Camouflage

For other uses, see protective camouflage used to disguise people, animals, or military targets.

Countershaded Ibex are almost invisible in the Israeli desert.

Camouflage, also known as cryptic coloration, is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples include a tiger's stripes and the battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word camoufler meaning "to disguise."

Natural camouflage

Main article: crypsis

In nature, there is a strong evolutionary pressure for animals to blend into their environment or conceal their shape; for prey animals to avoid predators and for predators to be able to sneak up on prey. Natural camouflage is one method that animals use to meet these. There are a number of methods of doing so. One is for the animal to blend in with its surroundings, while another is for the animal to disguise itself as something uninteresting or something dangerous.

There is a permanent co-evolution of the sensory abilities of animals for whom it is beneficial to be able to detect the camouflaged animal, and the cryptic characteristics of the concealing species. Different aspects of crypsis and sensory abilities may be more or less pronounced in given predator-prey pairs of species.

Some cryptic animals also simulate natural movement, e.g., of a leaf in the wind. This is called procryptic behaviour or habit. Other animals attach or attract natural materials to their body for concealment.

A few animals have chromatic response, changing color in changing environments, either seasonally (ermine, snowshoe hare) or far more rapidly with chromatophores in their integument (chameleon, the cephalopod family).

Some animals, notably in aquatic environments, also take steps to camouflage the odours they create that may attract predators.

Some herd animals adopt a similar pattern to make it difficult to distinguish a single animal. Examples include stripes on zebras and the reflective scales on fish.

Countershading (or obliterative camouflage), the use of different colors on upper and lower surfaces in graduating tones from a light belly to a darker back, is common in the sea and on land. This is sometimes called Thayer's law, after Abbott H. Thayer who published a paper on the form in 1896.

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  An infant Cuttlefish blends into the surrounding sand substrate.
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  A Dead Leaf Mantis from Madagascar.
• Anolis caroliensis showing blending camouflage and counter-shading
  Anolis caroliensis showing blending camouflage and counter-shading
• A flounder blends in with its environment.
  A flounder blends in with its environment.
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  The stripes of Plains Zebras blend together making it difficult to distinguish an individual animal.
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  A leaf insect
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  Sumatran Tiger
• Tawny Frogmouth blends in with color and texture of tree bark.
  Tawny Frogmouth blends in with color and texture of tree bark.

Camouflaging coloration

This is the most common form of camouflage, found to some extent in the majority of species. The simplest way is for an animal to be of a color similar to its surroundings. Examples include the "earth tones" of deer, squirrels, or moles (to match trees or dirt), or the combination of blue skin and white underbelly of sharks (which makes them difficult to detect from both above and below). More complex patterns can be seen in animals such as flounder, moths, and frogs, among many others. Some forms of camouflage use contrasting shades to break up the visual outline, as on a gull or zebra.

The type of camouflage a species will develop depends on several factors:

• The environment in which it lives. This is usually the most important factor.
• The physiology and behavior of an animal. Animals with fur need different camouflage than those with feathers or scales. Likewise, animals who live in groups use different camouflage techniques than those that are solitary.
• If the animal is preyed upon, then the behavior or characteristics of its predator can influence how the camouflage develops. For example, if the predator is color blind, then the animal will not need to match the color of its surroundings.

Animals produce colors in two ways:

• Biochromes — natural microscopic pigments that absorb certain wavelengths of light and reflect others, creating a visible color that is targeted towards its primary predator.
• Microscopic physical structures, which act like prisms to reflect and scatter light to produce a color that is different from the skin, such as the translucent fur of the Polar Bear, which actually has black skin.

Camouflage coloration can change as well. This can be due to just a changing of the seasons, or it can be in response to more rapid environmental changes. For example, the Arctic fox has a white coat in winter, and a brown coat in summer. Mammals and birds require a new fur coat and new set of feathers respectively, but some animals, such as cuttlefish, have deeper-level pigment cells, called chromatophores, that they can control. Other animals such as certain fish species or the nudibranch can actually change their skin coloration by changing their diet. However, the most well-known creature that changes color, the chameleon, usually does not do so for camouflage purposes, but instead to express its mood.

Beyond colors, skin patterns are often helpful in camouflage as well. This can be seen in common domestic pets such as tabby cats, but striping overall in other animals such as tigers and zebras help them blend into their environment, the jungle and the grasslands respectively. The latter two provide an interesting example, as one's initial impression might be that their coloration does not match their surroundings at all, but tigers' prey are usually color blind to a certain extent such that they cannot tell the difference between orange and green, and zebras' main predators, lions, are color blind. In the case of zebras, the stripes also blend together so that a herd of zebras looks like one large mass, making it difficult for a lion to pick out any individual zebra. This same concept is used by many striped fish species as well. Among birds, the white "chinstraps" of Canada geese make a flock in tall grass appear more like sticks and less like birds' heads.

Disguise

Main article: Mimic

The camouflage technique of disguise is not as common as coloration, but can be found throughout nature as well. Animals may disguise themselves as something uninteresting in the hopes that their predators will ignore them, or as something dangerous so that predators will avoid them.

The most famous example of the former is the stick insect, which looks like a stick, as well as its cousin the leaf insect, which looks like a leaf.

Disguising oneself as something dangerous is known as mimicry, such as the case of a Scarlet Kingsnake which looks like the poisonous coral snake.

Military camouflage

A simple example of common military style camouflage.

Main article: Military camouflage

Camouflage was not in wide use in early warfare. 19th-century armies tended to use bright colors and bold, impressive designs. These were intended to daunt the enemy, attract recruits, foster unit cohesion, or allow easier identification of units in the fog of war.

Smaller, irregular units of scouts in the 18th century were the first to adopt colors in drab shades of brown and green. Major armies retained their color until convinced otherwise. The British in India in 1857 were forced by casualties to dye their red tunics to neutral tones, initially a muddy tan called khaki (from the Urdu word for 'dusty'). White tropical uniforms were dyed by the simple expedient of soaking them in tea. This was only a temporary measure. It became standard in Indian service in the 1880s, but it was not until the Second Boer War that, in 1902, the uniforms of the entire British army were standardized on this dun tone for battledress. Other armies, such as the United States, Russia, Italy, and Germany followed suit either with khaki, or with other colors more suitable for their environments.

See also

• Advertising colouration - another opposite defense for animals
• Everett Warner
• Dazzle camouflage

References

• Harris, Tom. "How Animal Camouflage Works". How Stuff Works. Retrieved 2006-11-13.
• "How do a zebra's stripes act as camouflage?". How Stuff Works. Retrieved 2006-11-13.
• Roy R. Behrens - Art and Camouflage: An Annotated Bibliography
• Behrens, Roy R. (2002). FALSE COLORS: Art, Design and Modern Camouflage. Bobolink Books. ISBN 0-9713244-0-9.
• Jon Latimer, Deception in War, London: John Murray, 2001
• Everett L. Warner, “The Science of Marine Camouflage Design” in Transactions of the Illuminating Engineering Society 14 (5) 1919, pp. 215-219.
• Everett L. Warner, “Fooling the Iron Fish: The Inside Story of Marine Camouflage” in Everybody’s Magazine (November 1919), pp. 102-109.

External links

• Roy R. Behrens, "The Thinking Eye: a Chronology of Camouflage" 2006
• "An informal study into camoflage"