Today is Bat Appreciation Day and if you think we need to wait till October to be talking about bats get off my website. Anyway bats are mice evolved to have superpowers that would be extraordinarily powerful if it wasn't still mouse sized. They have two main tricks. The first is that they can fly with weird wing arms, not gliding like squirrels or sugar gliders but flying like birds do. The second is echolocation which is self explanatory, they use echoes to location.
All of this might be painfully obvious If you are old enough to be on this website (it's 14+ here if you skipped the FAQ) but sometimes it's worth restarting the obvious, just for calibration. That being said, the biggest type of bats are known as flying foxes and those guys are pretty big. The actual vampire bats that eat blood are actually really tiny, like golf ball sized.
This reminded me to go read the faq