Steve Parker - Camouflage

Humans are primarily visual. Compared to most creatures, our eyes see many colours and details. So, we think of camouflage in visual terms. But sight is of little use in habitats such as the deep sea, inside caves, in forests at night, or in the earth. Vast numbers of animals sense the world very differently to us. Some have olfaction (smell) as their main sense, others have hearing or detecting movements and vibrations.

Camouflage can work here too. Some moths have sound-absorbing hairy bodies and wing surfaces that disrupt the ultrasonic clicks used by bats to detect prey. Certain caterpillars, fish like the harlequin filefish (see ) and a few snakes emit chemical odours gained from their surroundings or their food, so they cannot be sniffed out by predators. Cave crickets, deep-sea fish and burrowing reptiles are able to modify their movements, and the vibrations these send out, again to avoid detection by enemies.

Some kinds, or species, of animals have an extensive geographic distribution across habitats with differing backgrounds. So they have a generalized, all-purpose camouflage, such as complex shades of grey, brown, tawny, rusty, reddish, cream and white for the grey wolf (see ). Also, wolves farther north are larger than those from their southern range, following Bergmanns rule bigger, warm-blooded animal bodies have less surface area compared to bulk volume, and so retain heat better in colder environments. Such variation in physical size also impacts camouflage colours and patterns.

Camouflage can be aggressive, a wolf in sheeps clothing, used by a predator to sneak up on or ambush prey. It may be defensive, employed by prey animals to remain unnoticed by predators. In some species, such as the peacock flounder (see ), it is both of these. Sometimes camouflage is referred to as mimicry. A leaf mantis might be said to mimic the leaves of its environment. However, in biology mimicry also has more specific meanings. For example, the harmless hoverfly is said to mimic a harmful wasp, since both have black and yellow coloration. Most predators learn to avoid wasps, and so they also avoid similar-looking hoverflies. The mimic, the hoverfly, thereby gains by resembling what is called its model, the wasp.

A very different type of camouflage is disruptive coloration or patterning. The aim is to break up or disrupt a creatures recognizable outline and form with bold, contrasting colours and shapes that are designed to be noticed. Black and white, as in killer whales and Malay tapirs (see ), are examples. If the onlookers attention is even briefly distracted by such a confusing and diverting appearance, there is time to escape or attack.

Other aspects of camouflage include self-adornment, shadow elimination and countershading. Some insects, snails, crabs (see ), insects, birds and others can flatten themselves and press down on to a surface, and also orientate themselves to the sun, to avoid giveaway shadows. Many animals have a darker upper side and are lighter underneath, known as countershading, to reduce the effect of sunlight from above lightening the upper surfaces and shadows darkening the underside.