Termite ecology in a tropical savanna grazed by cattle

Abstract

Aspects of termite ecology in a tropical savanna ecosystem grazed by cattle were investigated. The study area was C.S.I.R.O.’s Manbulloo Research Site (M.R.S.) located near Katherine in Northern Australia. Amitermes vitiosus mound density ranged from 70 mounds per hectare outside M.R.S. where cattle density was very low to 271 mounds per hectare inside M.R.S. where the cattle stocking rate was 0.8 steers/ha. A. vitiosus was the dominant species both inside and outside M.R.S., however the overall species diversity was greatest in natural savanna. The four times increase in density of A. vitiosus mounds inside M.R.S. is thought to be due to the ability of this species to utilize cattle dung as a food source. The relative roles of termites and dung beetles in dung removal were also assessed. The dung beetle species most active at M.R.S. were Qnthophagous gazella and Onitis alexis, both introduced species. These experiments indicated that exotic dung beetles and A. vitiosus have important and distinct roles in the decomposition and breakdown cattle dung. Termites utilize dry dung, and in the abscence of introduced dung beetles are able to remove dung pads in periods as short as three weeks. Dung beetles, however, attack fresh, moist dung, and rarely remove the entire pad. Where dung pads are attacked by dung beetles, they become unattractive to termites and hence in the long run less of the pad is removed in the presence of exotic dung beetles. Levels of many important nutrients are very high inside the mounds of A. vitiosus, compared to the the levels in the soil from which the mound material originated. The implications of the sequestering of these nutrients for plant growth and soil fertility are discussed. Show more