Disruptive coloration

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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. Podargus papuensis - Daintree River.jpg
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.

Disruptive coloration (also known as disruptive camouflage or disruptive patterning) is a form of camouflage that works by breaking up the outlines of an animal, soldier or military hardware 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.

Contents

The importance of high-contrast patterns for successful disruption was predicted in general terms by the artist Abbott Thayer in 1909 and explicitly by the zoologist Hugh Cott in 1940. Later experimental research has started to confirm these predictions. Disruptive patterns work best when all their components match the background.

While background matching works best for a single background, disruptive coloration is a more effective strategy when an animal or a military vehicle may have a variety of backgrounds.

Conversely, poisonous or distasteful animals that advertise their presence with warning coloration (aposematism) use patterns that emphasize rather than disrupt their outlines. For example, skunks, salamanders and monarch butterflies all have high-contrast patterns that display their outlines.

Early research

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. Disruptive Coloration by Hugh Cott 1940.jpg
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.

The artist Abbott Handerson Thayer in his 1909 book Concealing-Coloration in the Animal Kingdom argued that animals were concealed by a combination of countershading and "ruptive" marks, which together "obliterated" their self-shadowing and their shape. Thayer explained that: [2]

Markings... of whatever sort, tend to obliterate,—to cancel, by their separate and conflicting pattern, the visibility of the details and boundaries of form.... If the bird's or butterfly's costume consists of sharply contrasted bold patterns of light and dark, in about equal proportions, its contour will be "broken up" against both light and dark—light failing to show against light, dark against dark. Such is apparently the basal and predominant use of almost all the bolder patterns in animals' costumes.

— Thayer [2]

Hugh Cott's 1940 book Adaptive Coloration in Animals introduced ideas such as "maximum disruptive contrast". This uses streaks of boldly contrasting colour, which paradoxically make animals or military vehicles less visible by breaking up their outlines. He explains that in ideal conditions, background colour matching together with countershading would "suffice to render an animal absolutely invisible against a plain background", but at once adds that conditions are hardly ever ideal, as they are constantly changing, as is the light. Therefore, Cott argues, camouflage has to break up the perceived continuous surfaces of an object and its outlines. In his own words, "for effective concealment, it is essential that the tell-tale appearance of form should be destroyed." [3] He draws an analogy with a pickpocket who carefully distracts your attention, arguing that:

The function of a disruptive pattern is to prevent, or to delay as long as possible, the first recognition of an object by sight... irregular patches of contrasted colours and tones ... tend to catch the eye of the observer and to draw his attention away from the shape which bears them.

— Cott [3]

Further, Cott criticises unscientific attempts at camouflage, early in the Second World War, for not understanding the principles involved:

Various recent attempts to camouflage tanks, armoured cars and the roofs of buildings with paint reveal an almost complete failure by those responsible to grasp the essential factor in the disguise of surface continuity and of contour. Such work must be carried out with courage and confidence, for at close range objects properly treated will appear glaringly conspicuous. But they are not painted for deception at close range, but at ranges at which ... bombing raids are likely... And at these distances differences of tint ... blend and thus nullify the effect and render the work practically useless.

— Cott [3]

The pioneering work of Thayer and Cott is endorsed in the 2006 review of disruptive coloration by Martin Stevens and colleagues, which notes that they proposed a "different form of camouflage" from the traditional "strategy of background matching" proposed by authors such as Alfred Russel Wallace ( Darwinism , 1889), Edward Bagnall Poulton ( The Colours of Animals , 1890) and Frank Evers Beddard ( Animal Coloration , 1895); Stevens observes that background matching on its own would always fail because of "discontinuities between the boundary of the animal and the background". [4]

In animals

Egyptian nightjar, Caprimulgus aegyptius, rests on the sand, protected by its coloration, immobility, and concealment of shadow as it faces the sun Caprimulgus aegyptius.jpg
Egyptian nightjar, Caprimulgus aegyptius, rests on the sand, protected by its coloration, immobility, and concealment of shadow as it faces the sun

Disruptive patterns use strongly contrasting markings such as spots or stripes to break up the outlines of an animal or military vehicle. Some predators, like the leopard, and some potential prey like the Egyptian nightjar, use disruptive patterns. [4] Disruptive patterns are defined by A. Barbosa and colleagues as "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", as in the cuttlefish. [5]

