Mistletoes as Indicators of the Intensity of Browsing by Large Mammals in Kalahari Savanna

Abstract

The frequency, size and position of the mistletoe Tapinanthus oleifolius in its dominant host's canopy were strongly correlated with the degree of exposure to herbivory by the kudu (Tragelaphus strepsiceros) and especially the giraffe (Giraffa camelopardalis). Mistletoes exposed to herbivory are less frequent and smaller compared to those deeper within the host canopy, on steeper slopes and especially where herbivores are few or absent. Where exposed to herbivores, T. oleifolius was almost entirely restricted to the spinescent host Senegalia mellifera, whereas in herbivore-free areas, other tree species became hosts. The mistletoe Viscum rotundifolium was totally absent in areas with large herbivores. In herbivore-free areas, it was frequently found on Ehretia alba and Boscia albitrunca, both non-spinescent hosts. Mistletoes are thus excellent indicators of the extent of herbivory; their local absence probably indicates excessive herbivory, and a high presence indicates an absence of herbivory.