Crypsis

In zoology, crypsis is the ability of an organism to avoid observation. A cryptic animal may do this through camouflage, nocturnality, subterranean lifestyle, transparency, or mimicry. 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 which rely on flight to escape predators; and venomous or poisonous animals which 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).