PART II: METAL BIOACCUMULATION IN RACCOONS IN RELATION TO STABLE ISOTOPE LEVELS
INTRODUCTION
The stable isotope composition of biological materials provides keen insights into the life histories of wildlife species. It has been demonstrated that animal tissues are enriched in 15N in relation to their diet. The differences in isotopic composition between any tissue compartment of an animal and diet is represented by a tissue-diet enrichment factor etissue-diet where tissue-diet » d tissue - d die and d” is the delta value for the isotope of interest. Subsequently, the partitioning of nitrogen isotopes can be viewed as a steady state mass balance where excretory products are depleted in 15N and tissues are enriched in 15N compared with the diet, resulting in a etissue-diet of ~3%. This enrichment is expressed for every step in the trophic level throughout the food web of an ecosystem, resulting in high-level consumers that are significantly enriched in 15N compared with primary producers.
Several characteristics of raccoons make them potential agents of contaminant movement and dispersal including: (1) a broadly omnivorous diet which includes components of both terrestrial and aquatic food chains, (2) their ability and proclivity to travel extended distances, and (3) a propensity to utilize human-altered habitats in combination with an ability to move freely in and out of toxic waste sites. However, the fact that it is an opportunistic omnivore constrains studies that focus on contaminant uptake. Therefore most contaminant studies focus on species whose diets are more predictable. In this study we explore the possibility of using stable isotopic analyses as a mechanism to better understand how the feeding habits of this more omnivorous species may explain some of the variability associated with their contaminant burden.
Introduction