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Natural camouflageIn 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.
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.[citation needed]
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.
Camouflaging colorationThis 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:
Animals produce colors in two ways:
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. DisguiseThe 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 camouflageImage:Camo1.jpg A simple example of common military style 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
References
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