Puzzle: The Two Tribes

An island is inhabited by two tribes. Members of one tribe always tell the truth, members of the other tribes always lie.

A missionary met two of the natives, one tall and the other short. "Are you a truth teller?" he asked the taller one.

"Ba" the tall native answered. The missionary recognised this as a native word meaning either yes or no, but he could not recall which. The short native spoke English, so the missionary asked him what his companion had said.

"He say 'yes' " replied the short native, "but him big liar!". Which tribe did each native belong to?

Give your answer here.