Invasive lizards, reportedly as large as dogs, are spreading in the southern United States, with sightings in Georgia, South Florida, and South Carolina. The lizards, described as carnivorous and posing a potential threat, are said to be up to 4 or 6 feet in length. The extent of the threat and the lizards' exact origin and behavior are not entirely clear, but officials are warning of their presence and seeking help to control their population.