Wolf

Wolves are Neutral Mobs that were added in Update 0.9.0. The Player can tame them by feeding them Bones.

Wild
Wild Wolves spawn in Taiga Biomes and Roofed Forests. They wander aimlessly, but will sometimes coordinate and kill Sheep, Skeletons, and Rabbits. When doing so, they will gain the appearance of aggressive Wolves.

Aggressive
Wild Wolves may turn hostile towards the Player if they, or nearby Wolves, are attacked. Aggressive Wolves have red eyes and their fur has a rumpled appearance. Their tail is also raised higher than wild Wolves.

Tamed
Tamed Wolves follow the Player around the world, and teleport towards him/her if they are too far. They shake themselves dry after exiting any body of Water, and can be made to sit and stand by pressing the or the  button respectively. Tamed Wolves will chase and kill skeletons without provocation.

Tamed wolves will attempt to attack the Player if he/she shoots himself/herself with a Bow.

Wolves can be healed by tapping and holding them with any type of meat or any type of Fish. Their collars can be dyed by pressing them with any Dye, but by default, the collar is red.

Breeding
Tamed Wolves can be Bred using any type of meat if their Health is fully restored, including Rotten Flesh, which will not poison them. When bred, a tamed puppy spawns.

Wolves cannot be bred until they are tamed.

Combat
Tamed Wolves attack any Mob the Player attacks or attacks the Player, and will attempt to kill it. Wolves can easily kill Skeletons, Zombies and Spiders, but face trouble against Creepers and Endermen, the former due to their explosive power and the latter due to their high health and teleporting as ability.

Trivia

 * In early Update 0.9.0 beta builds, tamed Wolves had a black collar.
 * Tamed wolves can teleport into Glass
 * Wolves were the first tameable mob in the game followed by Ocelots in Update 0.12.1 and Horses in Update 0.15.0.
 * If hostile Wolves are successful in killing the Player, they revert to neutral state.
 * Feeding a Wolf Rotten Flesh makes their tails droop down.
 * Tamed Wolves can enter love mode while sitting.
 * However, they cannot breed until they are made to stand.
 * Version Exclusive: As of Update 0.16.0, Aggressive Wolves will damage the Player in Peaceful Difficulty.
 * Bug: Before Update 0.10.0, Baby Wolves couldn't swim in deep water and would drown.
 * Bug: In Update 0.13.1, Wolves' collars were white by default, and could not by dyed any other color.
 * Bug: Arrows bounce off tamed Wolves, but still do damage to them.
 * Wolves are one of the two mobs that can be Neutral, Passive and Hostile.
 * The other mob being the Polar Bear.