My oldest rat is obsessed with digging and tearing things apart. I've got a digging box in his cage with treats hidden in it, but he much prefers to scratch and dig at the side of his cage. Is there any way to stop this? Any toys that might help. I thought the digging box might get him to stop but nope. He had a cat scratching post which he loved, but then I caught him with a big ole hunk of yarn in his mouth and got scared he would choke and took it away from him. Any ideas?