Yep looks like a normal male Chipmunk to me, my four boys all indoors look like that at the moment but Tiny hasn't got his fully yet he is the youngest about 9 months old. The two adult boys bits receded about end of July last year and sometime in December descended again and only the last few weeks they have become very noticable especially on Nugget (nearly 3 years old) and Scabbers (11 months old). My oldest male is Asriel and he is nearly 4 years old.
The weirdest thing I had last breeding season was two Sisters trying to mate one another (that's what it looked like) infront of the male who was in with them, both were in season on the same day but the boy was only interested in breeding with one and I think the girl who was left out well she wasn't happy about it. 
You letting them girlies of yours watch too much Sexcetera?
I've never seen it myself, just heard about it! Honest!
