swolllen testicals: mice

Question
my mouse keeps having his testicals swell up and then go back down... what is going on with him?

Answer
Dear Lily,
thank you for your question.
It's probably perfectly normal. Male mice can hide their testicles, they are not always visible. They do it when they don't feel relaxed, when it's cold and for other reasons. So I would say that you have nothing to worry about, as long as the mouse doesn't seem to be in pain.
I hope I was of some help to you
Jennifer