Food selection by European roe deer (Capreolus capreolus): effects of plant chemistry, and consequences for the nutritional value of their diets
Résumé
We describe food selection by roe deer (Capreolus capreolus) in relation to the food quality of the plants available (the concentrations of fibres, sugars, crude protein, and of phenolics and terpenes). Seven tame roe deer feeding in an oak-beech woodland edge used the majority (80-94%) of the plant species available: they were therefore generalist feeders. However, they preferred only a small number of plant species in the different seasons: ivy (Hedera helix) in winter and autumn, dogwood (Cornus spp.) in summer, hornbeam (Curpinus betulus), hawthom (Crataegus spp.) and bluebells (Hyacinthoides non-scripta) in spring. No preference or avoidance could be demonstrated for 74-85% of the available species, but 7-12 species were avoided according to the season. Though the avoided species were sometimes common, they never comprised an important part of the diet. In contrast, the preferred species made up only 4-13% of the available green matter but composed a large part of the diet (22-49%). Although generalists, the roe deer were therefore also highly selective feeders. The use of the different plant species was influenced by their availability, but to a different extent in the different seasons. Use of the plant species correlated negatively with the fibre content, as predicted from the digestive morphology of this concentrate selector. Preference/avoidance was related to the concentrations of soluble sugars, but not the crude protein content. Contrary to expectation, the roe deer preferred plants with a high concentration of protein-binding phenolics, suggesting that this deer has specific mechanisms for de-activating these compounds. Among the nutritional consequences of the feeding strategy of roe were a 17-35% higher soluble sugar content of the diet compared with the available green plant tissues, and an even greater increase in the phenolics. The crude protein contents and the dry matter digestibility of the diets tended to be slightly higher, and the fibre contents were lower, than those of the available green plant tissues.