroevolutionary scale.
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Affiliation(s)
- Tim Caro
- Department of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- Center for Population Biology, University of California, 1 Shields Avenue, Davis, Davis, CA 95616, USA
| | - Kasey Brockelsby
- Department of Evolution and Ecology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Annie Ferrari
- Department of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Manisha Koneru
- Department of Evolution and Ecology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Konatsu Ono
- Department of Animal Biology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Edward Touche
- Department of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Theodore Stankowich
- Department of Biological Sciences, California State University, 1250 Bellflower Boulevard, Long Beach, CA 90840, USA
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12
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Echeverri SA, Miller AE, Chen J, McQueen EW, Plakke M, Spicer M, Hoke KL, Stoddard MC, Morehouse NI. How signaling geometry shapes the efficacy and evolution of animal communication systems. Integr Comp Biol 2021; 61:787-813. [PMID: 34021338 DOI: 10.1093/icb/icab090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Animal communication is inherently spatial. Both signal transmission and signal reception have spatial biases-involving direction, distance and position-that interact to determine signaling efficacy. Signals, be they visual, acoustic, or chemical, are often highly directional. Likewise, receivers may only be able to detect signals if they arrive from certain directions. Alignment between these directional biases is therefore critical for effective communication, with even slight misalignments disrupting perception of signaled information. In addition, signals often degrade as they travel from signaler to receiver, and environmental conditions that impact transmission can vary over even small spatiotemporal scales. Thus, how animals position themselves during communication is likely to be under strong selection. Despite this, our knowledge regarding the spatial arrangements of signalers and receivers during communication remains surprisingly coarse for most systems. We know even less about how signaler and receiver behaviors contribute to effective signaling alignment over time, or how signals themselves may have evolved to influence and/or respond to these aspects of animal communication. Here, we first describe why researchers should adopt a more explicitly geometric view of animal signaling, including issues of location, direction, and distance. We then describe how environmental and social influences introduce further complexities to the geometry of signaling. We discuss how multimodality offers new challenges and opportunities for signalers and receivers. We conclude with recommendations and future directions made visible by attention to the geometry of signaling.
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Affiliation(s)
| | - Audrey E Miller
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ
| | - Jason Chen
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biology, Emory University, Atlanta, GA
| | - Eden W McQueen
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Melissa Plakke
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS
| | - Michelle Spicer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Biology Department, University of Puget Sound, Tacoma, WA
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, CO
| | | | - Nathan I Morehouse
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biological Sciences, University of Cincinnati, Cincinnati, OH
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13
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Imada Y. Moss mimesis par excellence: integrating previous and new data on the life history and larval ecomorphology of long-bodied craneflies (Diptera: Cylindrotomidae: Cylindrotominae). Zool J Linn Soc 2020. [DOI: 10.1093/zoolinnean/zlaa177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Different physical structures play a central role in animal camouflage. However, in evolutionary studies of mimicry, the ecological and evolutionary significance of such structures has been poorly investigated. Larvae of long-bodied craneflies, Cylindrotominae, are all obligate herbivores and resemble plants. They are distinctively characterized by possessing numerous elongated cuticular lobes on the integument. A comprehensive overview of the biology and morphology of cylindrotomids, particularly their larval stages, is laid out, providing original data on nine species. To explore the ecological background of moss resemblance, host-plants of most examined species are clarified, revealing that terrestrial moss-feeding species tend to use specific groups of mosses, either belonging to Bryales or Hypnales. However, the evolution of cryptic forms remains paradoxical, due to the apparent absence of visual predators. Based on histological examinations, extensive internal musculatures within the cuticular lobes on the lateral side are discovered, shedding new light on their function in locomotion. Traditional functional explanations for these lobes, particularly as devices for respiration, locomotion and attachment, are challenged. This study promotes our understanding of the ecomorphology of mimicry devices, which is an angle often dismissed in evolutionary studies of mimicry.
