© The Independent, UK
A study by the University of California and Durham University found that animals with pupils shaped like vertical slits are more likely to be ambush-predator species such as cats and crocodiles.
Meanwhile, plant-eating “prey” species such as sheep and goats tend to have horizontal, elongated “letterbox” pupils. And circular pupils are linked to “active foragers” – animals that chase down their prey rather than creeping up and ambushing them.
The analysis of 214 species, which appears in the journal Science Advances, suggests that there are good evolutionary reasons for these differing optical designs.
Tests showed that eyes with horizontal-slit pupils offered an expanded field of view. Located on each side of the prey animal’s head, they provide a panoramic visual display that improves its chance of spotting approaching danger.
The slits also have the added advantage of limiting the amount of dazzling light from the sun, making it easier to see the ground.
“The first key visual requirement for these animals is to detect approaching predators, which usually come on the ground,” said the report’s lead scientist, Professor Martin Banks of the University of California at Berkeley. “They need to see panoramically on the ground with minimal blind spots. Once they do detect a predator, they need to see where they are running. They have to…