Monday, January 2, 2012

Camouflage

At the end of their lives, almost all animals are eaten by other organisms, but all aim to delay this fate as long as possible. Various mechanisms are used to help them escape from predators or on the other hand to enable hunters to catch their prey. One of the most important of these is camouflage, needed by all but burrowing creatures and the very largest of land animals.


The most basic form of camouflage is counter shading. Here the back of an animal is more intensely coloured than the underside. Light falling from above shadows the paler area, making the colour appear uniform. Experiments show that predators faced with counter shaded prey find them far more difficult to see than those without this form of camouflage.



Counter shading of often augmented with disruptive colouration. Many creatures are patterned with spots and stripes that make them nearly invisible in their background. Disruptive shapes formed by spines or flaps of tissue may add a further degree of camouflage. For instance, the sea dragon of Australian waters is so decorated with flaps of skin that it is almost undistinguishable from the seaweeds among which it lives. In some cases, disruptive shape may become an imitation of a particular environment, leaf and stick insects are spectacular examples. Other creatures such as wasps or ladybirds are brightly coloured to warn predators that they are well protected with stings or chemicals that taste unpleasant.