"Super pigs" — called the "most invasive animal on the planet" — threaten to invade northern U.S.

An exploding population of hard-to-eradicate "super pigs" in Canada is threatening to spill south of the border, and northern states like Minnesota, North Dakota and Montana are taking steps to stop the invasion.

In Canada, the wild pigs roaming Alberta, Saskatchewan and Manitoba pose a new threat. They are often crossbreeds that combine the survival skills of wild Eurasian boars with the size and high fertility of domestic swine to create a "super pig" that's spreading out of control.

Ryan Brook, a professor at the University of Saskatchewan and one of Canada's leading authorities on the problem, calls feral swine, "the most invasive animal on the planet" and "an ecological train wreck."