| Abstrakt: |
Simple Summary: Wild herbivores require minerals to grow and maintain their skeleton and to catalyze their metabolic reactions. Herbivores acquire minerals from forage plants and, ultimately, the soils and waters that support seasonal plant growth. We know that seasonal changes in the quality and abundance of forage plants drive the movements of wild ungulates. However, the role of minerals in the movement and production of ungulates is poorly understood because the mineral requirements of wild species are poorly described. We describe a framework to estimate the minimum concentration of forage minerals required by female caribou, a wild ungulate with both migratory and sedentary ecotypes. We used measures of body mass and milk yield to determine the demand for minerals as the food intake changed with the season. We found that the minimum dietary concentrations (mg·kg−1) of macro-minerals (Ca, P, Mg, Na, K) declined as the food intake increased over the summer. The minimum dietary concentrations of micro-minerals (Fe, Mn, Cu, Zn) were heavily influenced by body mass gain, which increased through late lactation as food intakes rose. Our framework may be applied to other wild ungulates to assess the impacts of changing forage supplies on individuals and populations. Mineral requirements are poorly described for most wildlife. Consequently, the role of forage minerals in movement and productivity are poorly understood for sedentary and migratory ungulates, such as reindeer and caribou (Rangifer tarandus). We applied estimates of maintenance, lactation, body mass change, and antler growth to production curves (body mass, daily intake, and milk yield) for female caribou to calculate their mineral requirements over summer. The total requirements (mg or g·d−1) were divided by the daily intake (kg·d−1) to estimate the minimum concentration of minerals required in the diet (mg or g·kg−1) to balance demand. The daily requirements (mg·d−1) of all minerals increased from parturition to the end of summer. The minimum dietary concentrations (mg·kg−1) of macro-minerals (Ca, P, Mg, Na, K) declined as food intake (kg·d−1) increased over summer. The minimum dietary concentrations (Fe, Mn, Cu, Zn) were heavily influenced by body mass gain, which increased through late lactation even though food intakes rose. Our modeling framework can be applied to other wild ungulates to assess the impacts of changing forage phenology, plant community compositions, or environmental disturbances on movement and productivity. [ABSTRACT FROM AUTHOR] |
