new rat old rat

Question
i just bought a wonderfully playful very energetic 4 month old dumbo rat. the introduction to my 1 1/2 year old rat went very well as he is a very calm non aggresive rat.but im worried because the young rat is always pestering him , jumping on him, climbing on him etc. probably just playing with his new friend but my older rat squeeks and squeels like hes in pain, he tolerates alot from the younger one but it just seems like the old one gets tired of the constant pestering. is this normal ? should i worry about my older rat being hurt by these "playful" interactions?

Answer
This is pretty normal. If they begin to fight or if your older rat begins to end up with wounds or looks beyond stressed (goes off his feed, begins to fall ill, etc.) then yes, I would separate them; however this is all very normal and to be expected. In time, they will learn to love each other, and most likely your older rat will tell the baby when he's had enough.