Age structure and grouping behaviour of elephants in Serengeti and Mikumi National Parks in Tanzania.

Abstract African elephants, Loxodonta africana, are mega-herbivores that utilise a variety of forage. Their large body size make them tolerant to diets of low nutritional quality. Subsequently, they mostly occur in moist-dystrophic savannas but also arid-eutrophic savannas. The arid-eutrophic savannas are characterised by nutrient-rich soils and small biomass of high quality forage while the moist-dystrophic savannas are characterised by nutrient-poor soils and large biomass of low quality forage. Female elephants are social, forming family groups consisting of genetically related individuals and young animals of both sexes. The social behaviour is influenced by forage availability which determine competition between group members. The differences in forage quantity between the savannas are expected to influence elephants grouping and reproduction. I predicted the elephants to form larger groups and to have higher reproductive efficiency in dystrophic savannas. I studied grouping behaviour and age structure of elephants in eutrophic Serengeti and dystrophic Mikumi National Parks in Tanzania during the dry season. I used park roads as transects, and when elephants were sighted, the car was stopped for data recording. Group size, group type (bachelor or family), and age composition of elephants were determined through direct observations. The Serengeti and Mikumi elephant populations differed in grouping behaviour and age structure, but opposite to my predictions. Serengeti had larger family groups and a larger proportion of young elephants 0–15 years old than Mikumi. The size of family groups differed between the parks while bachelor groups were similar. Further studies are recommended to compare elephant populations in contrasting savannas.