Cascading Consequences of the Loss of Large Mammals in an African Savanna

Abstract

African savannas are home to an abundant and diverse assemblage of wild herbivores, but the very grasses that sustain these wild herds also make savannas attractive to humans and their livestock. We used the Kenya Long-term Exclosure Experiment to investigate the ecological effects of different combinations of native and domestic grazers. The experimental removal of large grazing mammals set into motion a cascade of consequences, beginning with the doubling in abundance of a small grazing mammal, the pouched mouse (Saccostomus mearnsi). The presence of abundant mice attracted venomous snakes such as the olive hissing snake (Psammophis mossambicus); devastated seedlings of the dominant tree (Acacia drepanolobium); and doubled the abundance of fleas, which potentially increased the risk of transmission of flea-borne pathogens. Together, these results show the potential for the loss of large mammals to have cryptic consequences for African savannas, with important and often undesirable repercussions for humans.