Many animals, such as this grey reef shark, are countershaded.Illustration from the artist Abbot Thayer's 1909 book on camouflage of a Luna caterpillar Actias luna a) in position b) inverted.
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.[1] This pattern is found in many species of mammals, reptiles, birds, fish, and insects, both in predators and in prey.
When light falls from above on a uniformly coloured three-dimensional object such as a sphere, it makes the upper side appear lighter and the underside darker, grading from one to the other. This pattern of light and shade makes the object appear solid, and therefore easier to detect. The classical form of countershading, discovered in 1909 by the artist Abbott Handerson Thayer, works by counterbalancing the effects of self-shadowing, again typically with grading from dark to light. In theory this could be useful for military camouflage, but in practice it has rarely been applied, despite the best efforts of Thayer and, later, in the Second World War, of the zoologist Hugh Cott.
The precise function of various patterns of animal coloration that have been called countershading has been debated by zoologists such as Hannah Rowland (2009), with the suggestion that there may be multiple functions including flattening and background matching when viewed from the side; background matching when viewed from above or below, implying separate colour schemes for the top and bottom surfaces; outline obliteration from above; and a variety of other largely untested non-camouflage theories. A related mechanism, counter-illumination, adds the creation of light by bioluminescence or lamps to match the actual brightness of a background. Counter-illumination camouflage is common in marine organisms such as squid. It has been studied up to the prototype stage for military use in ships and aircraft, but it too has rarely or never been used in warfare.
The reverse of countershading, with the belly pigmented darker than the back, enhances contrast and so makes animals more conspicuous. It is found in animals that can defend themselves, such as skunks. The pattern is used both in startle or deimatic displays and as a signal to warn off experienced predators. However, animals that habitually live upside-down but lack strong defences, such as the Nile catfish and the Luna moth caterpillar, have upside-down countershading for camouflage.
^Argo, Emily (21 April 2017). "Countershading". Fishionary. American Fisheries Society. Retrieved 17 December 2022.
to light) countershaded Focke-Wulf Fw 190 Hannah Rowland, reviewing countershading 100 years after Abbott Thayer, observed that countershading, which she...
countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading,...
carried along by the winds and ocean currents. G. atlanticus makes use of countershading; the blue side of their bodies faces upwards, blending in with the blue...
below. An example of countershading in fish is the Atlantic bluefin tuna. Some fish are even known to have reverse countershading, being light on the dorsal...
The honey badger's reverse countershading makes it conspicuous, honestly signalling its ability to defend itself through its aggressive temperament and...
and Poulton), and especially about countershading. Beginning in 1892, he wrote about the function of countershading in nature, by which forms appear less...
surface of their body that results in the camouflage technique called countershading. A darker color on the upper side and lighter color on the underside...
military leaders, although his advocacy of countershading was unsuccessful, despite his patent for countershading submarines and surface ships. The earliest...
Equator. Highly adapted for life in the ocean water, penguins have countershaded dark and white plumage and flippers for swimming. Most penguins feed...
cream-colored courser, Cursorius cursor, is a well-camouflaged desert resident with its dusty coloration, countershading, and disruptive head markings....
correspondingly tawny, sandy or golden. In common with tigers, as an example of countershading, the underparts are pale. The specific pattern and color depend upon...
and blue coloration are the most common form of camouflage. Below, countershading is more common, with blue coloration on the dorsal side and white on...
Smithwick, F.M.; Nicholls, R.; Cuthill, I.C.; Vinther, J. (2017). "Countershading and Stripes in the Theropod Dinosaur Sinosauropteryx Reveal Heterogeneous...
striping or leg bars indicative of a red dun may be called a "dunalino." Countershading such as light dorsal stripes resulting from the presence of the gene...
may be made to look flat, and hence to blend into the background, by countershading. The outlines of many bovids are broken up with bold disruptive colouration...
cylindrical in shape, with a vertically elongated tail. This species exhibits countershading, with brilliant metallic blue coloration dorsally and white ventrally...
26 November 2014. Young, R. E.; Roper, C. F. (1976). "Bioluminescent countershading in midwater animals: evidence from living squid". Science. 191 (4231):...
black, with a scattering of white blotches and spots. Demonstrating countershading, the turtle's underside is lightly colored. Instead of teeth, the leatherback...
color as a form of camouflage in winter. Animals such as penguins are countershaded with white bellies, again as camouflage. The dove is an international...
equiangular spiral, although it is not a golden spiral. The shell exhibits countershading, being light on the bottom and dark on top. This is to help avoid predators...
accurate range finding". However, in the same letter, Kerr also called for countershading, the use of paint to obliterate self-shading and thus to flatten out...
the dorsal surface, fading to a lighter shade ventrally as a form of countershading camouflage. M. mola also exhibits the ability to vary skin coloration...
with other methods of crypsis including background colour matching and countershading; special cases are coincident disruptive coloration and the disruptive...
one of the first animals to be identified as being camouflaged with countershading to make it appear flat (shading being the main visual cue that makes...
color, with a paler underside to appear less conspicuous from below (countershading). At least two recognized subspecies exist, one in the North Atlantic...
Bagnall Poulton, author of The Colours of Animals (1890) described countershading in insects including the caterpillar larvae of the brimstone moth. The...
Lindsay; M. I. Latz (1999). Experimental evidence for luminescent countershading by some euphausiid crustaceans. American Society of Limnology and Oceanography...
Global Information
