Allelochemicals,minerals and herbivore population size

Foods containing hydrolysable or condensed tannins depleted mouse body sodium concentrations. Supplementation of tannin diets with minerals eliminated sodium depletion and reduced toxic effects caused by tannin ingestion. Similar results were obtained by providing both tannin and saponin containing foods. A triterpene saponin did not cause sodium depletion. Sodium is limiting to some herbivore populations and herbivores frequently exhibit appetites for sodium. Sodium appetites and sodium population limitation are associated with consumption of tannins or other plant allelochemicals likely to cause sodium depletion. Enhanced sodium (or other mineral) requirements provides a mechanism whereby plants may maintain herbivore carrying capacities below levels likely to result in severe damage to vegetation.