Botanical Composition of Determination of Range Herbivore Diets: A Review

Abstract

Procedures used for estimating the botanical composition of the range herbivore's diet include diet observation, utilization techniques, fistula sampling, and fecal analysis. Each of these procedures has important limitations. Direct observation requires minimal time and equipment inputs but accuracy and precision are a problem, particularly with wild animals. Utilization studies are generally unsuitable when plants are actively growing and more than one herbivore is using the area under study. Fistula methods are accurate but are difficult to use with wild animals. In addition they are costly and require considerable time. The esophageal fistula is preferable to the rumen fistula because it provides more accurate information and requires less labor. Stomach analysis involves animal sacrifice and, therefore, is generally restricted to wild animals with large populations. However, trocar sampling of the rumen contents is a new method that avoids this problem. Fecal analysis has been used extensively in recent years to evaluate diet botanical composition of wild herbivores. This procedure gives good precision but accuracy is a problem because of differential digestion between plant species. Techniques are available that can be used to reduce this source of error. Microhistological analysis has become the most widely used method for quantifying botanical composition of masticated forage or fecal material. Recent studies show microhistological analysis can give an accurate representation of percent diet botanical composition by weight if observers use had compounded diets to check their accuracy. A new procedure, infrared spectrophotometry, may have considerable potential for evaluating herbivore diet botanical composition of fistula or fecal samples.