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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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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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3
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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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4
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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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5
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Murali G. Now you see me, now you don't: dynamic flash coloration as an antipredator strategy in motion. Anim Behav 2018. [DOI: 10.1016/j.anbehav.2018.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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6
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Zlotnik S, Darnell GM, Bernal XE. Anuran predators overcome visual illusion: dazzle coloration does not protect moving prey. Anim Cogn 2018; 21:729-733. [PMID: 29922864 DOI: 10.1007/s10071-018-1199-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 05/19/2018] [Accepted: 06/13/2018] [Indexed: 10/28/2022]
Abstract
Predators everywhere impose strong selection pressures on the morphology and behavior of their prey, but the resulting antipredator adaptations vary greatly among species. Studies of adaptive coloration in prey species have generally focused on cryptic or aposematic prey, with little consideration of color patterns in palatable mobile prey. Complex color patterns have been proposed to decrease the ability of visual predators to capture moving prey (motion dazzle effect). Most support for this hypothesis, however, comes from experiments with human subjects and simulated prey. We tested the motion dazzle effect using, for the first time, natural predators (cane toads, Rhinella marina) and live prey (house crickets, Acheta domesticus) with altered color patterns. We found no support for the motion dazzle effect as striped crickets did not fare better than solid colored ones. Crickets that spent more time moving, however, were more likely to be eaten. Our results suggest that motion specialized visual predators such as toads overcome the motion dazzle effect and impose stronger selection pressure on prey behavior than on coloration. These findings emphasize the importance of sensory specializations of predators in mediating antipredator strategies.
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Affiliation(s)
- Sara Zlotnik
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA.
| | - Geena M Darnell
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Ximena E Bernal
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA.,Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama
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7
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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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8
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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: 101] [Impact Index Per Article: 16.8] [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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9
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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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11
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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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12
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Halperin T, Carmel L, Hawlena D. Movement correlates of lizards’ dorsal pigmentation patterns. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12700] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Topaz Halperin
- Risk‐Management Ecology Lab Department of Ecology, Evolution & Behavior The Alexander Silberman Institute of Life Sciences The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 91904, Israel
- Herpetological Collection National Natural History Collections The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 91904, Israel
| | - Liran Carmel
- Department of Genetics Faculty of Science The Alexander Silberman Institute of Life Sciences The Hebrew University of Jerusalem Edmond J. Safra Campus Givat Ram Jerusalem 91904, Israel
| | - Dror Hawlena
- Risk‐Management Ecology Lab Department of Ecology, Evolution & Behavior The Alexander Silberman Institute of Life Sciences The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 91904, Israel
- Herpetological Collection National Natural History Collections The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 91904, Israel
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13
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Hogan BG, Scott-Samuel NE, Cuthill IC. Contrast, contours and the confusion effect in dazzle camouflage. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160180. [PMID: 27493775 PMCID: PMC4968467 DOI: 10.1098/rsos.160180] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 06/08/2016] [Indexed: 05/16/2023]
Abstract
'Motion dazzle camouflage' is the name for the putative effects of highly conspicuous, often repetitive or complex, patterns on parameters important in prey capture, such as the perception of speed, direction and identity. Research into motion dazzle camouflage is increasing our understanding of the interactions between visual tracking, the confusion effect and defensive coloration. However, there is a paucity of research into the effects of contrast on motion dazzle camouflage: is maximal contrast a prerequisite for effectiveness? If not, this has important implications for our recognition of the phenotype and understanding of the function and mechanisms of potential motion dazzle camouflage patterns. Here we tested human participants' ability to track one moving target among many identical distractors with surface patterns designed to test the influence of these factors. In line with previous evidence, we found that targets with stripes parallel to the object direction of motion were hardest to track. However, reduction in contrast did not significantly influence this result. This finding may bring into question the utility of current definitions of motion dazzle camouflage, and means that some animal patterns, such as aposematic or mimetic stripes, may have previously unrecognized multiple functions.
