1
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Tan M, Zhang S, Stevens M, Li D, Tan EJ. Antipredator defences in motion: animals reduce predation risks by concealing or misleading motion signals. Biol Rev Camb Philos Soc 2024; 99:778-796. [PMID: 38174819 DOI: 10.1111/brv.13044] [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: 12/06/2022] [Revised: 12/13/2023] [Accepted: 12/15/2023] [Indexed: 01/05/2024]
Abstract
Motion is a crucial part of the natural world, yet our understanding of how animals avoid predation whilst moving remains rather limited. Although several theories have been proposed for how antipredator defence may be facilitated during motion, there is often a lack of supporting empirical evidence, or conflicting findings. Furthermore, many studies have shown that motion often 'breaks' camouflage, as sudden movement can be detected even before an individual is recognised. Whilst some static camouflage strategies may conceal moving animals to a certain extent, more emphasis should be given to other modes of camouflage and related defences in the context of motion (e.g. flicker fusion camouflage, active motion camouflage, motion dazzle, and protean motion). Furthermore, when motion is involved, defence strategies are not necessarily limited to concealment. An animal can also rely on motion to mislead predators with regards to its trajectory, location, size, colour pattern, or even identity. In this review, we discuss the various underlying antipredator strategies and the mechanisms through which they may be linked to motion, conceptualising existing empirical and theoretical studies from two perspectives - concealing and misleading effects. We also highlight gaps in our understanding of these antipredator strategies, and suggest possible methodologies for experimental designs/test subjects (i.e. prey and/or predators) and future research directions.
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Affiliation(s)
- Min Tan
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore
| | - Shichang Zhang
- Centre for Behavioural Ecology & Evolution, State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, Hubei, China
| | - Martin Stevens
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK
| | - Daiqin Li
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore
- Centre for Behavioural Ecology & Evolution, State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, Hubei, China
| | - Eunice J Tan
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore
- Division of Science, Yale-NUS College, 16 College Avenue West, Singapore, 138527, Singapore
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2
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Henríquez-Piskulich P, Stuart-Fox D, Elgar M, Marusic I, Franklin AM. Dazzled by shine: gloss as an antipredator strategy in fast moving prey. Behav Ecol 2023; 34:862-871. [PMID: 37744168 PMCID: PMC10516678 DOI: 10.1093/beheco/arad046] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 03/06/2023] [Accepted: 05/23/2023] [Indexed: 09/26/2023] Open
Abstract
Previous studies on stationary prey have found mixed results for the role of a glossy appearance in predator avoidance-some have found that glossiness can act as warning coloration or improve camouflage, whereas others detected no survival benefit. An alternative untested hypothesis is that glossiness could provide protection in the form of dynamic dazzle. Fast moving animals that are glossy produce flashes of light that increase in frequency at higher speeds, which could make it harder for predators to track and accurately locate prey. We tested this hypothesis by presenting praying mantids with glossy or matte targets moving at slow and fast speed. Mantids were less likely to strike glossy targets, independently of speed. Additionally, mantids were less likely to track glossy targets and more likely to hit the target with one out of the two legs that struck rather than both raptorial legs, but only when targets were moving fast. These results support the hypothesis that a glossy appearance may have a function as an antipredator strategy by reducing the ability of predators to track and accurately target fast moving prey.
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Affiliation(s)
| | - Devi Stuart-Fox
- School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Mark Elgar
- School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Ivan Marusic
- Department of Mechanical Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Amanda M Franklin
- School of BioSciences, The University of Melbourne, Parkville, Victoria 3010, Australia
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3
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Rebora M, Salerno G, Piersanti S, Kovalev A, Gorb SN. The origin of black and white coloration of the Asian tiger mosquito Aedes albopictus (Diptera: Culicidae). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2023; 14:496-508. [PMID: 37123532 PMCID: PMC10130904 DOI: 10.3762/bjnano.14.41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/30/2023] [Indexed: 05/03/2023]
Abstract
Micro- and nanostructures of the white and black scales on the tarsi of the mosquito Aedes albopictus are analysed using scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy. Reflectance spectra of the white areas are measured. No clear difference is present in the morphology of micro- and nanostructures of black and white scales in SEM and TEM, but black scales contain a dark pigment. The white colour of the scales has a structural origin. The structural white produced by the micro- and nanostructures of the scales on the tarsi of Ae. albopictus appears bright and is angle-dependent, since the reflected light changes according to the angle detection and according to the tarsus orientation. The optical appearance of the scale system of Ae. albopictus has a complex nature and can be explained by the combination of several effects. Among them, multiple refraction and reflection on the micro- and nanostructures of the scales are mainly responsible for the white appearance. The results suggest that mosquito scales, in addition to their superhydrophobic function, produce structural white. The biological role of white and black patches in mate recognition and defensive behaviour in the mosquitoes of the genus Aedes is hypothesized.
