Cross bred baby mice

Question
I recently adopted an adult female mouse (approximately 9 months old) and was told she had not been in contact with other mice, but had shared a cage for a short time with a (supposedly female) hamster.  She just gave birth to 6 younglings between yesterday morning and this afternoon.  She seems to be caring for the young very well, and there don't appear to be any complications.  I have given her extra water and lab pellets.  When we discovered the babies (quite suprising, that!) we immediately left them alone, without handling them, and the mother went back to nursing them about 5 minutes later.  We did notice that the babies had extremely short tails, and were wondering if mice's tails grew a considerable amount in the first two weeks of life, or if it was possible that the hamster our mouse had been housed with was actually a male.

Answer
Hi!

Cross-breeding hamsters and mice is absolutely not biologically possible, so you were either lied to (fortunately, as one should never, ever let mice in close contact with other species and I must say I got a bit shocked after reading this one!), or the person didn't know any better. The babies' tails will be growing quite a bit from the 'pinky-phase' to adulthood. Alot of useful information regarding mouse breeding can be found at the Finnish Show and Fancy Mice Club's site at: http://hiiret.fi/eng/breeding/index.html

Best of luck!