Black bear movements and habitat use relative to roads in Ocala National Forest: preliminary findings

Since 1976, the Ocala National Forest and surrounding areas have accounted for over 50 percent of all black bear roadkill in Florida. To better understand the dynamics involved with this source of mortality, the Florida Fish and Wildlife Conservation Commission, in partnership with the Florida Department of Transportation and the United States Forest Service, began investigating the movements, habitat use, and home range dynamics of black bears relative to roads in Ocala National Forest. This paper presents the preliminary findings from the first two years of the study and focuses on the characteristics of bear crossings of State Road 40. We captured 94 bears (36F, 58M) and collected more than 3,400 locations from 77 radio-collared individuals. Radio-collared bears crossed State Road 40 a total of 324 times, with both sexes crossing at similar frequencies. Concomitant with telemetry locations, we documented 752 sets of bear tracks along a 17.7-kilometer disced transect adjacent to State Road 40. Bears crossed State Road 40 most frequently during the fall, with other peaks in spring and summer. We compared crossing sites to the available habitat adjacent to State Road 40 and documented road mortality sustained by bears since 1976. Bears crossed in young to medium aged stands of sand/pine scrub at higher frequencies than would be expected by chance. Bears crossed in mature sand/pine scrub and scrub oak stands at lower frequencies than would be expected by chance. The sites at which bears were most often struck by vehicles did not coincide with locations where bears most frequently crossed the road. There seem to be highway design features that may contribute to this phenomenon

Microhabitat features influencing habitat use by Florida black bears

Understanding fine-scale habitat needs of species and the factors influencing heterogeneous use of habitat within home range would help identify limiting resources and inform habitat management practices. This information is especially important for large mammals living in fragmented habitats where resources may be scarcer and more patchily distributed than in contiguous habitats. Using bihourly Global Position System (GPS) location data collected from 10 individuals during 2011–2014, we investigated microhabitat features of areas within home ranges that received high vs. low intensity of use by Florida black bears (Ursus americanus floridanus) in north-central, Florida. We identified areas receiving high and low levels of use by bears based on their utilization distributions estimated with the dynamic Brownian bridge movement model, and performed vegetation sampling at bear locations within high- and low-use areas. Using univariate analyses and generalized linear mixed models, we found that (1) canopy cover, visual obstruction, and hardwood density were important in defining high-use sites; (2) the probability of high use was positively associated with principal components that represented habitat closer to creeks and with high canopy and shrub cover and higher hardwood densities, likely characteristic of forested wetlands; and (3) the probability of high use was, to a lesser extent, associated with principal components that represented habitat with high canopy cover, high pine density, and low visual obstruction and hardwood density; likely representing sand pine and pine plantations. Our results indicate that the high bear-use sites were in forested wetlands, where cover and food resources for bears are likely to occur in higher abundance. Habitat management plans whereby bears are a focal species should aim to increase the availability and quality of forested wetlands. Keywords: Habitat selection, Heterogeneous habitat use, Forest management, Microhabitat, Principal components analysis, Compositional features of microhabitat, Structural features of microhabitat, Ursus americanus, Vegetation samplin

Consequences of severe habitat fragmentation on density, genetics, and spatial capture-recapture analysis of a small bear population

<div><p>Loss and fragmentation of natural habitats caused by human land uses have subdivided several formerly contiguous large carnivore populations into multiple small and often isolated subpopulations, which can reduce genetic variation and lead to precipitous population declines. Substantial habitat loss and fragmentation from urban development and agriculture expansion relegated the Highlands-Glades subpopulation (HGS) of Florida, USA, black bears (<i>Ursus americanus floridanus</i>) to prolonged isolation; increasing human land development is projected to cause ≥ 50% loss of remaining natural habitats occupied by the HGS in coming decades. We conducted a noninvasive genetic spatial capture-recapture study to quantitatively describe the degree of contemporary habitat fragmentation and investigate the consequences of habitat fragmentation on population density and genetics of the HGS. Remaining natural habitats sustaining the HGS were significantly more fragmented and patchier than those supporting Florida’s largest black bear subpopulation. Genetic diversity was low (<i>A</i>_R = 3.57; <i>H</i>_E = 0.49) and effective population size was small (<i>N</i>_E = 25 bears), both of which remained unchanged over a period spanning one bear generation despite evidence of some immigration. Subpopulation density (0.054 bear/km²) was among the lowest reported for black bears, was significantly female-biased, and corresponded to a subpopulation size of 98 bears in available habitat. Conserving remaining natural habitats in the area occupied by the small, genetically depauperate HGS, possibly through conservation easements and government land acquisition, is likely the most important immediate step to ensuring continued persistence of bears in this area. Our study also provides evidence that preferentially placing detectors (e.g., hair traps or cameras) primarily in quality habitat across fragmented landscapes poses a challenge to estimating density-habitat covariate relationships using spatial capture-recapture models. Because habitat fragmentation and loss are likely to increase in severity globally, further investigation of the influence of habitat fragmentation and detector placement on estimation of this relationship is warranted.</p></div