Wolf

Wolves are new mobs introduced in Beta 1.4. Notch had confirmed the addition of these animals upon having breakfast with Peter Molyneux. On March 18th, 2011, a video was posted showing a preview of wolves, which were being made by Jeb. Another video was posted by a player after the 1.4 update was released, demonstrating the features of the new addition. Wolves will spawn in forest and taiga biomes. Wolves may also be considered the "pet dogs" as previously mentioned by Notch. Wild wolves are usually neutral. As of now, they are not known to drop anything, nor is it known how much health they have. At the moment you can also have as many wolves as you want until Mojang comes up with a way to limit the amount you can have tamed.

Taming
They are said to be rather rare, but they will not despawn once tamed. To tame a wolf, you have to give it bones until a puff of heart particles appears and it gains a red collar, which indicates that the wolf has been tamed. The number of bones required is random. You can tame more than one wolf.

Wolves do spawn in "Peaceful" Mode, however, tamed wolves are not removed from the game when the difficulty is changed to "Peaceful". Furthermore, wolves will attack the player if attacked first, even on Peaceful.

Once given enough bones, they will become friendly. They will now protect you, follow you around, and will attack mobs that you have attacked in melee. Tamed wolves will not attack mobs that you hit with arrows, nor will they attack creepers. Wolves will also not attack mobs if they are sitting. In their current developmental state, mobs will not attack your wolves (Subject to change). A wolf's tail will rise and lower depending on its health, and it can be restored with raw pork (and possibly other foods). They will be unable to climb ladders, but will teleport to you if you create a large distance between yourself and them as long as they are not sitting.

Trivia

 * When you hit an untamed wolf, its eyes turn red and will attack player with its pack
 * Wolves are the first tamable mob in Minecraft.
 * Tamed wolves have a small red band around their neck, resembling a collar. They also have a friendlier facial expression.
 * Wolves turn their head to the side and beg if the player is holding a raw pork or a bone. This may happen with other kinds of food.
 * When you right-click on them they will sit and stay put. If sitting they will not attack any mobs that you have attacked in melee.
 * Wolves can swim, and will shake water droplets off of their bodies when exiting water.
 * Jeb has said that wolves may have color variations, but he "would have to run that through notch".
 * When a wolf is tamed, their eyes will change from 1 white pixel and one black pixel to 2 white pixels and 1 black pixel. This change is meant to highlight a wolf's aggression when untamed.
 * Wolves were released in Beta 1.4, on March 31st, 2011.
 * Wolves will NOT attack you once tamed, making them somewhat passive.
 * Wolves hunt in packs.
 * When untamed, Wolves will wander aimlessly and sometimes attack animals mainly sheep.
 * Wolves, along with spiders(Starting in 1.4), will not trample crops. They will also not make step sounds, or make quieter ones than default.
 * Wolves will not travel through inactive portals on server, but can be pushed through them.
 * Wolves will teleport to you if they get too far behind if not right clicked.
 * Wolves will not attack what you attack if they are already attacking something.
 * Wolves can't dive.
 * Wolves will attack any mob except Creepers when the player hits the mob with their hand.
 * If another player on your PC enters your world, the tamed wolfs wont listen to them. Offline to online accounts also count.
 * If a wolf is put behind a wall and a mob is punched on the other side, the wolf will attempt to walk though the wall to the mob.