Crypsis

This article is about organisms that are difficult to detect. For organisms that are difficult to distinguish, see Cryptic species complex. For animals whose existence has not been demonstrated, see cryptozoology. For the genus of grasses, see Crypsis (genus).

This frog (facing right, on the upper left of the nearly-vertical stick on the rightmost third of the photo) is nearly invisible among the dead leaves in the Lower Rio Branco-Rio Jauaperi Extractive Reserve, Brazil.

Further information: Mimicry

The skin coloring of a Stenodactylus sthenodactylus is well integrated with the coloring of the ground and rocks of the Judean desert

A common snakeneck turtle covered in camouflaging algae; when resting this individual would look like an algae-covered rock

Camouflaging allows animals to capture prey more easily.

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]

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 that rely on flight to escape predators, and venomous or poisonous 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).

The distinction between camouflage and mimicry is arbitrary in that mimicry requires that the "model" be another organism, rather than the surroundings; the lack of distinction between the two phenomena can be seen by considering animals that resemble twigs, bark, leaves or flowers, which are classified both as camouflaged (a plant does constitute the "surroundings"), and 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. Also, 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

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 (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, after Abbott H. Thayer, who published a paper on the form in 1896.

Some animals, a notable one being 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, 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]

Auditory

Arctiid moths like the Garden Tiger, Arctia caja, have furry bodies to absorb sound, and make clicks to jam bat sonar

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]

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 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

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  A ground agama (Agama aculeata), blending into his environment at the petrified forest, east of Doro !Nawas, Namibia.

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  An infant Cuttlefish blends into the surrounding sand substrate.

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  A Dead Leaf Mantis from Madagascar.

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  Tawny Frogmouth blends in with color and texture of tree bark.

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  Countershaded Ibex are almost invisible in the Israeli desert.

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  Australian grasshopper with the shape and coloration of a leaf

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  The colouration of the leaf-nosed viper (Eristicophis macmahonii) blends with sand.

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  Mossy leaf-tailed gecko (Uroplatus sikorae) blends with a log

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  A crab spider ambush hunting on a flower

See also

• Animal colouration
• Antipredator adaptation
• Camouflage
• Crepuscular
• Matutinal
• Nocturnality
• List of nocturnal animals
• List of nocturnal birds

References

1. ^ Zuanon, J.; I. Sazima (2006). "The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators". Neotropical Ichthyology 4 (2): 219–214. doi:10.1590/S1679-62252006000100012. 
2. ^ Nguyen, L. P.; et al. (2007). "Using digital photographs to evaluate the effectiveness of plover egg crypsis". Journal of Wildlife Management 71 (6): 2084–2089. doi:10.2193/2006-471. 
3. ^ Raffa, K. R.; et al. (2007). "Can chemical communication be cryptic? Adaptations by herbivores to natural enemies exploiting prey semiochemistry". Oecologia 153 (4): 1009–1019. doi:10.1007/s00442-007-0786-z. PMID 17618465. 
4. ^ See some examples here.
5. ^ Michael R. Conover. Predator-Prey Dynamics: the role of olfaction. CRC Press. 2007. ISBN 978-0849392702
6. ^ Horace Donisthorpe. Mimicry of Ants by Other Arthropods. Transactions of the Royal Entomological Society of London. Volume 69, Issue 3-4, pages 307-311, January 1922. http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.1922.tb02812.x/abstract
7. ^ Lee A. Miller and Annemarie Surlykke. How Some Insects Detect and Avoid Being Eaten by Bats: Tactics and Countertactics of Prey and Predator. BioScience 51(7):570-581. 2001. http://www.bioone.org/doi/abs/10.1641/0006-3568%282001%29051%5B0570%3AHSIDAA%5D2.0.CO%3B2?journalCode=bisi
8. ^ Matt Kaplan. Moths Jam Bat Sonar, Throw the Predators Off Course. National Geographic News. July 17, 2009. http://news.nationalgeographic.com/news/2009/07/090717-moths-jam-bat-sonar.html

External links

• Sazima Network - Relevant Scientific Papers and Pictures.
• Dive Gallery: decorator crabs.
• Caterpillar that resembles bird droppings or leaves.