Project Accomplishments 2006--Monitoring and Tracking:
Gambian Giant Pouched Rats in the Florida Keys
The Gambian giant pouched rat (GGPR) has become an invasive species of concern for the State of Florida. An NWRC researcher worked with Florida WS in 2006 to develop information for planning the species' eradication from Grassy and Crawl Keys, where it is currently established. A pilot eradication campaign on Crawl Key, employing population monitoring methods developed by NWRC, was carried out in spring of 2006.
Recent camera surveys indicated no GGPR survival on Crawl Key following Hurricane Wilma and the pilot eradication effort. As a result, eradication efforts will now focus on the primary population on Grassy Key. The first step in the eradication process will be to monitor Grassy Key using a camera-indexing methodology cooperatively developed by NWRC and WS Operations personnel. This setup will determine current GGPR distributions and relative abundances throughout the island. Subsequent steps this fall will include the construction and deployment of bait stations especially designed to exclude native species. Bait-station density will be based on the results of the camera survey, with a higher density of bait stations in areas where GGPRs are found. Prebaiting will be done at all bait stations with nontoxic bait to acclimate GGPRs prior to using toxic bait.
The researcher has also been working with economists from the U.S. Department of Interior's U.S. Geological Survey who are attempting to model this invasive species' impacts should it escape the Keys and become established on the mainland. Work has focused on developing methods to place monetary values on imperiled natural resources, such as rare species and habitats. GGPRs likely would negatively impact agriculture through direct crop losses, contamination of harvested crops, reduced marketability of damaged produce, and contamination and consumption of livestock feed. GGPRs also could negatively impact populations of some threatened and endangered species, especially the endangered Key Largo woodrat, the Key Largo cotton mouse, and the Lower Keys marsh rabbit. GGPRs also have been associated with a variety of pathogenic diseases that could be spread to humans, livestock, or other wildlife.
Dramatic Reduction in Swine Damage to an Imperiled Habitat in Florida
An NWRC researcher collaborated with Florida WS and Eglin Air Force Base (EAFB) Natural Resources staff on studies to assess the amount and value of damage to imperiled habitats, and the efficacy of control measures beginning in 2003 through 2005. Only 1% of Florida's seepage slopes remain, with EAFB containing some of the largest tracts. Feral swine damage is among the greatest threats to this wetland habitat.
Before they initiated swine control, the research team found that areas open to hunting had a lower percent of seepage-slope area damaged (10.9%) than areas closed to hunting (25%). However, after only 8 months of control in only the unhunted areas, damage dropped to just 7.2%. Control in closed areas also impacted the open hunting areas not receiving control (5.6%) to such an extent that damage levels in the open and closed areas could not be distinguished statistically.
Another year of control brought damage in the closed area down to 5.6%, while the control-free open hunting area dropped to 4.3%, again indistinguishable from the controlled portion. Although it was applied only to the closed hunting area, control also reduced damage in the open hunting area, as swine move freely among areas. Precontrol, the combined value of swine damage to seepage slopes in open and closed hunting areas was $5.3 million. After 1.7 years of control, losses were reduced by nearly $4 million. The benefit-cost ratio over those 1.7 years of control was a noteworthy 27.5, meaning that every $1 invested yielded $27.50 worth of benefits. The economic benefits of control exceeded costs 55.2-fold the first year, when control's greatest impact would be expected.
The work at EAFB concluded with a training session provided by a Georgia Wildlife Services wildlife disease biologist on tissue-sampling methods for testing swine for brucellosis, PRV, and CSF.