Dykes Jacob L, Strickland Bronson K, Demarais Stephen, Reynolds Daniel B, Lashley Marcus A
Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mississippi State, MS, 39762, USA.
Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mississippi State, MS, 39762, USA.
Behav Processes. 2020 Oct;179:104196. doi: 10.1016/j.beproc.2020.104196. Epub 2020 Jul 23.
Herbivores must navigate a heterogeneous matrix of nutrients in plant communities to meet physiological requirements. Given that the only difference between an essential nutrient and a toxin is the concentration in the herbivores diet, heterogeneity of nutrient concentrations in plant communities likely force wild herbivores to balance intake of abundant nutrients that may reach toxic levels with the need to meet nutritional demands of rare nutrients (i.e., nutrient balance hypothesis). While this hypothesis has been demonstrated in controlled studies with captive herbivores, experiments testing the nutrient balance hypothesis with wild herbivores are rare. We designed a cafeteria-style experiment to measure use of forages with differing nutritional compositions by wild white-tailed deer (Odocoileus virginianus) to test the nutrient balance hypothesis. We predicted deer diet selection would be explained by attraction to some nutrients and avoidance of others. Deer selected forages with low sulfur concentrations, a nutrient that commonly reaches toxic levels in herbivores. However, deer secondarily selected forages with greater digestibility and crude protein. Thus, our data indicate that the nutrient balance hypothesis may explain diet selection in wild herbivores where they avoid reaching toxicity of abundant nutrients while secondarily maximizing intake of limiting nutrients.
食草动物必须在植物群落中复杂多样的营养物质环境中找到合适的食物，以满足生理需求。鉴于必需营养素和毒素之间的唯一区别在于食草动物饮食中的浓度，植物群落中营养物质浓度的异质性可能迫使野生食草动物在摄入可能达到有毒水平的丰富营养素与满足稀有营养素营养需求之间取得平衡（即营养平衡假说）。虽然这一假说已在圈养食草动物的对照研究中得到证实，但用野生食草动物来检验营养平衡假说的实验却很少见。我们设计了一个自助式实验，以测量野生白尾鹿（Odocoileus virginianus）对不同营养成分草料的利用情况，来检验营养平衡假说。我们预测，鹿的饮食选择可以通过对某些营养素的偏好和对其他营养素的回避来解释。鹿选择了硫浓度低的草料，硫是一种在食草动物体内通常会达到有毒水平的营养素。然而，鹿其次会选择消化率和粗蛋白含量更高的草料。因此，我们的数据表明，营养平衡假说可能解释了野生食草动物的饮食选择，即它们会避免摄入过多营养素达到中毒水平，同时在一定程度上最大化摄入限制营养素。
