camouflage

Peacock Flounder Bothus mancus demonstrating its ability to change its pattern and colours to match its environment

Modern military camouflage makes use of disruptively patterned equipment, face paint and natural materials

Camouflage is a method of concealment that allows otherwise visible animals, military vehicles, or other objects to remain unnoticed by blending with their environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly. Camouflage is a form of visual deception; the term probably comes from camouflet, a French term meaning smoke blown in someone's face as a practical joke.^[1] Military camouflage is part of a broad area of deception and concealment from all means of detection including sound and radar; it involves non-camouflage techniques such as use of decoys and electronic jamming.^[2][3]

According to Charles Darwin's theory of natural selection, characteristics such as camouflage that help an animal to survive will tend to evolve in any population.^[4]

Camouflage can be achieved in what may seem opposite ways. Mimesis means being seen, but resembling something else, whereas crypsis means being hidden.^[5] But in both cases, camouflage is achieved by not being noticed. A third approach, dazzle, means confusing the predator or enemy by moving a conspicuous pattern. The prey or target is visible but hard to hit. Dazzle found military application in the 20th century.

Camouflage is not the only form of animal coloration that helps animals to survive or creates striking natural patterns. Other adaptations include warning coloration, non-concealing forms of mimicry (as when a harmless hoverfly resembles a stinging wasp), the use of bright colours in sexual selection, and the use of pigment in the skin to protect against sunburn.

History

Charles Darwin (1809-1882)

Edward Poulton (1856-1943)

Abbott Thayer (1849-1921)

Disruptive coloration by Hugh Cott (1900-1987)

Camouflage has been a topic of interest and research in biology for well over a century. According to Charles Darwin's 1859 theory of natural selection,^[4] features such as camouflage evolved by providing individual animals with a reproductive advantage, enabling them to leave more offspring, on average, than other members of the same species. In his Origin of Species, Darwin wrote:^[6]

"When we see leaf-eating insects green, and bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse the colour of heather, and the black-grouse that of peaty earth, we must believe that these tints are of service to these birds and insects in preserving them from danger. Grouse, if not destroyed at some period of their lives, would increase in countless numbers; they are known to suffer largely from birds of prey; and hawks are guided by eyesight to their prey, so much so, that on parts of the Continent persons are warned not to keep white pigeons, as being the most liable to destruction. Hence I can see no reason to doubt that natural selection might be most effective in giving the proper colour to each kind of grouse, and in keeping that colour, when once acquired, true and constant."

In the 19th century, Edward Bagnall Poulton studied animal coloration, especially camouflage, classifying different types such as "special protective resemblance" (where an animal looks like another object), or "general aggressive resemblance" (where a predator blends in with the background, enabling it to approach prey).^[7]

The artist Abbott Handerson Thayer formulated "Thayer's Law", the principle of countershading.^[8]

In the 20th century, Hugh Cott worked to persuade the British army to use more effective camouflage techniques, including countershading. For example, he painted two rail-mounted coastal guns, one in conventional style, one countershaded. In aerial photographs, the countershaded gun is essentially invisible.^[9] Cott's 1940 book Adaptive Coloration in Animals introduced ideas such as "maximum disruptive contrast" (see illustration). This uses streaks of boldly contrasting colour, which paradoxically make animals or military vehicles less visible by breaking up their outlines.^[10]

Camouflage by mimesis

In mimesis (also called masquerade), the whole animal (or piece of military equipment) looks like some other object, which is of no special interest to the observing animal or enemy.^[11]:512,513 Mimesis is common in prey animals, for example when a Peppered Moth caterpillar mimics a twig, or a grasshopper mimics a dry leaf.^[5]:151

Mimesis is also employed by some predators (or parasites) to lure their prey. For example, a flower mantis mimics a particular kind of flower, such as an orchid.^[5]:134 This tactic has occasionally been used in warfare, for example with heavily armed Q-ships disguised as merchant ships.^[12][13]

As an example of mimesis, consider the Common Cuckoo, a brood parasite. The female lays her eggs in nests of other species of bird, always smaller than the cuckoo, one per nest. The female mimics a Sparrowhawk. This makes small birds take action to avoid the apparent predator. The female cuckoo then has time to lay her egg in their nest without being seen to do so.^[14] The cuckoo's egg itself mimics the eggs of the host species, reducing its chance of being rejected.^[15][16]

A different, non-camouflage strategy is mimicry, where an animal boldly resembles another animal that is poisonous or distasteful: it is then easily seen, but avoided.^[5]:6-42

Camouflage by crypsis

Crypsis means blending with the background, making the animal or military equipment hard to see (or to detect in other ways, such as by sound or scent: for details, see Crypsis). This can be achieved in many different ways, including:^[5]

• General resemblance to background
• Disruptive patterning (breaking up outline)
• Eliminating shadow
• Crypsis by behaviour
• Crypsis by changing skin pattern, colour
• Countershading
• Counterillumination

These ways of achieving crypsis are described below.