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Affiliation(s)
- Yume Imada
- Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime, Japan
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14
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Caro T, Koneru M. Towards an ecology of protective coloration. Biol Rev Camb Philos Soc 2020; 96:611-641. [PMID: 33258554 DOI: 10.1111/brv.12670] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 11/05/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022]
Abstract
The strategies underlying different forms of protective coloration are well understood but little attention has been paid to the ecological, life-history and behavioural circumstances under which they evolve. While some comparative studies have investigated the ecological correlates of aposematism, and background matching, the latter particularly in mammals, few have examined the ecological correlates of other types of protective coloration. Here, we first outline which types of defensive coloration strategies may be exhibited by the same individual; concluding that many protective coloration mechanisms can be employed simultaneously, particularly in conjunction with background matching. Second, we review the ecological predictions that have been made for each sort of protective coloration mechanism before systematically surveying phylogenetically controlled comparative studies linking ecological and social variables to antipredator defences that involve coloration. We find that some a priori predictions based on small-scale empirical studies and logical arguments are indeed supported by comparative data, especially in relation to how illumination affects both background matching and self-shadow concealment through countershading; how body size is associated with countershading, motion dazzle, flash coloration and aposematism, although only in selected taxa; how immobility may promote background matching in ambush predators; and how mobility may facilitate motion dazzle. Examination of nearly 120 comparative tests reveals that many focus on ecological variables that have little to do with predictions derived from antipredator defence theory, and that broad-scale ecological studies of defence strategies that incorporate phylogenetics are still very much in their infancy. We close by making recommendations for future evolutionary ecological research.
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Affiliation(s)
- Tim Caro
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, U.K.,Center for Population Biology, University of California, Davis, CA, 95616, U.S.A
| | - Manisha Koneru
- Department of Evolution and Ecology, University of California, Davis, CA, 95616, U.S.A
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15
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Galloway JAM, Green SD, Stevens M, Kelley LA. Finding a signal hidden among noise: how can predators overcome camouflage strategies? Philos Trans R Soc Lond B Biol Sci 2020; 375:20190478. [PMID: 32420842 PMCID: PMC7331011 DOI: 10.1098/rstb.2019.0478] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Substantial progress has been made in the past 15 years regarding how prey use a variety of visual camouflage types to exploit both predator visual processing and cognition, including background matching, disruptive coloration, countershading and masquerade. By contrast, much less attention has been paid to how predators might overcome these defences. Such strategies include the evolution of more acute senses, the co-opting of other senses not targeted by camouflage, changes in cognition such as forming search images, and using behaviours that change the relationship between the cryptic individual and the environment or disturb prey and cause movement. Here, we evaluate the methods through which visual camouflage prevents detection and recognition, and discuss if and how predators might evolve, develop or learn counter-adaptations to overcome these. This article is part of the theme issue ‘Signal detection theory in recognition systems: from evolving models to experimental tests'.
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Affiliation(s)
- James A M Galloway
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall TR10 9FE, UK
| | - Samuel D Green
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall TR10 9FE, UK
| | - Martin Stevens
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall TR10 9FE, UK
| | - Laura A Kelley
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall TR10 9FE, UK
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16
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Donohue CG, Hemmi JM, Kelley JL. Countershading enhances camouflage by reducing prey contrast. Proc Biol Sci 2020; 287:20200477. [PMID: 32396802 DOI: 10.1098/rspb.2020.0477] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A three-dimensional body shape is problematic for camouflage because overhead lighting produces a luminance gradient across the body's surface. Countershading, a form of patterning where animals are darkest on their uppermost surface, is thought to counteract this luminance gradient and enhance concealment, but the mechanisms of protection remain unclear. Surprisingly, no study has examined how countershading alters prey contrast, or investigated how the presence of a dorsoventral luminance gradient affects detection under controlled viewing conditions. It has also been suggested that the direction of the dorsoventral luminance gradient (darkest or lightest on top) may interfere with predators' abilities to resolve prey's three-dimensional shape, yet this intriguing idea has never been tested. We used live fish predators (western rainbowfish, Melanotaenia australis) and computer-generated prey images to compare the detectability of uniformly pigmented (i.e. non-countershaded) prey with that of optimally countershaded prey of varying contrasts against the background. Optimally countershaded prey were difficult for predators to detect, and the probability and speed of detection depended on prey luminance contrast with the background. In comparison, non-countershaded prey were always highly detectable, even though their average luminance closely matched the luminance of the background. Our findings suggest that uniformly pigmented three-dimensional prey are highly conspicuous to predators because overhead lighting increases luminance contrast between different body parts or between the body and the background. We found no evidence for the notion that countershading interferes with predator perception of three-dimensional form.
