Population Dynamics of Brown Bears after the Exxon Valdez Oil Spill

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We estimated survival and reproduction rates of brown bears (Ursus arctos) on the coast of Katmai National Park, Alaska, during 1989-95 to assess effects of the 1989 Exxon Valdez oil spill. Fifteen percent of fecal samples (n = 27) from brown bears captured in 1989 contained hydrocarbons indicative of exposure to crude oil. Females captured in 1989 and 1990 were divided into 2 groups: 12 with radiolocations that included oiled coastline and 21 that used unoiled areas. Survival rates during 1989-91 were not different (P > 0.90) between females from oiled versus unoiled areas. Based on the assumption that the availability and toxicity of oil was negligible by 1992, we also compared survival rates of both groups during 1989-91 with 1992-95 and observed no difference (P > 0.40). Recruitment rates during 1989-95 were not different (P = 0.12) between females from oiled and unoiled areas. Finite growth rates for the 2 groups suggested both were stable (λ = 1.003 and 1.014, respectively, for bears using oiled and unoiled areas).