Dynamics of herbivory in an altered post-war ecosystem at Gorongosa National Park, Mozambique

Abstract

Following a violent civil war that resulted in the loss of 90-100% of the individuals of all large mammal species in Gorongosa National Park in Mozambique, scientists observed a shift from grass dominance to forb dominance in the floodplain vegetation community. Understanding the vegetation shift is essential for restoration efforts because forbs generally provide less palatable plant biomass for herbivores, and we do not know if a forb-dominated floodplain will be able to support an abundant and diverse large herbivore population. To better understand the drivers of the novel floodplain dynamics, I explored the question: were the abundant herbivores present on the floodplain before the war responsible for maintaining the grass dominance? To address this question, I conducted clipping experiments to examine the effect of heavy grazing on the floodplain plant community. If the high level of pre-war herbivory was responsible for the grass dominance, then I would expect grasses to benefit from clipping and forbs to be negatively affected. I found no significant differences between the responses of grasses and forbs to clipping. However, the relationship between grazing and plant response is complex and further study is required to fully determine the potential differences between grass and forb responses to herbivory. Although most large mammal species are recovering slowly following the war, waterbuck have staged a spectacular recovery and are dominating the recovering park’s mammal community. In light of this, I asked the question: what effect is this dominance having on the park’s vegetation community and the recovery of other animals? To address this, I conducted observations of waterbuck to understand factors that affect their behavior. If waterbuck feed preferentially in grass-dominated areas, for example, they may be playing a role in preventing grasses from re-establishing dominance. I found no effect of vegetation type on feeding, though waterbuck spent more time moving in grass-dominated areas relative to forb-dominated areas. Several other factors, including group size and time of day, also affected time spent on different behaviors. Understanding the factors that affect waterbuck behavior will lead to better understanding of their influence on the habitat, which will in turn help restoration efforts.