Here we have less of a problem, true Wild Boar only breed once year, while the escaped domestic hogs and the Wild Boar domestic hybrids in the U.S. can throw a litter multiple times a year.

But we have a problem here also, part of the problem here is they are planting a lot of Corn, Corn seems to accelerate growth and make them sexually mature quicker.

And thirdly is over regulation, some by well meaning types who just can't resist drafting new laws and regulations (just to justify their own existence). And others who are anti hunting and think they are doing wildlife a favor by lobbying for ever stricter, hunting, Hunter and license laws. It is possible to regulate something to death or make it so difficult or complicated people just give up and go do something else.

One county/state here outlawed any hunting, you hear stories every day about Boar mugging little old ladies for their groceries on the way home from the store. In another state they are talking about active duty soldiers hunting them down. Might be fun for the soldiers, likely to be really dangerous for hikers and mushroom hunters. I have a mental image of the woods echoing with the sound of full auto fire.

https://media.giphy.com/media/v8omVdExrQ9ig/giphy.gif