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Affiliation(s)
- Manuela Rebora
- Dipartimento di Chimica, Biologia e Biotecnologie, University of Perugia, Via Elce di Sotto 8, 06121 Perugia, Italy
| | - Gianandrea Salerno
- Dipartimento di Scienze Agrarie, Alimentari e Ambientali, University of Perugia, Borgo XX Giugno, 06121 Perugia, Italy
| | - Silvana Piersanti
- Dipartimento di Chimica, Biologia e Biotecnologie, University of Perugia, Via Elce di Sotto 8, 06121 Perugia, Italy
| | - Alexander Kovalev
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, 24098 Kiel, Germany
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, 24098 Kiel, Germany
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4
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Urban S, Gerwin J, Hulsey CD, Meyer A, Kratochwil CF. The repeated evolution of stripe patterns is correlated with body morphology in the adaptive radiations of East African cichlid fishes. Ecol Evol 2022; 12:e8568. [PMID: 35154652 PMCID: PMC8820146 DOI: 10.1002/ece3.8568] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 12/20/2021] [Accepted: 12/30/2021] [Indexed: 01/01/2023] Open
Abstract
Color patterns are often linked to the behavioral and morphological characteristics of an animal, contributing to the effectiveness of such patterns as antipredatory strategies. Species-rich adaptive radiations, such as the freshwater fish family Cichlidae, provide an exciting opportunity to study trait correlations at a macroevolutionary scale. Cichlids are also well known for their diversity and repeated evolution of color patterns and body morphology. To study the evolutionary dynamics between color patterns and body morphology, we used an extensive dataset of 461 species. A phylogenetic supertree of these species shows that stripe patterns evolved ~70 times independently and were lost again ~30 times. Moreover, stripe patterns show strong signs of correlated evolution with body elongation, suggesting that the stripes' effectiveness as antipredatory strategy might differ depending on the body shape. Using pedigree-based analyses, we show that stripes and body elongation segregate independently, indicating that the two traits are not genetically linked. Their correlation in nature is therefore likely maintained by correlational selection. Lastly, by performing a mate preference assay using a striped CRISPR-Cas9 mutant of a nonstriped species, we show that females do not differentiate between striped CRISPR mutant males and nonstriped wild-type males, suggesting that these patterns might be less important for species recognition and mate choice. In summary, our study suggests that the massive rates of repeated evolution of stripe patterns are shaped by correlational selection with body elongation, but not by sexual selection.
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Affiliation(s)
- Sabine Urban
- Chair in Zoology and Evolutionary BiologyDepartment of BiologyUniversity of KonstanzKonstanzGermany
| | - Jan Gerwin
- Chair in Zoology and Evolutionary BiologyDepartment of BiologyUniversity of KonstanzKonstanzGermany
| | - C. Darrin Hulsey
- Chair in Zoology and Evolutionary BiologyDepartment of BiologyUniversity of KonstanzKonstanzGermany
- Present address:
School of Biology and Environmental ScienceUniversity College DublinBelfieldIreland
| | - Axel Meyer
- Chair in Zoology and Evolutionary BiologyDepartment of BiologyUniversity of KonstanzKonstanzGermany
| | - Claudius F. Kratochwil
- Chair in Zoology and Evolutionary BiologyDepartment of BiologyUniversity of KonstanzKonstanzGermany
- Present address:
Institute of Biotechnology, HiLIFEUniversity of HelsinkiHelsinkiFinland
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5
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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: 12] [Impact Index Per Article: 4.0] [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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6
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Hughes AE, Griffiths D, Troscianko J, Kelley LA. The evolution of patterning during movement in a large-scale citizen science game. Proc Biol Sci 2021; 288:20202823. [PMID: 33434457 PMCID: PMC7892415 DOI: 10.1098/rspb.2020.2823] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The motion dazzle hypothesis posits that high contrast geometric patterns can cause difficulties in tracking a moving target and has been argued to explain the patterning of animals such as zebras. Research to date has only tested a small number of patterns, offering equivocal support for the hypothesis. Here, we take a genetic programming approach to allow patterns to evolve based on their fitness (time taken to capture) and thus find the optimal strategy for providing protection when moving. Our ‘Dazzle Bug’ citizen science game tested over 1.5 million targets in a touch screen game at a popular visitor attraction. Surprisingly, we found that targets lost pattern elements during evolution and became closely background matching. Modelling results suggested that targets with lower motion energy were harder to catch. Our results indicate that low contrast, featureless targets offer the greatest protection against capture when in motion, challenging the motion dazzle hypothesis.
