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Estimating lion population variables: Prey and disease effects in Kruger National Park, South Africa

Sam M. Ferreira and Paul J. Funston

Abstract: Lion (Panthera leo) populations experience a range of ecological and human influences that affect their demography. Few lion populations have reliable estimates of population size, trends in these, or demographic profiles. We developed a statistically robust approach to estimate selected population variables and evaluated the perceived threat of bovine tuberculosis (BTb) in landscapes of varying prey biomass in the Kruger National Park. Lion population size was stable, but long intervals between present and historical estimates limit this conclusion. Density and survival rates associated positively with prey biomass. Some variation in survival rates associated with prevalence of BTb - survival was higher in areas that had high prevalence of BTb. Male survival was lower than that of females disregarding the effects of prey biomass or BTb prevalence. Body condition of lions was high with scores lower at low to medium prey density. The effect of an exotic disease on the Kruger lion population may be negligible at present. Intra-specific competition in areas where lions live in high densities affects survival rate. However, droughts could disrupt the hierarchical influences of prey biomass and BTb prevalence on lion densities and survival. To evaluate the effect of an exotic disease on lion demography, population surveys should include age- and sex-structure assessments complemented by focal studies of fecundity.

Dr Sam Ferreira