Their numbers are low--only 53 species of amphibians and reptiles are known to have been introduced to the U.S. All live in areas where it rarely freezes. Florida hosts 30 species; Hawaii 12. But the impact of a few have been devastating.

Image: HEAR Project

BROWN TREE SNAKE (Boiga irregularis) may be responsible for the most serious ecological disaster of the 20th century. It hitch-hiked into snake-free Guam on military equipment immediately after World War II and its population exploded at the expense of the native native bird, mammal and lizard populations. Only three species out of 13 native forest birds still exist; just three species of lizards--out of an original 12--retain the possibility of surviving. This snake crawls up trees and utility poles and has caused 1,500 power outages on the island. In addition, bites from the snake, which is mildly venomous, often require medical attention. It has since invaded Hawaii. The state's concern about the snake has prompted the federal government to invest $1.6 million per year in control efforts.
Data: Excerpted from Environmental and Economic Costs Associated with Non-indigenous Species in the United States

Back to Costly Interlopers