The Littles and the Bigs

Some sort of selection-slash-separation process seems to be going on in the mouse colony.  It could be that the teenagers are moving out on their own, or perhaps the adults have had it and have kicked their half-grown offspring out of the nest to fend for themselves.  Naturally, I put down grain for both tribes.  As I sit on the milking stand, to my left are the youngsters.  I have to look under the goat's belly to see the grownups on my right so I see more of the kids, and sometimes it's startling how much bigger the adults are.  I had thought that mice bred continuously throughout the year, but I realized it's been quite awhile since I've seen actual babies.

I have no scientific proof and Google doesn't provide much help, but observation alone tells me that there is a specific cycle going on.  The parents appear to raise one litter at a time, all at or near the same time, keeping the little ones close by until they're capable of being on their own.  That's when the dynamics and locations change.  Right now, the adults are enjoying some down time, taking a breather before starting a new family.  I haven't seen any obviously pregnant females in quite awhile.  According to what information I could find, estrus may come in March.  Some "experts" say that mice breed continuously.  Perhaps they do in captivity, but not from what I see with wild mice.  All agree that there is a 21-day gestation period, which would result in the first litters of hairless, blind pups arriving in April.  I'll have to pay more attention to the calendar and see how this plays out.

All I know for sure is that the Littles are on the left and the Bigs are on the right for the time being.  If the Littles become sexually active, will they move back to the right?  Will there be two colonies of Bigs?  If so, where will the new crop of Littles go?  Ahh, 'tis a mystery.