The dynamics and trophic ecology of grasshoppers (Acridoidea) in a South African savanna : Trophic ecology of grasshoppers in South African savanna.

1. A grasshopper population was monitored for three seasons in broad leaved savanna in South Africa. The biomass at corresponding times in successive seasons varied by up to a factor of four. Climatic factors may have been responsible. 2. The energetics of the grasshopper population are described for one year of intensive study. In this year a mean grasshopper biomass of 0.73 kg ha-1 ingested 94 kg ha-1 of plant material. In addition, 36 kg ha-1 was wasted in the course of feeding. Grasshoppers removed 16% of grass production, but this dropped to about 7% in the following year. 3. Production efficiency and ecological efficiency were lower than those measured for grasshoppers in other systems. Reasons are suggested. 4. Grasshopper diets were examined by epidermal analysis of crop fragments. All grasshopper species examined fed from a wide range of plant species, but diets could be grouped according to the physical characteristics of the food items. There was limited dietary overlap between the whole grasshopper population and large grazing mammals. 5. Vegetation structure is more significant than species composition as a determinant of habitat selection within the savanna type.