Crypsis

In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be part of a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and mimicry. Crypsis can involve visual, olfactory (with pheromones) 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 in nature.

There is a strong evolutionary pressure for prey animals to avoid predators through camouflage, and for predators to be able to detect camouflaged prey. There can be a self-perpetuating coevolution, in the shape of an evolutionary arms race, between the perceptive abilities of animals attempting to detect the cryptic animal and the cryptic characteristics of the hiding species.

Methods of crypsis include (visual) camouflage, nocturnality, and subterranean lifestyle. Camouflage can be achieved by a wide variety of methods, from disruptive coloration to transparency and some forms of mimicry, even in habitats like the open sea where there is no background.

As a strategy, crypsis is used by predators against prey and by prey against predators.

Crypsis also applies to eggs and pheromone production. Crypsis can in principle involve visual, olfactory, or auditory camouflage.

Many animals have evolved so that they visually resemble their surroundings by using any of the many methods of natural camouflage that may match the color and texture of the surroundings (cryptic coloration) and/or break up the visual outline of the animal itself (disruptive coloration). Such animals, like the tawny dragon lizard, may resemble rocks, sand, twigs, leaves, and even bird droppings (mimesis). Other methods including transparency and silvering are widely used by marine animals.

Some animals change color in changing environments seasonally, as in ermine and snowshoe hare, or far more rapidly with chromatophores in their integuments, as in chameleon and cephalopods such as squid.

Countershading, the use of different colors on upper and lower surfaces in graduating tones from a light belly to a darker back, is common in the sea and on land. It is sometimes called Thayer's law, after the American artist Abbott Handerson Thayer, who published a paper on the form in 1896 that explained that countershading paints out shadows to make solid objects appear flat, reversing the way that artists use paint to make flat paintings contain solid objects. Where the background is brighter than is possible even with white pigment, counter-illumination in marine animals, such as squid, can use light to match the background.