Their intelligence, in combination with their ability to mate year-round, is what has enabled wild pigs to evade capture and take over prairies, mountainvalleys and rugged deserts from Canada to Mexico.
The U.S. Environmental Protection Agency has singled out the greater Salt Lake region as having the nation's worst air for much of January, when an icy fog smothers mountainvalleys for days or weeks at a time and traps lung-busting soot.