Ecology of Florida black bears in the Okefenokee-Osceola ecosystem

Wildlife Monographs

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The population status of the Florida black bear (Ursus americanus floridanus) is problematic within many portions of its range and its potential listing as a federally threatened species has been the subject of legal debate. We studied Florida black bears in 2 areas in the Okefenokee-Osceola ecosystem in southeast Georgia (i.e., Okefenokee) and north Florida (i.e., Osceola) from 1995 to 1999 to evaluate relationships between population characteristics, habitat conditions, and human activities. Bears in Okefenokee were hunted and those in Osceola were not. We captured 205 different black bears (124M:81F) 345 times from June 1995 to September 1998. We obtained 13,573 radiolocations from 87 (16M:71F) individual bears during the study. In Okefenokee, black gum (Nyssa sylvatica) and saw palmetto (Serenoa repens) fruits were the most important foods for bears based on scat analysis. In Osceola, corn from white-tailed deer (Odocoileus virginianus) feeders was the most stable food source but saw palmetto was heavily used when available. Corn from deer feeders was not available in Okefenokee. Adult bears in Osceola were 29% heavier than those in Okefenokee (t82 = 3.55, P< 0.001). The mean annual home-range size for Osceola females (x = 30.3 km2 ?? 4.0 [SE], n = 53) varied little seasonally or annually and was almost half that of Okefenokee females (55.9 km2 ?? 6.9, n = 69; Z = -2.47, P = 0.014). In contrast, radiocollared females in Okefenokee expanded their home ranges during years of poor black gum production. That expansion was most apparent between autumn 1998 and 1999, when mean home-range size for Okefenokee females increased from 14.5 km2 to 78.4 km2, respectively, and included a larger proportion of upland areas open to sport hunting. As a result, 5 females were harvested in the Okefenokee study area during the 1999 bear hunting season compared with only 7 harvested from 1996 to 1998. Home ranges of adult female bears were located in areas with disproportionately high loblolly bay (Gordonia lasianthus) and gum-bay-cypress (Taxodium spp.) vegetation associations in Okefenokee and gum-bay-cypress associations in Osceola. The pine vegetation association ranked lower than most other associations within the home ranges of bears in both study areas even though much of the summer and autumn diets of bears included food items found almost exclusively in pine. Sixteen mortalities of radiocollared bears were documented in Okefenokee; hunting accounted for 11 (68.8%) of these deaths. The annual survival rate of radiocollared males in Okefenokee was 0.71 (95% CI = 0.53-0.88) whereas survival of females in Okefenokee was higher (Z= 18.87, P < 0.001) at 0.89 (95% CI = 0.83-0.95). The survival rate for females in Osceola was 0.97 (95% CI = 0.92-1.00). Overall, 67 bears (51M:16F) were killed by hunters in the Okefenokee study area from 1995 to 1999. Based on all radiocollared bears in Okefenokee, many of which resided within areas closed to hunting, we estimated an annual harvest rate of 0.22 (95% CI = 0.03-0.37) for males and 0.07 (95% CI = 0.01-0.12) for females. When we excluded those bears that were not in areas open to hunting, however, the annual harvest rate rose to 0.37 (95% CI = 0.07-0.58) for males and 0.39 (95% CI = 0.09-0.58) for females. Following a black gum shortage in autumn 1995, only 1 of 15 radiocollared females in Okefenokee produced cubs in winter 1996. That low reproductive rate was in contrast to winter 1997, which followed heavy black gum production, when 21 of 22 radiocollared females produced cubs. Reproductive output was more consistent in the Osceola study area, with 46 cubs being produced from 8, 5, and 9 litters in 1997, 1998, and 1999, respectively. To estimate population size, we maintained 88 and 94 barbed-wire hair traps during 1999 in the Okefenokee and Osceola study areas, respectively. Using DNA collected at the hair traps, mark-recapture models produced estimates of 71 bears (95% CI = 59-91) in Okefenokee

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Ecology of Florida black bears in the Okefenokee-Osceola ecosystem
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Wildlife Monographs
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