The presence of exotic, voracious Nile Monitor Lizards has been confirmed on Sanibel Island. The omnivorous reptiles can grow up to seven feet long. They have a high reproductive rate, and in South Florida no predators to keep them in check. Biologists say they’re a major threat to small mammals and birds, and that this poses a major problem on Sanibel Island, which is home to Ding Darling National Wildlife Refuge – known around the world as a major birding hot spot. Rob Jess is the refuge manger.