To start off I have 4 rats currently............the first one I got is about 2 1/2 - 3 months old, and the rest are younger yet. My oldest one is a jumper! We constructed a playpen sort of thing out of cardboard so that we could put it on the floor, and the girls could run around without us having to worry about them getting away, except my precious little saphire jumps! She will come crawl on you, pretending to be sweet when really she is attempting to get close enough to the wall to jump. It is over a foot high and she even manages to jump up and over from the floor. We have tried telling her a stern "no!" every time she does it, and tap her on the nose, but you put her back on the floor and immediately she does it agian. Now the other ones are trying it too, and my next oldest Jade is able to jump up and out. Help me train my little bratty rats! :?