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Affiliation(s)
- Callum G Donohue
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Jan M Hemmi
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia 6009, Australia.,The UWA Oceans Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Jennifer L Kelley
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia 6009, Australia.,The UWA Oceans Institute, The University of Western Australia, Crawley, Western Australia 6009, Australia
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17
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de Souza AR, Mayorquin AZ, Sarmiento CE. Paper wasps are darker at high elevation. J Therm Biol 2020; 89:102535. [PMID: 32364980 DOI: 10.1016/j.jtherbio.2020.102535] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 01/21/2020] [Accepted: 02/09/2020] [Indexed: 11/15/2022]
Abstract
High mountains are harsh environments in which colder temperatures and higher levels of UV-B radiation are common. These abiotic conditions strongly affect animals' biology, often constraining their survival and reproduction. As a result, adaptations to live in such habitats are expected to evolve. Body color is thought to be adaptive to the environment that animals experience. Tegument melanization improves heat gain and provides photoprotection. Therefore, at high elevation, ectotherms are expected to be darker (well-melanized). We test this prediction in the paper wasp Agelaia pallipes (Hymenoptera: Vespidae), a species distributed across an elevational gradient in the Colombian Andes. We used Malaise traps and sampled a total of 146 wasps along nine elevations, ranging from 2,600-3,380 m above sea level. Standard digital photography was used to measure the body luminance and colour patterning in different body parts of dry-preserved specimens. There was striking variation in body luminance (darker and lighter), color patterning (patched, smoothed, homogeneous) and surface texture (shiny and matte), but the kind and degree of variation depended on the body part examined. Wasps from higher elevations had darker thoraces, confirming our prediction. Besides, at high elevation, the frequency of wasps with a matte rather than a shiny face strongly increased. Overall, our findings support the thermal melanism hypothesis and suggest that intraspecific color variation might be an adaptation to the environment of paper wasps.
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Affiliation(s)
- André R de Souza
- Departamento de Biologia, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901, São Paulo, Brazil.
| | - Angie Z Mayorquin
- Universidad Nacional de Colombia, Instituto de Ciencias Naturales, Cr 30 No. 45 03 edif 425, of. 303, Bogotá, Colombia.
| | - Carlos E Sarmiento
- Universidad Nacional de Colombia, Instituto de Ciencias Naturales, Cr 30 No. 45 03 edif 425, of. 303, Bogotá, Colombia.
