Geographic variation in trace mineral concentrations in blood of mule deer from the Mojave Desert, California, USA

Minerals are important nutrients and are essential components of the diets of animals. Nutritional requirements or minimum concentrations of minerals for nutritional health are largely unknown for the majority of large, free-ranging herbivores. We investigated concentrations of 9 trace minerals in mule deer (Odocoileus hemionus) inhabiting 3 distinct geographic areas—Cima Dome, New York Mountains, and the Mid Hills—in the eastern Mojave Desert, San Bernardino Co., California from 2008 to 2016. These areas differed in vegetative communities, topography, water availability, and fire histories. Telemetered mule deer demonstrated high fidelity to each of these areas, and movement by those individuals between study areas was not detected. During our investigation, overall differences occurred in mean concentrations of magnesium (P < 0.001), calcium (P = 0.022), phosphorus (P = 0.023), potassium (P = 0.042), and selenium (P < 0.001) among the 3 geographic areas. Among years, differences occurred in concentrations of the trace elements investigated in the New York Mountains with the exceptions of magnesium and potassium; at Cima Dome with the exceptions of iron, sodium, potassium, and selenium; and in the Mid Hills with the exceptions of magnesium and zinc. A positive upward trend existed between selenium concentration in the New York Mountains and the year of sample collection (P < 0.05), and a similar—albeit not significant—upward trend was discernible in the Mid Hills, but no such relationship was apparent at Cima Dome. These results emphasize the importance of investigating micronutrient status of mule deer on a local scale and temporally and add to the sparse information available on trace mineral concentrations in mule deer. Despite limited samples (≤165), we make available for the first time reference values for mule deer inhabiting the Mojave Desert, to serve as a baseline against which to measure responses to future environmental perturbations or for comparison with deer occupying other disparate ecosystems, and further contribute to the derivation of reference values for mule deer in general.