Baseline levels of boron, fluorine, molybdenum, and copper are described for 18 mule deer (Odocoileus hemionus) and for 45 composite samples of deer mice (Peromyscus maniculatus) from the Piceance Creek Basin, Rio Blanco County, Colorado. These data were collected before oil shale mining took place, and can be used to compare with levels found after mining is initiated. The data can thus be used to monitor changes in levels in animal tissues and as a basis for mitigating possible harmful effects due to the mining.

Mean ppm (± S.D.) dry basis of each element is presented for selected tissues of each species. Results are also presented by habitat type for deer mice and by age for mule deer. Significant differences (P < 0.05) in molybdenum levels in deer mice were found between habitats. Significant differences (P < 0.05) were found between fawns and adult mule deer for boron levels, but not for the other elements. A need to standardize bone selection for analysis of fluorine was indicated. Kidneys appeared to be the organ of choice for baseline sampling of molybdenum and copper, and livers may be the organ of choice when toxic levels are suspected.