FEEDING-BEHAVIOR OF RED-DEER (CERVUS-ELAPHUS) OFFERED SITKA-SPRUCE SAPLINGS (PICEA-SITCHENSIS) GROWN UNDER DIFFERENT LIGHT AND NUTRIENT REGIMES

1. In addition to exhibiting preferences for particular plant species, vertebrate herbivores select particular individuals of these species whilst leaving others undamaged. This pattern of diet selection may re flect differences in the chemical composition (and hence nutritional q uality) between individual plants, and/or variability in the physical constraints on intake rate, such as plant structure. 2. An experiment was conducted to test the effects of environmental manipulations on th e morphology and chemical composition of Sitka Spruce saplings, and to evaluate the consequences for herbivory by Red Deer, Fertilizing the trees increased tree height, branch span and leader length, twig width and needle width, and decreased the concentrations of total phenolics , condensed tannins, fibre and lignin but monoterpene content was not altered. Shading also reduced phenolic and tannin concentrations. 3. W hen the fertilized and shaded trees were offered to deer in feeding tr ials, the probability of a tree being visited by a deer and the biomas s removed were influenced by tree morphological variables, as were the bite rate and intake rate of the deer. More biomass was removed from larger tries. 4. Once the effects of tree morphology had been taken in to account, there was no effect of the fertilizer and shade treatments on deer browsing behaviour that could be attributed to changes in che mical composition of the trees, The relationship between intake rate a nd bite size at each tree varied between individual deer, but the func tional response relationship between intake rate and bite size was not influenced by the treatments applied to the trees. 5. Tree morphology may have a larger influence on deer feeding behaviour than tree chemi cal composition.