Bats

Two vampire bats are hanging in their cave. One turns to the other and says, "Oh, I'm really thirsty for some fresh blood."

The other bat is amazed and says, "Well, it's a bit late. Daylight is almost here, and we can't be exposed to any light - you know we'll die."

"Yeah, I know," says the first bat, "but I'm really starving for it."

So he flies out of the cave and returns five minutes later with blood dripping from his mouth.

"You lucky thing. Where'd you find blood that quick?" asked the second bat.

"You see that tree over there in the distance?" mumbled the bat, his mouth full of blood.

"Yeah, I think I do!"

"Well, I didn't."