Foraging Strategy within African Elephant Family Units: Why Body Size Matters

Differences in intraspecific foraging strategies have been documented between sexes of strongly dimorphic large herbivore species. Body size implications on diet quality requirements, however, can be extended to within-species age-specific comparisons. We investigated the hierarchical separation of foraging behavior at the scale of plant type, plant species, plant part and vertically through the canopy. For this, we studied African elephant adult females (lower quality diet required) and weaned calves (higher quality diet) within the elephant family unit, which is socially constrained to traverse the landscape together. Grass and browse were used with similar seasonal frequency. Both females and calves tracked the phenology of woody species, including these species in the diet when new growth was available. Forage utilization differed at the plant part level, with calves selecting for less fibrous and more nutritious plant parrs (e.g., stripped leaves), while adult females selected branches, bark and roots with greater frequency. There was displacement of females to higher foraging levels in the canopy when these females fed <3m away from calves. Elephant family unit foraging strategies were driven by body size, age-specific nutritional requirements and intraspecific competition. This has broader application to other large herbivore species with great variance in intraspecific body size.