dilate

Ninja’s could tell time time by how dilated a cat’s pupils were as they dilate in a regular pattern throughout the day, regardless of ambient light. – WTF Fun Facts

Source: https://books.google.co.uk/books?id=kUHRAgAAQBAJ&pg=PT92&lpg=PT92&dq=ninja%27s+dilation+of+a+cats+pupils&source=bl&ots=nv1RKv7LED&sig=ACfU3U1vAb2RzmlG7Qlkfx3gkykZA0fLOg&hl=en&sa=X&ved=2ahUKEwjLmLydoJfpAhUlXhUIHc21CJoQ6AEwGnoECAwQAQ#v=onepage&q=ninja’s%20dilation%20of%20a%20cats%20pupils&f=false