Heard this joke on QI...Forget that bats have that echolocation thing.

 Two Vampire bats are hanging about in a cave and they're hungry - haven't had any blood in a good long time.

One bat says to the other, "fuck this, I'm going out there and I'll let you know if I find anything worth eating".

So the first bat biffs off for a bit and then returns with his face absolutely covered in blood.

The second bat goes, "Christ, what happened? Find anything good??"

The first one hangs upside down and points out the mouth of the cave, "You see that village out there?"

The second bat eagerly replies, "Yeah"

Bat one goes, "You see that steeple out there in the distance?"

The second one gets all excited, "yeah, yeah!!..."

"Right", the first bat says, "well I fucking didn't".