General resemblance to background

Some animals' colours and patterns resemble a particular natural background, for example the Peppered Moth adult blends in with tree bark.^[17]

Disruptive patterning

Disruptive patterns use strongly contrasting markings such as spots or stripes to break up an animal's outlines. Some predators, like the Leopard, and some potential prey like the Egyptian Nightjar, use disruptive patterns.^[18] Disruptive patterns "are characterized by high-contrast light and dark patches, in a nonrepetitive configuration, that also provide camouflage by disrupting the recognizable shape or orientation of the animal".^[19]

The presence of bold skin markings does not in itself prove that an animal relies on camouflage. According to Mitchell, adult giraffes are "inescapably conspicuous", making the conclusion that their patterns are for camouflage appear counterintuitive: but when standing among trees and bushes their camouflage is effective at even a few metres' distance.^[20]:70 Further, young giraffes are much more vulnerable to predation than adults: between 60% and 75% of calves die before their first birthday.^[20]:70 Mothers hide their calves, which spend much of the time lying down in cover. Since the presence of a mother does not affect survival, Mitchell suggests that young giraffes must be extremely well camouflaged. This is supported by the fact that coat markings are strongly inherited.^[20]:70 Conversely, far from hiding, adult giraffes move about to gain the best view of an approaching predator, relying on their size and ability to defend themselves even from lions.^[20]:69

Disruptive patterning is now common in military usage, both for uniforms and for military vehicles. Disruptive patterning, however, does not always achieve crypsis on its own, as an animal or a military target may be given away by other factors including shape, shine, and shadow.^[21]

Eliminating shadow

Some animals, such as the Horned Lizards of North America, have evolved elaborate measures to eliminate shadow. Their bodies are flattened, with the sides thinning to an edge; the animals habitually press their bodies to the ground; and their sides are fringed with white scales which "break up and camouflage any dark shadow line that might fall along the body's edge."^[22] The theory that the body shape of the Horned Lizards which live in open desert is adapted to minimize shadow is supported by the one species which lacks fringe scales, the Roundtail Horned Lizard, which lives in rocky areas and resembles a rock. "When threatened, it enhances this resemblance by hunching up its back, an act that displays rather than hides its three-dimensionality."^[22]

"Elimination of shadow" was identified as a principle of military camouflage during the Second World War.^[23]

Crypsis by behaviour

Decoration, keeping still, lying flat

Some animals actively seek to make themselves cryptic by using materials from their environment, such as twigs, sand, or pieces of shell to conceal their outlines, for example when a Caddis Fly larva builds a decorated case, or when a Decorator Crab covers its back with seaweed, sponges and stones.^[5] Most other forms of crypsis also require some animal behaviour, e.g. lying down and keeping still, as with young Giraffes,^[20] lying flat, as in the Flat-tail Horned Lizard,^[24] or swaying as if rippled by wind or water currents, as in the Leafy Sea Dragon.^[25]

Similar principles can be applied for military purposes, for example when a sniper wears a ghillie suit designed to be further camouflaged by decoration with materials such as tufts of grass from the sniper's immediate environment.

Motion camouflage

Most forms of camouflage break down when the camouflaged animal or object moves, because the motion is easily seen by the observing predator, prey or enemy.^[26] However some insects such as hoverflies^[27] and dragonflies use motion camouflage: the hoverflies to approach possible mates, and the dragonflies to approach rivals when defending territories.^[28][29] Motion camouflage is achieved by moving so as to stay on a straight line between the target and a fixed point in the landscape; the pursuer thus appears not to move, but only to loom larger in the target's field of vision. Numerical simulations show that motion camouflage can be more efficient than classical pursuit (moving straight towards the target at all times).^[30] The same technique can be used for military purposes, for example by missiles to minimise their risk of detection by the enemy.^[27] Missile engineers call the constant absolute target direction strategy "parallel navigation"; they have used the strategy since the 1940s, primarily for its efficiency. Bats use it for the same reason.^[31]

Crypsis by changing skin pattern, colour

Animals such as chameleon, flatfish, squid or octopus actively and rapidly change their skin patterns and colours using special chromatophore cells to resemble their current background (as well as for signalling).^[5][32]

On a longer timescale, some animals like the Arctic Hare, Arctic Fox, Stoat (also called Ermine), and Ptarmigan change their coat colour (by moulting and growing new fur or feathers) from brown or grey in the summer to white in the winter; the Arctic fox is the only species in the dog family (Canidae) to do so.^[33] However, Arctic hares which live in the far north of Canada, where summer is very short, remain white all year round.^[33][34]

Again, similar principles can be applied for military purposes. Active camouflage could in theory make use of both dynamic colour change and counterillumination. Simpler techniques such as changing uniforms and repainting vehicles for winter have been in use since the Second World War.

