Selection of seeds by harvester ants (Messor capensis) in relation to condition of arid rangeland

Food plant selection by herbivorous mammals and by harvester ants Messor capensis was compared for three sites differing in past and present management in the southern Karoo, South Africa. At all three sites the ants collected an estimated 4•1 million seeds (5•2 kg)/ha/y which amounted to 10% of the seeds and 18% of the annual seed biomass production of common plants. Seed removal by M. capensis did not appear to compound the effects of herbivorous mammals on the reproductive potential of plants, because ants concentrated on the most abundant seeds > 0•3 mg. Ant granaries on degraded rangeland contained more seeds of ruderals and of plant species unpalatable to sheep