The fallow deer is a generalist herbivore that eats different plants containing secondary compounds in various amounts. From observations of foraging behaviour it is known that large herbivores tend to eat from a variety of locations and, over the short term, typically ingest small quantities of a variety of foods and sample novel foods rather than making an immediate decision to either eat large amounts or to reject the food (Freeland and Janzen 1974). The diet choice of large herbivores is influenced by the presence of nutrients and toxins (Provenza 1995), but another factor that could influence the diet choice is the relative abundance of different plants and plant types. In order to study these effects we have performed experiments on the effect of the relative abundance of different food types on diet choice in fallow deer.