Male rats called bucks are usually laid back creatures. If males fight they do so to gain position in a pack, but rarely cause injury. They enjoy being held and will cuddle. Females (does) are more energetic and active. About every 5 days when a female is in heat, she can become jumpy. Actually they both make good pets as every rat has a different personality. Sometimes, just looking at them helps you decide, whether they are male or female.