In 2006, the US spent 1.2 billion dollars fighting invasive species. That figure does not include the costs of the animals themselves, which cause property damage, crowd out and eat endangered animals, root up crops, attack people, and just generally make things difficult.
These species are diverse, from all different continents, but they have one thing in common: people put them here. Whether unintentionally on shipments from Asia or Africa, or former pets released into the wild, these animals (and one plant) have turned America into their predator-free playground.
We've gathered up only nine invasive species in this slideshow, but there are literally hundreds more pest, plant, and animal immigrants out there.