Breeding for Temperament
I strongly select for genetic temperament since temperament is highly hereditary (this is well documented). Breeding for temperament is a key part of my breeding program and goals. Aiming to improve domesticated rats should involve selecting for not only health and structure, but also better temperament. Socialization shouldn't be NECESSARY, but it does help build early confidence. I socialize a mild amount for this reason. In the past, I did not socialize at all, but through some testing I have continuously found that regardless of socialization, poor genetic temperament is usually apparent. My mild socialization simply consists of me occasionally putting my hand in the cage, petting them, and getting them all playful and excited. I will also occasionally pick up babies and kiss them. When selecting for temperament, I look for curiousness, confidence, being relaxed when handled, friendliness, good scruff with ideally a perfect or good tuck, willingness to eat from my hand, and even the tendency to like water. The rat with the better temperament will become apparent when testing for all of these things. Temperament can ALWAYS be improved in one way or another.
I raise my hamsters similarly to my rats. Hamsters are more difficult to breed and raise, but when a female is pregnant after being paired with a male for her heat, she is left alone in her large bin cage for the pregnancy, the birth, and the raising. Hamsters are very prone to eating their babies when they are disturbed up until the babies are at least 14 days old. I will only disturb the new mothers for replacing food and water. I try to clean her cage and give her plenty of food before she has her babies so I won't have to bother her for a while.
Like with my rats, I am selecting for temperament, but I socialize them after deciding on who I will keep. The temperaments in my hamsters tend to me more independent (typical for hamsters), but I am actively selecting for hamsters with natural interest in people.
Hamsters are listed when they are five weeks old and let go to their new homes at six weeks old.