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18
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Affiliation(s)
- I. C. Cuthill
- School of Biological Sciences University of Bristol Bristol UK
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19
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Hughes A, Liggins E, Stevens M. Imperfect camouflage: how to hide in a variable world? Proc Biol Sci 2019; 286:20190646. [PMID: 31088268 PMCID: PMC6532520 DOI: 10.1098/rspb.2019.0646] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/25/2019] [Indexed: 12/12/2022] Open
Abstract
Camouflage is an important anti-predator strategy for many animals and is traditionally thought of as being tightly linked to a specific visual background. While much work focuses on optimizing camouflage against one background, this may not be relevant for many species and contexts, as animals may encounter many different habitats throughout their lives due to temporal and spatial variation in their environment. How should camouflage be optimized when an animal or object is seen against multiple visual backgrounds? Various solutions may exist, including colour change to match new environments or use of behaviour to maintain crypsis by choosing appropriate substrates. Here, we focus on a selection of approaches under a third alternative strategy: animals may adopt (over evolution) camouflage appearances that represent an optimal solution against multiple visual scenes. One approach may include a generalist or compromise strategy, where coloration matches several backgrounds to some extent, but none closely. A range of other camouflage types, including disruptive camouflage, may also provide protection in multiple environments. Despite detailed theoretical work determining the plausibility of compromise camouflage and elucidating the conditions under which it might evolve, there is currently mixed experimental evidence supporting its value and little evidence of it in natural systems. In addition, there remain many questions including how camouflage strategies should be defined and optimized, and how they might interact with other types of crypsis and defensive markings. Overall, we provide a critical overview of our current knowledge about how camouflage can enable matching to multiple backgrounds, discuss important challenges of working on this question and make recommendations for future research.
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Affiliation(s)
- Anna Hughes
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
| | - Eric Liggins
- QinetiQ, Cody Technology Park, Ively Road, Farnborough, Hampshire GU14 0LX, UK
| | - Martin Stevens
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
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20
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Brunyé TT, Martis SB, Kirejczyk JA, Rock K. Camouflage pattern features interact with movement speed to determine human target detectability. APPLIED ERGONOMICS 2019; 77:50-57. [PMID: 30832778 DOI: 10.1016/j.apergo.2019.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 11/19/2018] [Accepted: 01/20/2019] [Indexed: 06/09/2023]
Abstract
Applied ergonomics research examines not only the fit, form and function of military uniforms, but also their ability to effectively camouflage personnel as they perform job-related tasks. Many of these job-related tasks involve moving through environments, but existing literature examining camouflage effectiveness often assumes that movement effectively "breaks" even the best camouflage patterns, rendering them of limited utility for reducing the visual signature of a moving target. However, recent research demonstrates that animals equipped with adaptive camouflage change their patterning in predictable ways during movement and this adaptation decreases detectability, suggesting that uniform patterning may still hold value for reducing conspicuity during movement. The present experiment examined whether three visual pattern characteristics, local contrast, orientation, and spatial frequency, would influence the detectability of a moving human target. Participants attempted to detect and localize a simulated human target moving across a background scene, and a factorial design varied target movement speed, and the local contrast, spatial frequency, and orientation of its camouflage patterning. Results showed that target detectability was strongly influenced by target movement rate, pattern local contrast, and pattern spatial frequency, and these effects persisted even under conditions of very fast movement. Importantly, we found that the effect of local contrast was most robust under conditions of movement, suggesting its importance for reducing detectability of moving personnel. We conclude that movement is not always sufficient to break the concealment offered by a pattern with low contrast and a spatial frequency match with its background. Results are discussed in the context of visual processing theories and the application of these findings to the design and development of static and adaptive camouflage patterns for military personnel.
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Affiliation(s)
- Tad T Brunyé
- Center for Applied Brain and Cognitive Sciences, Medford, MA, USA; U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, USA; Tufts University, Department of Psychology, Medford, MA, USA.
