Spatially Explicit Population Estimates of the Florida Black Bear

The Florida black bear (Ursus americanus floridanus) is currently comprised of 7 isolated subpopulations: Apalachicola, Eglin, Osceola, Ocala/St. Johns, Chassahowitzka, Highlands/Glades, and Big Cypress. The last statewide assessment of Florida black bear population dynamics was conducted by Simek et al. (2005) using traditional capture-markrecapture methods. The subspecies was removed from Florida’s List of State Threatened Species in 2012 contingent upon the formulation of a management plan that would maintain viable subpopulations of black bears in suitable habitat. Accurate population estimates for each of the remaining black bear subpopulations in Florida were needed to achieve the management goals of this plan.

I used spatially explicit capture-recapture (SCR) within a maximum likelihood inference framework to estimate population density (D) and abundance (N) for the Osceola, Ocala/St. Johns, Eglin, Apalachicola, and Big Cypress subpopulations; these 5 subpopulations constitute the bulk of the statewide population. I constructed genetic capture histories for each subpopulation from genotyped hair samples taken from barbed-wire sampling stations (henceforth referred to in this document as hair snares). I used a 3 × 3 hair snare cluster layout with 2 km between hair snares and 16 km between cluster centers. I created covariates of density from land use/land cover (LULC) data to model heterogeneity in density across study areas. Model-averaged population estimates were 120.3 bears (95% CI = 61.1 – 269.1) or 0.025 bears/km² [bears per square kilometer] (95% CI = 0.013 – 0.056) for the Eglin subpopulation, 1,060.3 bears (95% CI = 825.4 – 1,385.9) or 0.082 bears/km² (95% CI = 0.064 – 0.107) for Apalachicola, 492.9 bears (95 % CI = 319.5 – 792.4) or 0.127 bears/km² (95% CI = 0.082 – 0.203) for Osceola, 1,192.6 bears (95% CI = 950.8 – 1,519.5) or 0.127 bears/km² (95% CI =0.101 – 0.161) for Ocala/St. Johns, and 1,037.4 bears (95% CI = 756.1 – 1,444.6) or 0.131 bears/km² (95% CI = 0.096 – 0.183) for Big Cypress. Effects of covariates on density estimates varied among study areas. The total population estimate was 3,908.8 bears (95% CI = 2,916.2 – 5,425.8). The cluster sampling method allowed abundance to be estimated across extensive areas that would not have been possible otherwise.