Echo Location

A vampire bat came flapping in from the night covered in fresh blood and parked himself on the cave's roof to get some sleep. Soon all the other bats smelled the blood and began hassling him about where he got it. He told them to shut up and let him get some sleep, but they persisted until he finally gave in.

"OK, follow me."

Down through a valley they flew, across a river and into a forest of trees. Finally he slowed down and all the other bats excitedly milled around him, licking their lips.

"Do you see that tree over there?"

"YES, YES, YES!!" the bats all screamed in a frenzy.

"Well...I didn't!"