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Affiliation(s)
- Benedict G. Hogan
- School of Biological Sciences, University of Bristol, Bristol, UK
- School of Experimental Psychology, University of Bristol, Bristol, UK
- Author for correspondence: Benedict G. Hogan e-mail:
| | | | - Innes C. Cuthill
- School of Biological Sciences, University of Bristol, Bristol, UK
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14
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Murali G, Kodandaramaiah U. Deceived by stripes: conspicuous patterning on vital anterior body parts can redirect predatory strikes to expendable posterior organs. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160057. [PMID: 27429765 PMCID: PMC4929900 DOI: 10.1098/rsos.160057] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/10/2016] [Indexed: 06/06/2023]
Abstract
Conspicuous coloration, which presumably makes prey more visible to predators, has intrigued researchers for long. Contrastingly coloured, conspicuous striped patterns are common among lizards and other animals, but their function is not well known. We propose and test a novel hypothesis, the 'redirection hypothesis', wherein longitudinal striped patterns, such as those found on the anterior body parts of most lacertilians, redirect attacks away from themselves during motion towards less vulnerable posterior parts, for example, the autotomous tail. In experiments employing human 'predators' attacking virtual prey on a touchscreen, we show that longitudinal striped patterns on the anterior half of prey decreased attacks to the anterior and increased attacks to the posterior. The position of stripes mattered-they worked best when they were at the anterior. By employing an adaptive psychophysical procedure, we show that prey with striped patterning are perceived to move slower, offering a mechanistic explanation for the redirective effect. In summary, our results suggest that the presence of stripes on the body (i.e. head and trunk) of lizards in combination with caudal autotomy can work as an effective anti-predator strategy during motion.
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Hogan BG, Cuthill IC, Scott-Samuel NE. Dazzle camouflage, target tracking, and the confusion effect. ACTA ACUST UNITED AC 2016; 27:1547-1551. [PMID: 27656087 PMCID: PMC5027625 DOI: 10.1093/beheco/arw081] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 05/09/2016] [Accepted: 05/15/2016] [Indexed: 11/22/2022]
Abstract
The influence of coloration on the ecology and evolution of moving animals in groups is poorly understood. Animals in groups benefit from the “confusion effect,” where predator attack success is reduced with increasing group size or density. This is thought to be due to a sensory bottleneck: an increase in the difficulty of tracking one object among many. Motion dazzle camouflage has been hypothesized to disrupt accurate perception of the trajectory or speed of an object or animal. The current study investigates the suggestion that dazzle camouflage may enhance the confusion effect. Utilizing a computer game style experiment with human predators, we found that when moving in groups, targets with stripes parallel to the targets’ direction of motion interact with the confusion effect to a greater degree, and are harder to track, than those with more conventional background matching patterns. The findings represent empirical evidence that some high-contrast patterns may benefit animals in groups. The results also highlight the possibility that orientation and turning may be more relevant in the mechanisms of dazzle camouflage than previously recognized.
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Affiliation(s)
- Benedict G Hogan
- Biological Sciences, University of Bristol, Bristol Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK and; Experimental Psychology, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK
| | - Innes C Cuthill
- Biological Sciences, University of Bristol , Bristol Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ , UK and
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16
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Hall JR, Cuthill IC, Baddeley R, Attwood AS, Munafò MR, Scott-Samuel NE. Dynamic Dazzle Distorts Speed Perception. PLoS One 2016; 11:e0155162. [PMID: 27196098 PMCID: PMC4872993 DOI: 10.1371/journal.pone.0155162] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/25/2016] [Indexed: 11/30/2022] Open
Abstract
Static high contrast (‘dazzle’) patterns, such as zigzags, have been shown to reduce the perceived speed of an object. It has not escaped our notice that this effect has possible military applications and here we report a series of experiments on humans, designed to establish whether dynamic dazzle patterns can cause distortions of perceived speed sufficient to provide effective defence in the field, and the extent to which these effects are robust to a battery of manipulations. Dynamic stripe patterns moving in the same direction as the target are found to increase the perceived speed of that target, whilst dynamic stripes moving in the opposite direction to the target reduce the perceived speed. We establish the optimum position for such dazzle patches; confirm that reduced contrast and the addition of colour do not affect the performance of the dynamic dazzle, and finally, using the CO2 challenge, show that the effect is robust to stressful conditions.
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Affiliation(s)
- Joanna R. Hall
- School of Experimental Psychology, University of Bristol, Bristol, United Kingdom
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
- * E-mail:
| | - Innes C. Cuthill
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Roland Baddeley
- School of Experimental Psychology, University of Bristol, Bristol, United Kingdom
| | - Angela S. Attwood
- School of Experimental Psychology, University of Bristol, Bristol, United Kingdom
| | - Marcus R. Munafò
- School of Experimental Psychology, University of Bristol, Bristol, United Kingdom
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