RELATIONSHIP BETWEEN DEER MOUSE-POPULATION PARAMETERS AND DIELDRIN CONTAMINATION IN THE ROCKY-MOUNTAIN ARSENAL NATIONAL WILDLIFE REFUGE

A small-mammal capture-recapture study was conducted in the Rocky Moun tain Arsenal National Wildlife Refuge to quantify the effects of soil contamination with dieldrin on demographic parameters of deer mouse (P eromyscus maniculatus) populations. Increased dieldrin concentrations were significantly associated with larger deer mouse populations, alth ough the size of populations on contaminated sites decreased during th e study. The most parsimonious model for estimating survival rates was one in which survival was a decreasing function of dieldrin concentra tion. A significantly higher proportion of female deer mice in the pop ulations residing on the more highly contaminated sites exhibited sign s of reproductive activity. Development of genetic resistance in P. ma niculatus to chronic chemical exposure is suggested as a possible mech anism responsible for the species' observed dominance and relatively h igh densities on contaminated sites. Under the additional stress of un favorable environmental conditions, however, these populations may suf fer disproportionately greater mortality. The design and analytical me thods presented offer a rigorous statistical approach to assessing the effects of environmental contamination on small mammals at the popula tion level.