Lion spatial socio-ecology : the effect of habitat on lion group dynamics.
Lions are social, territorial animals that form prides of 2-18 individuals and hold territories ranging in size from 20 to 500 square km. My aim was to investigate the effect of ecological processes on lion spatial demography, specifically to determine the effect of habitat structure, prey availability, and rainfall (predictability and variability) on lion group dynamics. I worked with an extensive database of lion observations (approximately -+7000 over 29 years) from the Kruger National Park that had been recorded on monthly predator returns and in ranger diaries. I used the hypothesis of ideal free distribution to explain group dynamics across four physical habitat structures, namely, thickets, woodlands, mountainous areas and open tree savanna. There were larger groups of adults and more sightings than expected in the open tree savanna, while subadult and cub group sizes peaked in the woodlands. Using the resource dispersion hypothesis (RDH) as a base, I investigated lion group dynamics in relation to prey availability, I found agreement with the RDH, in that larger groups formed where their favoured prey species were in greatest abundance. Exclusively adult male and exclusively adult female group sizes increased with increasing buffalo abundance, while groups of adult males and adult females in mixed groups increased with increasing impala abundance. I used the mechanism of risk sensitive foraging to explain the influence of rainfall on lion group dynamics. While group dynamics did not differ significantly across averaged mean annual rainfall regions or across seasons, it did differ between variability regions and between two years of extreme rainfall. The lions exhibited risk-prone behaviour across variability regions, forming larger groups in more variable environments. Finally, I combined the three factors to determine the relative importance of each in determining lion group dynamics across seasons. Wildebeest were important to adult female group dynamics, impala and buffalo to adult males, while buffalo abundance influenced functional group size. In the wet season, larger functional groups occurred in the areas of medium rainfall variability regardless of buffalo abundance. In the dry season, more groups of females than solitary females occurred in more variable environments with this trend reversed for males.