Alternative pathways for development of meso-scale wildlife hotspots in an East African savanna

Background/Question/Methods

For centuries, African savannas have supported both pastoral livelihoods and thriving wildlife populations. Periodic creation and abandonment of traditional thorn-fence livestock “bomas” (corrals) creates long-term nutrient-rich “glade” hotspots (0.5 -1.0 ha) characterized by distinctive plant communities and increased use by wild ungulates.  Traditional boma sites undergo three major manipulations: 1) the site is cleared of trees, 2) large brush pile fences are maintained on the site perimeter throughout the lifetime of the boma, and 3) corralled livestock fertilize the area via intense dung deposition throughout boma occupation. Although the combination of these three manipulations clearly leads to development of glade hotspots, it is not clear whether alternative pathways exist. For example, areas of tree clearing alone or high nutrient status alone may be sufficient to attract wild ungulates and/or stimulate conversion to glade-like plant communities. I therefore used a factorial experiment to ask how plant and wild ungulate communities responded to different combinations of tree-clearing, brush addition and dung addition. I assessed plant and animal responses in 20m x 20m treatment plots for four years following treatment application.

Results/Conclusions

Two of the most common ungulate species, zebras and Grant’s gazelles, responded to experimental treatments. Grant’s gazelles appeared to respond positively to areas where both trees had been cleared and dung applied, whereas zebras appeared to respond positively to areas cleared of trees and negatively to brush fences. Wildlife responses do not appear to be directly driven by plant community composition changes or nutritive value of grasses.  Consistent with other studies, animals appear to be responding positively at least partially to decreased tree cover. These results contribute to our understanding of how savanna plants and animals respond to different types of landscape heterogeneity, with potential applications for management of biodiversity in savanna rangelands.