Biology
What makes cat pupils remain slit-shaped?
Quick fact
Vertical pupils create a larger depth-of-field for horizontal contours, helping cats judge the distance to prey—and they can dilate from a 1mm slit to nearly full eye width in seconds.
Why this is interesting
A cat's vertical slit pupil isn't just for beauty—it allows them to hunt at night and in daylight by controlling light intake with extreme precision, giving them a depth-sensing advantage for pouncing.