Here is some information about the Tiny Chihuahuas Temperment and why some seem to have a bark or bite that is so fierce. Most Chi owners come to realize this is a Tiny breed with attitude to spare!.. When you understand a little about his heritage you'll start to understand why he's so fierce:
.
This small breed was originally bred by the Toltec Indians as Hunting companions, Guard Dogs and Family Pets. When the Spaniards raided against the Toltec, they brought several of these little dogs back home with them as they admired their braveness against their foe. They then bred them down in size to become Lap-Protection-Guard Dogs to the Ladies of the Court. They were bred so when anyone tried to reach for the Lady the little dog was to grown as a warning or to bite. In order for them to have this trait, they had to be bred to be hand shy.  As a result we still have some Chihuahuas of our present day who still carry this protective and handshy trait... A protective Chihuahua will lay down his life to protect his loved ones! ( hence most DO NOT make a good childs Pet.)