The importance to baboons of ready access to drinking water is emphasized in studies which have shown that most baboons, including the semi-desert dwelling hamadryas baboon, Papio hamadryas, drink free water daily (Kummer, 1968) or sometimes once every two days (Altmann and Altmann, 1970). Shifts in the position of water supplies have resulted in baboon troops adjusting their movement patterns so that they always have access to water within their daily ranges (Stoltz and Saayman, 1970; Hamilton, Buskirk and Buskirk, 1976). Hall (1962) provided the first evidence that baboons may not be absolutely reliant on free drinking water: on the Cape Peninsula the baboons he studied drank water irregularly and obtained moisture from dew and moist plant material. His study, however, was carried out in a high rainfall area and was based on observations made on one day per week for a year.