Abstract:
Direct effects of herbivory, and indirect effects through induced responses to herbivory, can
both influence the susceptibility of plants to subsequent attacks by herbivores. There has, however, been
very little research (if any) to investigate how the large-scale effects of browsing by megaherbivores (.1000
kg body mass) on woody plants might influence the subsequent use of those plants by phytophagous
insects. We conducted a field study in Kruger National Park, South Africa, to investigate whether browsing
by elephants (Loxodonta africana) on mopane trees (Colophospermum mopane) had any influence on the
subsequent selection of those trees by ovipositing mopane moths (Imbrasia belina). Our results showed that,
after controlling for differences in canopy volume, the density of egg masses was almost halved in mopane
woodlands recovering from severe elephant browsing in the previous season. This is despite the regrowth
on heavily browsed trees having lower tannin:protein ratios and longer shoots. Our suggested explanation
is that large monophagous caterpillars can only feed in the canopies of the trees in which they hatch and so
the quantity of food in each canopy is more important than its quality. There are implications for the
sustainable harvesting of mopane caterpillars, which represent an important food resource for rural
communities in southern Africa. Future avenues for research include patch selection by large herbivores in
response to local nutrient enrichment by frass deposited during caterpillar outbreaks.
