FILE - In this Feb. 18, 2009 file photo, feral pigs roam near a Mertzon, Texas ranch. Minnesota, North Dakota and Montana and other northern states are making preparations to stop a threatened invasion from Canada. Wild pigs already cause around $2.5 billion in damage to U.S. crops every year, mostly in southern states like Texas. But the exploding population of feral swine on the prairies of western Canada is threatening spill south. (AP Photo/Eric Gay, File) FEB 18 2009 FILE PHOTO
