Abstract
The Florida panther (Puma concolor coryi) is a federally listed endangered sub-species located in the Everglades and Big Cypress ecosystems of southern Florida. Environmental stressors, including environmental contaminants, low genetic variability and habitat loss may have contributed to the decline of this sub-species. The Florida Fish and Wildlife Conservation Commission (FWC) has monitored mercury (Hg) levels in the Florida Panther since 1978. Hair and blood were collected for analysis through live capture and liver, brain, muscle and kidney were collected during necropsies of salvaged dead cats. Concurrently, other metrics including body condition, presence of congenital defects, blood chemistry analysis, and reproductive success were also assessed as part of a larger investigation on health and fecundity of the population. The purpose of this study is twofold: first to compile and organize available data to investigate the spatial and temporal patterns in hair-Hg and blood-Hg from 1978 through 2007; and second to assess the potential influence of hydroperiod as an explanatory variable as it relates to methylation potential and habitat quality for prey species. All collected hair samples (n=478) had measureable amounts of mercury, with concentrations ranging from 0.086 mglkg to 100 mglkg. Likewise, all collected blood samples (n=338) had measurable concentrations of mercury, with values ranging from 0.009 mg/kg to 5.3 mg/kg. These data demonstrated that while average Hg levels have decreased in panthers in most areas, some individuals continued to attain high mercury burdens. With the numerous environmental and genetic stressors already pressing this population, risks associated with exposure to elevated levels should be examined. Previous study evaluating this risk to panthers (Barron et al. 2004) stated current risks from mercury exposure were low however, the data presented here does not support that conclusion. Also observed was an apparent increase in mercury levels, albeit small, in panthers from certain areas. As an endangered species suffering from numerous stressors, these maximum exposure concentrations remain a concern. These changes in tissue-Hg concentrations may be correlated with variations in hydroperiod indentified among the study regions. Regions experiencing repeated wetting and drying cycles and long hydroperiods were home to individuals with elevated tissue-Hg concentrations. Although the link between hydroperiod and mercury exposure of the cats could not be fully explored using the available secondary data from FWC, which was collected for other purposes, it continues to appear to play an important role in habitat creation for prey species as well as influencing methylation rates in these areas. Habitat management to support large populations of ungulate species as prey items for Florida panthers is an important part of decreasing their reliance on aquatic food web items and lowers their risk to adverse health effects as a result of exposure to Hg.
