The abundance of large termite mounds in Uganda in relation to their environment.
The density of large termite mounds was estimated from 638 counts spread throughout Uganda. The counts were compared with data for fourteen environmental variables, mainly climatic and soil measurements, as shown on published maps. The mounds were built by two species, Macrotermes bellicosus (Smeath.) and M. subhyalinus (Ramb.). Of five alternatives considered, the greatest correlations were obtained from parabolic transformations of the independent variables. This probably reflected the existence of optimal values in most cases. On the basis of the Ugandan data, lower limits for the occurrence of M. subhyalinus were predicted to be 300 mm rainfall and a mean minimum temperature of 9 deg C. For M. bellicosus, the corresponding figures were 700 mm and 12 deg C. These coincide well with the limits of their distributions in Africa as a whole. Parabolic transformations of the independent variables were used in multiple linear regressions to assess their relative significance. Relationships between the density of mounds and rainfall, minimum temperature and exchangeable bases were highly significant for both species. There is good evidence for a correlation between the abundance of M. bellicosus mounds and the rate of decomposition. It seems possible that the termite is the cause of this and of the low humus contents of soil where its mounds are numerous.