Why Animal Eyes Take On So Many Shapes

Plants and Animals





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Grazing prey animals have horizontally elongated pupils that expand their field of vision. Their eyes rotate so that the pupils stay aligned with the ground regardless of whether their head is upright or pitched down. Gordon Love/Durham University.

Pupils regulate the amount of light that hits an animal’s retina, and they come in a variety of shapes. Ours are round dots. Cats have vertical slits, sheep have horizontal slits. Researchers trying to understand why different pupil shapes evolved say it has to do with ecological niches: Are they the hunter or the hunted? The work is published in Science Advances this week.