According to Yahoo:
Gambian rats have been rapidly reproducing in the Florida Keys despite a decade-long effort to wipe them out. KeysNet reports the invasive, African native species first began showing up between 1999-2001 after a local exotic animal breeder released eight of the rats into the wild.
"We thought we had them whipped as of 2009," said Scott Hardin, exotic species coordinator for Florida's Fish and Wildlife Conservation Commission. "We think they have not moved far but they clearly reproduced," he said.