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Affiliation(s)
- Anna E Hughes
- Department of Psychology, University of Essex, Wivenhoe House, Colchester CO4 3SQ, UK
| | | | - Jolyon Troscianko
- Centre for Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
| | - Laura A Kelley
- Centre for Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
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7
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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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8
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Pembury Smith MQR, Ruxton GD. Camouflage in predators. Biol Rev Camb Philos Soc 2020; 95:1325-1340. [DOI: 10.1111/brv.12612] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/24/2020] [Accepted: 04/28/2020] [Indexed: 12/29/2022]
Affiliation(s)
| | - Graeme D. Ruxton
- School of Biology University of St Andrews, Dyers Brae House, St Andrews Fife KY16 9TH U.K
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9
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Baling M, Stuart‐Fox D, Brunton DH, Dale J. Spatial and temporal variation in prey color patterns for background matching across a continuous heterogeneous environment. Ecol Evol 2020; 10:2310-2319. [PMID: 32184983 PMCID: PMC7069320 DOI: 10.1002/ece3.6024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 12/23/2019] [Accepted: 01/02/2020] [Indexed: 11/30/2022] Open
Abstract
In heterogeneous habitats, camouflage via background matching can be challenging because visual characteristics can vary dramatically across small spatial scales. Additionally, temporal variation in signaling functions of coloration can affect crypsis, especially when animals use coloration seasonally for intraspecific signaling (e.g., mate selection). We currently have a poor understanding of how wild prey optimize background matching within continuously heterogeneous habitats, and whether this is affected by requirements of intraspecific signaling across biological seasons. Here, we quantified color patterns of a wild population of shore skink (Oligosoma smithi), a variably colored lizard endemic to New Zealand, to (a) investigate whether background matching varies across a vegetation gradient; (b) assess potential signaling functions of color; and (c) to determine whether there is a trade-off between requirements for crypsis and intraspecific signaling in coloration across seasons. Although all pattern types occurred throughout the vegetation gradient, we found evidence for background matching in skinks across the vegetation gradient, where dorsal brightness and pattern complexity corresponded with the proportion of vegetation cover. There was also a significant disparity between ventral color (saturation) of juveniles and adults, and also between sexes, suggestive of sex recognition. However, there was little indication that color was condition-dependent in adults. Despite some evidence for a potential role in signaling, crypsis did not greatly differ across seasons. Our study suggests that selection favors a mix of generalist and specialist background matching strategies across continuously heterogeneous habitats.
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Affiliation(s)
- Marleen Baling
- Unitec Institute of TechnologyAucklandNew Zealand
- School of Natural and Computational SciencesMassey University (Albany Campus)AucklandNew Zealand
| | - Devi Stuart‐Fox
- School of BioSciencesThe University of MelbourneMelbourneVICAustralia
| | - Dianne H. Brunton
- School of Natural and Computational SciencesMassey University (Albany Campus)AucklandNew Zealand
| | - James Dale
- School of Natural and Computational SciencesMassey University (Albany Campus)AucklandNew Zealand
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10
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Allen WL, Moreno N, Gamble T, Chiari Y. Ecological, behavioral, and phylogenetic influences on the evolution of dorsal color pattern in geckos. Evolution 2020; 74:1033-1047. [PMID: 31886521 DOI: 10.1111/evo.13915] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 12/04/2019] [Accepted: 12/15/2019] [Indexed: 12/13/2022]
Abstract
The dorsal surfaces of many taxonomic groups often feature repetitive pattern elements consisting of stripes, spots, or bands. Here, we investigate how distinct categories of camouflage pattern work by relating them to ecological and behavioral traits in 439 species of gecko. We use phylogenetic comparative methods to test outstanding hypotheses based on camouflage theory and research in other taxa. We found that bands are associated with nocturnal activity, suggesting bands provide effective camouflage for motionless geckos resting in refugia during the day. A predicted association between stripes and diurnal activity was not supported, suggesting that stripes do not work via dazzle camouflage mechanisms in geckos. This, along with a lack of support for our prediction that plain patterning should be associated with open habitats, suggests that similar camouflage patterns do not work in consistent ways across taxa. We also found that plain and striped lineages frequently switched between using open or closed habitats, whereas spotted lineages rarely transitioned. This suggests that pattern categories differ in how specialized or generalized their camouflage is. This result has ramifications for theory on how camouflage compromises to background heterogeneity and how camouflage pattern might influence evolutionary trajectories.
