Camouflage is a word used for animals in nature and humans in the military, when they are disguised. What does it mean to have camouflage? It is the use of any combination of materials, coloration or illumination for concealment. This has become one of the largest games between predator and prey. The prey will do whatever they can to not be detected and predators use it to be able to lay in lure and sneak attack. It is a technique used from Leopards (Panthera pardus) and giraffes (Giraffa camelopardalis) to seahorses (Hippocampus) and sharks (Elasmobranchii).
There are different ways on how camouflage work. Most of them are methods of blending in with the background. Some examples of camouflage are mimicry, colour matching, disruptive coloration, countershading, counter illumination, reflection and active camouflage.
All of these common camouflages are well used in the animal kingdom but some are more known then others by humans. Mimicry or mimic, is when the animal looks like something else, this is used by predators, to be able to lay in lure for their prey, and prey trying to avoid detection by the predators. Some animals that use mimicry are frogfishes (Antennariidae) that looks like seaweed, and Pygmy seahorses (Syngdathidae) that looks like the coral they live on.
Colour matching is when the animals resemble the background colour like the brown trout (Salmo trutta) or sting rays (Myliobatoidei). Disruptive coloration is having high contrast coloration that breaks up outlines so an observer fail to recognise the object. The best examples of this are Leopard and Giraffes, their spots make them break up and blends in to the habitat. Another type of disruptive coloration is to have a stripe running through the eye making this outstanding feature disappear, this is seen in a lot of reptiles.
Countershading is widely used in the ocean with two different types. It is side countershading and the above/below countershading. Side countershading is when the animals have graded toning from dark above to light below. This cancel out the apparent effect of self-shadowing when viewed from the side and are used by blue sharks (Prionace glauca) and bush buck (Tragelaphus sylvaticus). Above/ below countershading is having different colours or patterns on the top of the body compared to the bottom of the body. This is seen for example in the Great White sharks and penguins. Penguins have a black head and back body that hides them from above and a white belly to protect them from below.
The counter illumination is a camouflage that is seen in the deep oceans where a part (normally the belly) of the body lights up with bioluminescence. This has the same effect as countershading for the animal, but is not due to pigmentation, but to the actual effect of turning on a light. You can read more about bioluminescence next week. Reflection is almost exclusively found in the ocean and is used by fish. They will be silver in colour to reflect enough light, usually from the sides, to make the object show as a patch of the environment.
One of the last techniques is active camouflage where the animals change the coloration rapidly enough to maintain resemblance to the current background while moving. This is used by chameleons (Chamaeleonidae) and Octopus (Octopoda) where the octopuses are extremely fast in changing colour and disappearing into the environment.