Animal coloration

Zebras may possibly use motion dazzle, confusing a predator's attack by moving a bold pattern rapidly.

For fishes it has been demonstrated that chromatophores may respond directly to environmental stimuli like visible light, UV-radiation, temperature, pH, chemicals, etc.

Some animals, including many butterflies and birds, have microscopic structures in scales, bristles or feathers which give them brilliant iridescent colours.

Hence I can see no reason to doubt that natural selection might be most effective in giving the proper colour to each kind of grouse, and in keeping that colour, when once acquired, true and constant.Henry Walter Bates's 1863 book The Naturalist on the River Amazons describes his extensive studies of the insects in the Amazon basin, and especially the butterflies.

[8] The book introduced the concept of frequency-dependent selection, as when edible mimics are less frequent than the distasteful models whose colours and patterns they copy.

In the book, Poulton also coined the term aposematism for warning coloration, which he identified in widely differing animal groups including mammals (such as the skunk), bees and wasps, beetles, and butterflies.

"[12][13] Hugh Bamford Cott's 500-page book Adaptive Coloration in Animals, published in wartime 1940, systematically described the principles of camouflage and mimicry.

Indeed, Cott describes such applications:[14] the effect of a disruptive pattern is to break up what is really a continuous surface into what appears to be a number of discontinuous surfaces... which contradict the shape of the body on which they are superimposed.Animal coloration provided important early evidence for evolution by natural selection, at a time when little direct evidence was available.

In general aggressive resemblance, the predator or parasite blends in with the background, for example when a leopard is hard to see in long grass.

[20] Countershading was first described by the American artist Abbott Handerson Thayer, a pioneer in the theory of animal coloration.

Thayer observed that whereas a painter takes a flat canvas and uses coloured paint to create the illusion of solidity by painting in shadows, animals such as deer are often darkest on their backs, becoming lighter towards the belly, creating (as zoologist Hugh Cott observed) the illusion of flatness,[21] and against a matching background, of invisibility.

Its function is to make the animal, for example a wasp or a coral snake, highly conspicuous to potential predators, so that it is noticed, remembered, and then avoided.

As Peter Forbes observes, "Human warning signs employ the same colours – red, yellow, black, and white – that nature uses to advertise dangerous creatures.

[29] This can be achieved in several ways, by being any combination of: Warning coloration can succeed either through inborn behaviour (instinct) on the part of potential predators,[34] or through a learned avoidance.

To evolve, the mimicked species must have warning coloration, because appearing to be bitter-tasting or dangerous gives natural selection something to work on.

This is because even a small degree of protection reduces predation and increases the chance that an individual mimic will survive and reproduce.

For example, many species of hoverfly are coloured black and yellow like bees, and are in consequence avoided by birds (and people).

But when bees and wasps resemble each other, the young bird need only attack one from the whole group to learn to avoid all of them.

[39] Some animals such as many moths, mantises and grasshoppers, have a repertoire of threatening or startling behaviour, such as suddenly displaying conspicuous eyespots or patches of bright and contrasting colours, so as to scare off or momentarily distract a predator.

The behaviour is deimatic (startling) rather than aposematic as these insects are palatable to predators, so the warning colours are a bluff, not an honest signal.

[40][41] Some prey animals such as zebra are marked with high-contrast patterns which possibly help to confuse their predators, such as lions, during a chase.

[43] Many animals have dark pigments such as melanin in their skin, eyes and fur to protect themselves against sunburn[44] (damage to living tissues caused by ultraviolet light).

[53] For example, the bright yellow of an American goldfinch, the startling orange of a juvenile red-spotted newt, the deep red of a cardinal and the pink of a flamingo are all produced by carotenoid pigments synthesized by plants.

The shrimps derive their body colour from microscopic red algae, which like most plants are able to create their own pigments, including both carotenoids and (green) chlorophyll.

Chromatophores may respond to hormonal and/or neurobal control mechanisms, but direst responses to stimulation by visible light, UV-radiation, temperature, pH-changes, chemicals, etc.

[53] Structural coloration means the production of colour by microscopically-structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments: for example, peacock tail feathers are pigmented brown, but their structure makes them appear blue, turquoise and green.

[52] For example, the blue/green gloss on the plumage of birds such as ducks, and the purple/blue/green/red colours of many beetles and butterflies are created by structural coloration.

[57] Comb jellies such as Euplokamis are bioluminescent, creating blue and green light, especially when stressed; when disturbed, they secrete an ink which luminesces in the same colours.

A brilliantly-coloured oriental sweetlips fish ( Plectorhinchus vittatus ) waits while two boldly-patterned cleaner wrasse ( Labroides dimidiatus ) pick parasites from its skin. The spotted tail and fin pattern of the sweetlips signals sexual maturity; the behaviour and pattern of the cleaner fish signal their availability for cleaning service , rather than as prey
Bright coloration of orange elephant ear sponge, Agelas clathrodes signals its bitter taste to predators
Robert Hooke 's Micrographia
Warning coloration of the skunk in Edward Bagnall Poulton 's The Colours of Animals , 1890
In Roseate Spoonbills 1905–1909, Abbott Handerson Thayer tried to show that even the bright pink of these conspicuous birds had a cryptic function.
A camouflaged orange oak leaf butterfly, Kallima inachus (centre) has protective resemblance.
A flower mantis, Hymenopus coronatus , uses special Aggressive mimicry .
Cleaner wrasse signals its cleaning services to a big eye squirrelfish
Male Goldie's bird-of-paradise displays to a female
A venomous coral snake uses bright colours to warn off potential predators.
The black and yellow warning colours of the cinnabar moth caterpillar, Tyria jacobaeae , are avoided by some birds.
The hawk-cuckoo resembles a predatory shikra , giving the cuckoo time to lay eggs in a songbird's nest unnoticed
A praying mantis in deimatic or threat pose displays conspicuous patches of colour to startle potential predators. This is not warning coloration as the insect is palatable.
This frog changes its skin colour to control its temperature.
The olm 's blood makes it appear pink.
Side of zebrafish shows how chromatophores (dark spots) respond to 24 hours in dark (above) or light (below).
The red pigment in a flamingo's plumage comes from its diet of shrimps, which get it from microscopic algae.
Fish and frog melanophores are cells that can change colour by dispersing or aggregating pigment-containing bodies.
Squid chromatophores appear as black, brown, reddish and pink areas in this micrograph.
The brilliant iridescent colours of the peacock's tail feathers are created by Structural coloration .
Butterfly wing at different magnifications reveals microstructured chitin acting as diffraction grating.
A Euplokamis comb jelly is bioluminescent .