Viability Relationships Of Small Mammal Populations At Varying Distances From The Asarco Smelter In East Helena, Montana

Abstract

This research investigated the possible correlation between distance from the ASARCO lead smelter in East Helena, Montana, and small mammal population size. Due to smelter emissions, nearby soils have toxic levels of arsenic and heavy metals. Because these heavy metal and arsenic concentrations in the soil are inversely related to distance from the smelter, it follows that plants and animals would be better able to survive at a greater distance from the source of detrimental emissions released by the smelter. Fifty-four Sherman live traps were set in a rectangular grid, and mice were captured and released in order to estimate the population sizes in three areas of varying distance from the ASARCO smelter. Peromyscus maniculatus (deer mouse) was the most numerous species captured, but both Microtus montanus (mountain vole) and Sorex vagrans (vagrant shrew) were also collected. Total population and juvenile population estimates were considerably higher in the area farthest from the ASARCO smelter. Other data such as reproductive condition, weight and home range also suggested an improved environment with an increased distance from the smelter.