Crypsis by countershading

Countershading uses graded colour to create the illusion of flatness. Shadow makes an animal darker below than on top; countershading 'paints in' tones which are darkest on top, lightest below, making the countershaded animal nearly invisible against a matching background.^[35] American artist Abbott Handerson Thayer observed that "Animals are painted by Nature, darkest on those parts which tend to be most lighted by the sky's light, and vice versa". Accordingly the principle of countershading is sometimes called Thayer's Law.^[36]

Countershading is widely used by both terrestrial and marine animals. Examples include antelopes such as gazelles, and sharks.

Countershading is less often used for military camouflage, despite Second World War experiments that showed its effectiveness. English Zoologist Hugh B. Cott encouraged the use of techniques including countershading for concealment. He observed that soldiers viewed camouflage netting as "some kind of invisibility cloak: just throw it over the truck and now you don't see it", as Peter Forbes comments.^[37] At the same time in Australia, zoologist William John Dakin advised soldiers to copy animals' methods, using their instincts for wartime camouflage.^[38]

Crypsis by counterillumination

Counterillumination means producing light to match a background that is brighter than an animal's body. It is notably used by some species of squid, such as the Sparkling Enope Squid (Watasenia scintillans) and the Midwater Squid (Abralia veranyi). Abralia has light-producing organs (photophores) scattered all over its underside; these create a sparkling glow that prevents the animal from appearing as a dark shape when seen from below.^[39]

Counterillumination camouflage is the likely function of the bioluminescence of many marine organisms, though light is also produced to attract prey and for signalling.

Counterillumination has rarely been used for military purposes. "Diffused lighting camouflage" was trialled by Canada's National Research Council during World War II. It involved projecting light on to the sides of ships to match the faint glow of the night sky. The Canadian concept was trialled in American aircraft including B-24 Liberators. The planes were fitted with forward-pointing lamps automatically adjusted to match the brightness of the sky.^[40]

Dazzle patterning

Most forms of camouflage are made ineffective by movement: a deer or grasshopper may be highly cryptic when motionless, but instantly seen when it moves. But one form of 'camouflage' works only when in motion: dazzle patterning.^[41]

Military dazzle 'camouflage'

Dazzle patterning superficially resembles disruptive patterning, but has a different purpose. It was used on ships during the First World War, not to make vessels hard to see, but to make their speed, size, range and direction difficult to ascertain by eye.^[42] Dazzle patterning is therefore arguably (by definition) not camouflage, though it has been called camouflage since the First World War.^[42][43] Non-aligning dazzle patterns may have helped to confuse gunners using optical rangefinders, where two halves of the image had to be aligned by eye to estimate the range to the target ship. However the evidence for its success in naval warfare is mixed.^[42] Remarkably, some United States Navy camouflage schemes in World War II attempted to combine disruptive camouflage and dazzle.^[44]

Motion dazzle

Motion dazzle is caused by rapidly-moving bold patterns of contrasting stripes, as when zebras run from a lion. Motion dazzle may degrade predators' ability to estimate the prey's speed and direction accurately, giving the prey an improved chance of escape.^[43] Motion dazzle distorts speed perception, and is most effective at high speeds; stripes can also distort perception of size (and so, perceived range to the target).^[41] Since dazzle patterns (such as a zebra's stripes) make animals more difficult to locate accurately when moving, but easier to see when stationary, there is an evolutionary trade-off between dazzle and crypsis.^[43]

Fashion, art, society

Military camouflage patterns influenced Fashion from the time of the first world war onwards. In 1919, Chelsea Arts Club held a "Dazzle Ball". Those attending wore dazzle-patterned black and white clothing. The ball influenced fashion and art via postcards (see illustration) and magazine articles.^[45] The Illustrated London News announced

The scheme of decoration for the great fancy dress ball given by the Chelsea Arts Club at the Albert Hall, the other day, was based on the principles of 'Dazzle', the method of 'camouflage' used during the war in the painting of ships... The total effect was brilliant and fantastic.^[45][46]

