Puerto Rico, Isla del Encanto, Iguana Invasion. Invasive Species, estimate by US Fish and Wildlfe biologists, 6-8 Million. Average weight of an adult Iguana, 7-13 pounds. Hunted relentlessly with air rifles only. Conventional firearms are illegal to use. Shooting range: 25-50 yards. Devestating agricultural losses due to voracious appetites of the Iguanas. What a bloody ecological, agricultural/ environmental mess.