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    Animal Camouflage Experiments & Lesson Plans

    Animal Camouflage Background Information

    Definition

    Camouflage is a method of crypsis – avoidance of observation – that allows an otherwise visible organism or object to remain indiscernible from the surrounding environment through deception.

    Basics

    Camouflage is disguise for something normally visible. For instance, the natural colour of an animal that makes it look like its surroundings. A tiger's stripes in the long grass, and the battledress of a modern soldier are examples.

    Camouflage is a form of deception. The word camouflage comes from the French word camoufler, which means "to disguise".

    In nature, most animals blend into their environment or conceal their shape. They are very hard to see. This way they survive, and if they survive, then they can reproduce. There are exceptions: animals which are dangerous to eat (e.g. wasps) advertise with warning colouration:

    Prey animals hide from predators. Predators must search for prey without being seen. Natural camouflage is one way to do this: an animal can blend in with its surroundings. Another way is for the animal to disguise itself as something harmless.

    Some camouflaged animals also copy movements in nature, e.g., of a leaf blowing in the wind. Other animals attach natural materials to their body for concealment. A few animals change color in changing environments. Seasonally: (many Arctic animals, such as the Arctic fox, or hare). Or quickly, like the chameleon and the cuttlefish. Some herd animals adopt a similar pattern to make it difficult to distinguish a single animal.

    Most animals are dark on top and light underneath. With light coming from above, this contershading makes them less visible.

    Mimicry occurs when a species has features similar to another. Either one or both get protection when a third species cannot tell them apart. Often, these features are visual; one species looks like another; but similarities of sound, smell and behaviour may also make the fraud seem more real.

    Mimicry is related to camouflage and to warning signals, in which species manipulate or deceive other species which might do them harm. Although mimicry is mainly a defence against predators, sometimes predators also use mimicry, to fool their prey into feeling safe.

    Mimicry occurs in both animal and plant species. The mimic is the species which looks like the model. The model may be living, or not. Whole groups of animals go in for mimicry as a life style, such as leaf insects or stick insects. Camouflage, in which a species looks similar to its surroundings, is a form of visual mimicry.

    Animals that are dangerous, or foul to eat, usually advertise the fact. This is called warning or aposematic colouration. Alfred Russel Wallace, a British naturalist, explained it this way, in 1889:

      "The animals in question are possessors of some deadly weapons, as stings or poison fangs, or they are uneatable, and are thus so disagreeable to the usual enemies of their kind that they are never attacked when their peculiar powers or properties are known. It is, therefore, important that they should not be mistaken for defenceless or eatable species... since they might suffer injury, or even death, before their enemies discovered the danger or uselessness of their attack. They require some signal or danger flag which shall serve as a warning to would-be enemies..."

    Wallace predicted that birds and other predators would reject conspicuous prey whilst accepting cryptic prey. Later reports confirmed this.

    Topics of Interest

    Camouflage is a method of crypsis – avoidance of observation – that allows an otherwise visible organism or object to remain indiscernible from the surrounding environment through deception. Examples include a tiger's stripes and the battledress of a modern soldier. The theory of camouflage covers the various strategies which are used to achieve this effect.

    Camouflage in nature

    Cryptic coloration is the most common form of camouflage, found to some extent in the majority of species. The simplest way is for an animal to be of a color similar to its surroundings. Examples include the "earth tones" of deer, squirrels, or moles (to match trees or dirt), or the combination of blue skin and white underbelly of sharks via countershading (which makes them difficult to detect from both above and below). More complex patterns can be seen in animals such as flounder, moths, and frogs, among many others.

    The type of camouflage a species will develop depends on several factors:

    • The environment in which it lives. This is usually the most important factor.
    • The physiology and behavior of an animal. Animals with fur need camouflage different from those with feathers or scales. Likewise, animals who live in groups use different camouflage techniques than those that are solitary.
    • If the animal is preyed upon then the behavior or characteristics of its predator can influence how the camouflage develops. If the predator has achromatic vision, for example, then the animal will not need to match the color of its surroundings.