Mexican vine snake, Oxybelis aeneus, conceals its eye with a coincident dark stripe, contrasting with its pale underside Oxybelis aeneus (detail).jpg
Mexican vine snake, Oxybelis aeneus, conceals its eye with a coincident dark stripe, contrasting with its pale underside

The strategy appears paradoxical and counter-intuitive as a method of camouflage, since disrupting outlines depends on using patches of colour which contrast strongly with each other, so the patches are themselves conspicuous. [4] [6] While background matching works best for a single background, disruptive coloration is a more effective strategy when an animal or a military vehicle may have a variety of backgrounds. [6]

Martin Stevens and colleagues in 2006 made what they believed was the first experimental test that "disruptive coloration is effective even when some colour patches do not match the background and have a high contrast with both the background and adjacent pattern elements (disruptive contrast)". [4] They used "moth-like targets", some matching the lightness of the background oak tree bark, other mismatching it, each with a dead mealworm. If the mealworm was removed it was assumed a bird predator had taken it: this could be distinguished from visits by other predators. They found that disruptive coloration provided the best protection from bird predators when the pattern was matched to background luminance, but even when elements in a pattern did not match, disruptive patterns were still better at reducing predation than either non-disruptive patterns or plain (unpatterned) control targets. [4]

Disruptive and distractive camouflage both rely on conspicuous markings, but differ in their mechanisms and so in the size and position of the markings for greatest effectiveness. Disruptive versus Distractive Camouflage Markings.svg
Disruptive and distractive camouflage both rely on conspicuous markings, but differ in their mechanisms and so in the size and position of the markings for greatest effectiveness.

Disruptive patterns can also conceal specific features. Animals such as fish, birds, frogs and snakes can readily be detected by their eyes, which are necessarily round and dark. Many species conceal the eye with a disruptive eye mask, sometimes contrasting with a stripe above the eye, making it seem just part of a dark area of background. Cott called this a special case of a "coincident disruptive pattern". [7]

Another camouflage mechanism, distractive markings, also involves conspicuous marks and has for a century since Thayer's initial description been conflated with it, but the two require different kinds of marking. For distraction, the markings should be small and should avoid the prey's outline so as to take attention away from it, whereas disruptive markings should contact the outline so as to break it up. [8]

The opposite case: aposematism

Opposite of disruption: Fire salamander, Salamandra salamandra, advertises its inedibility with bright warning colours, in patches that emphasize its body shape Feuersalamander DE.jpg
Opposite of disruption: Fire salamander, Salamandra salamandra, advertises its inedibility with bright warning colours, in patches that emphasize its body shape

Many poisonous or distasteful animals that advertise their presence with warning coloration (aposematism) use patterns that emphasize rather than disrupt their outlines. For example, skunks, salamanders and monarch butterflies all have high contrast patterns that display their outlines. These advertising patterns exploit the opposite principle to disruptive coloration, for what is in effect the exactly opposite effect: to make the animal as conspicuous as possible. [9] Some Lepidoptera, including the wood tiger moth, are aposematic and disruptively coloured; against a green, vegetative background their bright aposematic coloration stands out, but on the ground their wings camouflage them among dead leaves and dirt. [10]

A disputed case: the giraffe

A conspicuous giraffe mother can defend herself, but her calf relies on its camouflage Giraffe mother and calf (cropped).jpg
A conspicuous giraffe mother can defend herself, but her calf relies on its camouflage

The presence of bold markings does not in itself prove that an animal relies on camouflage. [11] 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. [12]

Irregular outline of comma butterfly Polygonia c-album avoids a typical butterfly shape Polygonia c-album LC0238.jpg
Irregular outline of comma butterfly Polygonia c-album avoids a typical butterfly shape

Further, young giraffes are much more vulnerable to predation than adults: between 60% and 75% of calves die within a year. [12] 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. [12] 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. [12]

Other ways of hiding outlines

The outlines of an animal's body can be made hard to see by other methods, such as by using a highly irregular outline. For example, the comma butterfly, Polygonia c-album, is highly cryptic when its wings are closed, with cryptic colours, disruptive pattern, and irregular outer margins to the wings. [13]

In plants

Many understory plants such as the saw greenbriar, Smilax bona-nox are variegated with pale markings which may serve as camouflage. Smilax bona-nox, Colt Creek State Park, Lakeland, Florida.jpg
Many understory plants such as the saw greenbriar, Smilax bona-nox are variegated with pale markings which may serve as camouflage.

