Disturbance of coastal forests in East Africa: elephants promote forest butterflies while human impact supports Savannah species

Abstract Anthropogenic and natural disturbances can alter the structure and composition of forest ecosystems and thereby reshape the composition of plants and animals. Conservation management needs to disentangle the impact of both types of disturbance and their effects on biodiversity. Here, we use butterfly survey data from the Arabuko Sokoke dry coastal forest (south-eastern Kenya) to infer the disturbance effects of human and elephant activities. Butterflies were assessed in primary forest with and without elephants and secondary forest with elephants using bait traps (24 traps, eight per forests type). In total, we recorded 30 butterfly species, 23 in the primary forest with elephants, 19 in the primary forest without elephants, and 25 species in the secondary forest. The three forests types with different disturbance histories differed significantly in their butterfly communities. Although secondary forest had a higher butterfly species richness than primary forest, this higher richness was solely due to a higher proportion of Savannah species. In turn, primary forests had considerably higher proportions of forest species than secondary forests, with the highest proportions in the primary forest with elephant disturbance. Our findings hence underline that habitat disturbance can cause quite different outcomings. Conservation implications : While anthropogenic disturbance is negatively impacting the forest butterfly community, the natural disturbance by elephant activities seems to result in habitat structures even better for the performance of the typical forest butterflies than the undisturbed and hence more dense forest. This also calls for the idea that elephants and their activities were typical for the formerly continuous East African coastal forest belt.