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According to some researchers there must be something more than just the state of prey or predators to decide the shape of the eye.
Researchers from the Durham University, University of California and Berkeley have conducted a study which suggests that eye shape indicates whether animals are predators or prey. The study published in the journal Science Advances indicates that circular and vertical pupils are specific to predators, whereas prey animals have horizontal pupils.
The scientists analyzed 214 species of animals. They used computer models based on sheep’s eye in order to see why circular, vertical or horizontal eyes are beneficial for certain species. It was observed that horizontal eyes allow more light to be captured from the right and left of the eye. On the other hand less light is captured from above and below the eye. Since grazing animals possess this type of eyes this feature enables them to better see predators which might come from different directions.
When they observed a goat eating researchers discovered that their eyes rotate 50 degrees in order to keep the pupils parallel to the ground. So this is something which goes against logic since it would normally be expected that the pupil will become perpendicular to the ground. After analyzing other species researchers noted that the same phenomenon happens in the case of other prey animals as well such as antelopes and horses.
As far as vertical pupils are concerned researchers noted that they are more useful for predators because they sharpen the focus on a target and de depth of perception. In the case of taller animals there is no need to compensate for such visual cues so some large predators have circular pupils. Such species include lions and tigers
Gordon Love, co-author of the study, remarked:
We are learning all the time just how remarkable the eye and vision are. This work is another piece in the jigsaw puzzle of understanding how eyes work.”
Other researchers are skeptic regarding this research. For example, biology Ronald H.H. Kröger from Lund University in Sweden believes that there are too many exceptions to the rules which the authors of the study have discovered. According to him there must be something more than just the state of prey or predators to decide the shape of the eye.
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