Have you considered offering him a mouse instead and see if his response is different? I know you said you successfully converted him to rats, but maybe he's wanting a mouse again?
Sounds like a good idea to me. Seems like it would be worth a try to see what the response is.
1.0 Chihuahua (Elton)
1.1.0 Russian Tortoises (Forest and Royal)
0.0.1 Three-Toed box Turtle (Chip)
0.0.1 Normal Ball Python (Maverick)