Intracolonial demography, biomass and food consumption of Macrotermes natalensis (Haviland) (Isoptera: Termitidae) colonies in the northern Kruger National Park, South Africa

This thesis reports on the number of individuals in Macrotermes natalensis (Hav.) colonies, their biomass and food consumption in the northern Kruger National Park (KNP). The ecology of M. natalensis is largely undocumented despite the abundance of colonies in southern African savannas. New approaches to mound excavation, sub-sampling and data management are introduced. Via the intracolonial demography of colonies the contribution of each caste in number or proportion is determined. Using this information in combination with body mass and mound density data, biomass per unit area has been computed indicating the importance of this termite in synecology. The measurement of food consumption gives further insight as to how much litter is removed, fragmented and redistributed as nutrients in the ecosystem. Mounds were completely excavated, termites collected by means of vacuuming, and colony size estimated by sub-sampling. It was estimated that, on average, small mounds contain more than 5 000, medium mounds more than 45 000, and large mounds more than 200 000 individual termites. A highly significant relationship between total number of individuals (N ) and mound height (h ) was found, given by lnN = 7.893 + 1.093h (r = 0.92). The proportion of soldiers was found to change as colonies grew larger. In order to derive biomass estimates, a statistical bootstrap procedure was carried out using three databases: body mass, colony population sizes and mound density. Live biomass for small, medium and large mounds was found to be 0.17, 1.40 and 4.16 kg. Dry/wet body mass ratios were established for workers (23.7 %), major soldiers (20.3 %), minor soldiers (35.3 %), nymphs (17.1 %), king (35.4 %) and queen (20.8 %). Average live and dry biomass was calculated to be 0.51 kg/ha (0.051 g/m2) and 0.11 kg/ha (0.011 g/m2). Geology, geomorphology, elevation, local relief, soil patterns and annual rainfall were the abiotic factors shown to be most influential in determining termite biomass, either directly or indirectly. Termite biomass is high in undulating areas where the elevation is 250-400 m, where granitic and rhyolitic soils occur, and where annual rainfall is high (650-700 mm) in the context of the region. Major workers fetch woody litter outside the nest through ingestion into the section of the crop and gizzard. Gut contents were dried, weighed, ashed and reweighed. The ash mainly represents soil particles. The ash-free mass of food that is consumed during a single foraging trip by a foraging individual is 0.166 ± 0.009 mg (CI). Frequency of foraging trips between the mound and food source was observed using translucent tubing. The annual food consumption is given by the formula 365mnp/t , where m = individual mass of ashed crop-gizzard contents, n = number of foraging major workers, p = daily foraging period, and t = individual time spent between nest and food source. Food consumption of this termite in the northern KNP is calculated to be 20.2 kg/ha/yr. It is shown that termites are primary decomposers and contribute to litter fragmentation and the recycling of nutrients into the soil. This thesis gives greater insight into aspects such as colony development, biomass investment and resource utilization of M. natalensis in the northern KNP.