Shrnutí

Popis

The overall objective of this study was to determine population growth, sustainable yield, and factors influencing population dynamics of the species. We studied black bears Ursus americanus on 2 study areas in the OkefenokeeOsceola ecosystem in north Florida and southeast Georgia from 19951999 to determine population characteristics size, density, relative abundance, distribution, sex and age structure, mortality rates, natality, and recruitment and habitat needs. We captured 205 different black bears 124M: 81F 345 times from June 1995 to September 1998. Overall, adult bears on Osceola were 19 heavier than those on Okefenokee t 2.96, df 148, P 0.0036.We obtained 13,573 radiolocations from 87 16M:71F individual bears during the period of study. Seventeen mortalities of radio collared bears were documented on Okefenokee, with hunting mortality accounting for 70.6 of these deaths. We documented only 2 8 mortalities of radiocollared females from Osceola; both were illegally killed. Annual survival rates for radio collared females were lower on Okefenokee x 0.87, 95 CI 0.800.93 than on Osceola x 0.97, 95 CI 0.921.00; 2 0.05 3.98, 1 df, P 0.0460. Overall, 67 bears 51M:16F were taken by hunters on the Okefenokee study area from 19951999. Including the bears that were in protected areas and unavailable to harvest, the annual harvest rate was 10.1. Our annual survival estimate for Osceola females 0.97 was among the highest reported from any southeastern bear population, no doubt influenced by the closing of the bear hunting season in and around Osceola NF in 1992. When survival estimates for Okefenokee females were recalculated without hunting mortality, overall survival rates increased from 0.87 to 0.95, similar to that of the Osceola females. To estimate population size, we maintained 88 and 94 barbed wire hair traps during 1999 on the Okefenokee and Osceola study areas, respectively. Complete multilocus genotypes were obtained for 78 99 of the Okefenokee samples, of which 39individual bears were identified. On the Osceola study area, complete genotypes were obtained for 84 96 samples representing 37 individuals. After considering a number of markrecapture estimators, we concluded that the withinyear estimate of 71 bears 95 CI 5991 produced by the jackknife heterogeneity model Mh was the most appropriate for the Okefenokee hairtrapping data. Likewise, we selected the estimate of 44 bears 95 CI 4057 on the Osceola study area provided by the null model Mo as most appropriate during 1999. The estimated densities of black bears on the Okefenokee and Osceola study areas were 0.14 and 0.12 bearskm2, respectively. Based on a weighted average density of 0.135 bearskm2 and assuming a homogeneous distribution, we estimate that approximately 830 bears 95 CI 7071,045 inhabit the 6,147km2OkefenokeeOsceola ecosystem. We monitored 66 radiocollared bears 8M:58F from 19951998 for 132 possible denning occasions. Denning durations for females x 96.7 days, n 109, SE 2.7were longer than for male bears x 71.6 days, n 9, SE 8.8; Z 2.38, P 0.0174.Two male bears from Okefenokee denned in ground nests whereas tree cavities n 18and ground nests n 16 accounted for 65 of all dens used by Okefenokee females. In contrast, ground nests accounted for 100 n 37 of all documented den types used by female bears on the Osceola study area. Bears on Okefenokee used shrub, blackgum, mixed shrub, and cypress habitat types on 24, 23, 21, and 13 occasions, respectively. Interestingly, 90 n 74 of all radiocollared bears on the Okefenokee study area denned within the boundaries of ONWR during 19951998. Only 1 radiocollared female from each area denned in pine habitat during this study.