Seed dispersal by megaherbivores: do Asian elephants disperse Mallotus philippinensis, a main food tree in northern India and Nepal?

Abstract

Megaherbivores play an important role in dispersing forest trees. In lowland Nepal, we tested experimentally whether Asian elephants contributed to the spreading of Mallotus philippinensis in sal forest by ingesting seeds of this species. Seventy-seven dung samples and 200 ripe seeds were sown in plots. No germination was recorded in the dung plots, whereas > 90% of the seeds in the control plots germinated. In sal forest, the abundance of all age classes of Mallotus was higher along elephant tracks than along random transects, but differences were small and not statistically significant. The results did not support the elephant dispersal hypothesis. Instead, we conclude that the spreading of Mallotus and concurrent declining of sal might be the result of shifting ecological successions, triggered by more flooding and a more erratic rainfall pattern combined with less frequent forest fires, all of which are assumed to favour Mallotus and hamper regeneration of Shorea robusta.