SAVANNAH, Ga. (AP) – The small frogs that croaked in Diane Butler’s backyard pond had been silenced and her goldfish were disappearing. But she had bagged the culprit, and stashed the body in her freezer.

Butler’s capture of a 4½-inch Cuban tree frog in coastal Savannah has caused a nervous stir among wildlife biologists in Georgia and Florida.

The exotic amphibian invaded the Florida Keys nearly 80 years ago and slowly spread throughout the state, devouring native frogs and insects in its path. But Butler’s catch marks the first time the species has been documented in Georgia.

That’s bad news if the Cuban frogs, known to hitchhike to new homes in shipments of potted plants, are breeding in Georgia, biologists say. Previously, the northern boundary for U.S. populations was believed to be Jacksonville, Fla. – 120 miles south of Savannah.

“Because Savannah’s on the coast, where the temperature’s more moderate, oh boy, that’s where I get worried,” said Steve Johnson, a University of Florida ecologist who tracks the spread of Cuban tree frogs. “They could be anywhere between there and Jacksonville.”

Growing up to 51/2 inches long, large enough to fill a grown man’s hand, it is the largest tree frog in North America. Because of its size and warty skin, it could be mistaken for a toad if not for its large, padded toes.

Since its discovery in Key West, Fla., in the 1920s, the Caribbean frog has been considered an unwanted predator that disrupts ecosystems by dining on native species – including smaller tree frogs.

“They’re (a) huge relative to our native frogs,” said John Jensen, Georgia’s state herpetologist with the Department of Natural Resources. “Like pretty much all frogs, they eat anything they can catch and fit in their mouths.”

Butler, an office assistant at an advertising firm, believes the Cuban frog in her yard feasted on her pond frogs and goldfish before she caught it Sept. 23.

Her husband had noticed the frog weeks earlier outside their porch door, telling her it resembled “one of those weird African frogs.” Butler snapped a photo of it and searched the Internet trying to identify it.

Butler found a similar picture of a Cuban tree frog online and notified the U.S. Geological Society. Soon afterward, she got a phone call from Johnson, who wanted to see her photo immediately.

She had some qualms complying with Johnson’s second request – catch the frog, euthanize it in her freezer and send it to the university after preserving it in alcohol.

“I guess you’d say it’s kind of like kudzu – the species could just take off,” Butler said. “I had to look at it like that, as an invasive species.”

Jensen wants to determine if Butler’s frog was a lone hitchhiker or if others are breeding here.

“If people encounter them, they can kill them and send us the actual animal or they can take photos,” Jensen said. “But we definitely encourage folks to kill the animals if they find them.”

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