More recently, fashion designers have often used camouflage fabric for its striking designs, its "patterned disorder" and its symbolism.^[47][48]

The artist and camouflage pioneer Abbott Thayer attempted through words and paintings to show that all animal coloration is camouflage. Peacock in the Woods (1907) is his best-known painting.^[49] The painting depicts a brightly coloured male peacock in an equally bright, highly contrasting temperate forest, nothing like the bird's actual habitat in India.^[49]

The French Cubist artist André Mare (1885-1932) contributed his artistic skills in the first world war, painting artillery pieces in cubist style.^[50]

Modern artists such as Ian Hamilton Finlay have used camouflage to reflect on war. His 1973 screenprint of a leafily-camouflaged tank, Arcadia, 1973, is described by the Tate as drawing "an ironic parallel between this idea of a natural paradise and the camouflage patterns on a tank".^[51] The title refers to the Utopian Arcadia of poetry and art.

In the United States in the late 1960s and early 1970s, military clothing was often worn by anti-war protestors as a symbol of political protest.^[48]

See also

Wikimedia Commons has media related to: Animal camouflage

• Active camouflage
• Animal coloration (including mechanisms of colour production in animals)
• Antipredator adaptation
• Aposematism
• Mimicry
• Military camouflage
• Motion camouflage
• Ship camouflage
• Underwater camouflage and mimicry

References

Bibliography

Camouflage in nature

Pioneering research

• Cott, H.B. Adaptive Coloration in Animals. Methuen, London, 1940.
• Darwin, C. On the Origin of Species. London, 1859. Reprinted 1985, Penguin Classics, Harmondsworth.
• Poulton, E.B. The Colours of Animals: their meaning and use, especially considered in the case of insects. London, 1890.
• Thayer, A.H., Thayer, G.H. Concealing Colouration in the Animal Kingdom. New York, 1909.

Recent research

• Stevens, M., Merilaita, S. (editors) Animal Camouflage: Mechanisms and Function. Cambridge University Press, 2011.
• Stevens, M.; Cuthill, I. C; Windsor, A. M.M; Walker, H. J (2006). "Disruptive contrast in animal camouflage". Proceedings of the Royal Society B: Biological Sciences 273 (1600): 2433. doi:10.1098/rspb.2006.3614. PMC 1634902. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1634902. 

General reading

• Behrens, R.R. False Colors: Art, Design and Modern Camouflage. Bobolink Books, 2002. ISBN 0-9713244-0-9.
• Behrens, R.R. Camoupedia: A Compendium of Research on Art, Architecture and Camouflage. Bobolink Books, 2009. ISBN 978-0-9713244-6-6.
• Elias, A. Camouflage Australia: Art, Nature, Science and War. Sydney University Press, 2011. ISBN 978-1-920899-73-8.
• Forbes, P. Dazzled and Deceived: Mimicry and Camouflage. Yale, 2009.
• Wickler, W. Mimicry in plants and animals. McGraw-Hill, 1968.

Children's books

• Kalman, B., Crossingham, J. What are Camouflage and Mimicry?. Crabtree Publishing. (ages 4–8)
• Mettler, R. Animal Camouflage. Moonlight Publishing. First Discovery series, 2001. (ages 4–8)

Military camouflage

• Behrens, R.R. (editor) Ship Shape: A Dazzle Camouflage Sourcebook. Bobolink Books, 2012. ISBN 978-0-9713244-7-3.
• Gooden, H. Camouflage and Art: Design for Deception in World War 2. Unicorn Press, 2009. ISBN 978-0-906290-87-3.
• Latimer, J. Deception in War. John Murray, 2001.
• Newark, T. Camouflage. Thames and Hudson, with Imperial War Museum, 2007. ISBN 978-0-500-51347-7.

External links

Wikimedia Commons has media related to: Camouflage

• Ohio State University: The Camouflage Project - interplay of science and art
• Marine Biological Laboratory: Hanlon, R. - videos, photographs, research bibliography
• Behrens, R.R. "The Thinking Eye: a Chronology of Camouflage" 2006
• "An informal study into camouflage"
• Octopus camouflage video