The possibility of protective coloration in plants has been little studied. T. J. Givnish and Simcha Lev-Yadun have proposed that leaf variegation with white spots may serve as camouflage in forest understory plants, where there is a dappled background. Lev-Yadun has also suggested, however, that similar markings serve as conspicuous warning coloration in well-defended thorny plants of open habitats, where the background is uniformly bright. Givnish found a correlation of leaf mottling with closed habitats. Disruptive camouflage would have a clear evolutionary advantage in plants: they would tend to escape from being eaten by herbivores; and the hypothesis is testable. [15] [16] [14]

Military usage

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

Disruptive coloration is common in military usage, for military vehicles, for firing positions and other installations, and for individual soldiers, where uniforms, equipment such as helmets, and face paint may be used to break up outlines and features. [17] Disruptive coloration, 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. [18] [19]

US Woodland camouflage pattern US Woodland pattern.svg
US Woodland camouflage pattern

Many military camouflage patterns since the 1940s have been disruptively coloured, and with the issue of US Woodland pattern to United States armed forces from 1981, disruptive pattern became a dominant feature of military uniforms. [20] From 1969, Disruptive Pattern Material (DPM) began to replace plain material for uniforms in the British Armed Forces and was later used by many other armies. [21]

Challenges

Modern German Flecktarn 1990 is a non-digital pattern designed to disrupt outlines at different distances Flecktarn.jpg
Modern German Flecktarn 1990 is a non-digital pattern designed to disrupt outlines at different distances

Three major challenges face the design of disruptively patterned uniforms. Firstly, units frequently move from one terrain to another, where the background colours and contrasts may differ greatly. A uniform designed for woodland will be too strongly contrasting for desert use, and too green for urban use. Therefore, no single camouflage pattern is effective in all terrains. [22] [23] [24] The American UCP of 2004 attempted to suit all environments but was withdrawn after a few years of service. [25] Terrain specific patterns like "Berlin camouflage", which was applied to British vehicles operating in Berlin during the Cold War, have sometimes been developed but are ineffective in other terrains. [26] Secondly, the effectiveness of any pattern in disrupting a soldier's outlines varies with lighting, depending on the weather and the height of the sun in the sky. And thirdly, any given patch of printed colour varies in apparent size with distance from the enemy observing the pattern. A pattern printed with small patches of colour blends into a single perceived mass at a certain range, defeating the disruptive effect. Conversely, a pattern printed with large patches of colour appears conspicuous at shorter ranges. [27] This problem has been solved with pixellated shapes, often designed digitally, that provide a fractal-like range of patch sizes, enabling them to be effectively disruptive both at close range and at a distance. The first genuinely digital camouflage pattern was the Canadian CADPAT, soon followed by the American MARPAT. A pixellated appearance is not essential for this effect, though it is simpler to design and to print. [28]

Examples

Related Research Articles

<span class="mw-page-title-main">Camouflage</span> Concealment in plain sight by any means, e.g. colour, pattern and shape

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

<span class="mw-page-title-main">Dazzle camouflage</span> Family of ship camouflage

Dazzle camouflage, also known as razzle dazzle or dazzle painting, is a type of ship camouflage that was used extensively in World War I, and to a lesser extent in World War II and afterwards. Credited to the British marine artist Norman Wilkinson, though with a rejected prior claim by the zoologist John Graham Kerr, it consisted of complex patterns of geometric shapes in contrasting colours interrupting and intersecting each other.

<span class="mw-page-title-main">Abbott Handerson Thayer</span> American painter (1849–1921)

Abbott Handerson Thayer was an American artist, naturalist, and teacher. As a painter of portraits, figures, animals, and landscapes, he enjoyed a certain prominence during his lifetime, and his paintings are represented in major American art collections. He is perhaps best known for his 'angel' paintings, some of which use his children as models.

