The effect of monoterpene concentrations in Sitka spruce (Picea sitchensis) on the browsing behaviour of red deer (Cervus elaphus)

Abstract

The effect of monoterpene concentrations in Sitka spruce (Picea sitchensis) foliage on the browsing behaviour and preferences of red deer (Cervus elaphus) was studied in a series of 18 choice trials. During each trial, individual hinds were given access to 16 saplings arranged in a symmetrical array and aspects of their feeding behaviour were recorded over 15 min. The principal measures of preference were the number of bites and the biomass removed from each tree. Prior to each trial each tree was subjected to a series of detailed morphological measurements and a subset of trees was sampled for subsequent monoterpene analysis. Multiple regression analysis showed total terpene concentration of needles to have a significant negative influence on both the number of bites and the total biomass removed from each tree. Differences in susceptibility of Sitka spruce trees to browsing are discussed in relation to the observed high intertree variation in terpene concentrations.