What kind of heat is used on his enclosure? Those could also be burns if heat is from above, also low humidity. Poor snake...and live rodents left alone with a snake should NEVER happen.A rodent gets hungry and WILL chew on a snake; a snake that's not hungry generally doesn't not fight back...in the wild they
just move on (& they follow their instincts), but in a cage they obviously cannot do that...they just get injured or killed.