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IP07 Population-Level Ecological Risk Assessment
(IP059) Modeling the population-level effects of multiple stressors: p,p'DDE and food shortage in the burrowing owl.
Gervais, J1, Hunter, C2, Anthony, R3, 1 Utah State University, Logan, UT, USA2 Woods Hole Oceanographic Institution, Woods Hole, MA, USA3 Oregon Cooperative Fish and Wildlife Research Unit, Oregon State University, Corvallis, OR, USA
ABSTRACT- We evaluated the effects of low levels of p,p′DDE in burrowing owls (Athene cunicularia) when combined with fluctuations in the populations of a major prey species, the California vole (Microtus californicus). Levels of p,p′DDE not associated with negative effects in normal years were correlated with reduced reproduction when vole populations crashed following years of very high densities. Our primary goal was to determine whether the contaminant exposure levels detected in earlier work and their interactions with natural stress were great enough in either extent or severity to impair population-level processes. Our secondary goal was to evaluate the consistency of the conclusions drawn from different structured matrix population model analyses based on the inevitably incomplete ecological data. Finally, we explore the utility of these types of analyses in assessing risk to ecological populations. This population of burrowing owls appears to be far more affected by natural fluctuations in food supply than anthropogenic contaminants. This conclusion was consistent across all modeling strategies we examined.
Key words: multiple stressors, matrix models, population-level ecological risk assessment, population dynamics
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