THE INFLUENCE OF ELEPHANTS FORAGING ON TREE SPECIES REGENERATION AND ABUNDANCE IN ARABUKO-SOKOKE FOREST, KENYA

Abstract

Elephants play a significant role in structuring forest and savannah ecosystems. They influence plant regeneration patterns through their role in seed dispersal and germination, creation of forest gaps, pruning of vegetation and increasing habitat heterogeneity. Elephants also influence plant and animal communities and are recognized as keystone species as they are often the dominant mammalian biomass, and their activities influence nutrient and energy flow in habitats where they occur. Most research on the influence of elephants on community structure and tree regeneration patterns have focused on savannah habitats and lowland to mid altitude forests but their impact on tropical coastal forests of Eastern Africa has received less attention. This study investigated the role played by elephants in the regeneration and abundance of coastal forests’ tree species, specifically, the influence of elephant foraging activities on seed predation and germination rates and seedling growth rates with a special focus on Balanites maughamii and Manilkara sulcata. The study also examined the density and distribution of these elephant seed-dispersed trees along elephant trails and non-elephant forest trails. The results from seed predation experiments revealed a higher predation rate (25%) near parent trees compared to 15% away from parent trees as predicted by the Janzen-Connell hypothesis. The seed germination experiment showed that seeds that passed through the gut had higher germination success of 74% and lower germination latency of 47 days (about 1 and a half months) as compared to a germination success of 11% and germination latency of 96 days (about 3 months) for seeds that did not go through the elephant gut. However, there was no notable difference in seedling germination rates and latency between seeds that went through the elephant gut and planted in elephant dung as manure and those seeds that were planted without elephants’ dung, suggesting an extremely limited effect of manure. The growth rate of Balanites seedlings from seeds planted with elephant dung manure had a vi growth rate 0.33 cm (about 0.13 in) per day compared to 0.42 cm (about 0.17 in) per day of the control but this difference was not statistically different. The results also revealed a higher density of elephant dispersed trees (Balanites maughamii and Manilkara sulcata) along elephant trails compared to random trails. Moreover, the distribution of these elephant dispersed trees differed across vegetation categories examined. These results revealed that elephant foraging behavior had a positive influence on tree species regeneration in the Arabuko-Sokoke coastal forest reserve. Elephants should be maintained as an integral part of the Arabuko-Sokoke ecosystem and suggest a need to monitor elephant’s density to assess whether their impact on tree regeneration persists under high elephant densities.