Their skin appears deceptively tough, but in reality it is so delicate that an elephant can feel the pain of an insect bite. A bullhook can easily inflict pain and injury on an elephant's sensitive skin.
Trainers use the hook on soft tissue behind the ears, inside the ear or mouth, in and around the anus, and in tender spots under the chin and around the feet.
During performances, trainers with bullhooks often stand on the side as a constant reminder to the elephants of what will happen if they get out of line.
So how do you get an elephant from "wild" to "circus-ready"?