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Affiliation(s)
- William L Allen
- Department of Biosciences, Swansea University, Swansea, UK, SA2 8PP
| | - Nickolas Moreno
- Department of Biology, University of South Alabama, Mobile, Alabama, 36688
| | - Tony Gamble
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin, 53233.,Bell Museum of Natural History, University of Minnesota, Saint Paul, Minnesota, 55113.,Milwaukee Public Museum, Milwaukee, Wisconsin, 53233
| | - Ylenia Chiari
- Department of Biology, University of South Alabama, Mobile, Alabama, 36688.,Department of Biology, George Mason University, Manassas, Virginia, 20110
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11
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Kodandaramaiah U, Palathingal S, Bindu Kurup G, Murali G. What makes motion dazzle markings effective against predation? Behav Ecol 2019. [DOI: 10.1093/beheco/arz154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Motion dazzle markings comprise patterns such as stripes and zig-zags that are postulated to protect moving prey by making predators misjudge the prey’s speed or trajectory. Recent experiments have provided conflicting results on their effect on speed perception and attack success. We focus on motion dazzle stripes and investigate the influence of four parameters—stripe orientation, stripe contrast, target size, and target speed—on perceived speed and attack success using a common experimental paradigm involving human “predators” attacking virtual moving targets on a computer touchscreen. We found that high-contrast stripes running parallel or perpendicular to the direction of motion reduce attack success compared to conspicuous uniform targets. Surprisingly, parallel stripes induced underestimation of speed, while perpendicular stripes induced overestimation of speed in relation to uniform black, suggesting that misjudgment of speed per se is sufficient to reduce attack accuracy. Across all the experiments, we found some support for parallel stripes inducing underestimation of target speed but these stripes reduced attack success only when targets were small, moved at an intermediate speed, and had high internal contrast. We suggest that prey features (e.g., size or speed) are an important determinant of capture success and that distortion of speed perception by a color pattern does not necessarily translate to reduced capture success of the prey. Overall, our results support the idea that striped patterns in prey animals can reduce capture in motion but are effective under a limited set of conditions.
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Affiliation(s)
- Ullasa Kodandaramaiah
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, India
| | - Shuaib Palathingal
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, India
- Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, India
| | - Gayathri Bindu Kurup
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, India
| | - Gopal Murali
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, India
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12
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Affiliation(s)
- I. C. Cuthill
- School of Biological Sciences University of Bristol Bristol UK
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13
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Murali G, Kumari K, Kodandaramaiah U. Dynamic colour change and the confusion effect against predation. Sci Rep 2019; 9:274. [PMID: 30670756 PMCID: PMC6342951 DOI: 10.1038/s41598-018-36541-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 11/22/2018] [Indexed: 11/09/2022] Open
Abstract
The confusion effect - the decreased attack-to-kill ratio of a predator with increase in prey group size - is thought to be one of the main reasons for the evolution of group living in animals. Despite much interest, the influence of prey coloration on the confusion effect is not well understood. We hypothesized that dynamic colour change in motion (due to interference coloration or flash marks), seen widely in many group living animals, enhances the confusion effect. Utilizing a virtual tracking task with humans, we found targets that dynamically changed colour during motion were more difficult to track than targets with background matching patterns, and this effect was stronger at larger group sizes. The current study thus provides the first empirical evidence for the idea that dynamic colour change can benefit animals in a group and may explain the widespread occurrence of dynamic colorations in group-living animals.
