Invasive species often thrive in new environments and overrun native species because they have an unfair advantage. “Invasive species end up with about half the parasites, or diseases, they had at home,” says U.S. Geological Survey ecologist Kevin Lafferty. “Parasites are to invasive species what kryptonite is to Superman. Back on planet Krypton, kryptonite was a regulator, keeping Superman ordinary. Freed from kryptonite on earth, he gained super powers.”
Animals that have an average of 16 parasites on their home turf only bring about three of them to their new location. And only about four new parasites will adapt to attack the invading species. That makes 7 parasites?less than half of what they had at home.