Raids with Drakes won't happen anymore after you killed a specific boss (might be Moder).
Bats can't get in closed buildings. -> Put your boars in an enclosed pen and you're golden (or closer to it).

I had the fortune of populating the surroundings of my base with wolfs (they multiply on their own now) before bats even existed but I did loose a bunch of boars to Drakes even after building a roof over the pen.
The Drakes shot out a fence and the boars ran into the slaughter :-/