Toxicological significance of grit replacement times for juvenile mallards

Grit ingestion may be an important exposure route for environmental contami nants in waterfowl. Our objective was to determine turnover rate of grit in juvenile mallards (Anas platyrhynchos) by measuring the time required for juveniles to totally replace grit in the gizzard. To demonstrate the releva nce of turnover rate for assessing contaminant exposure, we evaluated the s uitability of wetlands receiving oil-sand effluent generated by the mining industry, as viable habitat for waterfowl. Captive mallards were allowed fr ee access to pools of colored grit, the grit color was changed and the time required for color 1 to be replaced by color 2 determined. hn exponential relationship between percent grit turnover and time was fitted to the data to obtain a grit turnover rate, k = 0.02/hr. This rate was used to determin e amount of contaminants that would be ingested over 21 days by juvenile ma llards using oil-sand wetlands as habital. We demonstrate that grit ingesti on could be a significant route of contaminant exposure, specifically for o il-sand related compounds such as oil and grease and naphthenic acids, to w aterfowl.