Articles related to camouflage v t e Vision in animals Vision Birds Cats Dinosaurs Dogs Fish Horses Toads Eyes Arthropod eye Eye shine Simple eye in invertebrates Mammalian eye Human eye Mollusc eye Cephalopod eye Gastropod eye Parietal eye Evolution Evolution of the eye Evolution of color vision Evolution of color vision in primates Coloration Animal coloration Aposematism Camouflage Chromatophore Counter-illumination Countershading Crypsis Eyespot (mimicry) Structural coloration Underwater camouflage and mimicry Related topics Animal senses Blind animals Eyespot apparatus Feature detection Infrared sensing in snakes Mimicry Monocular deprivation Underwater vision Visual perception v t e Modelling ecosystems – trophic components General Abiotic component Abiotic stress Behaviour Biogeochemical cycle Biomass Biotic component Biotic stress Carrying capacity Competition Ecosystem Ecosystem ecology Ecosystem model Keystone species List of feeding behaviours Metabolic theory of ecology Productivity Producers Autotrophs Chemosynthesis Chemotrophs Foundation species Mixotrophs Myco-heterotrophy Mycotroph Organotrophs Photoheterotrophs Photosynthesis Photosynthetic efficiency Phototrophs Primary nutritional groups Primary production Consumers Apex predator Bacterivore Carnivores Chemoorganotroph Foraging Generalist and specialist species Intraguild predation Herbivores Heterotroph Heterotrophic nutrition Insectivore Mesopredator release hypothesis Omnivores Optimal foraging theory Predation Prey switching Decomposers Chemoorganoheterotrophy Decomposition Detritivores Detritus Microorganisms Archaea Bacteriophage Environmental microbiology Lithoautotroph Lithotrophy Microbial cooperation Microbial ecology Microbial food web Microbial intelligence Microbial loop Microbial mat Microbial metabolism Phage ecology Food webs Biomagnification Ecological efficiency Ecological pyramid Energy flow Food chain Trophic level Example webs Cold seeps Hydrothermal vents Intertidal Kelp forests Lakes North Pacific Subtropical Gyre Rivers San Francisco Estuary Soil Tidal pool Processes Ascendency Bioaccumulation Cascade effect Climax community Competitive exclusion principle Consumer-resource systems Copiotrophs Dominance Ecological network Ecological succession Energy quality Energy Systems Language f-ratio Feed conversion ratio Feeding frenzy Mesotrophic soil Nutrient cycle Oligotroph Paradox of the plankton Trophic cascade Trophic mutualism Trophic state index Defense/counter Animal coloration Antipredator adaptations Camouflage Herbivore adaptations to plant defense Mimicry Plant defense against herbivory Predator avoidance in schooling fish v t e Modelling ecosystems – other components Population ecology Abundance Allee effect Depensation Ecological yield Effective population size Intraspecific competition Logistic function Malthusian growth model Maximum sustainable yield Overpopulation in wild animals Overexploitation Population cycle Population dynamics Population modeling Population size Predator–prey equations Recruitment Resilience Small population size Stability Species Biodiversity Density-dependent inhibition Ecological effects of biodiversity Ecological extinction Endemic species Flagship species Gradient analysis Indicator species Introduced species Invasive species Latitudinal gradients in species diversity Minimum viable population Neutral theory Occupancy-abundance relationship Population viability analysis Priority effect Rapoport's rule Relative abundance distribution Relative species abundance Species diversity Species homogeneity Species richness Species distribution Species-area curve Umbrella species Species interaction Antibiosis Biological interaction Commensalism Community ecology Ecological facilitation Interspecific competition Mutualism Storage effect Spatial ecology Biogeography Cross-boundary subsidy Ecocline Ecotone Ecotype Disturbance Edge effect Foster's rule Habitat fragmentation Ideal free distribution Intermediate Disturbance Hypothesis Island biogeography Landscape ecology Landscape epidemiology Landscape limnology Metapopulation Patch dynamics r/K selection theory Source–sink dynamics Niche Ecological niche Ecological trap Ecosystem engineer Environmental niche modelling Guild Habitat Limiting similarity Niche apportionment models Niche construction Niche differentiation Other networks Assembly rules Bateman's principle Bioluminescence Ecological collapse Ecological debt Ecological deficit Ecological energetics Ecological indicator Ecological threshold Ecosystem diversity Emergence Extinction debt Kleiber's law Liebig's law of the minimum Marginal value theorem Thorson's rule Xerosere Other Allometry Alternative stable state Balance of nature Biological data visualization Constructal theory Ecocline Ecological economics Ecological footprint Ecological forecasting Ecological humanities Ecological stoichiometry Ecopath Ecosystem based fisheries Endolith Evolutionary ecology Functional ecology Industrial ecology Macroecology Microecosystem Natural environment Systems ecology Theoretical ecology List of ecology topics v t e Evolutionary ecology Patterns of evolution Convergent evolution (List) · Parallel evolution · Divergent evolution Signals Antipredator adaptation · Aposematism · Mimicry · Camouflage  · Unkenreflex