| | - Shaina B Martis
- Center for Applied Brain and Cognitive Sciences, Medford, MA, USA
| | - John A Kirejczyk
- U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, USA
| | - Kathryn Rock
- U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, USA
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21
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Smith CCD, Layloo I, Maritz RA, Maritz B. Sexual dichromatism does not translate into sex‐based difference in morphology or diet for the African boomslang. J Zool (1987) 2019. [DOI: 10.1111/jzo.12670] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- C. C. D. Smith
- Department of Biodiversity and Conservation Biology University of the Western Cape Bellville South Africa
| | - I. Layloo
- Department of Biodiversity and Conservation Biology University of the Western Cape Bellville South Africa
| | - R. A. Maritz
- Department of Biodiversity and Conservation Biology University of the Western Cape Bellville South Africa
| | - B. Maritz
- Department of Biodiversity and Conservation Biology University of the Western Cape Bellville South Africa
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22
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Stevens M, Ruxton GD. The key role of behaviour in animal camouflage. Biol Rev Camb Philos Soc 2019; 94:116-134. [PMID: 29927061 PMCID: PMC6378595 DOI: 10.1111/brv.12438] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 01/24/2023]
Abstract
Animal camouflage represents one of the most important ways of preventing (or facilitating) predation. It attracted the attention of the earliest evolutionary biologists, and today remains a focus of investigation in areas ranging from evolutionary ecology, animal decision-making, optimal strategies, visual psychology, computer science, to materials science. Most work focuses on the role of animal morphology per se, and its interactions with the background in affecting detection and recognition. However, the behaviour of organisms is likely to be crucial in affecting camouflage too, through background choice, body orientation and positioning; and strategies of camouflage that require movement. A wealth of potential mechanisms may affect such behaviours, from imprinting and self-assessment to genetics, and operate at several levels (species, morph, and individual). Over many years there have been numerous studies investigating the role of behaviour in camouflage, but to date, no effort to synthesise these studies and ideas into a coherent framework. Here, we review key work on behaviour and camouflage, highlight the mechanisms involved and implications of behaviour, discuss the importance of this in a changing world, and offer suggestions for addressing the many important gaps in our understanding of this subject.
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Affiliation(s)
- Martin Stevens
- Centre for Ecology and Conservation, College of Life and Environmental SciencesUniversity of Exeter, Penryn CampusPenryn, TR10 9FEU.K.
| | - Graeme D. Ruxton
- School of BiologyUniversity of St AndrewsSt Andrews, KY16 9THU.K.
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23
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Brunyé TT, Martis SB, Horner C, Kirejczyk JA, Rock K. Visual salience and biological motion interact to determine camouflaged target detectability. APPLIED ERGONOMICS 2018; 73:1-6. [PMID: 30098624 DOI: 10.1016/j.apergo.2018.05.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/23/2018] [Accepted: 05/31/2018] [Indexed: 06/08/2023]
Abstract
Target visual salience and biological motion independently influence the accuracy and latency of observer detection. However, it is currently unknown how these target parameters might interact in modulating the detectability of camouflaged human targets. In two experiments, observers performed a visual target detection task. In a pilot experiment, observers detected a static human target with parametrically varied visual salience, superimposed on a complex background scene. As expected, results demonstrated varied target detectability as a function of salience, with observers showing higher hit rates and faster response times as a function of increased salience. In the Main Experiment, observers detected simulated human targets walking across a complex scene at five different speeds and three different levels of visual salience (as validated in the pilot experiment). We found strong effects of both movement rate and visual salience, and the two parameters interacted. Specifically, increasing the rate of biological motion increased detectability for even the least salient camouflage patterns. In other words, biological motion can "break" even the least conspicuous camouflage pattern. In contrast, a very salient pattern was highly detectable under static and moving conditions. Results are considered in relation to theories of camouflage detectability, and trade-offs between camouflage development efforts versus advanced training in military maneuvering.
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Affiliation(s)
- Tad T Brunyé
- Center for Applied Brain and Cognitive Sciences, Medford, MA, United States; U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, United States; Tufts University, Department of Psychology, Medford, MA, United States.
