User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-3062343-20111219023622/@comment-76.69.7.125-20111219205349

Alternate theory: environment issues. If an animal can't survive in one place, it will go somewhere else. It's why birds migrate, it's why polar bears are going south, etcetera. They don't just stay in place.

In fact, sometimes a bug or other animal can accidentally be transported into a new ecosystem and completely destroy it.