Research has revealed the puzzle behind the shape of pupils in various animals. Based on a new study conducted at University of California-Berkley, one direction means the animal is a predator and the other means it’s prey. So which is which? Well, the study’s abstract statement can fully explain this.
“There is a striking correlation between terrestrial species’ pupil shape and ecological niche (that is, foraging mode and time of day they are active). Species with vertically elongated pupils are very likely to be ambush predators and active day and night. Species with horizontally elongated pupils are very likely to be prey and to have laterally placed eyes. Vertically elongated pupils create astigmatic depth of field such that images of vertical contours nearer or farther than the distance to which the eye is focused are sharp, whereas images of horizontal contours at different distances are blurred. This is advantageous for ambush predators to use stereopsis to estimate distances of vertical contours and defocus blur to estimate distances of horizontal contours. Horizontally elongated pupils create sharp images of horizontal contours ahead and behind, creating a horizontally panoramic view that facilitates detection of predators from various directions and forward locomotion across uneven terrain.”
Cats in particular, have vertical eyes, which are predatory eyes, The Escapist reports. Having pupils that are positioned vertically reportedly allows the predators to perfectly zoom in and out on their prey. These vertical pupils also allow the preying animal to see well in both day and night. Recently, lead researcher Martin Banks at UC Berkley explained the importance of vertical eyes in predatory animals.
“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.”
For the study, the researcher focuses on a few particular animals, however focusing on the cat and the sheep alone can bring the research into perspective. While the cat has been proven predatory by its vertical-slit pupils, the sheep is considered prey for pretty much the opposite reason. Based on the data obtained through the research, sheep have horizontal eyes to make it easier for the animal to watch out for its prey. Horizontal eyes, the study found, strengthen an animal’s peripheral vision.
Based on the data, many reptiles, felines, and fowl are considered predators, while many cattle, and other mammals are prey. Snakes, through the study, have proven to be one of the most predatory animals of all by contained species with both vertical-slit and round shaped pupils.
This study which analyses pupils as a way to determine an animals place in the food chain is published in the Journal of Science Advances.
[Images via Flickr]