Photosynthetic Systems, Carbon Isotope Discrimination And Herbivore Selectivity In Kenya

Abstract

The flora of the lowlands of East Africa possesses both C3 and C4 plants with nearly all grasses being C4. These photosynthetic systems discriminate differently against 13C. We have utilized the ‘label’ provided by the δ13C values to initiate studies of energy flow and vegetation utilization by East African herbivores. Preliminary data are reported here to illustrate the usefulness of this technique and to suggest its potential role in the numerous plant-herbivore studies already under way in East African systems. The δ13C values from faecal samples of East African herbivores allows us to estimate their immediate dependency on plant growth forms. Buffalo, zebra, waterbuck and wildebeest select 90–100% of their food at Amboseli from C4 plants (mainly grasses); elephant, Grant's and Thompson's gazelle, warthog and ostrich were more generalized feeders; and dik-dik and giraffe were nearly wholly dependent on C3 plants (trees and shrubs). A similar pattern was found at Samburu, but in the Aber-dares the generalized feeders were nearly exclusively dependent upon C3 vegetation.