How do whales see us?

Surprisingly, whales cannot see the colour blue, which is the hue that best penetrates the depths of the marine universe. This inactive nature of the cones associated with the colour blue might be explained by the fact that whales’ ancestors inhabited coastal waters, where the ability to perceive blue is less of an advantage.

However, although whales’ eyes contain few cones, they do contain many rods. The function of cones is to capture colour, while rods allow an organism to see better in low light. Whales therefore seem to have prioritized night vision over colour vision!

Cetaceans have three adaptations that allow them to see as clearly in water as they do in air. Firstly, whales have two areas of high cell density on their retina, i.e. areas where their vision is optimal. In comparison, humans only have one such area. Secondly, the cornea of ​​a whale’s eye is curved so that focusing is as effective in the water as it is in the air. Whales are therefore not short-sighted when they’re in the air, so they do not see us as a fuzzy blur!

Thirdly, the distinctive attributes of a whale’s pupil allow it to adapt to the changes in light it experiences as it moves through the water column. Whales can thus see both when they are on the water surface (or in translucent waters) where the light is strong, and when they dive into the dark depths of the sea.

Despite their ease in spotting prey, whales have poor three-dimensional vision. The eyes of cetaceans are located on either side of their heads. They therefore benefit from a wide field of vision, which is ideal for staying in tune with what is happening around them, but they cannot accurately gauge the distance of objects in their environment.

The positioning of the eyes in cetaceans is surprising. The majority of carnivorous mammals have close, forward-facing eyes and are characterized by wide binocular vision, i.e., the fields of view of their two eyes overlap, which allows their brain to assess the depth of an object. This adaptation in predators allows them to focus on their prey and hunt them most effectively. Prey species, on the other hand, often have laterally-placed eyes in order to maximize their field of vision and adequately detect the presence of predators.