Date of Award
Master of Science
Wildlife and Fisheries Science
Michael R. Pelton
David Buehler, Joe Clark, Sally Horn
Black bear (Ursus americanus) home range dynamics, habitat utilization, denning chronology, and denning habitat use were studied from May 1992 to May 1994 on the Neuse/Pamlico Peninsula (NPP) of eastern North Carolina. Habitat models for the entire coastal region of North Carolina were also developed based on 20 years of bear distribution data. The NPP, representative of much of eastern and coastal North Carolina, is an intensively managed area consisting of pine plantations and agricultural areas interspersed with remnants of pocosin and hardwoods. Two study areas, the Big Pocosin and the Gum Swamp, were located on the peninsula.
Eighty-nine individual bears were captured 102 times, and 50 bears were radio-collared and monitored one to four times per week by ground triangulation. Over 3650 radio locations were collected, and 2065 were used for home range and habitat use analyses. Annual home range sizes were calculated using the 95% harmonic mean (HM) and the 95% and 50% convex polygon (CP) methods. Seasonal home ranges were calculated with the 95% CP method. Habitat utilization was analyzed using Geographic Information System (GIS) technology with program Arclnfo, and land use/land cover (LULC) data were obtained from the Albemarle/Pamlico Estuarine Study conducted by the North Carolina Center for Geographic Information and Analysis. Seven habitat components were statistically ranked in each study area based on usage versus availability using the Johnson ranking method which employs the Waller/Duncan multiple comparison Procedure.
For females, annual 50% CP and 1993 spring, summer, and fall 95% CP home ranges were smaller in the Gum Swamp than in the Big Pocosin. Furthermore, Gum Swamp females exhibited a higher degree of home range overlap than Big Pocosin females. The above factors combined may indicate higher habitat quality in the Giun Swamp area than in the Big Pocosin.
A GIS was used to match LULC with bear locations. Twelve habitat types were used by bears, and these types were grouped into eight categories representative of habitats available to bears. Six categories were common to both study areas, and each area contained one distinct component. Two techniques were used to determine available habitat. One method assumed each bear had a different Area of Availability (ADA) based on an area buffered around each bear's center of activity, and the second method assumed bears had available habitat throughout the Entire Study Area (ESA) which was based on the composite of all AOA areas.
During spring, differences in habitat components were not different for Big Pocosin females using ESA and AOA methods. Grouping of habitat categories, due to low spring sample sizes, eliminates the opportunity to determine specific rankings for the seven individual habitat components. Using aU seven habitat types during summer, pocosin, low vegetation, and mixed pine/hardwood stands were ranked #1, #2, and #3, respectively (by ESA). Summer AOA habitat components did not differ. In fall, both ESA and AOA methods exhibited differences within habitat components. For females, using the ESA method, pocosin, low vegetation, and mixed stands ranked #1, #2, and #3, respectively. However using the AOA method, bottomland hardwood, pocosin, and low vegetation ranked #1, #2, and 3, respectively. During one significant summer (ESA) and two significant fall (ESA and AOA) analyses for BP females, pine ranked #7, #5, and #4 out of the seven habitat types.
For Gum Swamp females, spring sample sizes were large enough to analyze all seven individual habitat components. Marsh, formed areas (cleared), and pocosin were ranked #1, #2, and #3, respectively, using the ESA method while the AOA components were not different. The importance of marsh, low vegetation, and farmed areas (cleared) were shown in summer because these habitat types ranked #1, #2, and #3 using the ESA method, and the AOA components did not differ. Also, marsh, farmed areas (cleared), and low vegetation were ranked #1, #2, and #3, respectively, in fall using the ESA method while AOA components were not different. Pine habitats ranked #7 during spring, summer, and fall for GS females using the ESA method.
Males were combined between study areas due to low sample sizes. Low vegetation and cleared habitats ranked #1 and #2, respectively, using the ESA method during summer. AOA habitat components did not differ. Summer was the only season sample sizes were large enough to rank habitat components for males.
All monitored bears denned for at least part of the winter period (1 January through 31 March). Adult females exhibited significantly longer denning periods than subadults due to earlier den entry dates. However, den emergence dates did not differ. Pine plantations in very specific age classes, pocosins, hardwood (bottomland and upland), and areas of low vegetation such as clearcuts were utilized as denning areas. Bears denned in hardwoods (upland and bottomland) and pocosin more often than e?q)ected based on availability. Bears also chose pine plantations of very specific age and structural composition. Nine of 10 den sites in pine plantations were located in pine stands 3-8 or 15-20 years old (3-8 years post disturbance or thinning). Pine woodlands in these age classes contain very similar vegetative structures related to the time since last disturbance (disturbance includes planting at age 0 or thinning at approximately age 12).
Habitat models for the coastal plain identified the importance of large continuous blocks of forested habitat and areas of bottomland hardwoods for black bear populations in the region. Additionally, area and type of cropland appears critical for black bears in eastern North Carolina. Grain crop foods may substitute for hardwood mast foods in areas of sufficient forested habitat with escape cover and denning. Managers in the region should consider the juxtaposition of remaining continuous forested blocks, oak/gum/cypress forests, and areas of important crop foods (com, wheat, soybeans).
Because home ranges in 1993 were significantly larger in the Big Pocosin than the Gum Swamp, and Gum Swamp females exhibited a higher degree of home range overlap than Big Pocosin females, there is evidence of higher habitat quality in the Gum Swamp. Managers should attempt to mimic the diverse habitat characteristics of the Gum Swamp which contains areas of pocosin, marsh, and bottomland interspersed with remote croplands. Future management efforts in the coastal region should maintain or restore pocosin, marsh, and bottomland hardwood to provide habitats similar to the Gum Swamp.
If predicted declines in "natural" habitats continue, pine habitats will become increasingly important as feeding areas. Cooperation with the forest industry will be imperative to ensure adequate bear habitat in the future. Management plans should be designed with consideration for maintaining areas of low vegetation by using control burning and thinning to enhance areas for soft mast production. Such disturbed pine plantations, providing berries and other food items, may be substitutes for bottomlands and pocosin when supplemented by nearby food crops. However, the quality of these pine dominated environments for reproduction and survival remains unknown. Pine management should be designed with consideration for balancing areas of low vegetation for feeding with areas of thick pines for denning habitat. The juxtaposition of managed pine woodlands and areas of croplands containing important bear foods should be considered.
Grain croplands are clearly critical for bears in the region, yet agricultural predictions indicate that areas of grain crops will decline and cotton will increase. Wildlife managers should focus bear management efforts in regions of the coastal plain such as occupied bear habitat in the lower coastal plain or tidewater area where soils and agricultural conditions are conducive to the continued growing of grain crops. This will be particularly critical as remnant areas of thick pocosin and suitable bottomlands are lost. Landscape-scale management and cooperation between wildlife managers and the forest industry and the agricultural community will be essential in order to ensure black bear viability in the rapidly developing coastal plain.
Jones, Mark Dwight, "Black bear use of forest and agricultural environments in coastal North Carolina. " Master's Thesis, University of Tennessee, 1996.