<span class="mw-page-title-main">Military camouflage</span> Camouflage used to protect from enemy observation

Military camouflage is the use of camouflage by an armed force to protect personnel and equipment from observation by enemy forces. In practice, this means applying colour and materials to military equipment of all kinds, including vehicles, ships, aircraft, gun positions and battledress, either to conceal it from observation (crypsis), or to make it appear as something else (mimicry). The French slang word camouflage came into common English usage during World War I when the concept of visual deception developed into an essential part of modern military tactics. In that war, long-range artillery and observation from the air combined to expand the field of fire, and camouflage was widely used to decrease the danger of being targeted or enable surprise. As such, military camouflage is a form of military deception in addition to cultural functions such as political identification.

<span class="mw-page-title-main">Hugh B. Cott</span> English zoologist and camouflage expert (1900–1987)

Hugh Bamford Cott was a British zoologist, an authority on both natural and military camouflage, and a scientific illustrator and photographer. Many of his field studies took place in Africa, where he was especially interested in the Nile crocodile, the evolution of pattern and colour in animals. During the Second World War, Cott worked as a camouflage expert for the British Army and helped to influence War Office policy on camouflage. His book Adaptive Coloration in Animals (1940), popular among serving soldiers, was the major textbook on camouflage in zoology of the twentieth century. After the war, he became a Fellow of Selwyn College, Cambridge. As a Fellow of the Zoological Society of London, he undertook expeditions to Africa and the Amazon to collect specimens, mainly reptiles and amphibians.

<span class="mw-page-title-main">Countershading</span> Camouflage to counteract self-shading

Countershading, or Thayer's law, is a method of camouflage in which an animal's coloration is darker on the top or upper side and lighter on the underside of the body. This pattern is found in many species of mammals, reptiles, birds, fish, and insects, both in predators and in prey.

<span class="mw-page-title-main">Animal coloration</span> General appearance of an animal

Animal colouration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are brightly coloured, while others are hard to see. In some species, such as the peafowl, the male has strong patterns, conspicuous colours and is iridescent, while the female is far less visible.

<span class="mw-page-title-main">Multi-scale camouflage</span> Type of camouflage that combines patterns

Multi-scale camouflage is a type of military camouflage combining patterns at two or more scales, often with a digital camouflage pattern created with computer assistance. The function is to provide camouflage over a range of distances, or equivalently over a range of scales, in the manner of fractals, so some approaches are called fractal camouflage. Not all multiscale patterns are composed of rectangular pixels, even if they were designed using a computer. Further, not all pixellated patterns work at different scales, so being pixellated or digital does not of itself guarantee improved performance.

<span class="mw-page-title-main">Underwater camouflage</span> Camouflage in water, mainly by transparency, reflection, counter-illumination

Underwater camouflage is the set of methods of achieving crypsis—avoidance of observation—that allows otherwise visible aquatic organisms to remain unnoticed by other organisms such as predators or prey.

<i>Adaptive Coloration in Animals</i> 1940 textbook on camouflage, mimicry and aposematism by Hugh Cott

Adaptive Coloration in Animals is a 500-page textbook about camouflage, warning coloration and mimicry by the Cambridge zoologist Hugh Cott, first published during the Second World War in 1940; the book sold widely and made him famous.

<i>The Colours of Animals</i> 1890 book by Edward Bagnall Poulton

The Colours of Animals is a zoology book written in 1890 by Sir Edward Bagnall Poulton (1856–1943). It was the first substantial textbook to argue the case for Darwinian selection applying to all aspects of animal coloration. The book also pioneered the concept of frequency-dependent selection and introduced the term "aposematism".

<i>Concealing-Coloration in the Animal Kingdom</i> Book by Abbott Handerson Thayer

Concealing-Coloration in the Animal Kingdom: An Exposition of the Laws of Disguise Through Color and Pattern; Being a Summary of Abbott H. Thayer's Discoveries is a book published ostensibly by Gerald H. Thayer in 1909, and revised in 1918, but in fact a collaboration with and completion of his father Abbott Handerson Thayer's major work.

<i>Animal Coloration</i> (book) 1892 book by Frank Evers Beddard

Animal Coloration, or in full Animal Coloration: An Account of the Principal Facts and Theories Relating to the Colours and Markings of Animals, is a book by the English zoologist Frank Evers Beddard, published by Swan Sonnenschein in 1892. It formed part of the ongoing debate amongst zoologists about the relevance of Charles Darwin's theory of natural selection to the observed appearance, structure, and behaviour of animals, and vice versa.

