Abundance and Density of Florida Black Bears in Okefenokee National Wildlife Refuge and Osceola National Forest

The Florida black bear (Ursus americanus floridanus) exists as 7 relatively disjunct populations in Alabama, Florida, Georgia, and possibly Mississippi. In 1974, the Florida Fish and Wildlife Conservation Commission listed the Florida black bear as threatened statewide because of habitat loss and illegal killing. Although the species has not been afforded federal protection, the U.S. Fish and Wildlife Service is currently involved in a lawsuit over this issue. Although a judge's decision is still pending in the case, the earlier ruling by the USFWS could be reversed and the Florida black bear would be granted federal protection as a ''threatened" species.

I investigated population size and density of Florida black bears in the Okefenokee-Osceola ecosystem in southeast Georgia and northcentral Florida. I sampled bears at the Okefenokee National Wildlife Refuge (ONWR) and Osceola National Forest (ONF). This study provided a rare opportunity to compare estimates between a hunted (ONWR) and unhunted (ONF) assemblage of bears within the same population.

In addition to livetrapping, I also sampled each study area using a non-obtrusive sampling technique of collecting hair samples from free-ranging bears using baited barbed-wire enclosures. Individual identification was facilitated by microsatellite analysis of DNA extracted from collected hair samples.

From 1995-1998, I, along with other project personnel, live captured 123 individual bears 208 times on the Okefenokee area and 79 bears 132 times on the Osceola area. During the 15 weeks of hair sampling, 435 and 742 bear visits resulted in the collection of 374 and 637 hair samples on the Okefenokee and Osceola study areas, respectively. A subsample of 79 hair samples was randomly selected for analysis from the Okefenokee data. Complete multi-locus genotypes were obtained for 78 of those samples, of which 39 individual bears were identified. Eighty-eight hair samples were chosen for analysis from the Osceola data; complete multi-locus genotypes from 37 bears were obtained from 84 samples. All samples were analyzed at the same 8 microsatellite loci.

The heterogeneity model M_h produced an estimate of 71 (95% CI= 59-91) bears for the Okefenokee study area, corresponding to a density of 0.14 bears/km². On the Osceola study area, the null model M_o estimated population size at 44 (95% CI= 40-57) bears, or 0.12 bears/km².

The hair-sampling technique is a promising new tool for mark-recapture experiments and bear research. Because large areas can be sampled at one time, spatial and temporal variation in capture probabilities can be overcome. Likewise, trap response bias is likely minimized because the "capture" involves no physical restraint or undo stress. Based on the above, large sample sizes can be collected in a relatively short period of time. Thereby facilitating the use of closed models for estimating population size.