The Florida Keys' battle with an invasive species of giant rats isn't over yet.
On Grassy Key, a glut of Gambian giant pouched rats — originally bred and released by a local — have been foiling conservation officials' efforts to eradicate them, KeysNet reported Sunday.
Officials worry that if the hungry cat-sized rats make it to the mainland, they could wipe out some crops and upset delicate ecological balance.
"We thought we had them whipped as of 2009," said Scott Hardin, exotic species coordinator for Florida's Fish and Wildlife Conservation Commission.
About 20 of the creatures, which grow to nine pounds and are often mistaken for possums, were trapped on the island during a trio of commission efforts last year, Hardin said.
"I would not imagine there's more than another couple of dozen at most. We've caught them all within a half-mile of each other," he said.
"We think they have not moved far but they clearly reproduced," he added.
Plans are in place to begin another round of trapping of the vermin in July or August.
The massive rodents first appeared on the island over ten years ago after a local exotic pets breeder let some escape, and they've proved plenty pesky since.
For years, the Fish and Wildlife Conservation Commission, with the help of the U.S. Department of Agriculture, has been trying to kill off the remaining rats with poison-laced bait.
The primary kinds of bait used, said Hardin: cantaloupe and peanut butter.