A wolf can become a dog if the player gives it enough bones. When they become a dog, their colors will change to brown, they obtain a collar, and heart particles spawn around it. If the dog is given Bone Meal, the dog's collar will switch color from red to white.
If you attack or hit a mob and a dog is not in sitting position, the dog will attack the mob until it dies, or its target changes in the middle of the fight. Shift-clicking on them will make them sit. In this sitting position, they cannot move or attack a mob, but if a mob goes near them, they will take damage.
The dog's health can be measured by the height of it's tail. If the tail is pointing downward, it's health is low. Beware! You can actually damage your own dogs and kill them, getting exp.
You may feed them food, such as pork and chicken to regain their health, but you can't breed them.
If a dog gets trapped somewhere and you walk off screen, it will transport back to you in a few seconds.
Sometimes they get stuck in walls. Then they start climbing them!!!