Distractive markings

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In 1909, Abbott Handerson Thayer described the snowy owl's black markings on its white snow camouflage as distractive. Bubo scandiacus male Muskegon (cropped).jpg
In 1909, Abbott Handerson Thayer described the snowy owl's black markings on its white snow camouflage as distractive.

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.

Contents

Distractive markings were first noticed by the American artist Abbott Handerson Thayer in 1909, but the mechanism was for a century confused with disruptive coloration, another mechanism for delaying recognition that also relies on conspicuous markings. Distractive markings however need to be small and to avoid outlines, to avoid drawing attention to them, whereas disruptive markings work best when they touch the outline, breaking it up.

Distractive camouflage marks are sometimes called dazzle markings, but the mechanism differs from motion dazzle.

History

The American artist Abbott Handerson Thayer described distractive markings in his 1909 book on camouflage, Concealing-Coloration in the Animal Kingdom . [2] Thayer wrote that

several snow-land animals ... [such as] Arctic hares and foxes, the boreal weasels and ... the ptarmigans, the snow buntings, the snowy owl ... have a few sharp black markings in their mainly immaculate white costumes. These evidently serve as what may be called 'distractive' or 'fixed dazzling' marks. They are, in most cases, too small to show except in a very near view—when, by their sharp but isolated and noncommittal conspicuousness, they tend to draw and hold the eye's attention, in a sense, to dazzle it, so that it less readily discerns the faintly shown snow-white body of their wearer. [1]

Mechanism

Disruptive and distractive camouflage both rely on conspicuous markings, but differ in their mechanisms, and therefore in the most effective size and position of the markings. Disruptive versus Distractive Camouflage Markings.svg
Disruptive and distractive camouflage both rely on conspicuous markings, but differ in their mechanisms, and therefore in the most effective size and position of the markings.

For camouflage to succeed, an individual has to pass undetected, unrecognized or untargeted, and hence it is the processing of visual information that needs to be deceived. Camouflage is therefore an adaptation to the perception and cognitive mechanisms of another animal.

S. Merilaita, N. E. Scott-Samuel, I. C. Cuthill [4]

Many prey animals have conspicuous high-contrast markings which paradoxically attract the predator's gaze, [2] like other camouflage mechanisms, especially masquerade, working by exploiting weaknesses in the predator's cognitive mechanisms to delay detection or recognition of the prey. [4] [5] These distractive markings serve as camouflage by distracting the predator's attention from recognising the prey as a whole, for example by keeping the predator from identifying the prey's outline. Experimentally, search times for blue tits increased when artificial prey had distractive markings. The researchers, M. Dimitrova and colleagues, note that Thayer's suggestion that such marks take up the predator's attention is plausible, since visual attention is limited, and stimuli effectively compete for attention. They note, too, that bright features are preferentially given attention in human vision, so it is possible the same happens in other species. Another possible explanation according to Dimitrova is lateral masking, suppression of peripheral perception; this is known to be strong, again in human perception, when a (single) high-contrast stimulus is provided, but it is doubtful whether a pattern containing small distractive markings could form such a stimulus. [3]

There is an apparent conflict between background matching and disruptive markings. Background matching relies on choosing coloration and brightness similar to the background, but disruptive markings must stand out from the background. Dimitrova and colleagues note that Thayer suggested that such markings must be small; this, they argue, would enable the markings to fit in with background matching at any great distance, and would prevent predators from learning a search image and then detecting prey with that type of marking. [3]

Hugh Cott, author of the 1940 Adaptive Coloration in Animals , [6] followed by many other researchers, conflated distractive markings with disruptive coloration. [2] [3] Both mechanisms require conspicuous marks. However, the two mechanisms are different, and according to Dimitrova 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. [3]

Distractive camouflage marks are sometimes called dazzle markings, but the mechanism differs from motion dazzle, which relies on conspicuous markings to interfere with an observer's ability to estimate the target's speed and direction. [2]

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, as well as making general aiming easier. 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 family 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">Aposematism</span> Honest signalling of an animals powerful defences

Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the prey difficult to kill and eat, such as toxicity, venom, foul taste or smell, sharp spines, or aggressive nature. These advertising signals may take the form of conspicuous coloration, sounds, odours, or other perceivable characteristics. Aposematic signals are beneficial for both predator and prey, since both avoid potential harm.

<span class="mw-page-title-main">Crypsis</span> Aspect of animal behaviour and morphology

In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and mimicry. Crypsis can involve visual, olfactory or auditory concealment. When it is visual, the term cryptic coloration, effectively a synonym for animal camouflage, is sometimes used, but many different methods of camouflage are employed by animals or plants.

<span class="mw-page-title-main">Motion camouflage</span> Camouflage by choosing path to avoid seeming to move against background

Motion camouflage is camouflage which provides a degree of concealment for a moving object, given that motion makes objects easy to detect however well their coloration matches their background or breaks up their outlines.

<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">Eyespot (mimicry)</span> Eye-like marking used for mimicry or distraction

An eyespot is an eye-like marking. They are found in butterflies, reptiles, cats, birds and fish.

<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">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.

<span class="mw-page-title-main">Disruptive coloration</span> Camouflage to break up an objects outlines

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.

<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>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.

Deception in animals is the transmission of misinformation by one animal to another, of the same or different species, in a way that propagates beliefs that are not true.

<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.

Martin Stevens is a British sensory and evolutionary ecologist, an underwater photographer and a natural history and popular science writer. He is known for his work on disruptive coloration in animal camouflage.

<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.

References

  1. 1 2 Thayer, Gerald H.; Thayer, Abbott H. (1909). 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 Disclosures. New York: Macmillan. pp.  151–152, 246–247.
  2. 1 2 3 4 Stevens, M.; Merilaita, S. (2009). "Defining disruptive coloration and distinguishing its functions". Philosophical Transactions of the Royal Society B: Biological Sciences. 364 (1516): 481–488. doi:10.1098/rstb.2008.0216. PMC   2674077 . PMID   18990673.
  3. 1 2 3 4 5 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.
  4. 1 2 Merilaita, Sami; Scott-Samuel, Nicholas E.; Cuthill, Innes C. (2017). "How camouflage works". Philosophical Transactions of the Royal Society B: Biological Sciences. 372 (1724): 20160341. doi:10.1098/rstb.2016.0341. PMC   5444062 . PMID   28533458.
  5. Skelhorn, John; Rowe, Candy (2016). "Cognition and the evolution of camouflage". Proceedings of the Royal Society B: Biological Sciences. 283 (1825): 20152890. doi:10.1098/rspb.2015.2890. PMC   4810834 . PMID   26911959.
  6. Cott, Hugh B. (1940). Adaptive Coloration in Animals . Methuen.