The uninvited visitor to her Key Largo yard showed little concern over being discovered, said Lauren Norman.
"He was only a couple feet away and he just looked at me," Norman recounted.
The trespasser -- a carnivorous reptile called a tegu lizard -- joins the list of unwelcome invasive species confirmed to be at large in the Florida Keys.
Tegus have become a concern not only in South Florida but in the Tampa area, with sightings as far north as the Panhandle.
One species of the lizard, native to South America, carries the ominous name of giant Argentine tegu.
A popular pet among reptile fanciers, biologists suspect the black-and-white tegu seen on Key Largo's Ocean Shores Drive, off mile marker 99, may have escaped from a local collector.
Tegu colonies have been established in southern Miami-Dade County and portions of the Everglades, but last Thursday's encounter with the reptile may be the first in the Florida Keys.
"I had no idea what kind of lizard it was," Norman said. "It looked like a really dark, really large iguana."
Norman went upstairs to get a camera and returned to find the 2-foot creature "still sitting there," she said. As she approached for a photo, the tegu wandered away but left "moving very slowly."
Norman called her husband, a Florida Fish and Wildlife Conservation Commission officer, for advice. "He said don't let the puppy go outside."
Tegus, unlike the vegetarian iguana, will dine on small animals in addition to plants. They also will eat unattended pet food left outside.
"They eat anything from insects to rodents and eggs, so they are a threat to our native species," FWC spokeswoman Carli Segelson said. "They don't belong here. Our native wildlife is not equipped to deal with them."
Matt Palazzolo of Key Largo stopped his car when he spotted the "nasty looking" tegu on Ocean Shores Drive.
When Palazzolo went for a photo, the reptile "kind of raised up a little bit." "It bummed me out," Palazzolo said. "I love the Keys and I hate to see this stuff crawling in here. I hope they catch it."
Tegus are active during the daylight hours. As weather cools in late October, they often dig themselves underground for a three-month period of dormancy, called a "brumation."
Tegus can endure winter temperatures far colder than usually seen in the Keys.
Wildlife experts caution against trying to grab a tegu.
"While a tegu is not likely to be innately aggressive, it will defend itself if aggravated or threatened," says a state report. "Tegus have sharp teeth, strong jaws, and sharp claws which they will use to defend themselves."
Tegus are easier to catch in traps than invasive pythons, Segelson noted.
Sightings can be reported over the phone to the FWC exotic-species hotline, (888) 483-4681, or online at www.IveGot1.org.