Camouflage

• 1. Introduction

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  Camouflage is one of nature's most ancient strategies, and Aristotle noticed it more than two thousand years ago. Writing in his Historia animalium, he observed that the octopus seeks its prey by changing its colour to match the stones adjacent to it, and does so also when alarmed. That single observation opens a door onto a subject of staggering breadth. How does a creature made of flesh and pigment disappear before our eyes? Why does a leopard's spotted coat serve the same function as the dazzle-painted hull of a First World War troopship? And what draws artists, fashion designers, and anti-war protestors to the same visual language that evolved to keep prey alive in a dangerous world? The answers reach from the genetics of deer mice on sand dunes to the surrealist painter Roland Penrose writing a camouflage manual for the British Home Guard.

• 2. Natural History of Hiding

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  Charles Darwin's 1859 theory of natural selection gave scientists the framework to explain why animals are coloured the way they are. In his Origin of Species, Darwin pointed to the alpine ptarmigan white in winter, the red grouse the colour of heather, and the black grouse the colour of peaty earth, arguing that these tints preserve birds and insects from danger. The English zoologist Edward Bagnall Poulton built systematically on this in his 1890 book The Colours of Animals, classifying what he called "special protective resemblance" and "general aggressive resemblance," and demonstrating through experiments that swallow-tailed moth pupae matched the backgrounds on which they were reared as larvae.

  Frank Evers Beddard, writing in 1892, noted that tree-frequenting animals are often green, pointing to parrots, iguanas, tree-frogs, and the green tree-snake. He also described the mackerel's coloration: pelagic fish commonly have a dark upper surface and a white lower surface, making them inconspicuous from both above and below. This principle, later called countershading, would become central to the entire field.

  The artist Abbott Handerson Thayer put countershading on a formal footing, and the principle of it is sometimes called Thayer's Law. His 1909 book Concealing-Coloration in the Animal Kingdom argued that every pattern and colour in every animal that preys or is preyed upon serves concealment. Thayer illustrated his claims with paintings such as Peacock in the Woods from 1907. The argument was overstated, and Thayer was roundly mocked for it, including by Teddy Roosevelt.

  The English zoologist Hugh Cott corrected these errors in his 1940 book Adaptive Coloration in Animals, writing that Thayer had strained the theory to a fantastic extreme. Cott's 500-page textbook built a comprehensive view of camouflage around maximum disruptive contrast and countershading, supported by hundreds of examples. Even so, experimental evidence that camouflage actually helps prey survive predators did not arrive until 2016, when ground-nesting birds, plovers and coursers, were shown to survive according to how well their egg contrast matched the local environment.

• 3. Genetics and Evolution

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  Camouflage does not have a single genetic origin, which makes its evolution across thousands of species all the more remarkable. In many cephalopods, the ability to change colour actively is controlled through neural activity, and the genome of the common cuttlefish contains 16 copies of the reflectin gene. That gene grants the cuttlefish remarkable control over coloration and iridescence, and it is thought to have originated through transposition from symbiotic Aliivibrio fischeri bacteria, which provide bioluminescence to their hosts. This makes it a rare example of camouflage arising through horizontal gene transfer from an endosymbiont.

  Across many lineages, the Agouti genes are orthologous genes that produce yellow and red coloration, working in competition with genes that produce black and brown colours. In eastern deer mice, over roughly 8,000 years, a single agouti gene developed nine mutations that each strengthened the expression of yellow fur under natural selection, largely eliminating black fur. All-black domesticated cats show the opposite: they carry deletions of the agouti gene that prevent any yellow or red from being produced.

  Peppered moths carry camouflage-related genes that stem from transposition events, and their story is a demonstration of natural selection operating in real time. Their coloration evolved between 1860 and 1940 to match tree trunks that shifted from pale and mottled to nearly black in polluted industrial areas. As the fossil record rarely preserves soft tissue, direct evidence of ancient camouflage is scarce, but rare fossilised skin from the Cretaceous period shows that mosasaurs and leatherback turtles were countershaded, their skins pigmented with dark eumelanin. A 120-million-year-old fossil of a Psittacosaurus has been preserved with countershading, and there is evidence of camouflaged insects from more than 100 million years ago, including lacewing larvae that covered themselves in debris much as their modern descendants do.

• 4. The Principles at Work

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  Background matching is the most widespread method of camouflage, and the source material that describes it reads almost like a naturalist's field notes. Tree-dwelling parakeets are mainly green; woodcocks on the forest floor are brown and speckled; reedbed bitterns are streaked brown and buff; desert animals run in tones of sand, buff, ochre, and brownish grey, from the gerbil and the fennec fox to the desert lark, the sandgrouse, the skink, and the horned viper.

