Echolocation. The bat can't use its blindsight while deafened.
Keen Hearing. The bat has advantage on Wisdom (Perception) checks that rely on hearing.
Bite. Melee Weapon Attack: +0 to hit, reach 5 ft., one creature. Hit: 1 piercing damage.
How does a bat get a 5ft reach with it's bite?
dart in, bite, dart back to normal range
A "5ft reach" means the square next to you. It is the minimum range on melee attacks.