Originally posted by Gladi8er65:

In the Boars' "wild state", they are afraid of fire, but once they are tamed, your torches, fires, etc won't scare them anymore, and all the new piglets are born tamed so once you have the original adults tamed, you can definitely add lights back in, and not cause issues.

This.

Only wild boars are scared of fire. They will be fine with campfires & torches once tamed.

Another thing, keep an ear out for high pitched squealing all of a sudden, if the piggys (the baby boars) are running around like crazy, there is another mob around somewhere, and they are usually the first to detect them as they get close.