I recently lost one of my two rats (managed to find a hole in a bathroom cupboard and released herself into the wild). I now need to find a new cage mate for my remaining female. Do I put in the new one in a seperate cage right next to hers and leave it that way for a few days? Do I let them sniff noses without bars (me holding her)? Either way I'm not just dumping one in there. I haven't had to deal with this before, since usually one dies and the next follows soon after (usually both are the same age). The remaining on, Jupiter, is under a year old.