<span class="mw-page-title-main">Snow camouflage</span> Camouflage coloration for winter snow

Snow camouflage is the use of a coloration or pattern for effective camouflage in winter, often combined with a different summer camouflage. Summer patterns are typically disruptively patterned combinations of shades of browns and greys, up to black, while winter patterns are dominated by white to match snowy landscapes.

<span class="mw-page-title-main">Coloration evidence for natural selection</span> Early evidence for Darwinism from animal coloration

Animal coloration provided important early evidence for evolution by natural selection, at a time when little direct evidence was available. Three major functions of coloration were discovered in the second half of the 19th century, and subsequently used as evidence of selection: camouflage ; mimicry, both Batesian and Müllerian; and aposematism.

<span class="mw-page-title-main">Coincident disruptive coloration</span> Camouflage joining up separate parts of body

Coincident disruptive coloration or coincident disruptive patterns are patterns of disruptive coloration in animals that go beyond the usual camouflage function of breaking up the continuity of an animal's shape, to join up parts of the body that are separate. This is seen in extreme form in frogs such as Afrixalus fornasini where the camouflage pattern extends across the body, head, and all four limbs, making the animal look quite unlike a frog when at rest with the limbs tucked in.

<span class="mw-page-title-main">Distractive markings</span>

Distractive markings serve to camouflage animals or military vehicles by drawing the observer's attention away from the object as a whole, such as noticing its outline. This delays recognition. The markings necessarily have high contrast and are thus in themselves conspicuous. The mechanism therefore relies, as does camouflage as a whole, on deceiving the cognition of the observer, not in blending with the background.

<span class="mw-page-title-main">Disruptive eye mask</span> Camouflage to conceal the eye

Disruptive eye masks are camouflage markings that conceal the eyes of an animal from its predators or prey. They are used by prey, to avoid being seen by predators, and by predators to help them approach their prey.

<i>Dazzled and Deceived</i> Camouflage book by Peter Forbes

Dazzled and Deceived: Mimicry and Camouflage is a 2009 book on camouflage and mimicry, in nature and military usage, by the science writer and journalist Peter Forbes. It covers the history of these topics from the 19th century onwards, describing the discoveries of Henry Walter Bates, Alfred Russel Wallace and Fritz Müller, especially their studies of butterflies in the Amazon. The narrative also covers 20th-century military camouflage, begun by the painter Abbot Thayer who advocated disruptive coloration and countershading and continued in the First World War by the zoologist John Graham Kerr and the marine artist Norman Wilkinson, who developed dazzle camouflage. In the Second World War, the leading expert was Hugh Cott, who advised the British army on camouflage in the Western Desert.