| | - Shaina B Martis
- Center for Applied Brain and Cognitive Sciences, Medford, MA, United States
| | - Carlene Horner
- Center for Applied Brain and Cognitive Sciences, Medford, MA, United States
| | - John A Kirejczyk
- U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, United States
| | - Kathryn Rock
- U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, United States
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24
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Nityananda V, Read JCA. Stereopsis in animals: evolution, function and mechanisms. ACTA ACUST UNITED AC 2018; 220:2502-2512. [PMID: 28724702 PMCID: PMC5536890 DOI: 10.1242/jeb.143883] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Stereopsis is the computation of depth information from views acquired simultaneously from different points in space. For many years, stereopsis was thought to be confined to primates and other mammals with front-facing eyes. However, stereopsis has now been demonstrated in many other animals, including lateral-eyed prey mammals, birds, amphibians and invertebrates. The diversity of animals known to have stereo vision allows us to begin to investigate ideas about its evolution and the underlying selective pressures in different animals. It also further prompts the question of whether all animals have evolved essentially the same algorithms to implement stereopsis. If so, this must be the best way to do stereo vision, and should be implemented by engineers in machine stereopsis. Conversely, if animals have evolved a range of stereo algorithms in response to different pressures, that could inspire novel forms of machine stereopsis appropriate for distinct environments, tasks or constraints. As a first step towards addressing these ideas, we here review our current knowledge of stereo vision in animals, with a view towards outlining common principles about the evolution, function and mechanisms of stereo vision across the animal kingdom. We conclude by outlining avenues for future work, including research into possible new mechanisms of stereo vision, with implications for machine vision and the role of stereopsis in the evolution of camouflage. Summary: Stereopsis has evolved independently in different animals. We review the various functions it serves and the variety of mechanisms that could underlie stereopsis in different species.
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Affiliation(s)
- Vivek Nityananda
- Wissenschaftskolleg zu Berlin, Institute for Advanced Study, Wallotstraße 19, Berlin 14193, Germany .,Newcastle University, Institute of Neuroscience, Henry Wellcome Building, Framlington Place, Newcastle Upon Tyne NE2 4HH, UK
| | - Jenny C A Read
- Newcastle University, Institute of Neuroscience, Henry Wellcome Building, Framlington Place, Newcastle Upon Tyne NE2 4HH, UK
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25
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Niu Y, Sun H, Stevens M. Plant Camouflage: Ecology, Evolution, and Implications. Trends Ecol Evol 2018; 33:608-618. [DOI: 10.1016/j.tree.2018.05.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 05/24/2018] [Accepted: 05/29/2018] [Indexed: 11/15/2022]
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26
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Penacchio O, Lovell PG, Harris JM. Is countershading camouflage robust to lighting change due to weather? ROYAL SOCIETY OPEN SCIENCE 2018; 5:170801. [PMID: 29515822 PMCID: PMC5830711 DOI: 10.1098/rsos.170801] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 12/11/2017] [Indexed: 05/16/2023]
Abstract
Countershading is a pattern of coloration thought to have evolved in order to implement camouflage. By adopting a pattern of coloration that makes the surface facing towards the sun darker and the surface facing away from the sun lighter, the overall amount of light reflected off an animal can be made more uniformly bright. Countershading could hence contribute to visual camouflage by increasing background matching or reducing cues to shape. However, the usefulness of countershading is constrained by a particular pattern delivering 'optimal' camouflage only for very specific lighting conditions. In this study, we test the robustness of countershading camouflage to lighting change due to weather, using human participants as a 'generic' predator. In a simulated three-dimensional environment, we constructed an array of simple leaf-shaped items and a single ellipsoidal target 'prey'. We set these items in two light environments: strongly directional 'sunny' and more diffuse 'cloudy'. The target object was given the optimal pattern of countershading for one of these two environment types or displayed a uniform pattern. By measuring detection time and accuracy, we explored whether and how target detection depended on the match between the pattern of coloration on the target object and scene lighting. Detection times were longest when the countershading was appropriate to the illumination; incorrectly camouflaged targets were detected with a similar pattern of speed and accuracy to uniformly coloured targets. We conclude that structural changes in light environment, such as caused by differences in weather, do change the effectiveness of countershading camouflage.
