On the relationship of a large herbivore community to environmental and anthropogenic influences in the Serengeti ecosystem

Background/Question/Methods

To predict how a community of East African large herbivores could respond to altered environmental conditions and management strategies, the environmental conditions defining preferred habitats must be characterized. The influences of habitat characteristics (both natural and anthropogenic) on a suite of aggregate community measures (species richness, total abundance, total biomass, and cumulative basal metabolic rate) are compared in this study of Serengeti National Park and neighboring protected areas in Tanzania, East Africa. Aerial census data provide estimates of densities of animals within 5 km x 5 km grid cells across the study landscape. We examined nine annual surveys from 1988-2006. Twelve herbivore species with sufficient data were included in the study. Influences of seventeen environmental and anthropogenic habitat characteristics (e.g., road density, distance to river, plant nutrients, tree cover) on each community measure were assessed using spatial regression models.

Results/Conclusions

The aggregate community measures of total abundance, total biomass, and total basal metabolic rate were strongly cross-correlated in each survey. There were some similarities, as well as differences, in the spatial pattern of species richness compared to the other metrics; species richness, however, was often greater at lower values of the aggregate measures. The ungulate community appears vulnerable to the effects of humans in surrounding areas -- these measures tend to be depressed near edges of the park adjacent to human activity. Roads within the protected areas do not negatively effect these herbivores. The resources most strongly influencing the community distributions are plant nutrients and NDVI (i.e., plant productivity). Fire, although prominent in savannas, does not markedly affect herbivore community distributions at a broad landscape level. Efforts to manage for species richness would involve emphasizing habitat characteristics different from those that would maximize total abundance, biomass, or metabolic rate. Future management practices might strive to identify the mechanisms responsible for negative effects emanating from human populations in neighboring areas.