What is different between "pretty old" and "very old"? Why does she use "pretty", not "very"?
Native speaker’s answer
Rebecca
"Pretty" in this case means fairly, somewhat, or a little. The word "very" is usually stronger than "pretty", and is used to describe something that is a high degree of something. So "pretty old" here means that the animal is old, but it is less old than one which is "very old."