A tourist and his trail guide were walking along a path when all of a sudden the guide runs up the hillside to a cave, yells "Wooo wooo," listens for a moment, and goes charging into the cave, stripping off his clothes on the run. He returns in about 15 minutes. The same scenario occurs again, after which the tourist asks about this strange behavior. The guide explains that if one of the young ladies of his town is in an amorous mood, she goes into a dark cave. If she hears "Wooo wooo," she responds "Wooo wooo" to signal that she is ready and willing. No one knows who is who and everyone is happy.
The tourist is amazed and asks if he might partake in this local custom at the next cave. The guide doesn’t see any problem with this. At the next cave the tourist runs to the entrance and calls out "Wooo wooo." To his delight, he hears a sonorous and enticing "Wooo wooo" sung back to him from the recesses of the cave. He takes off his clothes, rushes headlong into the cave, and gets run over by a train.