Camouflage

Wikipedia:

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. 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.

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.

Camouflage can be achieved in what may seem opposite ways. Mimesis means being seen, but resembling something else, whereas crypsis means being hidden. 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

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, 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:

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).

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

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. 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.

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. Mimesis is common in prey animals, for example when a Peppered Moth caterpillar mimics a twig, or a grasshopper mimics a dry leaf.

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. This tactic has occasionally been used in warfare, for example with heavily armed Q-ships disguised as merchant ships.

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. The cuckoo's egg itself mimics the eggs of the host species, reducing its chance of being rejected.

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.

Peppered Moth caterpillars are superb twig mimics on birch (left) and willow (right) branches

Flower Mantis lures its insect prey by mimicking a Phalaenopsis orchid blossom

Hooded Grasshopper Teratodus monticollis, superbly mimics a leaf with a bright orange border

This Grasshopper hides from predators by mimicking a dry leaf

WWII Battle Tank hid from the enemy by mimicking a truck

Armed WW1 Q-ship lured enemy submarines by mimicking a merchantman

Cuckoo adult mimics Sparrowhawk, giving female time to lay eggs parasitically

Cuckoo eggs mimicking smaller eggs, in this case of Reed Warbler

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:

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.

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. 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".

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. Further, young giraffes are much more vulnerable to predation than adults: between 60% and 75% of calves die before their first birthday. 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. 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.

Leopard: a disruptively camouflaged (and countershaded) predator

Egyptian Nightjar nests in open sand with only its disruptive plumage to protect it

Papuan Frogmouth Podargus papuensis, superbly disruptive

Jumping Spider: a disruptively camouflaged invertebrate predator

A soldier applying a disruptive pattern to his face; his helmet and jacket are both disruptively patterned

Conspicuous giraffe mother can defend herself, but calf hides for much of day, relying on disruptive camouflage

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.

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." 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."

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

Three countershaded and cryptically coloured Ibex almost invisible in the Israeli desert

"Shape, shine, shadow" make these 'camouflaged' military vehicles easily visible

The Flat-tail Horned Lizard's body is flattened and fringed to minimise its shadow

Camouflage netting is draped away from a military vehicle to reduce its shadow

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. Most other forms of crypsis also require some animal behaviour, e.g. lying down and keeping still, as with young Giraffes, lying flat, as in the Flat-tail Horned Lizard, or swaying as if rippled by wind or water currents, as in the Leafy Sea Dragon.

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.

Sniper camouflaged with a Ghillie suit and plant materials from the environment

Crab camouflaged with algae from the environment

Leafy Sea Dragon camouflaged by pattern, shape, colour and swaying like the seaweed that it mimics

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. However some insects such as hoverflies and dragonflies use motion camouflage: the hoverflies to approach possible mates, and the dragonflies to approach rivals when defending territories. 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). The same technique can be used for military purposes, for example by missiles to minimise their risk of detection by the enemy. 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.

Male Syritta pipiens hoverflies use motion camouflage to approach females

Male Australian Emperor dragonflies use motion camouflage to approach rivals

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).

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. However, Arctic hares which live in the far north of Canada, where summer is very short, remain white all year round.

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.

Rock Ptarmigan, changing colour in springtime. The male is still mostly in winter plumage

Norwegian volunteer soldiers in Winter War, 1940, with white camouflage overalls over their uniforms

Arctic Hares in the low arctic change from brown to white in winter

Snow-camouflaged German vehicles in Russia, October 1941

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. 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.

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. At the same time in Australia, zoologist William John Dakin advised soldiers to copy animals' methods, using their instincts for wartime camouflage.

Countershaded Dorcas Gazelle, Gazella dorcas

Countershaded Reef Shark, Carcharhinus amblyrynchos

Countershaded US Navy Vigilante aircraft in jungle colours

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.

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.

Sparkling Enope Squid uses bioluminescence to make its underside as bright as the sea surface above it

Forward-looking counterillumination camouflage was trialled in B-24 Liberators from 1943 onwards

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.

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. Dazzle patterning is therefore arguably (by definition) not camouflage, though it has been called camouflage since the First World War. 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. Remarkably, some United States Navy camouflage schemes in World War II attempted to combine disruptive camouflage and dazzle.

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. 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). 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.

A ship painted with dazzle camouflage to confuse enemy gunners as to her speed, direction, and range

The Zebra's bold pattern may momentarily confuse predators, especially when many animals are close together and moving rapidly

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. The Illustrated London News announced

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

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. 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.

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

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". 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.

Postcard of costumes at the 'Dazzle Ball' held by the Chelsea Arts Club, 1919

A camouflage patterned skirt as a fashion item

Abbott Thayer's Peacock in the Woods tried to show the peacock's iridescent plumage as camouflage; Thayer did not believe in sexual selection.

André Mare's Cubist sketch of a 280 calibre gun illustrates the interplay of art and war, as artists like Mare contributed their skills to improve military camouflage.

Ian Hamilton Finlay's Arcadia screenprint uses camouflage in art to contrast leafy peace and military hardware.

Camouflage clothing in an anti-war protest, 1971

Bibliography

Camouflage in nature

Pioneering research

Recent research

General reading

Children's books

Military camouflage