Do whales see in colour?
Whales see in black and white—or almost! In fact, they might be able to see red, but in the ocean, only blue light reaches the depths. How can we explain this surprising contradiction?
Colour vision is made possible by cones, which are light-sensitive receptors. Different types of cones detect different wavelengths of light—that is, different colours. The vast majority of mammals are “dichromats”: they have cones for short wavelengths (blue) and for medium or long wavelengths (green or red).
Whales have only the cones that allow them to see red (monochromacy). They do possess the gene for blue cones, but it is defective. We can therefore surmise that their ancestor was dichromatic, like other mammals.
Why did they lose their colour vision, which is often considered an evolutionary advantage? And above all, why didn’t they evolve to see blue? Early whales lived in coastal waters. In this environment, depth and turbidity mean that red and green penetrate better than blue, unlike in the open ocean. Thus, blue cones do not confer an advantage on them. This hypothesis is supported by a very similar scenario among seals, which have vision similar to that of whales and which also evolved in coastal waters.
Jeanne Picher-Labrie
Jeanne Picher-Labrie joined the GREMM’s team in 2019 as a writer at Whales Online and a naturalist at the Interpretation centre on marine mammals. With a Bachelor's degree in biology and training in science journalism under her belt, she is back in 2021 to tell new whale stories. By immersing herself in scientific studies, she tries to learn more and more about the mysterious life of cetaceans.
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