The reason why a cat's pupils become round at night is mainly because cats are nocturnal animals, and their ancestors were primarily hunters. Rounding their pupils at night helps them see prey clearly. Cats have relatively good night vision, so this is a normal phenomenon.
Analysis of changes in a cat's pupils: A cat's pupils can contract and dilate depending on the intensity of light. If a cat is in a bright place, its pupils will constrict; if it is in a dark place, its pupils will dilate. This allows the cat to see changes in its environment well, day or night, which was more suitable for its ancestors' hunting in the wild.
