During June 1990 - November 1993 I measured the responses of black bears (Ursus americanus) in Shenandoah National Park (SNP), Virginia to gypsy moth (Lymantria dispar) induced oak (Quercus spp.) mortality. Oak species composed >50% of the forest canopy of SNP, and oak mortality rates ranged from 1- ≥48%. I compared black bear population dynamics, food habits, movements and habitat use to preinfestation data collected in SNP from 1982 - 1985. Scat analysis indicated that the current diet of SNP’s black bear population includes proportionally more soft mast in the fall and more soft mast and ants (Formicidae spp., P<0.0001) in the summer than did the preinfestation diet. Fewer acorns (Quercus spp. mast, P=0.03) and squawroot (Conopholis americana, P=0.01) were consumed in the fall and summer respectively. No decline in the physical condition of adult females (P=0.91), subadult males (P=0.34) or subadult females (P=0.94) was evident. Adult male physical condition declined (P=0.03) for unknown reasons. The mean age of neither female (P=0.99) nor male bears (P=0.54) was different from preinfestation data. Mean litter size - 2.25 cubs - did not differ (P=0.49) froma preinfestation mean of 2.0 cubs. Survival of radio-collared female bears was 100%, indicating that the female survival rate has not declined from a high preinfestation survival rate. Minimum cub survival rate to 1 year was 64.7%. Fall and annual home ranges of female bears were smaller (P=0.001 and P=0.002, respectively) than during preinfestation years. Use of forest cover types differed from availability during the summer (P<0.01), early fall (P<0.0001) and late fall (P<0.001) and when compared to preinfestation data. Use of stands with different levels of oak mortality was not different from availability during the summer (P=0.1) but was different during the early fall (P<0.005) and late fall (P<0.001). / Master of Science

I investigated the effect of defoliation by the gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae) on the radial growth of tree species that differ in their acceptability as hosts for gypsy moth larvae. Annual growth rings were measured from 1950 to 1992 on increment cores taken from three species: red oak (Quercus rubra L.), a preferred species, sugar maple (Acer saccharum Marsh.), an acceptable species, and white ash (Fraxinus americana L.), an avoided species. The number of gypsy moth larvae on these same individual trees had already been recorded from 1979 to 1992. To remove the potentially-confounding effects of climate on radial growth, I developed regression models of growth on climate in a pre-gypsy moth period (1950 to 1975), and then used these models to predict growth in a post-gypsy moth period (1978 to 1992). The residuals from these growth models were then examined with respect to gypsy moth numbers. (Abstract shortened by UMI.)

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