I never really thought about it till now. We know where the bears came from. I would assume they were imported with rabbits and chickens (the one Goodwin killed in season 2 with the Tailies). Although the rabbits were imported likely for testing, this the numbers.
It would be a smart animal to import... Breed like roaches, plenty of foliage, etc to eat. They'd have been an excellent meat source for essentially no cost. I don't recall seeing the boars in the 70"s episodes

