Why different animals have different-shaped pupils

Los Angeles Times : Terrestrial animals have different-shaped pupils: Nocturnal predators, such as cats, tend to have vertically elongated pupils, and prey, such as sheep and other herbivores, tend to have horizontally elongated pupils. To better understand why, Martin Banks of the University of California, Berkeley, and colleagues looked at 214 land-based species. They found that vertical pupils are better at gauging distance, so they help predators leap out at their prey. Horizontal pupils, on the other hand, create a better panoramic view, which helps the animals watch for predators. Moreover, as certain herbivores, such as goats, sheep, and horses, put their heads down to graze, their eyes rotate to keep their pupils in line with the horizon. Animals with round pupils, such as humans, tend to be predators that hunt both day and night. The researchers plan to continue their study by looking at animals with other shapes and types of pupils, such as those with multiple apertures, like geckos’.