Animals’ Eye Shapes Related to Place in the Ecological System

A new study out of University of California, Berkley, emphasizes the fact that an animal’s eye shape is related to their place in the ecological system.

The scientific study addresses the issue of why orientation matters. For instance, a horizontal shape of an animal’s eye confers them a panoramic view suited to detecting predators approaching from almost any angle.

 The scientific circle started with the basis of a classic 1942 writing on the physiology of the eye that suggested that slit-shaped pupils permitted a more significant range of light entering the eye and allowed for different musculature.

Martin Banks, professor of optometry at Berkley, and Gordon Love, director of the Center for Advanced Instrumentation at Durham, learned something else, in comparison with the previous text. For instance, mongooses exhibit forward-facing eyes but horizontal pupils, cuttlefish have W-shaped pupils, whereas geckos display circular pupils of exceedingly great size when dilated which diminish to several discrete pinholes when constricted.

The research team included in their studies other animals, such as horses, antelopes, and other animals which feed on growing grasses and herbage and found out that these too have the ability to rotate their eyes.

 Banks and his colleagues discovered that animals with round pupils have the tendency to be active predators or foragers that are both diurnal and nocturnal creatures. They gathered information on 2014 species.

However, the theory did not explain initially why the pupils were either horizontal or vertical.

Prof. Banks said that horizontally oriented pupils were normally encountered in grazing herbivores with their eyes on the side of their head, which helped them see all around to spot predators. Species with vertical pupil slits have the tendency to pertain to the class of ambush predators, active both day and night.

Prof. Gordon Love reported that they looked at the visual benefits of different pupil orientation and discovered a strong correlation between that and how animals feed -whether they are the hunter or the hunted. Provided the pupil follows the pitch of the head, they would become more vertical and the theory would become unsteady.

However, a solid pattern was born with their studies. That would be pretty important for an animal that might need to drop everything and run if a mountain lion attacks, expressly an animal with its eyes on the side of its head, Banks continued.

He said that foxes had vertical pupils, but the discrepancy was that wolves had round pupils, though. He continued by saying that cats and other slit-pupil predators are inclined to use blur, to estimate horizontal distances.

Moreover, prey species of the likes of goats and sheep could be perceived distinctly by their “letterbox” pupils, whereas cats, crocodiles and other predators display vertical slit-pupils.

Another aspect of the study involved the fact that grazing prey animals had horizontally elongated pupils that expanded their field of vision.

A surprising study characteristic was that goats’ eyes rotate so that the pupils stay aligned regardless of whether their head is upright or pitched down, which was remarkable as the eyes would have to spin in opposite directions in the head.

As a conclusion, it can be claimed that, in general, nocturnal or polyphasic ambush predators (i.e. which sleep in shifts during the day) display vertical slit-shaped pupils, whereas predators who hunt during the day have round pupils, and herbivores exhibit horizontal pupils.

Photo Credits static.nautil.us