Was able to get him to the vet a month or so ago. It was a tumor. The vet told me that many rats can't handle the anesthesia to get it removed. So, decided to let the quality of life determine his fate. However, the damn tumor would not stop growing! My strong little guy finally gave up yesterday morning. It was a horrible thing to watch, helpless. Cuddled him til he seized to his fate...now, after some reading and research, I found out, not to wait to get his cagemate a new buddy. Anyone know the best way to introduce the new ratty? What size/age should he be???