All the traits that we are designed with serve for a purpose. Some animals are furry as to protect themselves from harsh life conditions and cold, some have the ability to change their color in order to hide from predators, like chameleons do, some have long legs, such as herbivores who must run fast from predators, and the list can go on with explanations and reasons why species are the way they are. A recent research explains why is that kittens have vertical pupils.
Scientists have wondered for a long time why some animals, including goats, have horizontally shaped pupils, while others, such as rattlesnakes and cats have vertical structures. The answer is strongly linked to the fact that this particular trait offers animals a survival edge. Vertical pupils and circular pupils help predators hunt while horizontal pupils help other species spot predators from afar. A more compact pupil can help predators focus better and target their prey while a wider pupil widens perspective as well and helps animals better monitor their area of action.
It seems that although the explanation has a logical background, not all vision scientists agree with it.
Findings were based on a research conducted by a team of scientists from the University of California, Berkeley and Durham University in Britain and the results were published in the journal Science Advances. To come up with the conclusions, the team used computer models based on a sheep’s eye to support theories about why horizontal, vertical and circular pupil shapes benefit different species of animals.
A horizontal pupil allows for more light to be captured from both left and right sides of the eye and in contrast, less light can be captured from below and above. As previously stated, it allows grazing animals to better detect predators approaching from different directions.
Researchers made another breakthrough discovery while taking photos of goats. They found that their eyes rotate as much as 50 degrees when their head turns downward, which keeps the pupils parallel to the ground. This was also found to be true in horses, antelopes and other grazing animals.
Vertical pupils help an ambush predator better estimate the distance to its pray, as depth is sharpened and focus on the target is better envisioned.
However, large predators, such as tigers and lions that ambush prey have circular pupils, not vertical. From the range of felines, kittens have vertical pupils and they are predators. At the same time, chinchilla, eats grass but has vertical slit pupils.
There are many exceptions to the rule that “there has to be more to pupil shape than being predator or prey, big or small”, critics explained.
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