Fecal Indices to Dietary Quality of Cervids in Old-Growth Forests

Abstract

Determination of dietary quality for wild ungulates can be both time-consuming and expensive. Because fistulation is usually not possible, determinations require a measure of diet (e.g., fecal analyses, direct feeding observations, tame animals, etc.) and simultaneous measures of nutritional attributes of each dietary component. An alternative approach is to measure a chemical characteristic of fecal material that bears a relationship to the quality or quantity of ingested diets (e.g., Cordova et al. 1978, Holechek et al. 1982b). Fecal nitrogen (FN) is a common index that has been shown to be positively correlated with intake (Arnold and Dudzinski 1963, Langlands et al. 1963, Stallcup et al. 1975), dietary digestibility (Lancaster 1949, Greenhalgh et al. 1960, Marten et al. 1963, Holloway et al. 1981), dietary protein (Raymond 1948, Greenhalgh and Corbett 1960, Hebert 1973, Arman et al. 1975, Erasmus et al. 1978, Mould and Robbins 1981, Holechek et al. 1982a), and weight changes (Gates and Hudson 1981) in a variety of wild and domestic ruminants. Difficulties with using FN as an index of dietary quality have usually resulted from seasonal changes in digestibility of forages (Greenhalgh et al. 1960, Minson and Kemp 1961, Holloway et al. 1981). Fecal indices to dietary quality have received limited application in wildlife management. Arman et al. (1975) contended that FN could be a valuable index if the relationships of dietary nitrogen (DN) and FN could be established for a particular ruminant in a given locality; widespread use was limited because of variability in species, forages, and seasons. Mould and Robbins (1981:327) rejected its utility as a simple indicator of dietary quality of wild ruminants because of protein-complexing properties of phenolics and other secondary metabolites in plants (McLeod 1974) that may elevate FN irrespective of DN. However, Gates and Hudson (1981) found that FN reflected changes in quality of forages used by Rocky Mountain elk (Cervus elaphus nelsoni). This paper summarizes the relationships of FN and fecal phosphorus (FP) to DN, dietary phosphorus (DP), and dietary digestibility (DD) of Roosevelt elk (C. e. roosevelti) and Columbian black-tailed deer (Odocoileus hemionus columbianus) in old-growth, coniferous forests of western Washington.