SOME ASPECTS OF THE INTERACTION BETWEEN MAMMALIAN HERBIVORES AND ACACIA ERIOBOLA E. MEY

SUMMARY

Acacia erioloba is an arid adapted species closely associated with the Kalahari Sands and their fringes. Its foliage and pods represent important food sources for both wild and domestic herbivores. The highly nutritious pods and their seeds are the largest of all the Acacia spp. These indehiscent pods, which persist on the trees throughout the year have evolved to ensure seed dispersal from the parent, though this strategy carries with it the dangers of its seeds being attacked by three genera of bruchid beetles over a long period. A. erioloba is an important source of fodder for the giraffe, which is evidenced by the striking browse line on the lower canopy surface. Studies at Vaalboschfontein examined the size of pods above and below the browse line for trees exposed to giraffe predation and extrapolated to those in an adjacent exclosure. The study revealed that the pods above the browse-line were significantly larger than those below the browse line, for both the browsed and the exclosed tree. This indicates that this effect appears to be one related to a long evolutionary exposure to browsing by giraffe.