The activity of five seed-harvesting and ten non-harvesting species of ants was examined over a 2-year period. The ant community appeared to be stable in the long term, but there was considerable variability in the numbers and species of ants active at any one time, both on a seasonal and diel basis. Only four species were active throughout the year, with activity reduced in winter. Two species were consistently nocturnal, nine were mainly diurnal, and the remaining four species switched from diurnal to more nocturnal activity with increasing temperatures.
The changes in the diurnal pattern and intensity of foraging activity were shown to be controlled by several climatic and biotic variables. These were classed as either ‘stimulatory-inhibitory’ which determined whether activity would occur or not, or ‘regulatory’, which set the physical limits to activity and controlled foraging intensity. Factors such as forage availability and colony satiation were placed in the first category, and soil temperature, moisture stress and light intensity were placed in the second.
There was no simple response to the combination of variables, and individual species responded differently to the various factors. The resulting temporal separation probably reduces competitive interactions between species.