Tourists in Africa

Two tourists, strangers, were traveling in a tour bus in Africa.

One of them kept clicking his fingers continually, which got on his fellow traveler's nerves. After about an hour he said "Do you have to do that?"

The other replied, "Yes, I must. It keeps the tigers away."

"But there aren't any tigers here" said the first.

"See," said the other, "It works!"