i have sat in my rat room and watched some of the rats in our harem cages for hours on end. I can tell you that when a male breeds a female, it last for about two seconds. So, unless you stand over them and watch them for a week, it is quite possible that you would miss the breeding. Now that they have been introduced, I would say that within about a week at the most, your femalse should be prego. They typically take about 28 days to have a litter. So, after all of that, I would say to expect some pinkies in about 5 weeks. Hope that helps. Also, it just came to mind, but my rats typically breed more at night, when they are the most active.