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In ecology, crypsis is the ability of an organism to avoid observation. A form of antipredator adaptation, methods range from camouflage, nocturnality, subterranean lifestyle, transparency, or mimicry. The word can also be used in the context of eggs and pheromone production.

Overview

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 sneak up on prey. (Exceptions include: large herbivores without natural enemies; brilliantly-colored birds which rely on flight to escape predators; and venomous or poisonous animals which 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).

The distinction between camouflage and mimicry is arbitrarily defined in that mimicry requires that the "model" be another organism, rather than the surroundings; the arbitrary nature of this distinction between the two phenomena can be seen by considering animals that resemble twigs, bark, leaves or flowers, in that they are often classified as camouflaged (a plant does constitute the "surroundings"), but sometimes classified as mimics (a plant is also an organism). Either way, the animal is considered cryptic.

Crypsis is usually most effective when an animal is still. Cryptic animals that forage during daylight may be ambush predators, taking advantage of their ability to blend into their background. Alternatively, cryptic animals may be active predators in darkness and use their crypsis while inactive. Some cryptic animals also simulate natural movement, e.g., of a leaf in the wind. This is called procryptic behaviour or habit. Other animals attach or attract natural materials to their body for concealment.

Varieties of crypsis

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.

Visual

Camouflaging allows animals to capture prey more easily.
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.

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 (or obliterative camouflage), 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, 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.

Olfactory

Some animals, notably in aquatic environments, have adapted to camouflage the odours they create that may attract predators.

Effects

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 a 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.

Gallery

Image:Camouflage.jpg|An infant Cuttlefish blends into the surrounding sand substrate.image:bristol.zoo.dead.leaf.mantis.arp.jpg|A Dead Leaf Mantis from Madagascarmarker.File:Tawny Frogmouth camouflage.jpg|Tawny Frogmouth blends in with color and texture of tree bark.Image:Ibexes.jpg|Countershaded Ibex are almost invisible in the Israeli desert.Image:LeafShapedGrasshopper.JPG|Australian grasshopper with the shape and coloration of a leafImage:Leaf-nosed viper.jpg|The colouration of the leaf-nosed viper (Eristicophis macmahonii) blends with sand.Image:Gekkoninae Uroplatus sikorae camouflage horiz.png|Mossy leaf-tailed gecko (Uroplatus sikorae) blends with a logImage:Thomisus labefactus sep04.jpg|A crab spider ambush hunting on a flower

References

  1. See some examples here.


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