Many domestic cats have vertical-slit pupils because this shape helps regulate incoming light and may improve distance judgment for a predator that hunts close to the ground. Comparative research found links between pupil shape, hunting style, and eye height. It does not mean that every cat species has vertical slits or that pupil shape has only one function.
Pupils regulate how much light enters
The pupil changes size to control light reaching the retina. A vertical slit can close down to a narrow opening in bright conditions and expand in dim light. Domestic cats are active across a range of light levels, so a pupil capable of a large change in size is useful. [1]
Shape is linked to how an animal hunts
A comparative study of pupil shapes found that vertical slits are common in ambush predators that are active both day and night and hunt near the ground. The shape may help estimate distances to prey while reducing blur in the vertical plane. The study compared many species; it proposes an ecological explanation rather than proving the full purpose of every cat’s eye. [2]
Not all cats have the same pupil
Lions and tigers have round pupils, unlike many smaller cats. Body size, eye height, activity times, and hunting strategy may help explain these differences. Vertical pupils are an adaptation that fits a particular visual niche, not a universal feature shared by every member of the cat family.
Eye shape and low-light vision
A vertical pupil can change from a thin slit to a much wider opening, helping control incoming light across bright and dim conditions. The shape is only one part of feline vision; retinal cells and reflective tissue also affect how cats see.
The reflective layer behind a cat’s retina is why many cats’ eyes shine in low light. Read why cats’ eyes appear to glow for that separate adaptation. Pupil shape and eyeshine are related to vision, but they are not the same mechanism.
Sources and evidence
- Nature — The eyes have it ↗
Pupil size changes and the function of different pupil shapes.
- Science Advances / PMC — Why do animal eyes have pupils of different shapes? ↗
Comparative study connecting pupil orientation to ecological niche and hunting strategy.
Sources consulted: 15 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial publication; the explanation was checked against the linked institutional and research sources, with uncertainty stated where relevant.