Spatial Distribution of Elephants in an African National Park in Relation to Environmental Sodium

Dry season counts of large mammals at man-made waterholes on aeolian sands in Wankie National Park in Central Africa showed pronounced variation in the spatial distribution of elephants. This could not be correlated with the distribution of other species or with geological, climatic or vegetational differences. A close correlation has been established between the sodium content of the water supplied for drinking and the numbers of elephants recorded. Elephant numbers were highest at water with a high sodium content, and smaller numbers were recorded from waters with lower sodium content, if deposits of watersoluble sodium were available in the soil. Few elephants were recorded from regions with little sodium either in water or in soil, even where browse was plentiful. It is likely that population density is dependent on environmental sodium in this region. Possible reasons for a high sodium dietary requirement are discussed in relation to data from East Africa, and it is shown that the sodium budget of the elephant may be precarious. Selective utilisation of sodium rich soil and water will often result in the ingestion of quantities of calcium, magnesium, potassium and other minerals with which the sodium is associated.