Do mammalian herbivores influence invertebrate communities via changes in the vegetation? Results from a preliminary survey in Kruger National Park, South Africa

Abstract

We investigated the indirect influence of mammalian herbivores on invertebrates, by utilising long-term mammalian herbivore exclosures in Kruger National Park. The exclosures span three distinct habitat types (crest, footslope and riparian) on a catena. By performing invertebrate collections in the exclosures and in a control area we were able to assess the indirect effect of mammalian herbivory on the invertebrate community and if this influence varied across habitat types. Our results indicate that large mammalian herbivores (notably elephants) had significant negative effects on total invertebrate abundance, while medium-sized mammalian herbivores affected the abundance and richness of beetles and grasshoppers negatively. Habitat type affected the invertebrates; spider abundance and richness peaked on the footslope, while beetles were the most abundant and taxon-rich in the riparian zone. Hence, our results suggest that indirect effects of mammalian herbivores on the invertebrate community may be significant, and in most cases negative, but also that the effects of mammalian herbivores vary across invertebrate groups. Thus, to better understand the broad-scale implications of changed mammalian herbivore pressures for the functioning of savanna systems, it may be important to take effects on invertebrate communities into account.