Sudden baby mice in all female cage

Question
When starting to clean out my daughters mouse cage 2 weeks ago we noticed babies in there. We researched what to do and left her alone for another 5 days and then started to handle the babies.We took the mice to the vets this week only to be told all 3 of our adult mice are female which is what we thought we had, my daughter has had the mum mouse for over a year. the only thing we can think is that a wild mouse of some kind managed to get into the cage, is this possible and will the babies be ok for my daughter to keep. there are 7 of them and they are all dark brown with black/dark eyes, mum is a black and white fancy mice with dark eyes.

Answer
Dear Georgie,

This is a common issue. In fact, it has even happened to me!  

First generation hybrid mice are notably pretty wild. But yours can be the test case if you can handle them at least once (twice is better)  a day. When it happened to me, I was bottle feeding a kitten and didn't have the time to really handle them. I had ten babies, and one turned out to be extremely sweet and tame.

My recommendation is to put in the time and love to tame them, and see what happens. All baby mice get a little crazy a day or so after they open their eyes, so expect that. However, if you are lucky they will calm down some. Then you just need to decide whether they want to be pets. You should be able to figure this out by six weeks.

I gave all of mine away but two. When they were about five weeks old they made up their minds. One of them started to bite. The other climbed into my hand on her own and was a wonderful little pet. It was a beautiful, warm Spring day, and I was in the country, so I let the first one go. Although her life would be much shorter out there, she would be happier. I was amazed at how tame the second one became almost overnight, suddenly deciding to climb into my hand. Of course I kept her as a pet. Contacting the people who took the others, one person had them in cages but was not handling them; and the other had lost them in her room and they were nesting under her bed in a suitcase, a true recipe for disaster!

In order to avoid having second generation hybrids, separate the babies two weeks after they open their eyes. Of course, it would be very interesting to know about second generation hybrids, if you do leave them together! I have only heard this about first generation, which makes me wonder.

The way to handle a jumpy mouse is this: use your thumb and forefinger of your left hand (assuming you are right handed) to hold the very base of the mouse's tail, by its rump, gently but firmly. Sit the mouse on the palm of your right hand and close your fingers over it. Although you can let your fingers "give" a little where the mouse is poking its nose, don't open your fingers until it is calm. Then open them cautiously. Talk to the mouse and give her kisses. Anytime she gets crazy, close your hand over her again. Don't let go of that tail unless you are absolutely sure that the mouse is calm. It is best to do this in an uncluttered bathroom, after stuffing all escape holes with newspaper and putting a towel against the door crack on the floor. You may even want to sit in the tub, though don't think the mice won't be able to jump! Baby mice around 16 days old have extremely strong legs and weigh basically nothing. Even fancy mice, who are descended from house mice, can jump two feet straight up into the air (this is called the "flea stage" or "popcorn phase"); maybe wild ones can jump even higher.

So you should be able to tell by 6 weeks whether they want to be pets. A mouse that bites, spends its time trying to get out of the cage, and/or simply can't be held, wants to be let go.

I would really appreciate you letting me know what happens. As I said, you would be the test case.  I know that I didn't socialize mine well enough, and although it is known that these hybrids are a little crazy, I don't know how much attention they were given in other cases. Someone used to fancy mice might not know that these guys are going to need more time. So do let me know, so I know what to tell the next case!

And certainly tell me if you decide to have second generation hybrids!

Best of luck!

Squeaks n giggles,

Natasha