|The following is based on Van Buren and is not canon.|
The Devil Dog is sick with something like rabies. It makes him aggressive and intractable. If you cure his sickness before you tame him, it means he wanders away from Blackfoot territory, possibly to be found in a high-Outdoorsman encounter later in the game. If you tame him first, he gets sicker and sicker (and more and more aggressive and stubborn), until he becomes seriously fatigued and then dies shortly after. A good doggie owner will try to cure him before that happens.
Character type completion breakdown
- Science Boy - Can develop the cure, or (if your skill is too low) medicine to stave off the symptoms for a while (repeat doses will be necessary).
- DiploBoy - Can talk someone else into making the cure or medicine.