  Disruptive coloration works on a different principle. Strongly contrasting, non-repeating markings such as spots or stripes break up the outlines of an animal or a military vehicle. The leopard uses disruptive camouflage to approach prey; the common frog uses it to avoid becoming prey itself. Disruptive patterns that involve visible symmetry carry a cost: research suggests they reduce survivability and increase predation, because symmetry recognition is a predator's tool. For butterflies and moths viewed from above against a homogeneous background like tree bark, symmetry is less costly. Natural selection drives species with variable habitats to move symmetrical patterns away from the body's centre, disrupting the predator's recognition.

  Thayer observed that animals are painted by nature darkest on those parts most lit by the sky, and lightest below, and this is countershading's core logic. Countershading is used by gazelles and grasshoppers on land, sharks and dolphins at sea, and snipe and dunlin in the air. A separate meaning of the word describes simply the matching of upper and lower surfaces to different backgrounds, such as the bright water surface or the sky.

  Horned lizards of North America carry shadow elimination to an extreme. Their bodies are flattened, with sides thinning to an edge; they press their bodies to the ground; and white fringe scales hide any remaining shadow under the edge of the body. The one species lacking fringe scales, the roundtail horned lizard, lives in rocky areas and resembles a rock; when threatened, it curves its back to emphasise its three-dimensional shape. The speckled wood butterfly, Pararge aegeria, takes a different route: it minimises its shadow when perched by closing its wings, aligning its body with the sun, and tilting toward it so the shadow becomes a thin line rather than a broad patch.

  In motion dazzle, rapidly moving bold contrasting stripes degrade a predator's ability to estimate speed and direction accurately. Hoverflies use motion camouflage to approach possible mates, and dragonflies use it to approach rivals while defending territories, moving so as to stay on a straight line between the target and a fixed point in the landscape. A study by Tim Caro in 2012 suggested that the zebra's bold stripes reduce the attractiveness of stationary models to biting flies such as horseflies and tsetse flies. A simulation study by Martin How and Johannes Zanker in 2014 proposed that when the zebra moves, the stripes confuse observers through the wagon-wheel effect and the barberpole illusion.

• 5. Transparency, Silvering, and Light

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  In the open ocean, where there is no background to blend into, animals rely on transparency, silvering, and light itself. Gelatinous planktonic animals are between 50 and 90 percent transparent. A transparency of 50 percent is enough to make an animal invisible to a predator such as cod at a depth of 650 metres; achieving invisibility in shallower water requires greater transparency because light is brighter there. A cod can see prey that are 98 percent transparent in optimal lighting in shallow water.

  The marine hatchetfish is extremely flattened laterally, leaving the body just millimetres thick. Its silvering works through microscopic structures: stacks of between 5 and 10 crystals of guanine spaced about one wavelength apart to achieve nearly 100 percent reflection. In the deep waters where the hatchetfish lives, only blue light at a wavelength of 500 nanometres percolates down, so mirrors 125 nanometres apart provide effective camouflage. In shallower fish like the herring, the mirrors must reflect a mixture of wavelengths and accordingly come in stacks of varying spacing.

  Counter-illumination takes the principle further by producing light to match a background brighter than the animal's body. The firefly squid and the midwater squid both use this method. The midwater squid has photophores scattered all over its underside, creating a sparkling glow that prevents it from appearing as a dark shape when seen from below. During the Second World War, Canada's National Research Council trialled what it called diffused lighting camouflage, projecting light onto the sides of ships to match the faint glow of the night sky. The American Yehudi lights project refined this concept for aircraft including B-24 Liberators and naval Avengers, fitting them with forward-pointing lamps automatically adjusted to match sky brightness. The planes could approach a target within 3,000 yards before being seen. Radar made the method obsolete before either system entered active service.

  At the other extreme, some deep-sea fishes have evolved ultra-black skin that reflects under 0.5 percent of ambient light. Oneirodes was particularly remarkable, reflecting only 0.044 percent of 480-nanometre wavelength light. The ultra-blackness is produced by a thin continuous layer of melanosomes in the dermis, which both absorb most of the light and scatter rather than reflect the rest. Modelling suggests this camouflage reduces the distance at which such a fish can be detected by a factor of six compared to a fish with a nominal 2 percent reflectance.

• 6. Military Camouflage

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  Philostratus, writing around 172 to 250 AD, recorded that Mediterranean pirate ships were painted blue-gray for concealment. Vegetius, writing around 360 to 400 AD, noted that during the Gallic Wars Julius Caesar sent reconnaissance boats along the coast of Britain painted entirely in bluish-green wax, sails, ropes and crew the same colour. On land, two unusual ceramics depict men in Peru's Mochica culture from before 500 AD hunting birds with blowpipes fitted with a shield near the mouth, possibly to hide the hunters' hands and faces. Jamaican Maroons are said to have used plant materials as camouflage in the First Maroon War, roughly 1655 to 1740.

