During 1985-89 in Shenandoah National Park (SNP), Virginia, a severe gypsy moth (Lymantria dispar) infestation resulted in wide-spread overstory canopy defoliation and a complete acorn crop failure in defoliated areas. We believed canopy opening and food supply alterations would lead to increased black bear (Ursus americanus) movements, especially in the fall as bears searched for acorns, and consequently, greater seasonal range sizes than prior to the infestation (1982-94). Female bear convex and concave polygon range areas determined with radio telemetry were not significantly different before and during defoliation in spring or summer. Fall range areas, however, were twice as large for bears in defoliated areas of SNP during infestation (P = 0.025 and 0.001 for convex and concave areas, respectively) and resulted in significantly larger annual areas used by bears (mean convex areas: 26.7 km2 before versus 40.7 km2 during infestation for solitary females and 14.6 before versus 34.2 km2 during for females with cubs-of-the-year). Seasonal movements of females were consistent with range area data. Distances of shifts in seasonal geometric range centers were not different for spring to summer or early to late fall moves. However, summer to early fall shifts were twice as great (P = 0.072) during 1987-89 in defoliated areas than during 1982-84. Although acorn failure may have stimulated some bears to initiate fall moves, in 35 of 59 cases monitored bears remained in their traditional spring-summer ranges throughout the fall. Of those that did move, only 14 of 24 found acorns. Most females in this study successfully relied on soft mast fruits as alternative fall foods.
- Volume 10
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- Pages 259-267
- Publication Date 1 January 1998
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- File Size 347.63 KB
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