Why are some animals so well camouflaged?

Sphaenorhyncus lacteus, the greater hatchet-faced treefrog. Photo by Phil Torres

A katydid. Photo by Jeff Cremer.

A Plica plica tree runner camouflages against the bark of a large Ficus tree. Photo by Phil Torres

Another related katydid- some camouflage against dead leaves, others against live, green leaves. Photo by Jeff Cremer

Predators like monkeys and birds have remarkable visual, pattern recognition, and learning abilities. Young birds can quickly learn which butterflies are distasteful or poisonous, and monkeys can learn which 'fake leaf,' like the katydids pictured, are actually edible insects. Because of that learning ability, many of these camouflaged species are polymorphic- meaning they have varied forms of camouflage. Within a single species, some katydids will look more like a live leaf while others have dead-leaf venation. The variation ensures that a monkey can't learn one single pattern to eat and will have a more difficult time identifying the katydids as prey.

The pressure that predators put on populations of these animals means that only the most well camouflaged survive to reproduce, and the others get eaten! This effect, over millions of generations, has helped produce species with the detailed camouflage we see today.