We can't be sure, but we think he died of shock. I had him out in the evening--he and Chester were helping me make Baby Girl's birthday banner. I put him back in the cage so we could go to dinner, then I went in when we came back to give them French fries. He was lying on the cage floor and the tip of his tail was gone. I bandaged it, wrapped him up, and put him on a heating pad. I tried to give him some warm honey water, but he wouldn't take it. He died about ten minutes later.
Yaya is devastated, of course. He's afraid to touch the other rats now, I think. I don't blame him. The other day, he came to me crying because Rude Pete was squeaking and he was afraid he was going to die, too. I did my best to reassure him, and I can only hope that he takes it to heart.
Goodbye, Blue. You were a good rat. We miss you.