In ecology, crypsis is the ability of an organism to avoid observation or detection by other organisms. It may be either a predation strategy or an antipredator adaptation, and methods include camouflage, nocturnality, subterranean lifestyle, transparency,[1] and mimicry. The word can also be used in the context of eggs[2] and pheromone production.[3]
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There is a strong evolutionary pressure for animals to blend into their environment or conceal their shape, for prey animals to avoid predators and for predators to be able to avoid detection by prey. (Exceptions include large herbivores without natural enemies, brilliantly-colored birds that rely on flight to escape predators, and venomous animals that advertise with bright colors.) Cryptic animals include the tawny frogmouth (feather patterning resembles bark), the tuatara (hides in burrows all day; nocturnal), some jellyfish (transparent), the leafy sea dragon, and the flounder (covers itself in sediment).
Crypsis may occur in a variety of ways, each of which causes the organism in question to blend with its background in at least one of the senses, although visual crypsis is the best known.
Many animals have evolved so that they visually resemble their surroundings, using some sort of natural camouflage that may match the color of the surroundings (cryptic coloration) and/or break up the visual outline of the animal itself. Such animals may resemble rocks, sand, twigs, leaves, and even bird droppings.[4]
A few animals have chromatic response, changing color in changing environments, either seasonally (ermine, snowshoe hare) or far more rapidly with chromatophores in their integument (chameleon, cephalopods).
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. This is sometimes called Thayer's law, after Abbott H. Thayer, who published a paper on the form in 1896.
Some animals, notably decorator crabs, attach other plants or animals to their bodies, allowing themselves to blend in with any environment, and even to change their camouflage.
Some animals, in both terrestrial and aquatic environments, appear to camouflage their odour, which might otherwise attract predators.[5] Numerous arthropods, both insects and spiders, mimic ants, whether to avoid predation, to hunt ants, or (for example in the Large Blue Butterfly caterpillar) to trick the ants into feeding them.[6]
Some insects, notably the Noctuid moths (such as the Large Yellow Underwing) and the Arctiid moths (such as the Garden Tiger), defend themselves against predation by echolocating bats, both by passively absorbing sound with soft fur-like body coverings, and by actively creating sounds to mimic echoes from other locations or objects.[7][8]
There is often a self-perpetuating co-evolution, or evolutionary arms race, between the perceptive abilities of animals for whom it is beneficial to be able to detect the cryptic animal, versus the cryptic characteristics of the hiding species. Different aspects of crypsis and sensory abilities may be more or less pronounced in given predator-prey species pairs.
Zoologists need special methods to study cryptic animals including biotelemetry techniques such as radio tracking, mark and recapture, and enclosures or exclosures.
Cryptic animals tend to be overlooked in studies of biodiversity and ecological risk assessment.
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