male mouse chasing females

Question
QUESTION: I recently got 2 male and 4 female mice from the pet store to be breeders/pets, I also have snakes who will not eat frozen/thawed prey items so I need live prey item for them and it was getting hard to keep up, so I decided to breed the food and keep the extra as pets because mice are cute, but I got them home and then one of the females was running on the wheel and the male went up on the wheel sniffed her and looked liker he tried to bite her behind the head and then later on he was in the hide box with the other one and I heard a ton of squeaking and the box was shaking like crazy until I gave it a lite smack and then they both came running out. Is it anything I should be worried about? Because the other male and 2 females get along just fine and I've had them together for about a week now.

ANSWER: Hi Randy,

Mouse breeding is never as easy or as pleasant as most might initially think.  Unless you see bite marks (blow the fur back and look for little scabs or missing fur), the squeaking and chasing is part of the deal.  He might be overly aggressive about it, but the copulation is never pleasant for the female involved.  The nipping around the head might be sexual grooming, but you should keep a very close eye out for resulting injuries.  Real biting should never, ever be allowed - you don't want to pass that on to the offspring!

Since it's so unpleasant for the girls, it's usually a good idea to remove females after 2 weeks or once you know they are pregnant, whichever comes first (but not more than 2 weeks at a time), so the female can have some peace and raise her pups without the added stress of the male.  You'll probably want to do this anyways, because the females can get pregnant again immediately after giving birth and this can result in a much higher risk of birthing complications (that are not only tragic but may lose you a good doe).  Since the usual gestation period is 19-21 days, two weeks prevents the male from accidentally being around for the birth - not all bucks are good dads.  Once you fall into a schedule you can use this 2 week pairing system to keep the right number and size of mice on hand for your snakes, and still give your females a bit of peace and quiet in between litters.

This page, especially the "Essentials" section, is an excellent first source for any mouse breeding stuff you might not already know:  http://www.hiiret.fi/eng/breeding/index.html  It's great for beginners and experts alike (and I still keep finnmouse on my bookmarks list) so I really do recommend checking it out.  If you have any more questions just let me know!

Best of luck!
-Tam

---------- FOLLOW-UP ----------

QUESTION: Thanks I think one of the females is with the other male is either pregnant or just got really fat really quick 'cause it looks like she swallowed a golf ball, so she's been put in a different cage right next to them, there are no visible marks anywhere except a few light pink lines that I never noticed on the males tail, and they only seem to do for a day or two after I clean the cage out, I clean every thing so that it all smells new could it be because they think that it's all new?

Answer
It's possible.  Try putting a small handful of dirty bedding in with the new and mix it all up.  That way the male will feel comfortable and like he's already scented the place, and it might calm them down a bit.

Sounds like she's preggers, congratulations on the upcoming litter!  :)

-Tam