Countershading

July 17, 2011
By Damond Benningfield
Episode:

The “tuxedo” pattern that a penguin wears is more than just a snappy style -- it’s a type of camouflage. It doesn’t help on the ice, but in the water the pattern of black and white helps hide the penguin from both prey and predators.

The penguin is a drastic example of countershading. Credit: National Oceanic and Atmospheric Administration

Marine creatures use many techniques to keep from being seen. Some use a combination of texture and color patterns to blend in with the background. Others are virtually transparent. And still others can change color as they move across the ocean floor.

The most common type of marine camouflage is that used by the penguin -- a two-toned countershading. The top half of the animal is dark, so when it’s seen from above, it blends in with the dark waters below it. And the bottom half is light, so when seen from below, it blends in with the sunlit waters above it.

The penguin is probably the most drastic example of this sporty two-toned look, but it’s found on many other creatures as well. Most of them stay close to the surface, where there’s more light and hence a greater need for camouflage. The list includes mammals like whales and dolphins, and many species of fish, all the way up to Great White sharks.

Countershading is also used by birds, and it’s even been used on fighter planes and bombers. But it isn’t perfect -- it’s no Harry Potter invisibility cloak. When silhouetted against bright sunlight, for example, a creature casts a shadow that can alert everything in the water below it. Even so, countershading is a technique that never goes out of style.