Effects of traditional pastoralism on grasshopper (Caelifera) assemblages in East Africa

Abstract

In East Africa, traditional pastoralists increase landscape heterogeneity by creating traditional livestock corrals (bomas). When these bomas are abandoned they serve as long-term hotspots of increased nutrients and unique vegetation. However, the effect of bomas on insect populations is unclear. Grasshopper (Suborder Caelifera) assemblages are thought to reflect vegetation and within Caelifera, the subfamily Oedipodinae is known to be associated with degraded areas. We sampled vegetation and collected grasshoppers inside of abandoned bomas, 50m from abandoned bomas, and 250m from abandoned bomas. Bomas had significantly lower grass abundance than background vegetation. Total grasshopper abundance was positively correlated with grass and forb abundance, while the proportion of grasshoppers in the subfamily Oedipodinae was negatively correlated with grass abundance. Grasshopper abundance was significantly lower inside of bomas than outside of them, but the proportion of grasshoppers in the subfamily Oedipodinae was significantly higher inside of bomas than outside of them. This suggests that the decreased vegetation in abandoned bomas supports fewer grasshoppers, but a higher fraction of the grasshopper assemblage in abandoned bomas is composed of Oedipodinae. Thus, traditional pastoralists can have long-term effects on the size and composition of grasshopper assemblages through the use of bomas.