The U.S. Woodland is a camouflage pattern that was used as the default camouflage pattern issued to the United States Armed Forces from 1981, with the issue of the Battle Dress Uniform, until its replacement in the mid to late 2000s. It is a four color, high contrast disruptive pattern with irregular markings in green, brown, sand and black. It is also known unofficially by its colloquial moniker of "M81" after the Battle Dress Uniform it was first used on, though this term was not officially used by the U.S. military.
U.S. Army National Guardsmen on an exercise in 2000 while wearing Woodland BDUs and PASGT helmets
Russian Internal Troops wearing LES, a Russian camouflage pattern similar to the woodland camouflage
Disruptive coloration is a form of camouflage that works by breaking up the outlines of an animal, soldier or military vehicle with a strongly contrasting pattern. It is often combined with other methods of crypsis including background colour matching and countershading; special cases are coincident disruptive coloration and the disruptive eye mask seen in some fishes, amphibians, and reptiles. It appears paradoxical as a way of not being seen, since disruption of outlines depends on high contrast, so the patches of colour are themselves conspicuous.
The coloration of the Papuan frogmouth Podargus papuensis, its outline disrupted by its plumage, its eye concealed in a stripe, is an effective anti-predator adaptation.
The principle of "maximum disruptive contrast" in Hugh Cott's 1940 Adaptive Coloration in Animals, "showing the distractive effect upon the eye of patterns which contrast as violently as possible with the tone of their background". The examples are of a fish, an antelope, and a bird.
Egyptian nightjar, Caprimulgus aegyptius, rests on the sand, protected by its coloration, immobility, and concealment of shadow as it faces the sun
Mexican vine snake, Oxybelis aeneus, conceals its eye with a coincident dark stripe, contrasting with its pale underside