Mountain Sheep: An Environmental Epidemiological Survey of Variation in Metal Exposure and Physiological Biomarkers Following Mine Development

Abstract

Problem Statement: Anthropogenic activities, such as mining and industrial operations, are a major environmental source of metal exposure for wildlife. Quantitative data regarding biochemical effects of exposure to mineral extraction on mountain sheep, Ovis canadensis, are limited, although their habitats are becoming increasingly affected by expanded resource development. Decisions relating to environmental protection and wildlife conservation should be based on sound scientific understanding of the interaction of released metals with the biota. Approach: Because understanding of the biogeochemistry, food webs, and metals as stressors was limited for arid environments, scientists and managers need to take a monitoring approach that incorporates a longer time scale using resembling designs. We tested the hypothesis that mountain sheep exposed to mining activities would express elevated levels of biomarkers compared with a reference group that was not directly exposed to mining activities. During this study, conducted in the Mojave Desert of California, USA, from 1995-1997, we analyzed concentrations of selected metals in blood of mountain sheep as biomarkers of exposure using a simultaneous treatment-reference design. We included common physiological biomarkers of effect, such as haptoglobin and interleukin-6. These variables were measured in two subpopulations of female mountain sheep inhabiting distinct geographic areas (mined and non-mined) within a single mountain range over 2 years. Results: Although the sample size was small, metal exposure was significantly higher in mountain sheep inhabiting the mined area. Plasma protein levels in these sheep inhabiting the mined area were also significantly higher than for mountain sheep in the non-mined area. Conclusion: Local biomonitoring studies during mining and other developments were important sources of baseline information about the health of wildlife populations, which allowed managers to establish benchmarks related to exposure.