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Affiliation(s)
- Gopal Murali
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala PO, Vithura, Thiruvananthapuram, 695 551, India.
| | - Kajal Kumari
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala PO, Vithura, Thiruvananthapuram, 695 551, India
| | - Ullasa Kodandaramaiah
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala PO, Vithura, Thiruvananthapuram, 695 551, India
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14
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Hall JR, Baddeley R, Scott-Samuel NE, Shohet AJ, Cuthill IC. Camouflaging moving objects: crypsis and masquerade. Behav Ecol 2018; 28:1248-1255. [PMID: 29622927 PMCID: PMC5873248 DOI: 10.1093/beheco/arx085] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/07/2017] [Accepted: 05/30/2017] [Indexed: 11/14/2022] Open
Abstract
Motion is generally assumed to “break” camouflage. However, although camouflage cannot conceal a group of moving animals, it may impair a predator’s ability to single one out for attack, even if that discrimination is not based on a color difference. Here, we use a computer-based task in which humans had to detect the odd one out among moving objects, with “oddity” based on shape. All objects were either patterned or plain, and either matched the background or not. We show that there are advantages of matching both group-mates and the background. However, when patterned objects are on a plain background (i.e., no background matching), the advantage of being among similarly patterned distractors is only realized when the group size is larger (10 compared to 5). In a second experiment, we present a paradigm for testing how coloration interferes with target-distractor discrimination, based on an adaptive staircase procedure for establishing the threshold. We show that when the predator only has a short time for decision-making, displaying a similar pattern to the distractors and the background affords protection even when the difference in shape between target and distractors is large. We conclude that, even though motion breaks camouflage, being camouflaged could help group-living animals reduce the risk of being singled out for attack by predators.
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Affiliation(s)
- Joanna R Hall
- School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK.,School of Biological Sciences, University of Bristol, Bristol Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK, and
| | - Roland Baddeley
- School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK
| | - Nicholas E Scott-Samuel
- School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK
| | - Adam J Shohet
- Stealth Materials Group, QinetiQ, Cody Technology Park, Farnborough GU14 0LX, UK
| | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, Bristol Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK, and
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15
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Merilaita S, Scott-Samuel NE, Cuthill IC. How camouflage works. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0341. [PMID: 28533458 DOI: 10.1098/rstb.2016.0341] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/11/2016] [Indexed: 11/12/2022] Open
Abstract
For camouflage to succeed, an individual has to pass undetected, unrecognized or untargeted, and hence it is the processing of visual information that needs to be deceived. Camouflage is therefore an adaptation to the perception and cognitive mechanisms of another animal. Although this has been acknowledged for a long time, there has been no unitary account of the link between visual perception and camouflage. Viewing camouflage as a suite of adaptations to reduce the signal-to-noise ratio provides the necessary common framework. We review the main processes in visual perception and how animal camouflage exploits these. We connect the function of established camouflage mechanisms to the analysis of primitive features, edges, surfaces, characteristic features and objects (a standard hierarchy of processing in vision science). Compared to the commonly used research approach based on established camouflage mechanisms, we argue that our approach based on perceptual processes targeted by camouflage has several important benefits: specifically, it enables the formulation of more precise hypotheses and addresses questions that cannot even be identified when investigating camouflage only through the classic approach based on the patterns themselves. It also promotes a shift from the appearance to the mechanistic function of animal coloration.This article is part of the themed issue 'Animal coloration: production, perception, function and application'.
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Affiliation(s)
- Sami Merilaita
- Department of Biosciences, Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland
| | - Nicholas E Scott-Samuel
- Department of Experimental Psychology, University of Bristol, 12A Priory Road, Bristol BS8 1TN, UK
| | - Innes C Cuthill
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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Hughes AE, Jones C, Joshi K, Tolhurst DJ. Diverted by dazzle: perceived movement direction is biased by target pattern orientation. Proc Biol Sci 2017; 284:20170015. [PMID: 28275144 PMCID: PMC5360933 DOI: 10.1098/rspb.2017.0015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 02/09/2017] [Indexed: 11/12/2022] Open
Abstract
'Motion dazzle' is the hypothesis that predators may misjudge the speed or direction of moving prey which have high-contrast patterning, such as stripes. However, there is currently little experimental evidence that such patterns cause visual illusions. Here, observers binocularly tracked a Gabor target, moving with a linear trajectory randomly chosen within 18° of the horizontal. This target then became occluded, and observers were asked to judge where they thought it would later cross a vertical line to the side. We found that internal motion of the stripes within the Gabor biased judgements as expected: Gabors with upwards internal stripe motion relative to the overall direction of motion were perceived to be crossing above Gabors with downwards internal stripe movement. However, surprisingly, we found a much stronger effect of the rigid pattern orientation. Patches with oblique stripes pointing upwards relative to the direction of motion were perceived to cross above patches with downward-pointing stripes. This effect occurred only at high speeds, suggesting that it may reflect an orientation-dependent effect in which spatial signals are used in direction judgements. These findings have implications for our understanding of motion dazzle mechanisms and how human motion and form processing interact.