References

  1. ↑ Cott 1940, p. 53.
  2. 1 2 Thayer & Thayer 1909, pp. 77–78, and throughout.
  3. 1 2 3 Cott 1940, pp. 47–67.
  4. 1 2 3 4 5 Stevens, M.; Cuthill, I.C.; Windsor, A.M.M.; Walker, H.J. (7 October 2006). "Disruptive contrast in animal camouflage". Proceedings of the Royal Society B. 273 (1600): 2433–2436. doi:10.1098/rspb.2006.3614. PMC   1634902 . PMID   16959632.
  5. ↑ Barbosa, A; Mäthger, L. M.; Buresch, K. C.; Kelly, J; Chubb, C; Chiao, C. C.; Hanlon, R. T. (2008). "Cuttlefish camouflage: The effects of substrate contrast and size in evoking uniform, mottle or disruptive body patterns". Vision Research. 48 (10): 1242–1253. doi:10.1016/j.visres.2008.02.011. PMID   18395241.
  6. 1 2 Endler, J. A. (October 2006). "Disruptive and cryptic coloration". Proceedings of the Royal Society B. 273 (1600): 2425–2426. doi:10.1098/rspb.2006.3650. PMC   1634903 . PMID   16959630.
  7. ↑ Cott 1940, pp. 68–93.
  8. ↑ Dimitrova, M.; Stobbe, N.; Schaefer, H. M.; Merilaita, S. (2009). "Concealed by conspicuousness: distractive prey markings and backgrounds". Proceedings of the Royal Society B: Biological Sciences. 276 (1663): 1905–1910. doi:10.1098/rspb.2009.0052. PMC   2674505 . PMID   19324754.
  9. ↑ Cott 1940, pp. 96, 193–199.
  10. ↑ Honma, Atsushi; Mappes, Johanna; Valkonen, Janne K. (November 2015). "Warning coloration can be disruptive: aposematic marginal wing patterning in the wood tiger moth". Ecology and Evolution. 5 (21): 4863–4874. doi:10.1002/ece3.1736. PMC   4662304 . PMID   26640666.
  11. ↑ Roosevelt, Theodore (1911). "Revealing and concealing coloration in birds and mammals". Bulletin of the American Museum of Natural History. 30 (Article 8): 119–231. hdl:2246/470. Roosevelt attacks Thayer on page 191, arguing that neither zebra nor giraffe are "'adequately obliterated' by countershading or coloration pattern or anything else."
  12. 1 2 3 4 Mitchell, G.; Skinner, J. D. (2003). "On the origin, evolution and phylogeny of giraffes Giraffa camelopardalis" (PDF). Transactions of the Royal Society of South Africa. 58 (1): 51–73. doi:10.1080/00359190309519935. S2CID   6522531.
  13. ↑ Cott 1940, p. 96.
  14. 1 2 Givnish, T. J. (1990). "Leaf Mottling: Relation to Growth Form and Leaf Phenology and Possible Role as Camouflage". Functional Ecology. 4 (4): 463–474. doi:10.2307/2389314. JSTOR   2389314. S2CID   5029364.
  15. ↑ Lev-Yadun, Simcha (2003). "Why do some thorny plants resemble green zebras?". Journal of Theoretical Biology. 224 (4): 483–489. Bibcode:2003JThBi.224..483L. doi:10.1016/s0022-5193(03)00196-6. PMID   12957121.
  16. ↑ Lev-Yadun, Simcha (2006). Teixeira da Silva, J.A. (ed.). Defensive coloration in plants: a review of current ideas about anti-herbivore coloration strategies. Global Science Books. pp. 292–299. ISBN   978-4903313092.{{cite book}}: |work= ignored (help)
  17. ↑ Department of the Army (30 August 1999). Field Manual Headquarters No. 20-3.{{cite book}}: |work= ignored (help)
  18. ↑ Sweet, K.M. (2006). Transportation and Cargo Security: Threats and Solutions. Prentice Hall. p. 219.
  19. ↑ U. S. War Department (1944). FM 5–20, CAMOUFLAGE.
  20. ↑ Christine O. Hardyman, ed. (1988). "Chapter 7: Support Services". Department of the Army Historical Summary FY 1981. United States Army Center of Military History. Archived from the original on 14 December 2007. Retrieved 7 February 2013.
  21. ↑ "Trousers, Camouflage DPM Combat Dress 1968 pattern". Imperial War Museum. Retrieved 31 October 2015.
  22. ↑ US Army. FM 21-76 US ARMY SURVIVAL MANUAL. U.S. Department of the Army. Retrieved 8 January 2013.
  23. ↑ US Army (2009). Photosimulation Camouflage Detection Test. U.S. Army Natick Soldier Research, Development and Engineering Center. p. 27. Retrieved 5 October 2012.
  24. ↑ Brayley, Martin J. (2009). Camouflage uniforms : international combat dress 1940–2010. Crowood. ISBN   978-1-84797-137-1.
  25. ↑ Freedberg Jr., S.J. (25 June 2012). "Army Drops Universal Camouflage After Spending Billions". Aol Defence. Archived from the original on 31 August 2012. Retrieved 27 September 2012.
  26. ↑ Davies, W. "Berlin Brigade Urban Paint Scheme". Newsletter. Ex-Military Land Rover Association. Archived from the original on 12 March 2013. Retrieved 25 September 2012.
  27. ↑ Craemer, Guy. "Dual Texture – U.S. Army digital camouflage". United Dynamics Corp. Retrieved 27 September 2012.
  28. ↑ Engber, D. (5 July 2012). "Lost in the Wilderness, the military's misadventures in pixellated camouflage". State. Retrieved 27 September 2012.
  29. ↑ Stirling, Robert (2012). SAS Ultimate Guide to Combat. Osprey Publishing. p. 181. ISBN   978-1-78096-399-0.[ permanent dead link ]

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