If you’ve ever suspected you were sharing the water with a shark you’ll feel that, however well a shark sees, it is seeing far too well. However, new research shows that sharks actually lack a key component of sight: they are completely color blind.
Researchers at the University of Western Australia and the University of Queensland in Australia examined the retinas of sharks, which were safely deceased, and found that sharks lack the receptors needed to distinguish between colors.
“Our study shows that contrast against the background, rather than color per se, may be more important for object detection by sharks,” Professor Nathan Hart of the University of Western Australia said in a statement.
This finding doesn’t come as too much of a surprise. Most animals with limited or no color vision tend to not be terribly colorful themselves. For example, parrots come in a rainbow of hues and can see color, while sea lions, like sharks, come in about 50 shades of grey and brown and cannot see color.
Color vision is far less common for ocean creatures too, with the notable exception of colorful reef dwellers near the surface. The further you sink in the sea, the more wavelengths of light are filtered out, with long blue wavelengths being the last to go. It’s much less important to see blue when all there is to look at is blue. So, most sea life have dedicated their limited eye space to light and contrast sensitive rods rather than color detecting cones.
Sharks have monochromancy, or “total color blindness,” as opposed to the more common forms of color blindness in which colors are perceived atypically, like red-green color blindness that affects about eight percent of men with Northern European ancestry.
The lesson for swimmers, surfers, and other ocean lovers who want to safely share the sea with sharks is to reduce your contrast. Boards and suits that match the water will help you keep a low profile. You might still smell delicious, but you’ll be harder for the shark to find.
Photo via Wikimedia