  The decisive shift came in the 19th century, when the replacement of the inaccurate musket with weapons such as the Baker rifle made personal concealment in battle essential. Two Napoleonic-era skirmishing units, the 60th Foot and the 95th Rifles, were the first British units to adopt camouflage in the form of a rifle green jacket, while other troops continued in red coats. A study by the British artist and army officer Charles Hamilton Smith in 1800 found that grey uniforms were less visible than green ones at a range of 150 yards. The Bengal Army's Corps of Guides adopted khaki in 1848 when Sir Harry Lumsden and his second-in-command William Stephen Raikes Hodson introduced a drab uniform at Peshawar. Hodson wrote that it would help make his troops invisible in a land of dust. By 1896 khaki drill was used everywhere outside Europe, and by the time of the Second Boer War six years later it was used throughout the British Army. The Imperial German Army introduced feldgrau in 1907.

  In the First World War, the French army formed a camouflage corps led by Lucien-Victor Guirand de Scévola, employing artists called camoufleurs. The term camouflage probably comes from camoufler, a Parisian slang term meaning to disguise, possibly influenced by camouflet, a French term meaning smoke blown in someone's face. In April 1917, with German U-boats sinking large numbers of British ships, the marine artist Norman Wilkinson devised dazzle camouflage. In his own words, it was designed not for low visibility but to break up a ship's form and confuse a submarine officer as to the course on which she was heading. In early 1916 the Royal Naval Air Service began creating dummy airfields with decoy homes and fake runways lit with flares; the strategy was not common practice initially but in 1918 it caught the Germans off guard multiple times.

  In the Second World War, the zoologist Hugh Cott worked to persuade the British army to adopt countershading. He painted two rail-mounted coastal guns, one in conventional style, one countershaded; in aerial photographs, the countershaded gun was essentially invisible. The Soviet Union's Red Army developed the comprehensive deception doctrine of Maskirovka; during the Battle of Kursk, General Katukov noted that the enemy did not suspect their well-camouflaged tanks were waiting. The Camouflage Development and Training Centre was founded at Farnham Castle; the surrealist painter Roland Penrose became a lecturer there, writing the practical Home Guard Manual of Camouflage. The film-maker Geoffrey Barkas ran the Middle East Command Camouflage Directorate during the 1941-1942 war in the Western Desert, overseeing the successful deception of Operation Bertram. In Australia, the Sydney Camouflage Group was formed under Professor William John Dakin of Sydney University; Max Dupain, Sydney Ure Smith, and William Dobell were among its members, working at Bankstown Airport, RAAF Base Richmond, and Garden Island Dockyard.

  After 1945, radar made camouflage for fixed-wing aircraft largely obsolete. The first genuinely digital camouflage pattern was the Canadian Disruptive Pattern, CADPAT, issued to the army in 2002, soon followed by the American Marine pattern, MARPAT. The American Universal Camouflage Pattern of 2004 attempted to suit all environments but was withdrawn after a few years. In 2011, BAE Systems announced their Adaptiv infrared camouflage technology, using about 1,000 hexagonal panels on the sides of a tank, heated and cooled to match either the vehicle's surroundings or another object when viewed in infrared.

• 7. Art, Fashion, and Culture

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  Military camouflage patterns entered art and fashion from the time of the First World War. Gertrude Stein recalled Pablo Picasso's reaction when the first camouflaged truck passed on the Boulevard Raspail in around 1915. Picasso looked at it and cried out that it was cubism.

  In 1919, the Chelsea Arts Club hosted a dazzle ball at the Albert Hall where attendants wore dazzle-patterned black and white clothing. The Illustrated London News announced the event, describing the decoration as based on the principles of dazzle used during the war in the painting of ships, and calling the total effect brilliant and fantastic. The ball spread its influence through postcards and magazine articles.

  Anti-war protestors in the late 1960s and early 1970s in the United States ironically wore military clothing during demonstrations against American involvement in the Vietnam War. Wearing clothing with a camouflage design is illegal for civilians in some countries, including Barbados, Jamaica, and Saint Lucia.

  The artist Ian Hamilton Finlay used camouflage to reflect on war in his 1973 screenprint Arcadia, depicting a tank camouflaged in a leaf pattern. The Tate describes it as drawing an ironic parallel between the idea of a natural paradise and the camouflage patterns on a tank. The title refers to the Latin phrase Et in Arcadia ego, which recurs throughout Hamilton Finlay's work. In 1986, Andy Warhol began a series of monumental camouflage paintings that helped transform camouflage into a popular print pattern. A year later, in 1987, New York designer Stephen Sprouse used Warhol's camouflage prints as the basis for his Autumn Winter 1987 collection. In 1986 the hunter Bill Jordan created cryptic clothing for hunters printed with images of specific kinds of vegetation such as grass and branches, bringing the military aesthetic back to the natural world that first inspired it.