    Animals produce colors in two ways:

    • Biochromes: natural microscopic pigments that absorb certain wavelengths of light and reflect others, creating a visible color that is targeted towards its primary predator.
    • Microscopic physical structures, which act like prisms to reflect and scatter light to produce a color that is different from the skin, such as the translucent fur of the Polar Bear, which actually has black skin.

    Cryptic coloration can change as well. This can be due to just a changing of the seasons, or it can be in response to more rapid environmental changes. For example, the Arctic fox has a white coat in winter, and a brown coat in summer. Mammals and birds require a new fur coat and new set of feathers respectively, but some animals, such as cuttlefish, have deeper-level pigment cells, called chromatophores, that they can control. Other animals such as certain fish species or the nudibranch can actually change their skin coloration by changing their diet. However, the most well-known creature that changes color, the chameleon, usually does not do so for camouflage purposes, but instead to express its mood.

    Beyond colors, skin patterns are often helpful in cryptic coloration as well. The Craik-O'Brien-Cornsweet illusion describes visual perception as occurring through contrasts of outlines. One recognizes a dog, for example, not by its color as much as by its shape. Often what matters most for good cryptic coloration is to break up the outline of a creature's body. This can be seen in common domestic pets such as tabby cats, but striping overall in other animals such as tigers and zebras help them blend into their environment, the jungle and the grasslands respectively. The latter two provide an interesting example, as one's initial impression might be that their coloration does not match their surroundings at all, but tigers' prey are usually color blind to a certain extent such that they cannot tell the difference between orange and green, and zebras' main predators, lions, are color blind. In the case of zebras, the stripes also blend together so that a herd of zebras looks like one large mass, making it difficult for a lion to pick out any individual zebra. This same concept is used by many striped fish species as well. Among birds, the white "chinstraps" of Canada geese make a flock in tall grass appear more like sticks and less like birds' heads.

    In nature, 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. Natural camouflage is one method that animals use to meet these. There are a number of methods of doing so. One is for the animal to blend in with its surroundings, while another is for the animal to disguise itself as something uninteresting or something dangerous.

    There is a permanent co-evolution of the sensory abilities of animals for whom it is beneficial to be able to detect the camouflaged animal, and the cryptic characteristics of the concealing species. Different aspects of crypsis and sensory abilities may be more or less pronounced in given predator-prey pairs of species.

    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. 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 (the cephalopod family). Some animals, notably in aquatic environments, also take steps to camouflage the odours they create that may attract predators. Some herd animals adopt a similar pattern to make it difficult to distinguish a single animal. Examples include stripes on zebras and the reflective scales on fish.

    Crypsis is the ability of an organism to avoid observation or detection by other organisms. 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.

    Antipredator adaptations are evolutionary adaptations developed over time, which assist prey organisms in their constant struggle against their predators. There are several ways antipredator adaptations can be classified, such as behavioral or non-behavioral or by taxonomic groups.

    Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The opposite is diurnality. The intermediate crepuscular schedule (twilight activity) is also common. Some species are active both in daytime and at night. Living at night can be seen as a form of niche differentiation, where a species' niche is partitioned not by resources but by time itself, i.e. temporal division of the ecological niche. It can also be viewed as a form of crypsis, in other words an adaptation to avoid or enhance predation. There are other reasons for nocturnality as well, such as keeping out of the heat of the day. This is especially true in deserts, where many animals' nocturnal behavior prevents them from losing precious water during the hot, dry daytime. This is an adaptation that enhances osmoregulation.

    Mimicry is the similarity in appearance of one species to another that protects one or both. Mimicry occurs when a group of organisms, the mimics, evolve to share common perceived characteristics with another group, the models. The evolution is driven by the selective action of a signal-receiver, or dupe. For example, birds that use sight to identify palatable insects (the mimics), whilst avoiding the noxious models.

    Batesian mimicry is a form of mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator. It is named after the English naturalist Henry Walter Bates, after his work in the rainforests of Brazil.

    Some chameleon species are able to change their skin colors. Different chameleon species are able to change different colors which can include pink, blue, red, orange, green, black, brown, light blue, yellow and turquoise. to blend in with their surroundings, as an effective form of camouflage.

    Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)

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