Believe it or not, Catalina Island out here in so. california had a very large free roaming bison heard. How you ask? They were brought over for a movie shoot in the 1920's and never rounded up. I dont know how many there are now but 30 years ago there were several hundred.
They also had the wild boars from the movie still roaming the north side of Catalina island as well. I ran into one when I was camping on the north side of the island in the 80's.
If he's still alive they should go get the renegade bull that lived above the quary and made a practice of challanging vehicles and pushing them over the cliff into the ocean. Last time I saw him was over 30 years ago.