Recent population explosion may be explained by introduction of exotic species like Russian boar for sport hunting where there were previously no pig population.
The Russian boars are the exact same species as the domestic hogs we have here. "Russian boars" and "wild boars" (same thing) have been introduced several times into the US by various indiviuals and the problem didn't materialize (as noted previously) until just recently...or did it? Well, the current problem is new, but being overrun with hogs isn't.
There are some other species of hogs that have been brought to the US, but we don't seem to have a problem with bearded pigs or warty pigs.
In OK the hog hunting "ranches" are a big part of the problem. They buy hogs for their clients to hunt in their spot and stalk areas. Those hogs get out and multiply like rats. It is also fashionable for Okies to release domestic hogs in the wild: It's illegal but no one enforces it. Some of the hogs i trap and shoot look like dirty show pigs.
For the last few years, I have read various accountings of hogs being introduced into the wild, the tie to the first Spanish releases, unintentional losses, the apparent and highly celebrated subsequent introduction of known Eurasian stock for hunting, etc. Somehow, the distribution of hogs, population, etc. seems difficult to account for even with their long history in the US and long period of occasional escapees.
A few weeks ago, I was chatting with my father who grew up outside of Cooper, Texas. He was responsible for the raising of pigs and part of his daily chores were to unpen the pigs in the morning and turn them out to the bottoms so that they could free range all day long. In the evening, he would have to round them up again. Over time, they would lose a few hogs, gain a few, and occasionally have to get with neighbors who did the exact same thing and return errant hogs. In short, the program meant that the hogs could be fed on the cheap by letting the hogs find most of their own food, kept the amount of hog refuse in the pen down to what accumulated overnight, and kept an active breeding program that prevented inbreeding. No doubt it also meant that there were free range hogs that simply opted to never go home. Let's face it. Folks have enough problems keeping penned and fenced hogs from escaping and so you know there would be losses, er, escapes from free-ranging hogs. That was back in the 1930s and 1940s.
Go back nearly 100 years. Hogan in "The Republic of Texas" (1946, p. 34, UT Press) talks about this same process where hogs were "raised in the woods in great abundance" with no corn except a little to help keep them gentle. In other words, people basically kept free range hogs using corn to keep them from straying too far, not keeping them fenced or penned at all.
I certainly don't doubt that the free-range raising of hogs has been commonplace throughout the south with a long standing tradition that undoubtedly would have contributed significantly to likely establishing in many areas, maintaining, and certainly expanding feral hog populations. In fact, free-ranging of hogs appears to have been a dominant norm historically across many parts of the US and even back in the 1600s, the problem of free-range hogs going feral and the population exploding was noted (see Virginia below).
Other references...
Free-ranged swine in New York in 1842 (pp. 384-385)
http://books.google.com/books?id=d6...0CEEQ6AEwAg#v=onepage&q=raising swine&f=false
New London Company's importation of hogs in Virginia in 1600 that were allowed to free range had resulted in the colony nearly being overrun by 1627 as they had become wild feeding in the woods (p. 63). Free-ranging was also noted in several other colonies at this time. Page 64 also refers to native hogs of the west, the description being of feral hogs from various earlier settlements.
http://books.google.com/ebooks/reader?id=bwGP2onSFioC&printsec=frontcover&output=reader
In this 1812 report, swine in Louisiana are common and raised without expense by allowing to [free] range in the woods. See pages 168, 185-186, 229-230, 379.
http://books.google.com/ebooks/reader?id=HikVAAAAYAAJ&printsec=frontcover&output=reader
Free-ranging mentioned in this 1888 volume on page 252.
http://books.google.com/ebooks/reader?id=YtBCAAAAYAAJ&printsec=frontcover&output=reader
Free-ranged swine in New York in 1842 (pp. 384-385)
http://books.google.com/books?id=d6...0CEEQ6AEwAg#v=onepage&q=raising swine&f=false
More feral hogs addressed here in 1897, p. 1134.
http://books.google.com/ebooks/reader?id=VxhOAAAAYAAJ&printsec=frontcover&output=reader
1881 notation of free-ranging of hogs in Texas and efforts to keep them from going feral as they turn feral quickly.
http://books.google.com/ebooks/reader?id=HF5JAAAAYAAJ&printsec=frontcover&output=reader
Page 62 of this 1858 Texas Almanac noted hogs subject to running wild in Denton County, but there were losses attributed to bear that were aplenty, and also to wild hog claimants.
http://books.google.com/ebooks/reader?id=mFtNAAAAYAAJ&printsec=frontcover&output=reader
I currently reside in Denton County, Texas and we don't have bears here anymore.
No doubt the Spanish released some hogs that went feral, but by and large, the feral hog population looks like it has been steadily and continually salted (pun intended), populated, and repopulated by the use of free-range ranching methods of domestic hogs from at least as early as the first part of the 1600s to at least the mid 1900s. And now as alsaqr is noting, people are still releasing hogs into the wild. I don't doubt that there are folks who still free range their hogs where they can as well. Free ranging and limited tending of domesticates has been common at least for the past 3500 years (based on early writings).
...i have personally been part of a team that has completely eliminated three pig populations.
I don't think those words mean what you think they mean.
