I got a guinea pig!

Question
Hi.  I just recieved a two year-old albino guinea pig from a friend who's moving.  She's a little intimidated by the new home, but she's getting adjusted.  Well, I'll be holding her and petting her and then all of a sudden she'll pee or poop on my hand.  Is there any way to know when a guinea pig is going to go to the bathroom, and is there anything that I can do?

Thanks for your help. :)

Answer
The only way to know and it isn't a very good way of knowing is that they will raise up their back feet a bit.  However, it will happen so fast it is hard to catch.  There is really nothing you can do about it.  The best thing you can do is to have a towel under her when you hold her.  Best of luck to you with your new friend.