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Affiliation(s)
- Olivier Penacchio
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife KY16 9JP, UK
| | - P. George Lovell
- Division of Psychology, Social and Health Sciences, Abertay University, Dundee DD1 1HG, UK
| | - Julie M. Harris
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife KY16 9JP, UK
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27
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Smithwick FM, Nicholls R, Cuthill IC, Vinther J. Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous Habitats in the Early Cretaceous Jehol Biota. Curr Biol 2017; 27:3337-3343.e2. [PMID: 29107548 DOI: 10.1016/j.cub.2017.09.032] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 08/14/2017] [Accepted: 09/14/2017] [Indexed: 11/26/2022]
Abstract
Countershading is common across a variety of lineages and ecological time [1-4]. A dark dorsum and lighter ventrum helps to mask the three-dimensional shape of the body by reducing self-shadowing and decreasing conspicuousness, thus helping to avoid detection by predators and prey [1, 2, 4, 5]. The optimal countershading pattern is dictated by the lighting environment, which is in turn dependent upon habitat [1, 3, 5, 6]. With the discovery of fossil melanin [7, 8], it is possible to infer original color patterns from fossils, including countershading [3, 9, 10]. Applying these principles, we describe the pattern of countershading in the diminutive theropod dinosaur Sinosauropteryx from the Early Cretaceous Jehol Biota of Liaoning, China. From reconstructions based on exceptional fossils, the color pattern is compared to predicted optimal countershading transitions based on 3D reconstructions of the animal's abdomen, imaged in different lighting environments. Reconstructed patterns match well with those predicted for animals living in open habitats. Jehol is presumed to have been a predominantly closed forested environment [3, 11, 12], but our results indicate a more heterogeneous range of habitats. Sinosauropteryx is also shown to exhibit a "bandit mask," a common pattern in many living vertebrates, particularly birds, that serves multiple functions including camouflage [13-18]. Sinosauropteryx therefore shows multiple color pattern features likely related to the habitat in which it lived. Our results show how reconstructing the color of extinct animals can inform on their ecologies beyond what may be obvious from skeletal remains alone. VIDEO ABSTRACT.
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Affiliation(s)
- Fiann M Smithwick
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
| | - Robert Nicholls
- Palaeocreations, 35 Hopps Road, Kingswood, Bristol BS15 9QQ, UK
| | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Jakob Vinther
- School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK; School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
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28
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Penacchio O, Harris JM, Lovell PG. Establishing the behavioural limits for countershaded camouflage. Sci Rep 2017; 7:13672. [PMID: 29057907 PMCID: PMC5651847 DOI: 10.1038/s41598-017-13914-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/20/2017] [Indexed: 11/09/2022] Open
Abstract
Countershading is a ubiquitous patterning of animals whereby the side that typically faces the highest illumination is darker. When tuned to specific lighting conditions and body orientation with respect to the light field, countershading minimizes the gradient of light the body reflects by counterbalancing shadowing due to illumination, and has therefore classically been thought of as an adaptation for visual camouflage. However, whether and how crypsis degrades when body orientation with respect to the light field is non-optimal has never been studied. We tested the behavioural limits on body orientation for countershading to deliver effective visual camouflage. We asked human participants to detect a countershaded target in a simulated three-dimensional environment. The target was optimally coloured for crypsis in a reference orientation and was displayed at different orientations. Search performance dramatically improved for deviations beyond 15 degrees. Detection time was significantly shorter and accuracy significantly higher than when the target orientation matched the countershading pattern. This work demonstrates the importance of maintaining body orientation appropriate for the displayed camouflage pattern, suggesting a possible selective pressure for animals to orient themselves appropriately to enhance crypsis.
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Affiliation(s)
- Olivier Penacchio
- School of Psychology and Neuroscience, University of St. Andrews, St. Andrews, Fife KY16 9JP, UK.
| | - Julie M Harris
- School of Psychology and Neuroscience, University of St. Andrews, St. Andrews, Fife KY16 9JP, UK
| | - P George Lovell
- Division of Psychology, Social and Health Sciences, Abertay University, Dundee, DD1 1HG, UK
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29
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Kelley JL, Taylor I, Hart NS, Partridge JC. Aquatic prey use countershading camouflage to match the visual background. Behav Ecol 2017. [DOI: 10.1093/beheco/arx093] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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