Atsatt Peter R, Ingram Trudy
Department of Ecology & Evolutionary Biology, University of California, 92717, Irvine, CA, USA.
Oecologia. 1983 Oct;60(1):135-142. doi: 10.1007/BF00379333.
Neotoma fuscipes, a small mammalian herbivore with apparently generalized food habits, was laboratory tested to determine its degree of dietary specialization. Woodrats from both oak woodland and coastal sage communities preferred Quercus agrifolia leaves (containing 40% phenolics and about 16% condensed tannin) over foliage from other dominant species. Approximately one-third of the oak phenolics and less than 10% of the oak condensed tannin remained in the feces. Their performance on pure oak leaves was comparable to that on a mixed diet of Quercus, Salvia, Eriogonum, and Rhus, with respect to weight maintenance, digestive efficiency and total amount ingested. Digestive efficiency was low on the oak diet (55%) relative to Salvia (77%), and to achieve similar weight levels, approximately twice as much oak as Salvia was ingested. Woodrats retained more nitrogen as oak consumption increased. Intake of oak and other foods increased with each experimental day. A sympatric species, N. lepida, was unable to maintain weight on oak leaves, although its digestive and polyphenolic-degrading capabilities, and nitrogen retention efficiency were equivalent to those of N. fuscipes. On a weight-adjusted basis, N. lepida ate about half as much oak per day as N. fuscipes. Oak intake may have been reduced by an inability to rapidly degrade fiber, which constitutes about 30% of the oak diet. In natural populations, N. fuscipes selectively feeds on evergreen sclerophyll vegetation high in fiber, tannins and related polyphenolics. Individuals ingest 2-3 plant types at a time, with a single species (oak when available) constituting most of the material consumed. Neotoma lepida diets are also dominated by a single species. The diversity of plant types eaten by different populations of N. lepida suggests that local dietary specializations may be developmentally acquired.
棕足林鼠是一种小型食草哺乳动物，食性看似广泛，为确定其饮食特化程度，在实验室对其进行了测试。来自橡树林地和沿海鼠尾草群落的林鼠更喜欢食用加州栎树叶（含有40%的酚类物质和约16%的缩合单宁），而不是其他优势物种的叶子。大约三分之一的栎树酚类物质和不到10%的栎树缩合单宁残留在粪便中。就体重维持、消化效率和总摄入量而言，它们在纯栎树叶上的表现与在由栎树、鼠尾草、荞麦属植物和盐肤木组成的混合饮食上的表现相当。相对于鼠尾草（77%），栎树饮食的消化效率较低（55%），为达到相似的体重水平，摄入的栎树量约为鼠尾草的两倍。随着栎树摄入量的增加，林鼠保留了更多的氮。随着实验天数的增加，栎树和其他食物的摄入量也增加。同域物种，即细纹林鼠，尽管其消化和多酚降解能力以及氮保留效率与棕足林鼠相当，但无法依靠栎树叶维持体重。按体重调整后，细纹林鼠每天食用的栎树量约为棕足林鼠的一半。栎树摄入量可能因无法快速降解纤维而减少，纤维约占栎树饮食的30%。在自然种群中，棕足林鼠选择性地以富含纤维、单宁和相关多酚的常绿硬叶植被为食。个体每次摄取2 - 3种植物类型，其中单一物种（如有栎树则为栎树）构成大部分摄入物质。细纹林鼠的饮食也以单一物种为主。不同种群的细纹林鼠所食用植物类型的多样性表明，当地的饮食特化可能是在发育过程中获得的。
