Have you ever watched an action-packed scene unfold around you and you try your best to focus on a certain object moving? Or have you ever watched your house cat hunt and noticed that they don’t lose focus of what they are chasing in front of them?
I asked the question whether this is discipline or is it a predatory adaptation that happens automatically? After mulling over it for a while, I did some research.
I found an article on the pupils of land animals by researchers at the University of California in Berkeley and how they have adapted their eyes due to their niches. They tested the pupils of 214 species of land animals, both predator and prey.
Predators on land have eyes facing forward, giving them the ability to focus on their prey.
Prey species on the other hand – but more specifically many herbivores – have eyes facing to the side, giving them great peripheral vision. Interestingly enough, it is their pupils that can differ the most between species, conferring different advantages upon them.
Some animals have a round pupil, like us, some have a vertical slit-shaped pupil and some have a horizontal slit-shaped pupil.
Predators that ambush their prey and hunt both day and night tend to have vertical slit-shaped pupils – like a house cat. The researchers then concluded that the shape of the pupils depends on how the animal hunts. However, lions and leopards are also ambush hunters, yet their pupils are round. Researchers then concluded that predators that have round pupils are more “active foragers” since they chase down their prey. This confused them too so they furthered their research. They found out that pupil shapes are not only dependent on the predators’ hunting techniques but also their size.
Being closer to the ground, making it difficult to focus on the object in front of them (it’s difficult to focus on prey when you’re much shorter than the grass/logs), smaller predators need to use “focus blur” which will help them judge the distance more accurately than taller predators. That I found incredible! We, like taller predators, don’t have that much worry of tall grass getting in our way so we don’t need to use focus blur as much to judge distance, hence our circular pupils.
But what about the prey species’ pupils? Most prey animals, like antelope and especially grazers, have horizontal slit-shapes pupils. The researchers used technology to see exactly how these animals see. They saw that the horizontal slit-shaped eyes allowed them to see in perfect alignment with the ground as they feed and more light is let in from the front, the sides and behind them. Not only does this help them spot predators in their periphery, but if/when chased, it allows them to have superior collision avoidance, detecting obstacles that might cause them to stumble while running.
They say the devil’s in the details, but when it comes to the different pupil types in the wild, it’s more like life and death that you can find in the details!