One thing to keep in mind on rats - although they are less inclined towards cannabalistic agression (think I used to play lead guitar for them) stress can induce it, be it lack of food/water, unsanitary conditions - or as it seems in my case a towering german shepherd prowling the room. Litter #1 came off no hitches and they all went for a good Sumatran cause. Litter #2 disappeared one day and the only problem I can attribute it to was Freya (our shepherd) repeatedly playing peek-a-boo with em (SHE thinks of em as buddies but I imagine they were terrified).