After extensive bait trapping and surveillance in 2007 and 2008, state Fish and Wildlife Conservation Commission and U.S. Department of Agriculture officials thought the fight against Gambian giant pouch rats on Grassy Key was over.</p><p>The invasive exotic is an African species that can grow up to nine pounds and reportedly appeared on Grassy Key sometime between 1999 and 2001, when they were released by a resident who had been breeding them.</p><p>"We thought we had them whipped as of 2009," said Scott Hardin, exotic-species coordinator for the FWC. "In the early part of 2011, a resident e-mailed me and said he saw one of the rats. We were skeptical but went back and talked to people and [saw] there were rats that we missed."</p><p>Hardin said trapping efforts began again in May last year and that pregnant females were found. More trapping was done in August and again during a 10-week period in November and December.</p><p>"We trapped about 20 since we started. 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," Hardin said. "We think they have not moved far but they clearly reproduced. We are surveying the area and been taking pictures of rats ever since."</p><p>The rats apparently are mostly confined to the area between Kyle and Pecan avenues along Morton Street. Hardin said they've typically been found in homeowners' yards.</p><p>"These are burrowers and there's just some features around the houses that substitute for that. It's hard to burrow in all that coral, plus there's fresh-water sources," he said.</p><p>Grassy Key resident Nancy Auten lives a short distance from where the remaining rats are believed to be and has seen traps around the island.</p><p>"I was just concerned because a lot of other animals get in there. As a concerned citizen, I was worried some other critter was going to get in there," she said.</p><p>Auten said she's never seen a Gambian rat on Grassy Key and -- along with several neighbors -- doesn't let the FWC trap in her yard because a fixed feral cat lives underneath her home.</p><p>Hardin says the Gambian rat matures and is able to reproduce within five months of birth.</p><p>"We're going to try to trap at least that often until we see signs that we have knocked them back," he said.</p><p>Hardin said another round of trapping is planned for July or August. Some 200 traps are baited primarily with cantaloupe and some peanut butter.