Seasonal movements, habitat selection, and food habits of black bears (Urus americanus) in Shenandoah National Park, Virginia
Garner, Nathan Paul
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The seasonal movements, food habits, and habitat selection of black bears (Ursus americanus) in Shenandoah National Park, Virginia were studied from May 1982 to April 1985. A total of 47 collared bears, including 25 adult females, 17 adult males, and 5 subadult males < 3.5 years old, was located 3973 times during the study. Adult males had larger (P<0.001) home ranges (100% X=195 km², 95% X=116 km²) than adult females (100% X=38 km², 95% X=22 km²). Subadult males had larger (P<0.10) home ranges (100% X=542 km², 95% X=289 km²) than adult males and females. Extensive home range overlap occurred among each sex and age group. At least three subadult males dispersed from the Park during the study. Female bears with cubs were less mobile than solitary females during the spring. Fall cubs were large and did not restrict females' movements. Large fall home ranges for females were related to the scattered supply of acorns relative to the concentrated sources of soft mast used in the summer. Two females with cubs and 2 subadult males remained active during the winter months. Adult and subadult males generally had less stable home ranges than adult females. Female bears displayed infidelity to given areas during the fall from year-to-year due to variation in the distribution of hard mast (acorns). Male bears made long excursions onto the Piedmont Plateau east of the Park mainly during the spring and early fall. Females were not exposed to as much human induced mortality as males because they were located within the Park 17% more frequently than males. Males avoided fire roads (P<0.001), light duty roads (P<0.001), and primary roads (P<0.01) year around. Female bears preferred fire roads during summer (P< 0.001) and early fall (P<0.01) and avoided heavier traveled roads such as light duty roads (P<0.001) and primary roads (P<0.001) year around. Both male and female bears preferred foot trails for travel (P<0.05). Bears rarely came within 100 meters of campgrounds, picnic areas, and other human disturbance areas within the Park. Both sexes used low (P<0.10) elevations during the summer and high (P<0.10) elevations during early and late fall. Bears showed the greatest use of small rivers and streams during the driest months of summer. Geographic land forms of specific aspects, contours, and varying steepness were used differently by male and female bears. Twelve stomachs and 854 scats were analyzed for food content. Forbs, graminoids, squawroot (Conopholis americana), corn, and the fruits of trees, shrubs, and vines composed 90 percent volume of the annual diet. Eight percent of the food consumed was animal matter from mammals, birds, and invertebrates. During all seasons, females used yellow poplar (Liriodendron tulipifera) forests more (P<0.05) than males while males used yellow poplar forests less (P<0.05) than expected; males used black locust (Robinia pseudoacacia) \ black cherry (Prunus serotina) forests more (P<0.05) than females and more (P<0.05) than expected. Shifts in use of chestnut oak (Quercus prinus) \ northern red oak (Q. rubra) forests and northern red oak \ white oak (Q. alba) forests by both males and females in early and late fall was attributed to annual variation in oak mast production, preference for white oak acorns, foraging strategy, and the importance of mountain laurel (Kalmia latifolia) shrub cover in late fall. Seasonal use of domestic fruits at 330 abandoned homesites was determined. Distance-to-nearest-homesite measurements indicated that males were never closer (P>0.10) to homesites than females or random points during any season while females were closer (P<0.001) to homesites than males and random points during summer. Only females were located at homesites (≤ 100m) more (P<0.001) than expected during summer and early fall. Bears consumed apples (Malus spp.) and sweet cherries (Prunus avium) at abandoned homesites mainly in summer, early fall, and late fall. Bears used homesites in late fall more than distance measures indicated. Domestic fruits were an important nutritional food for black bears in relation to total soft fruits eaten.
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