Bib. p. 101-104

The diurnal pattern of daily maintenance behaviour is determined by grazing, periods of rumination and rest occurring between periods of grazing. The primary determinant of when animals graze is daylength, with major grazing periods around dawn and dusk. However, temperature and humidity may alter the times that grazing periods begin and end. The time spent grazing depends on the physiological state of the animal, its age, and the availability of both herbage and supplementary feed. Dispersion of animals in an environment is influenced by a wide range of factors such as topography, location of shelter and water, weather conditions, and distribution of vegetation. Dispersion is rarely uniform, either during a day or over long periods of time. As a consequence, different areas of the same type of vegetation are utilised to quite different extents in the same paddock or range. Choice between types of vegetation and between plants species or parts of a plant is determined by the responses to chemical stimuli received through the animal's senses of smell, taste and touch. Little is known about these responses. An indication is given of the effect on acceptability of a plant or plant part of constituents such as sugars, organic acids, tannins and alkaloids. Differences between animals of different ages and breeds are small but different species may select different diets when grazing together. There seems to be litte good evidence to show that preferences are primarily motivated by nutritional wisdom