They have been in southern New Mexico since the homesteading days. There are still folks who trap feral hogs and ear-mark them and then turn them loose to forage for themselves until fall mast crops fatten them up. However, in my experience, they are not common anywhere on public land. Most of the live water and riparian habitat in New Mexico is private--except for the high mountain ranges, most public land is arid and poorly watered, compared to the private land.
I managed a large ranch in southern New Mexico that had abundant feral hogs, especially during the years when our El Nino winters boosted our annual rainfall totals. I used to get requests for access from as far away as southern Colorado and the urban areas of Phoenix and especially Tucson.
Initially, I looked on it as a good way to thin their numbers a bit, but it turned out that most of the "hunters" wanted to drive their jeeps and ATVs around the ranch for a few days, and maybe shoot a hog on their way out. I would direct folks to areas where the hogs were causing problems with their rooting, but the only hogs that would get taken were pretty much shot from a vehicle or an ATV in chance encounters.
I ended up limiting the hog hunting to a few ranch families in the area that would take a few hogs to supplement beef and venison in their larders. Even though I have been gone from the ranch for over two years, I still get calls and e-mails from folks who want to hunt hogs...
