The limiting factor in populations of large mammals which are not controlled top-down by predation is food, i.e., such populations are controlled by bottom-up processes. However, there is little evidence of density dependence in large- to mega-herbivores. Conservationists have managed Critically Endangered megaherbivores like rhinoceros as if their population growth were density dependent.
This study did not find evidence for density dependence in black rhinoceros. Reproductive performances were better where PAM (‘soil moisture’) was high, PAN (‘soil fertility’) was low and woody cover was sparse. PAM was found to be directly correlated with quality of diet.
Black rhinoceros populations appeared controlled more by bottom-up processes through key resources. It was apparent that the density dependence concept still requires more investigation. Deliberate efforts should be made to secure high PAM – low PAN – sparse woody cover areas for conservation of black rhinoceros. Conservation managers are advised to consider set percentage translocations.