A team of researchers was able to link the shape of animals' pupils to whether they are more likely to be predators or prey.
According to The Guardian, authors of a study published in the journal Science Advances detailed what pupils can reveal about an animal. But the pupil shapes of these animals are not strictly identifiers, they are practical as well.
"The first key visual requirement for these animals is to detect approaching predators, which usually come from the ground, so they need to see panoramically on the ground with minimal blind spots," Martin Banks, a professor of optometry at the University of California - Berkeley, said in a press release. "The second critical requirement is that once they do detect a predator, they need to see where they are running. They have to see well enough out of the corner of their eye to run quickly and jump over things."
The researchers examined 214 land animal species and identified three distinct shapes of pupils: horizontal, vertical, and round.
Animals with horizontal pupils were more likely to have their eyes lie on the sides of their faces and therefore needed additional side-to-side range. Those with vertical pupils to be able to take in additional light for nighttime hunting. Animals with round pupils were often foragers, neither hunting nor being hunted.
Despite these findings, the researchers could definitively say why the shapes of the animals' pupils evolved the way they did.
"For species that are active both night and day, like domestic cats, slit pupils provide the dynamic range needed to help them see in dim light yet not get blinded by the midday sun," Banks said. "However, this hypothesis does not explain why slits are either vertical or horizontal. Why don't we see diagonal slits? This study is the first attempt to explain why orientation matters."
