What makes them so dangerous is not exactly their attacks, which do only moderate damage, but when they're killed they explode and deal a considerable amount of damage, as well as knock down any unfortunate blokes in the range of their explosion. This is similar to the effect of a Powder Keg Runner, fortunately not as long range - but they should still be dealt with cautiously because the amount of damage their death blast causes depends on the level of the pirate attacking the aforementioned bat, and can knock out somewhat inexperienced Pirates almost immediately with ferocious bites.
No one is sure why they explode or whether they may actually be completely supernatural creatures.
Fire Bats ARE known to give Cursed Blades on very rare occasions.
They can be found on: