my 3 mice

Question
i have 2 female mice and 1 male..ive had the 2 females for over a year and the male for about 6 months..we were hopin they would have babies but neither one of the females have gotten pregnant but one of the females has been a lil on the heavy side but recently we noiticed she was a lil fatter the usual with a pear like look..could she be pregnant?? and why hasnt either one have babies??

Answer
Hi Jesusita,

It could be fertility of the mice you are trying, but I do have some suggestions you can try first.  Regarding their fertility - some males are simply not interested in mating, or make too aggressive or too passive of an attempt for the females to allow him to.  In that case, trying a new male may be your best bet.  Also, fertility in females decreases after a year of age - that's not to say it's impossible for older females to get pregnant, but litters can become harder to achieve and you may get fewer pups, as well as a higher risk of complications in the females.  Overweight mice of both genders can also have a more difficult time successfully creating offspring.

As far as what you can do with the meeces you have now - there are a few simple tweaks you can make to speed mating along.  First, try moving the male to a cage of his own.  Some males only feel comfortable breeding if they are in a space they've claimed as their own little bachelor pad.  Additionally, the females should be more receptive if they are not constantly around him, which can be stressful.  Do go ahead and add some of his dirty bedding to theirs each cage change - the scent of his urine will keep them cycling even in his absence.  Once he's been in his cage for a week or so and gotten adjusted, rotate the females through HIS cage one at a time for 11-14 days at a time.  This might be longer than you're willing to wait, but it's how I've had the most success.  This gives the females at least 2 cycles of estrus with a male present (they cycle about every 5 days), and makes sure a female is with him most of the time with breaks now and then.  The time while the other female is in with the male gives you a little time to see if she successfully bred or not - since the gestation time is 3 weeks and you'll be 2-3 weeks by the time it's her turn to swap in with him and try again.  Remember, of course, that a female can give birth up to three weeks from the last day she was in with the male, so allow for that time - sometimes they don't round out until a few days before having pups!

As far as the female who appears to be putting on weight - the best way to tell if she is pregnant is to wait for babies!  Keep her environment as stress free as possible and make sure there is plenty of food and water to go around.  Give her torn up tissues to nest with, keep the cage clean, and give her a space to hide away.  Keep their light cycle fairly regular (don't leave lights on at night - this is when they are most inclined to mate and also when they are most likely to give birth) and try not to disturb them at night.  I'd also remove the male simply because not all male mice are pup-friendly, and it would be a very sad loss if you had a litter and they were in danger from the dad!  Since the female has had her friend for over a year now, I'd leave those two together to keep from stressing out potential mommy.  :)

Best of luck, and congrats on your future litters!  Let me know if you have anymore questions.
-Tam