Hierarchy of Water and Energy Turnover of Desert Mammals

Abstract

MAMMALS inhabiting desert regions might be expected to have similar physiology, particularly in rates of water use. Groups of ungulates in the field, however, show a wide range of water consumption. We measured, over periods of weeks, the uninhibited intake of water and food by groups of animals grazing together on the same territory and this was integrated with metabolic water from oxidation of hydrogen. Using this approach1 we found that buffalo (Bos bubalus bubalis) have the highest water turnover of any unstressed animal so far measured—200 ml./kg/24 h. Bos taurus in the same tropical climate were next in rank order, then Bibos banteng and the least water-demanding of the cattle group were Bos indicus (123 ml./kg/24 h). In the summer deserts of Australia and northern Kenya, the highest water turnover rates occurred in cattle, with sheep at about half their rate, goats somewhat less and camels (Camelus dromedarius) least in their water requirements, at half to one-third the rate of cattle2. In temperate environments the same rank order of genera and species was sustained. Because of different degrees of fatness (body solids, Table 1) it is useful to rank the animals by mol/l.0.82, which relates to the number of molecules passing through the size-adjusted volumes of body water.