Adaptive management requires for population viability analyses (PVAs) to be updated and reevaluated as conservation strategies are implemented, changes in the population or the environment occur, and new demographic data become available. The Florida panther (Puma concolor coryi) population has been monitored continuously since 1981 and has been the subject of several PVA studies, the most recent of which was based on field data collected through 2007. Considering the constant alteration of habitat in South Florida as well as the risks inherent to small, isolated populations, a periodic reevaluation of Florida panther PVA is warranted. Our goal was to assess the dynamics and persistence of the Florida panther population using an individual-based model (IBM) tailored to the life history of the Florida panther and parameterized with recent empirical estimates of demographic parameters. We used the IBM to analyze quasi-extinction risks as well as the effects of parameter uncertainty, environmental stochasticity, and density dependence on predicted risks.
Results/Conclusions
We defined quasi-extinction risk as the probability of the population size falling below 10 individuals, or individuals of only one sex remaining. Based on 100 bootstraps to account for parameter uncertainty and 100 simulations for each bootstrap, the risk of quasi-extinction within 200 years was 7% (1st and 99th percentiles: 0-99) without environmental stochasticity or density dependence. The quasi-extinction risk increased to 15% (0-99) when environmental stochasticity was included, or decreased to 1% (0-4) when density dependence was included. Our most comprehensive model, which included both environmental stochasticity and density dependence, predicted a quasi-extinction risk of 0.3% (0-11). The average time to quasi-extinction was 82 years (59-100), conditional on quasi-extinction within 200 years. These results need to be interpreted with caution, because our estimate of density dependence is based on an index of abundance (rather than estimates of population size), which potentially caused density dependence to be overestimated, and consequently extinction risk to be underestimated. Our results indicate that management strategies adopted for the Florida panther in the last two decades appear to have averted the extinction of the Florida panther for the time being.