In the 1990s, Lee County residents rejected calls to cull Gasparilla Island's growing population of non-native black spiny-tailed iguanas, which they saw as harmless and even a tourist attraction. Ten thousand iguanas later, their novelty seems to have worn off.

With the support of locals, the Lee County Commission recently voted to allow residents to trap or humanely kill the iguanas, which are popping up in toilets, falling through ceilings and hitching rides to other parts of the county. Even worse, the thousands of iguanas are endangering the stability of the island's dune system by burrowing deeply into the sand and threatening the gopher turtles, who unwittingly share their tunnels.

"The dunes at the southern end in the state park are riddled with the burrows to the extent that if we were to have a storm surge that hit the dunes, the dunes would collapse. It could cause real devastation," says Jerome Jackson, a professor of biology at Florida Gulf Coast University.

Scientists surmise the species was introduced to the Gulf Coast barrier island in the late 1970s, when a local boat captain returned from Mexico with several reptiles that he intended to raise as pets. He released them years later near the Rear Range Light House in Boca Grande. Today, the prolific lizards have migrated to Placida, Cape Haze, Gulf Cove, Cayo Costa, Keewaydin Island and Little Marco Island. Biologists worry that if the iguanas make it to Cape Coral, they will decimate the population of protected burrowing owls.

Meanwhile, the county is keeping close watch on another non-native lizard. Cape Coral has become home to a population of Nile monitors, aggressive African lizards that can grow nearly 8 feet long. "We don't really have a good handle on how many there are," says Jackson.