They root, wallow and eat everything from seeds to snakes and lambs.
They're wild pigs, and the only thing keeping Arizona from being overrun by them are our vast stretches of bone-dry desert.
Two spots in Southern Arizona are known to have populations of wild pigs - not javelinas but domestic swine that have escaped or been released and taken to living in the wild.
One of the places is northeast of Tucson in the San Pedro River valley near Redington, said David Bergman of the U.S. Department of Agriculture's wildlife services division in Phoenix. The other Southern Arizona spot is near Bowie and Willcox in northern Cochise County. In the past, there also was a population of wild pigs in and around the Buenos Aires National Wildlife Refuge southwest of Tucson.
Rancher Jim Dykes who lives in the San Pedro Valley said he's had run-ins with "big, black, Russian boar-looking things" in his yard as recently as three weeks ago.
But his biggest conflicts with the hogs came in the fall of 2008. An irrigation pipe was repeatedly broken during the night, and the animals left huge tracks, he said. So Dykes set up a motion-sensing camera and quickly captured pictures of mobs of pigs marauding in his yard.
Eventually, Dykes shot one of the pigs, and when he tracked it behind a workshop, another 15 or 20 were there looking at him.
While the San Pedro area's population appears relatively small, it is an example of a growing problem around the country and the world, said Jack Mayer, a Georgia zoologist who co-authored the book "Wild Pigs in the United States." Wild pigs live in pretty much every state, Mayer said, and have even populated four Canadian provinces. They're also a big problem in Australia.
The worst infestation is in Texas, where wild pigs have seriously damaged the land and agriculture in some areas, Mayer said. Estimates put the U.S. wild-pig population at 2 million to 6 million, and about half of those are in Texas.
The pigs are admirable for their adaptability, but they can upset an ecosystem.
"They eat pretty much anything they can get their mouth around that's got a calorie in it," Mayer said.
While pigs are known for digging for roots, they'll also chase down baby animals such as whitetail fawns, calves, goat kids, and also hunt birds such as wild turkeys.
They can easily harm watercourses and other lands they frequent.
"When pigs get into areas with water, they act like pigs," Mayer said. "They wallow around in it and poop in it and really impact water quality."
San Manuel hunting guide Duwane Adams said he's seen wild pigs three times at the San Pedro. Some hunters actively pursue the wild swine - no hunting license is necessary and there is no bag limit - but Adams has never wanted to, he said.
His reason: "They're a lot of work - they're gigantic."
"Most of them are 200, and some of them are up to 400 pounds. They're big, big, big pigs," Adams said.
Not only that, they live in thick, tangled vegetation by the river where the only way in for humans is on hands and knees, he said.
Flagstaff hunting guide Lance Crowther led a family bowhunting trip to Southern Arizona in January and ran into wild pigs while hunting javelina, he said. The group ended up taking 13 javelina and two wild hogs.
Where did they find them? Crowther's not saying. But he added, "If we knew where we could find some all the time, we'd probably book hunts for them."
Other places in Arizona that have wild-pig populations are the Virgin River in the far northwest corner of the state; Dugas, near Cordes Junction in central Arizona; and the Havasu National Wildlife Refuge on the Colorado River on Arizona's western border.
As Dykes and Adams understand it, the San Pedro hogs were introduced to a ranch in the San Pedro Valley at least 20 years ago. They scattered from the ranch and, despite an effort to kill off the population, bred faster than hunters could bag them.
That's a typical scenario, Mayer said. More than a thousand fenced shooting preserves offer wild boar hunts. And whether a person buys pigs for hunting or for traditional livestock-rearing, they are difficult to fence in.
"You can go buy trailer loads of these things, bring them to where you want them, turn them loose. The pigs do the rest," Mayer said.
Fortunately for Arizona, they don't have a lot of room in this state to do the rest.
While pigs are extremely adaptable, they need to be near surface water, of which there is precious little, Bergman said. If pig populations expand around the state's few riparian areas, he said, they could cause significant damage to land and water and to endangered species that may live there.
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The Arizona Game and Fish Department, which regulates hunting in Arizona, doesn't oversee wild pigs, spokesman Bob Miles said via e-mail. There is no statewide season, bag limit or licensing requirement for hunting wild pigs. However, individual landowners - public or private - may have regulations or laws governing hunting wild pigs on their land. And be aware - wild pigs are similar in appearance to javelina, which cannot be hunted without a proper license.
Contact reporter Tim Steller at 807-8427 or at firstname.lastname@example.org