Humpback whales make the journey from Alaska to Hawaii every year. Salmon run inward, against the flow, from the ocean to the river to spawn. Geese fly south for the winter in their iconic V formations. The arctic tern migrates roughly the entire circumference of the Earth each year. Many species naturally migrate, and humans have done a lot to interfere with these natural patterns. Skyscrapers and cell towers kill millions of migratory birds each year. Other obstacles like roads, dams, and fences pose risks to transient animals. Then, of course, there are the animals that never used to migrate but now, thanks to humans, are taking over unfamiliar environments.
Here are a few foreign species that have invaded American soil.