for National Geographic News
Homestead Air Reserve Base near Miami, Florida, is dealing with a different sort of small ground invasion: the Nile monitor lizard.
These invasive reptiles—possibly former family pets or escapees from nearby breeding facilities—occasionally lumber onto the base's tarmac to soak up the sun's rays.
"When you have an airplane coming in to land or take off, and you have a 6-foot [1.8-meter] reptile laying on the runway, it causes a substantial human health and safety problem," said Parker Hall, a wildlife biologist with the U.S. Department of Agriculture's Wildlife Services.
Agency employees patrol the runways on a regular basis to shoo away birds, capture lizards, and deal with any other pests that may show up.
But that's a tall order given the base's close proximity to both the Everglades and Biscayne National Parks, both home to diverse arrays of wildlife that regularly spill into the base's vast woodlands and wetlands.
Invasive lizards in southern Florida—such as the monitor, native to Africa—now outnumber native species, experts say.
These hefty predators—weighing up to 30 pounds (13.6 kilograms)—have a voracious appetite, and have been observed eating protected species such as the burrowing owl.
In nearly two decades monitor lizards have been spotted in seven Floridian counties, with the biggest breeding population living in Cape Coral, a city on the state's west coast.
(Related: "Alien Iguanas Overrun Florida Island.")
The animals began showing up near the air reserve base last year, said Scott Hardin, exotic species coordinator for Florida's Fish and Wildlife Conservation Commission.
The population isn't as big as the one in Cape Coral, he said, but the lizards are more than likely reproducing.
"I'm not sure we can go as far as saying they've established [a permanent population]," he said, "and we don't have any idea of what kind of impact they've had, if any."
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