Trace mineral supplies for populations of little and large herbivores

Abstract

Copper (Cu), iron (Fe), and zinc (Zn) are essential trace minerals for the reproduction, growth, and immunity of mammalian herbivore populations. We examined the relationships between Cu, Fe, and Zn in soils, common plants, and hepatic stores of two wild herbivores to assess the effects of weather, sex, and population density on the transfer of trace minerals from soils to mammals during the growing season. Soils, grasses, woody browse, hispid cotton rats (Sigmodon hispidus), and white-tailed deer (Odocoileus virginianus) were sampled across 19 sites. Concentrations of Cu, Fe, and Zn in grasses and browse species were not correlated with concentrations of those minerals in soils sampled from the same areas. Leaves of woody browse were higher in Cu, lower in Fe, and similar in Zn when compared with grasses. Available concentrations of soils were positively related to liver Cu and Zn in hispid cotton rats, which was consistent with the short lives and high productivity of these small mammals that rely on grass seed heads. Interactions between soil concentrations and weather also affected liver Cu and Fe in deer, which reflected the greater complexity of trophic transfers in large, long-lived, browsing herbivores. Population density was correlated with liver concentrations of Cu, Fe, and Zn in hispid cotton rats, and concentrations of Cu and Fe in deer. Liver Cu was < 5 mg/kg wet weight in at least 5% of animals at two of eight sites for hispid cotton rats and < 3.8 mg/kg wet weight in at least 5% of animals at three of 12 sites for deer, which could indicate regional limitation of Cu for populations of mammalian herbivores. Our data indicate that supplies of trace minerals may contribute to density dependence of herbivore populations. Local population density may therefore influence the prevalence of deficiency states and disease outbreak that exacerbate population cycles in wild mammals.

To be browsed or not to be browsed: differences in nutritional characteristics of blackthornPrunus spinosasubject to the long-term pressure of herbivores

“…The Fe concentrations in both the browsed and unbrowsed blackthorns lie within the optimal range suggested for ungulates, whereas the Zn level in both browsed and unbrowsed plants was below the required range for ungulates (Suttle 2010;Ceacero et al 2015;Hollingsworth et al 2021). We did not detect any difference between the two groups as regards the concentrations of these two elements.…”

“…Our results indicate that the Cu content is higher in the browsed blackthorns. In mammals, Cu is essential for the proper growth of skeletal mass and in their metabolism (Miller et al 2003; Hollingsworth et al 2021). These results partially contradict the literature, where deer have been shown to prefer plants with lower Cu levels (Suttle 2010; Ceacero et al 2015).…”

“…The lower concentration of Mg is responsible for the structural changes of the ribosomes and reduces rates of photosynthesis (Mehne-Jakobs, 1996). This element is also known to be essential for muscle contraction and energy metabolism in mammals (Miller et al 2003; Ceacero et al 2015; Hollingsworth et al 2021). Our results indicated that the Mg content was lower in the browsed blackthorns and that Mg was the element making the greatest contribution to the dimension representing the unbrowsed bushes.…”

Implications of forage quality for population recovery of bighorn sheep following a pneumonia epizootic

“…Yet a greater concentration of Mn has been associated with negative fitness consequences for moose (Wam et al 2018). Notably, there were no consistent or biologically relevant differences between nutrient content of Cu, Zn, Fe, and Se, all particularly important for immune function and susceptibility to infection (Chandra 1996, Hollingsworth et al 2021). The lack of differences in nutrient concentrations between most functional groups and most genera between the ranges indicates that nutritional limitations occurring in Whiskey Mountain are likely linked to biomass, species diversity, and overall ease of access to nutrients on summer range, a phenomenon observed in other ungulate populations (Tveraa et al 2013, Proffitt et al 2016, Merems et al 2020).…”

“…Neonate survival was >2.5 times greater in free‐ranging black‐tailed deer ( Odocoileus hemionus columbianus ) with supplemental selenium compared to unsupplemented deer (Flueck 1994), indicating that deficiencies in specific micronutrients can have strong effects on reproduction. Furthermore, micronutrients vitamins A, C, and E, selenium, copper, zinc, and iron support immune function and can influence susceptibility to infections (Chandra 1996, McGraw and Ardia 2003, Cha et al 2010, Hollingsworth et al 2021). The quality of a range ultimately constrains how well nutritional demands are supported within a population, and sufficient macro‐ and micronutrients are important to a high‐quality range (Monteith et al 2014, Stephenson et al 2020).…”