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Affiliation(s)
- Anna E Hughes
- Department of Psychology and Language Sciences, University College London, 26 Bedford Way, London WC1H 0AP, UK
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
| | - Christian Jones
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
| | - Kaustuv Joshi
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
| | - David J Tolhurst
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
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Hogan BG, Cuthill IC, Scott-Samuel NE. Dazzle camouflage and the confusion effect: the influence of varying speed on target tracking. Anim Behav 2017; 123:349-353. [PMID: 28123185 PMCID: PMC5226095 DOI: 10.1016/j.anbehav.2016.11.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The formation of groups is a common strategy to avoid predation in animals, and recent research has indicated that there may be interactions between some forms of defensive coloration, notably high-contrast ‘dazzle camouflage’, and one of the proposed benefits of grouping: the confusion effect. However, research into the benefits of dazzle camouflage has largely used targets moving with constant speed. This simplification may not generalize well to real animal systems, where a number of factors influence both within- and between-individual variation in speed. Departure from the speed of your neighbours in a group may be predicted to undermine the confusion effect. This is because individual speed may become a parameter through which the observer can individuate otherwise similar targets: an ‘oddity effect’. However, dazzle camouflage patterns are thought to interfere with predator perception of speed and trajectory. The current experiment investigated the possibility that such patterns could ameliorate the oddity effect caused by within-group differences in prey speed. We found that variation in speed increased the ease with which participants could track targets in all conditions. However, we found no evidence that motion dazzle camouflage patterns reduced oddity effects based on this variation in speed, a result that may be informative about the mechanisms behind this form of defensive coloration. In addition, results from those conditions most similar to those of published studies replicated previous results, indicating that targets with stripes parallel to the direction of motion are harder to track, and that this pattern interacts with the confusion effect to a greater degree than background matching or orthogonal-to-motion striped patterns. Variation in speed in groups induces the oddity effect, reducing predator confusion. Dazzle camouflage does not ameliorate this oddity effect. Parallel striped targets in groups are harder to track than other targets.
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Affiliation(s)
- Benedict G Hogan
- Biological Sciences, University of Bristol, Bristol, U.K.; Experimental Psychology, University of Bristol, Bristol, U.K
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Hogan BG, Hildenbrandt H, Scott-Samuel N, Cuthill IC, Hemelrijk C. The confusion effect when attacking simulated three-dimensional starling flocks. ROYAL SOCIETY OPEN SCIENCE 2017; 4:160564. [PMID: 28280553 PMCID: PMC5319319 DOI: 10.1098/rsos.160564] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 12/09/2016] [Indexed: 05/14/2023]
Abstract
The confusion effect describes the phenomenon of decreasing predator attack success with increasing prey group size. However, there is a paucity of research into the influence of this effect in coherent groups, such as flocks of European starlings (Sturnus vulgaris). Here, for the first time, we use a computer game style experiment to investigate the confusion effect in three dimensions. To date, computerized studies on the confusion effect have used two-dimensional simulations with simplistic prey movement and dynamics. Our experiment is the first investigation of the effects of flock size and density on the ability of a (human) predator to track and capture a target starling in a realistically simulated three-dimensional flock of starlings. In line with the predictions of the confusion effect, modelled starlings appear to be safer from predation in larger and denser flocks. This finding lends credence to previous suggestions that starling flocks have anti-predator benefits and, more generally, it suggests that active increases in density in animal groups in response to predation may increase the effectiveness of the confusion effect.
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Affiliation(s)
- Benedict G. Hogan
- School of Biological Sciences, University of Bristol, Life Sciences Building, Bristol BS8 1TQ, UK
- School of Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TH, UK
- Author for correspondence: Benedict G. Hogan e-mail:
| | - Hanno Hildenbrandt
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, 9747 AG, The Netherlands
| | | | - Innes C. Cuthill
- School of Biological Sciences, University of Bristol, Life Sciences Building, Bristol BS8 1TQ, UK
| | - Charlotte K. Hemelrijk
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, 9747 AG, The Netherlands
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