then they make a little divot with their front teeth, and they put their jaw up against that hole and they lick and drink and pee. it is completely creepy. who else does that? >> i'll tell you who else. a serial killer does that. however, vampire bats don't kill their victims. they just act like a mammal sized parasite. i've heard you say that the weirdness of bats was scientifically interesting to you. >> the faces of bats is a perfect example of that. if you take a bat that has a weird flap on its nose, you think that's a strange looking adornment, it turns out a lot of bats have food in their mouth when they're trying to echo locate and it is hard to shout when you have food in your mouth so they hum. that weird flap actually points echo location sound where they want it to go. >> most bats navigate and hunt for food in the dark using echo location in which they emit sound from their nose and mouth and then listen for the echo